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  • 151.
    Chrobok, Daria
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Law, Simon R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Brouwer, Bastiaan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Linden, Pernilla
    Ziolkowska, Agnieszka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Liebsch, Daniela
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Narsai, Reena
    Szal, Bozena
    Moritz, Thomas
    Rouhier, Nicolas
    Whelan, James
    Gardeström, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Keech, Olivier
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Dissecting the Metabolic Role of Mitochondria during Developmental Leaf Senescence2016Inngår i: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 172, nr 4, s. 2132-2153Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The functions of mitochondria during leaf senescence, a type of programmed cell death aimed at the massive retrieval of nutrients from the senescing organ to the rest of the plant, remain elusive. Here, combining experimental and analytical approaches, we showed that mitochondrial integrity in Arabidopsis (Arabidopsis thaliana) is conserved until the latest stages of leaf senescence, while their number drops by 30%. Adenylate phosphorylation state assays and mitochondrial respiratory measurements indicated that the leaf energy status also is maintained during this time period. Furthermore, after establishing a curated list of genes coding for products targeted to mitochondria, we analyzed in isolation their transcript profiles, focusing on several key mitochondrial functions, such as the tricarboxylic acid cycle, mitochondrial electron transfer chain, iron-sulfur cluster biosynthesis, transporters, as well as catabolic pathways. In tandem with a metabolomic approach, our data indicated that mitochondrial metabolism was reorganized to support the selective catabolism of both amino acids and fatty acids. Such adjustments would ensure the replenishment of alpha-ketoglutarate and glutamate, which provide the carbon backbones for nitrogen remobilization. Glutamate, being the substrate of the strongly up-regulated cytosolic glutamine synthase, is likely to become a metabolically limiting factor in the latest stages of developmental leaf senescence. Finally, an evolutionary age analysis revealed that, while branched-chain amino acid and proline catabolism are very old mitochondrial functions particularly enriched at the latest stages of leaf senescence, auxin metabolism appears to be rather newly acquired. In summation, our work shows that, during developmental leaf senescence, mitochondria orchestrate catabolic processes by becoming increasingly central energy and metabolic hubs.

  • 152. Ciereszko, I
    et al.
    Johansson, H
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Hurry, Vaughan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Kleczkowski, L.A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Phosphate status affects the gene expression, protein content and enzymatic activity of UDP-glucose pyrophosphorylase in wild-type and pho mutants of Arabidopsis.2001Inngår i: Planta, ISSN 0032-0935, Vol. 212, nr 4, s. 598-605Artikkel i tidsskrift (Fagfellevurdert)
  • 153. Ciereszko, I
    et al.
    Johansson, H
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Kleczkoski, L.A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Sucrose and light regulation of a cold-inducible UDP-glucose pyrophosphorylase gene via a hexokinase-independent and abscisic acid-insensitive pathway in Arabidopsis.2001Inngår i: Biochemical Journal, Vol. 354, nr 1, s. 67-72Artikkel i tidsskrift (Fagfellevurdert)
  • 154. Ciereszko, I
    et al.
    Kleczkowski, Leszek A
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Effects of phosphate deficiency and sugars on expression of rab18 in Arabidopsis: hexokinase-dependent and okadaic acid-sensitive transduction of the sugar signal2002Inngår i: Biochimica et Biophysica Acta, Gene Structure and Expression, ISSN 0167-4781, E-ISSN 1879-2634, Vol. 1579, nr 1, s. 43-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The lack of phosphorus in the nutrient medium increased the expression of rab18, an abscisic acid (ABA)-responsive gene, in leaves of Arabidopsis thaliana. The expression of this gene was also upregulated after feeding the excised leaves with D-mannose and sucrose for both wild-type (wt) and aba1 (ABA-deficient) mutant plants. For aba1 mutants, both the phosphate deficiency and sugar effects on rab18 were weaker than in wt plants, suggesting possible involvement of both ABA-dependent and ABA-independent components in signalling. Transgenic Arabidopsis plants with increased hexokinase (HXK) expression had a much higher sucrose-dependent level of rab18 mRNA, implying the HXK involvement in sensing/transmitting the sugar signal. Sucrose-related induction of rab18 was completely inhibited by okadaic acid (OKA), suggesting the involvement of specific protein phosphatase(s) in transduction of the sugar signal. The results suggest that rab18 is regulated via interaction of a plethora of signals, including ABA, sugar and phosphate deficiency, and that the sugar effect is transmitted via a HXK-pathway, involving OKA-sensitive component(s). The findings prompt caution in linking the expression of rab18 solely to ABA signalling. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 155. Ciereszko, I
    et al.
    Kleczkowski, Leszek A
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Glucose and mannose regulate the expression of a major sucrose synthase gene in Arabidopsis via hexokinase-dependent mechanisms2002Inngår i: Plant physiology and biochemistry (Paris), ISSN 0981-9428, E-ISSN 1873-2690, Vol. 40, nr 11, s. 907-911Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sucrose synthase (SuSy) is an important enzyme involved in sucrose synthesis/breakdown in all plants. Sus1, a major SuSy gene in Arabidopsis thaliana, was upregulated by sucrose, glucose and D-mannose, but not 3-O-methylglucose, when those compounds were fed to excised leaves. Mannos, was more effective than glucose or sucrose in the induction of Sus1, with strong effects observed at a concentration as low as 20, mM. When fed to the excised leaves, N-acetyl-glucosamine, an inhibitor of hexokinase (HXK) enzymatic activity, decreased sucrose- and glucose-dependent, but not mannose-dependent, upregulation of Sus1. The sucrose/glucose-dependent Sus1 expression was strongly induced in transgenic Arabidopsis HXK-overexpressing (OE) plants, whereas mannose-dependent Sus1 expression markedly decreased in OE, but not in HXK-"antisense", Arabidopsis plants. Feeding with sucrose resulted in a marked increase of glucose content in leaves, suggesting that it is glucose rather than sucrose that serves as a signal in upregulating Sus1 expression in sucrose-fed plants. The data suggest that Sus1 is regulated by a HXK-dependent pathway, with glucose and mannose effects differentially sensed/transmitted via the HXK step. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

  • 156. Ciereszko, Iwona
    et al.
    Johansson, Henrik
    Kleczkowski, Leszek
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Interactive effects of phosphate deficiency, sucrose and light/dark conditions on gene expression of UDP-glucose pyrophosphorylase in Arabidopsis.2005Inngår i: Journal of Plant Physiology, ISSN 0176-1617, Vol. 162, nr 3, s. 343-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of inorganic phosphate (Pi) status, light/dark and sucrose on expression of UDP-glucose pyrophosphorylase (UGPase) gene (Ugp), which is involved in sucrose/ polysaccharides metabolism, were investigated using Arabidopsis wild-type (wt) plants and mutants impaired in Pi and carbohydrate status. Generally, P-deficiency resulted in increased Ugp expression and enhanced UGPase activity and protein content, as found for wt plants grown on P-deficient and complete nutrient solution, as well as for pho1 (P-deficient) mutants. Ugp was highly expressed in darkened leaves of pho1, but not wt plants, daily tight exposure enhanced Ugp expression both in wt and pho mutants. The pho1 and pho2 (Pi-accumulating) mutations had Little or no effect on leaf contents of glucose and fructose, regardless of light/dark conditions, whereas pho1 plants had much higher Levels of sucrose and starch in the dark than pho2 and wt plants. The Ugp was up-regutated when leaves were fed with sucrose in wt plants, but the expression in pho2 background was much less sensitive to sucrose supply than in wt and pho1 plants. Expression of Ugp in pgm1 and sex1 mutants (impaired in starch/sugar content) was not dependent on starch content, and not tightly correlated with soluble sugar status. Okadaic acid (OKA) effectively blocked the P-starvation and sucrose -dependent expression of Ugp in excised leaves, whereas staurosporine (STA) had only a small effect on both processes (especially in -P leaves), suggesting that P-starvation and sucrose effects on Ugp are transmitted by pathways that may share similar components with respect to their (in)sensitivity to OKA and STA. The results of this study suggest that Ugp expression is modulated by an interaction of signals derived from P-deficiency status, sucrose content and dark/ light conditions, and that light/ sucrose and P-deficiency may have additive effects on Ugp expression. (c) 2004 Elsevier GmbH. All rights reserved.

  • 157. Ciereszko, Iwona
    et al.
    Kleczkowski, Leszek
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Expression of several genes involved in sucrose/starch metabolism as affected by different strategies to induce phosphate deficiency in Arabidopsis2005Inngår i: Acta Physiologiae Plantarum, Vol. 27, s. 147-155Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of inorganic phosphate (Pi) deficiency on expression of genes encoding ADP-glucose pyrophosphorylase small and large subunits (ApS and ApL1, ApL2, ApL3 genes), UDP-glucose pyrophosphorylase (Ugp gene), sucrose synthase (Sus1), soluble and insoluble acid invertases (Inv and Invcw) and hexokinase (Hxk1 gene), all involved in carbohydrate metabolism, were investigated in Arabidopsis thaliana (L.) Heynh. We used soil-grown pho mutants affected in Pi status, as well as wild-type (wt) plants grown under Pi deficiency conditions in liquid medium, and leaves of wt plants fed with D-mannose. Generally, ApS, ApL1, Ugp and Inv genes were upregulated, although to a varied degree, under conditions of Pi-stress. The applied conditions had differential effects on expression of other genes studied. For instance, Sus1 was downregulated in pho1 (Pi-deficient) mutant, but was unaffected in wt plants grown in liquid medium under P-deficiency. Mannose had distinct concentration-dependent effects on expression of genes under study, possibly reflecting a dual role of mannose as a sink for Pi and as glucose analog. Feeding Pi (at up to 200 mM) to the detached leaves of wt plants strongly affected the expression of ApL1, ApL2, Sus1 and Inv genes, possibly due to an osmotic effect exerted by Pi. The data suggest that ADP-glucose and UDP-glucose pyrophosphorylases (enzymes indirectly involved in Pi recycling) as well as invertases (sucrose hydrolysis) are transcriptionally regulated by Pi-deficiency, which may play a role in homeostatic mechanisms that acclimate the plant to the Pi-stress conditions.

  • 158. Ciereszko, Iwona
    et al.
    Kleczkowski, Leszek
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Phosphate deficiency dependent upregulation of UDP-glucose pyrophosphorylase genes is insensitive to ABA and ethylene status in Arabidopsis leaves2006Inngår i: Acta Physiologiae Plantarum, Vol. 28, s. 387-393Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of inorganic phosphate (Pi) deficiency and ABA/ethylene status on expression of UDP-glucose pyrophosphorylase (UGPase) genes (Ugp), involved in sucrose/polysaccharide metabolism, were investigated. Both wild-type (wt), aba and abi mutants (ABA-deficient and -insensitive), etr, ein and eto (ethylene resistant and overproducing) grown on Pi-deficient and complete nutrient solution, as well as pho1 (Pi-deficient) mutants of Arabidopsis thaliana were used for experiments. Generally, Pi-deficiency conditions (including mannose feeding to decrease cytosolic Pi pool) resulted in an increase of Ugp expression in the leaves, under all experimental conditions. Mutant backgrounds reflecting differences in ABA or ethylene status/ sensitivity had no effect on the level of Ugp up-regulation by Pi-stress. Furthermore, feeding ABA to the leaves of wt and pho1 plants had no effect on Ugp expression, regardless of the sucrose status in the leaves. The data suggest that Pi deficiency leading to up-regulation of Ugp acts independently of ABA and ethylene status.

  • 159. CLARKE, AK
    et al.
    CAMPBELL, D
    Gustafsson, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    DYNAMIC-RESPONSES OF PHOTOSYSTEM-II AND PHYCOBILISOMES TO CHANGING LIGHT IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC-79421995Inngår i: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 197, nr 3, s. 553-562Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have examined the molecular and photosynthetic responses of a planktonic cyanobacterium to shifts in light intensity over periods up to one generation (7 h). Synechococcus sp. PCC 7942 possesses two functionally distinct forms of the D1 protein, D1:1 and D1:2. Photosystem II (PSII) centers containing D1:1 are less efficient and more susceptible to photoinhibition than are centers containing D1:2, Under 50 mu mol photons m(-2). s(-1), PSII centers contain D1:1, but upon shifts to higher light (200 to 1000 mu mol photons m(-2). s(-1)), D1:1 is rapidly replaced by D1:2, with the rate of interchange dependent on the magnitude of the light shift. This interchange is readily reversed when cells are returned to 50 mu mol photons m(-2). s(-1). If, however, incubation under 200 mu mol photons m(-2). s(-1) is extended, D1:1 content recovers and by 3 h after the light shift D1:1 once again predominates. Oxygen evolution and chlorophyll (Chi) fluorescence measurements spanning the light shift and D1 interchanges showed an initial inhibition of photosynthesis at 200 mu mol photons m(-2). s(-1), which correlates with a proportional loss of total D1 protein and a cessation of growth. This was followed by recovery in photosynthesis and growth as the maximum level of D1:2 is reached after 2 h at 200 mu mol photons m(-2). s(-1) Thereafter, photosynthesis steadily declines with the loss of D1:2 and the return of the less-efficient D1:1. During the D1:1/D1:2 interchanges, no significant change occurs in the level of phycocyanin (PC) and Chl a, nor of the phycobilisome rod linkers. Nevertheless, the initial PC/Chl a ratio strongly influences the magnitude of photoinhibition and recovery during the light shifts. In Synechococcus sp. PCC 7942, the PC/Chl a ratio responds only slowly to light intensity or quality, while the rapid but transient interchange between D1:1 and D1:2 modulates PSII activity to limit damage upon exposure to excess light.

  • 160. CLARKE, AK
    et al.
    Gustafsson, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    LIDHOLM, JA
    IDENTIFICATION AND EXPRESSION OF THE CHLOROPLAST CLPP GENE IN THE CONIFER PINUS-CONTORTA1994Inngår i: Plant Molecular Biology, ISSN 0167-4412, E-ISSN 1573-5028, Vol. 26, nr 3, s. 851-862Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The clpP gene from the conifer Pinus contorta was identified and isolated from a chloroplast genomic library by heterologous hybridisation to the second exon of the chloroplast clpP gene in tobacco. DNA sequencing of two overlapping clones revealed an uninterrupted 615 bp open-reading frame with 41 to 65% similarity to the clpP genes in five other chloroplast genomes and Escherichia coli. The 615 bp sequence in P. contorta contained perfectly matched motifs for the serine and histidine active sites of the GlpP protease in E. coli. The location of the clpP gene was determined using a physical map of the P. contorta chloroplast genome, and was found to lie within a 10 kb region between the psbE/F and vpoB genes. Sequencing of the regions adjacent to the clpP gene revealed the first exon of the rps12 gene located 135 bp downstream. The genomic position of the first exon of the rps12 gene in relation to the clpP gene is conserved for all other chloroplast clpP genes identified so far. Northern blot analysis showed that the clpP gene in both P. contorta and P. sylvestris was present in several transcript of different length, ranging from 0.8 to 2.4 kb. The two longer transcripts in P. contorta also included the first exon of the rps12 gene. Mapping of the 5' end of the clpP transcripts by primer extension, however, revealed a single transcription initiation site 53 bp upstream of the first ATG codon. Analysis of total RNA isolated from The two pine species grown in darkness or moderate light conditions (250 mu mol photons m(-2) s(-1)) showed no significant difference in the level of expression of the clpP gene. The results suggest that the clpP gene in conifers is part of an operon which includes the first exon of the rps12 and the entire rp120 gene, and is expressed in a light-independent manner as a polycistronic precursor which later undergoes post-transcriptional processing to give the mature monocistronic clpP mRNA.

  • 161. CLARKE, AK
    et al.
    HURRY, VM
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Gustafsson, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    2 FUNCTIONALLY DISTINCT FORMS OF THE PHOTOSYSTEM-II REACTION-CENTER PROTEIN D1 IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC 79421993Inngår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 90, nr 24, s. 11985-11989Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The cyanobacterium Synechococcus sp. PCC 7942 possesses a small psbA multigene family that codes for two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We showed previously that the normally predominant D1 form (D1:1) was rapidly replaced with the alternative D1:2 when cells adapted to a photon irradiance of 50 mumol/m-2.s-1 are shifted to 500 mumol.m-2.s-1 and that this interchange was readily reversible once cells were allowed to recover under the original growth conditions. By using the psbA inactivation mutants R2S2C3 and R2K1 (which synthesize only D1:1 and D1:2, respectively), we showed that this interchange between D1 forms was essential for limiting the degree of photoinhibition as well as enabling a rapid recovery of photosynthesis. In this report, we have extended these findings by examining whether any intrinsic functional differences exist between the two D1 forms that may afford increased resistance to photoinhibition. Initial studies on the rate of D1 degradation at three photon-irradiances (50, 200, and 500 mumol.m-2.s-1) showed that the rates of degradation for both D1 forms increase with increasing photon flux density but that there was no significant difference between D1:1 and D1:2. Analysis of light-response curves for oxygen evolution for the mutants R2S2C3 and R2K1 revealed that cells with photosystem II reaction centers containing D1:2 have a higher apparent quantum yield (almost-equal-to 25%) than cells possessing D1:1. Further studies using chlorophyll a fluorescence measurements confirmed that R2K1 has a higher photochemical yield than R2S2C3; that is, a more efficient conversion of excitation energy from photon absorption into photochemistry. We believe that the higher photochemical efficiency of reaction centers containing D1:2 is causally related to the preferential induction of D1:2 at high light and thus may be an integral component of the protection mechanism within Synechococcus sp. PCC 7942 against photoinhibition.

  • 162. CLARKE, AK
    et al.
    SOITAMO, A
    Gustafsson, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    RAPID INTERCHANGE BETWEEN 2 DISTINCT FORMS OF CYANOBACTERIAL PHOTOSYSTEM-II REACTION-CENTER PROTEIN-D1 IN RESPONSE TO PHOTOINHIBITION1993Inngår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 90, nr 21, s. 9973-9977Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied photoinhibition of photosynthesis in the cyanobacterium Synechococcus sp. PCC 7942, which possesses two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We report here that when cells adapted to a growth irradiance of 50 mumol.m-2.s-1 are exposed to an irradiance of 500 mumol.m-2.s-1, the normally predominant D1 form (D1:1) is rapidly replaced with the alternative D1:2. This interchange is not only complete within the first hour of photoinhibition but is also fully reversible once cells are returned to 50 mumol.m-2.s-1. By using a mutant that synthesizes only D1:1, we show that the failure to replace D1:1 with D1:2 during photoinhibition results in severe loss of photosynthetic activity as well as a diminished capacity to recover after the stress period. We believe that this interchange between D1 forms may constitute an active component in a protection mechanism unique among photosynthetic organisms that enables cyanobacteria to effectively cope with and recover from photoinhibition.

  • 163. Coimbra, Sílvia
    et al.
    Jones, Brian
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Umeå Plant Science Centre.
    Pereira, Luis Gustavo
    Arabinogalactan proteins (AGPs) related to pollen tube guidance into the embryo sac in Arabidopsis2008Inngår i: Plant Signaling & Behavior, Vol. 3, nr 7, s. 455-456Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Some AGP molecules or their sugar moieties are probably related to the guidance of the pollen tube into the embryo sac, in the final part of its pathway, when arriving at the ovules. The specific labelling of the synergid cells and its filiform apparatus, which are the cells responsible for pollen tube attraction, and also the specific labelling of the micropyle and micropylar nucellus, which constitutes the pollen tube entryway into the embryo sac, are quite indicative of this role. We also discuss the posibility that AGPs in the sperm cells are probably involved in the double fertilization process.

  • 164.
    Collani, Silvio
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Max Planck Institute for Developmental Biology,Department of Molecular Biology, Tübingen, Germany.
    Neumann, Manuela
    Yant, Levi
    Schmid, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Max Planck Institute for Developmental Biology,Department of Molecular Biology, Tübingen, Germany; Beijing Advanced Innovation Centre for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, People’s Republic of China.
    FT Modulates Genome-Wide DNA-Binding of the bZIP Transcription Factor FD2019Inngår i: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 180, nr 1, s. 367-380Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The transition to flowering is a crucial step in the plant life cycle that is controlled by multiple endogenous and environmental cues, including hormones, sugars, temperature, and photoperiod. Permissive photoperiod induces the expression of FLOWERING LOCUS T (FT) in the phloem companion cells of leaves. The FT protein then acts as a florigen that is transported to the shoot apical meristem, where it physically interacts with the Basic Leucine Zipper Domain transcription factor FD and 14-3-3 proteins. However, despite the importance of FD in promoting flowering, its direct transcriptional targets are largely unknown. Here, we combined chromatin immunoprecipitation sequencing and RNA sequencing to identify targets of FD at the genome scale and assessed the contribution of FT to DNA binding. We further investigated the ability of FD to form protein complexes with FT and TERMINAL FLOWER1 through interaction with 14-3-3 proteins. Importantly, we observed direct binding of FD to targets involved in several aspects of plant development. These target genes were previously unknown to be directly related to the regulation of flowering time. Our results confirm FD as a central regulator of floral transition at the shoot meristem and provide evidence for crosstalk between the regulation of flowering and other signaling pathways, such as pathways involved in hormone signaling.

  • 165. Conn, Vanessa M.
    et al.
    Hugouvieux, Veronique
    Nayak, Aditya
    Conos, Stephanie A.
    Capovilla, Giovanna
    Cildir, Gokhan
    Jourdain, Agnes
    Tergaonkar, Vinay
    Schmid, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Zubieta, Chloe
    Conn, Simon J.
    A circRNA from SEPALLATA3 regulates splicing of its cognate mRNA through R-loop formation2017Inngår i: Nature Plants, ISSN 2055-026X, Vol. 3, nr 5, artikkel-id 17053Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Circular RNAs (circRNAs) are a diverse and abundant class of hyper-stable, non-canonical RNAs that arise through a form of alternative splicing (AS) called back-splicing. These single-stranded, covalently-closed circRNA molecules have been identified in all eukaryotic kingdoms of life(1), yet their functions have remained elusive. Here, we report that circRNAs can be used as bona fide biomarkers of functional, exon-skipped AS variants in Arabidopsis, including in the homeotic MADS-box transcription factor family. Furthermore, we demonstrate that circRNAs derived from exon 6 of the SEPALLATA3 (SEP3) gene increase abundance of the cognate exon-skipped AS variant (SEP3.3 which lacks exon 6), in turn driving floral homeotic phenotypes. Toward demonstrating the underlying mechanism, we show that the SEP3 exon 6 circRNA can bind strongly to its cognate DNA locus, forming an RNA: DNA hybrid, or R-loop, whereas the linear RNA equivalent bound significantly more weakly to DNA. R-loop formation results in transcriptional pausing, which has been shown to coincide with splicing factor recruitment and AS(2-4). This report presents a novel mechanistic insight for how at least a subset of circRNAs probably contribute to increased splicing efficiency of their cognate exon-skipped messenger RNA and provides the first evidence of an organismal-level phenotype mediated by circRNA manipulation.

  • 166. Cooke, Janice E. K.
    et al.
    Eriksson, Maria E.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Junttila, Olavi
    The dynamic nature of bud dormancy in trees: environmental control and molecular mechanisms2012Inngår i: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 35, nr 10, s. 1707-1728Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In tree species native to temperate and boreal regions, the activity-dormancy cycle is an important adaptive trait both for survival and growth. We discuss recent research on mechanisms controlling the overlapping developmental processes that define the activity-dormancy cycle, including cessation of apical growth, bud development, induction, maintenance and release of dormancy, and bud burst. The cycle involves an extensive reconfiguration of metabolism. Environmental control of the activity-dormancy cycle is based on perception of photoperiodic and temperature signals, reflecting adaptation to prevailing climatic conditions. Several molecular actors for control of growth cessation have been identified, with the CO/FT regulatory network and circadian clock having important coordinating roles in control of growth and dormancy. Other candidate regulators of bud set, dormancy and bud burst have been identified, such as dormancy-associated MADS-box factors, but their exact roles remain to be discovered. Epigenetic mechanisms also appear to factor in control of the activity-dormancy cycle. Despite evidence for gibberellins as negative regulators in growth cessation, and ABA and ethylene in bud formation, understanding of the roles that plant growth regulators play in controlling the activity-dormancy cycle is still very fragmentary. Finally, some of the challenges for further research in bud dormancy are discussed.

  • 167.
    Courtois-Moreau, Charleen L
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Pesquet, Edouard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Sjödin, Andreas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Muñiz, Luis
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Bollhöner, Benjamin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Kaneda, Minako
    Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
    Samuels, Lacey
    Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Tuominen, Hannele
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    A unique program for cell death in xylem fibers of Populus stem2009Inngår i: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 58, nr 2, s. 260-274Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Maturation of the xylem elements involves extensive deposition of secondary cell-wall material and autolytic processes resulting in cell death. We describe here a unique type of cell-death program in xylem fibers of hybrid aspen (Populus tremula x P. tremuloides) stems, including gradual degradative processes in both the nucleus and cytoplasm concurrently with the phase of active cell-wall deposition. Nuclear DNA integrity, as determined by TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) and Comet (single-cell gel electrophoresis) assays, was compromised early during fiber maturation. In addition, degradation of the cytoplasmic contents, as detected by electron microscopy of samples fixed by high-pressure freezing/freeze substitution (HPF-FS), was gradual and resulted in complete loss of the cytoplasmic contents well before the loss of vacuolar integrity, which is considered to be the moment of death. This type of cell death differs significantly from that seen in xylem vessels. The loss of vacuolar integrity, which is thought to initiate cell degradative processes in the xylem vessels, is one of the last processes to occur before the final autolysis of the remaining cell contents in xylem fibers. High-resolution microarray analysis in the vascular tissues of Populus stem, combined with in silico analysis of publicly available data repositories, suggests the involvement of several previously uncharacterized transcription factors, ethylene, sphingolipids and light signaling as well as autophagy in the control of fiber cell death.

  • 168.
    Courtois-Moreau, Charleen, Laetitia
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Umeå Plant Science Centre.
    Programmed Cell Death in Xylem Development2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Concerns about climate changes and scarcity of fossil fuels are rising. Hence wood is becoming an attractive source of renewable energy and raw material and these new dimensions have prompted increasing interest in wood formation in trees, in both the scientific community and wider public. In this thesis, the focus is on a key process in wood development: programmed cell death (PCD) in the development of xylem elements. Since secondary cell wall formation is dependent, inter alia, upon the life time of xylem elements, the qualitative features of wood will be affected by PCD in xylem, about which there is little information.

    This thesis focuses on the anatomical, morphological and transcriptional features of PCD during xylem development in both the stem of hybrid aspen, Populus tremula (L.) x tremuloides (Michx.) and the hypocotyl of the herbaceous model system Arabidopsis thaliana (L. Heynh.). In Populus, the progressive removal of organelles from the cytoplasm before the time of death (vacuolar bursts) and the slowness of the cell death process, illustrated by DNA fragmentation assays (such as TUNEL and Comet assays), have been ascertained in the xylem fibres by microscopic analyses. Furthermore, candidate genes for the regulation of fibre cell death were identified either from a Populus EST library obtained from woody tissues undergoing fibre cell death or from microarray experiments in Populus stem, and further assessed in an in silico comparative transcriptomic analysis of Arabidopsis thaliana. These candidate genes were either putative novel regulators of fibre cell death or members of previously described families of cell death-related genes, such as autophagy-related genes. The induction of the latter and the previous microscopic observations suggest the importance of autophagy in the degradation of the cytoplasmic contents specifically in the xylem fibres. Vacuolar bursts in the vessels were the only previously described triggers of PCD in the xylem, which induce the very rapid degradation of the nuclei and surrounding cytoplasmic contents, therefore unravelling a unique previously unrecorded type of PCD in the xylem fibres, principally involving autophagy. Arabidopsis is an attractive alternative model plant for exploring some aspects of wood formation, such as the characterisation of negative regulators of PCD. Therefore, the anatomy of Arabidopsis hypocotyls was also investigated and the ACAULIS5 (ACL5) gene, encoding an enzyme involved in polyamine biosynthesis, was identified as a key regulator of xylem specification, specifically in the vessel elements, though its negative effect on the cell death process.

    Taken together, PCD in xylem development seems to be a highly specific process, involving unique cell death morphology and molecular machinery. In addition, the technical challenges posed by the complexity of the woody tissues examined highlighted the need for specific methods for assessing PCD and related phenomena in wood.

  • 169. Covey-Crump, Elizabeth M
    et al.
    Bykova, Natalia V
    Affourtit, Charles
    Hoefnagel, Marcel H N
    Gardeström, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Atkin, Owen K
    Temperature-dependent changes in respiration rates and redox poise of the ubiquinone pool in protoplasts and isolated mitochondria of potato leaves2007Inngår i: Physiologia Plantarum, Vol. 129, s. 175-184Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In many environments, leaves experience large diurnal variations in temperature. Such short-term changes in temperature are likely to have important implications for respiratory metabolism in leaves. Here, we used intact leaf, protoplasts and isolated mitochondria to determine the impact of short-term changes in temperature on respiration rates (R), adenylate concentrations and the redox poise of the ubiquinone (UQ) pool in mitochondria of potato leaves. The Q10 (i.e. proportional change in R for each 10°C rise in temperature) of respiration was 1.8, both for intact leaves and protoplasts. In protoplasts, the redox poise of the extracted UQ pool (UQR/UQT) increased from 0.33 at 22°C, to 0.76 at 15°C. Further decreases in temperature (from 15 to 5°C) resulted in UQR/UQT decreasing to 0.40. Adenylate ratios in protoplasts were also temperature dependent. At high adenosine 5'-triphosphate (ATP) adenosine 5'-diphosphate (ADP) ratios (i.e. low ADP concentrations), UQR/UQT values were low, suggesting that adenylates restricted flux via the UQ-reducing pathways more than they restricted flux via pathways that oxidized UQH2. To assess whether high rates of alternative oxidase (AOX) activity could have uncoupled respiratory flux (and thus UQR/UQT) from adenylate restriction of the cytochrome (Cyt) pathway, we constructed kinetic curves of O2 uptake (via the two pathways) vs UQR/UQT in isolated mitochondria, measured at two temperatures (15 and 25°C); measurements were made for mitochondria operating under state 3 (i.e. +ADP) and state 4 (i.e. −ADP) conditions. In contrast to the Cyt pathway, flux via the AOX was temperature insensitive, with maximal rates of AOX activity representing 21–57% of total O2 uptake in isolated mitochondria. We conclude that temperature-dependent variations in UQR/UQT are largely dependent on temperature-dependent changes in adenylate ratios, and that flux via the AOX could in some circumstances help reduce maximal UQ values.

  • 170.
    Crawford, Tim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Lehotai, Nóra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Strand, Åsa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    The role of retrograde signals during plant stress responses2018Inngår i: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 69, nr 11, s. 2783-2795Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Chloroplast and mitochondria not only provide the energy to the plant cell but due to the sensitivity of organellar processes to perturbations caused by abiotic stress, they are also key cellular sensors of environmental fluctuations. Abiotic stresses result in reduced photosynthetic efficiency and thereby reduced energy supply for cellular processes. Thus, in order to acclimate to stress, plants must re-program gene expression and cellular metabolism to divert energy from growth and developmental processes to stress responses. To restore cellular energy homeostasis following exposure to stress, the activities of the organelles must be tightly co-ordinated with the transcriptional re-programming in the nucleus. Thus, communication between the organelles and the nucleus, so-called retrograde signalling, is essential to direct the energy use correctly during stress exposure. Stress-triggered retrograde signals are mediated by reactive oxygen species and metabolites including beta-cyclocitral, MEcPP (2-C-methyl-D-erythritol 2,4-cyclodiphosphate), PAP (3'-phosphoadenosine 5'-phosphate), and intermediates of the tetrapyrrole biosynthesis pathway. However, for the plant cell to respond optimally to environmental stress, these stress-triggered retrograde signalling pathways must be integrated with the cytosolic stress signalling network. We hypothesize that the Mediator transcriptional co-activator complex may play a key role as a regulatory hub in the nucleus, integrating the complex stress signalling networks originating in different cellular compartments.

  • 171. Crutsinger, G M
    et al.
    Sanders, N J
    Albrectsen, Benedicte R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Abreu, Ilka Nacif
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Wardle, D A
    Ecosystem retrogression leads to increased insect abundance and herbivory across an island chronosequence2008Inngår i: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 22, nr 5, s. 816-823Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [sv]

    1. Ecosystem retrogression, the decline-phase of ecosystem development, occurs during the long-term absence of catastrophic disturbance. It usually involves increased nutrient limitation over time, and leads to reductions in primary productivity, decomposition, and nutrient cycling.

    2. As a consequence, retrogression can alter the quality and abundance of host plants as food resources, but little is known about how these changes influence herbivore densities and foliage consumption.

    3. In this study, we used a 5000-year-old chronosequence of forested islands in northern Sweden on which retrogression occurs in the absence of lightning-induced wildfire. We asked whether retrogression affected the abundance and herbivory of a dominant herbivorous weevil (Deporaus betulae) and the quality and productivity of a dominant host-tree, mountain birch (Betula pubescens).

    4. Betula pubescens trees on retrogressed islands were less productive and produced smaller, tougher leaves that were lower in nutrients and higher in secondary metabolites than did those trees on earlier-successional islands.

    5. Despite the lower density and what ecologists might perceive as poorer quality of host plants, we observed several-fold higher weevil abundance and damage on retrogressed islands. This suggests that weevils might prefer the poorer quality leaves with higher secondary metabolites that occur on nutrient stressed host trees.

    6. Our results show that ecosystem retrogression increases susceptibility of B. pubescens trees to attack by herbivorous weevils.

    7. Our study provides evidence that ecosystem retrogression and associated shifts in the quantity and quality of available resources can operate as an important driver of abundance of a dominant insect herbivore.

  • 172. Cruz-Ramírez, Alfredo
    et al.
    Díaz-Triviño, Sara
    Blilou, Ikram
    Grieneisen, Verônica A.
    Sozzani, Rosangela
    Zamioudis, Christos
    Miskolczi, Pál
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Department of Forest Genetics and Plant Physiology, Umeå Plant Science Center, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Nieuwland, Jeroen
    Benjamins, René
    Dhonukshe, Pankaj
    Caballero-Pérez, Juan
    Horvath, Beatrix
    Long, Yuchen
    Mähönen, Ari Pekka
    Zhang, Hongtao
    Xu, Jian
    Murray, James A. H.
    Benfey, Philip N.
    Bako, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Department of Forest Genetics and Plant Physiology, Umeå Plant Science Center, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Marée, Athanasius F. M.
    Scheres, Ben
    A Bistable Circuit Involving SCARECROW-RETINOBLASTOMA Integrates Cues to Inform Asymmetric Stem Cell Division2012Inngår i: Cell, ISSN 0092-8674, E-ISSN 1097-4172, Vol. 150, nr 5, s. 1002-1015Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In plants, where cells cannot migrate, asymmetric cell divisions (ACDs) must be confined to the appropriate spatial context. We investigate tissue-generating asymmetric divisions in a stem cell daughter within the Arabidopsis root. Spatial restriction of these divisions requires physical binding of the stem cell regulator SCARECROW (SCR) by the RETINOBLASTOM-RELATED (RBR) protein. In the stem cell niche, SCR activity is counteracted by phosphorylation of RBR through a cyclinD6;1-CDK complex. This cyclin is itself under transcriptional control of SCR and its partner SHORT ROOT (SHR), creating a robust bistable circuit with either high or low SHR-SCR complex activity. Auxin biases this circuit by promoting CYCD6;1 transcription. Mathematical modeling shows that ACDs are only switched on after integration of radial and longitudinal information, determined by SHR and auxin distribution, respectively. Coupling of cell-cycle progression to protein degradation resets the circuit, resulting in a "flip flop" that constrains asymmetric cell division to the stem cell region.

  • 173.
    Dahrendorf, Julia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Analysis of nitrogen utilization capability during proliferation and maturation of Norway spruce (Picea abies L. Karst) somatic embryogenesis2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Around 70 % of the standing trees in northern Europe are conifers, with Norway spruce being most important. To meet future wood demands, vegetative propagation methods are offering a flexible and effective way to multiply superior genotypes. The development of nitrogen metabolism during embryogenesis is not well understood and only few studies cover conifers. Norway spruce plants prefer ammonium over nitrate as an inorganic nitrogen source. However, the proliferation of somatic embryo cultures requires organic nitrogen, and ammonium nitrate as sole nitrogen source limits somatic embryo development. This raises the question how nitrogen utilization capability advances throughout the embryo development and plant formation in Norway spruce and suggests a developmental switch in nitrogen utilization capability before the plant is fully developed. Of special interest in this context is the development and activity of three key enzymes of nitrogen metabolism: nitrate reductase (NR), glutamine synthetase (GS) and arginase.

    The aim of this study was to investigate the importance of L-glutamine as an organic nitrogen source and its impact on these key enzymes of nitrogen metabolism in the proliferation and maturation stage of Norway spruce somatic embryogenesis. Therefore media with modified nitrogen sources have been used to study the effects of presence and withdrawal of L-glutamine. Pro-embryogenic masses (PEMs) grown with L-glutamine (Gln) or L-glutamine and nitrate (Gln + NO3) showed a strongly improved proliferation rate in comparison to PEMs grown on ammonium nitrate (NH4NO3). Interestingly, GS and NR were inactive enzymatically in PEMs. Arginase activity was observed, and was unaffected by the presence or absence of L-glutamine. For analyzing the importance of L-glutamine as an organic nitrogen source during maturation, somatic embryos have been generated on media with modified nitrogen sources that included also autoclaved casein hydrolysate, an amino-acid mixture that lacks L-glutamine after autoclaving. Somatic embryos matured furthest regarding size and cotyledon development on Gln + NO3. Maturation on NH4NO3 resulted in well-developed cotyledonary stage somatic embryos that were smaller in size than in the presence of L-glutamine. In mature somatic embryos GS and NR were active. NR activity was highest, if embryos were matured on Gln + NO3 and notably lower if matured on Gln or NH4NO3. The tendentially highest GS activity was found if embryos were generated on NH4NO3. A striking change in nitrogen metabolism was the steady increase in GS activity from not detectable at proliferation stage, through easily detectable during maturation up to high activity in SE plantlets.

  • 174.
    Damkjær, Jakob T
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Kereïche, Sami
    Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands.
    Johnson, Matthew P
    School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, United Kingdom.
    Kovacs, Laszlo
    Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6726 Szeged, Hungary.
    Kiss, Anett Z
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Boekema, Egbert J
    Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands.
    Ruban, Alexander V
    School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, United Kingdom.
    Horton, Peter
    Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, United Kingdom.
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    The photosystem II light-harvesting protein Lhcb3 affects the macrostructure of photosystem II and the rate of state transitions in Arabidopsis2009Inngår i: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 21, s. 3245-3256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main trimeric light-harvesting complex of higher plants (LHCII) consists of three different Lhcb proteins (Lhcb1-3). We show that Arabidopsis thaliana T-DNA knockout plants lacking Lhcb3 (koLhcb3) compensate for the lack of Lhcb3 by producing increased amounts of Lhcb1 and Lhcb2. As in wild-type plants, LHCII-photosystem II (PSII) supercomplexes were present in Lhcb3 knockout plants (koLhcb3), and preservation of the LHCII trimers (M trimers) indicates that the Lhcb3 in M trimers has been replaced by Lhcb1 and/or Lhcb2. However, the rotational position of the M LHCII trimer was altered, suggesting that the Lhcb3 subunit affects the macrostructural arrangement of the LHCII antenna. The absence of Lhcb3 did not result in any significant alteration in PSII efficiency or qE type of nonphotochemical quenching, but the rate of transition from State 1 to State 2 was increased in koLhcb3, although the final extent of state transition was unchanged. The level of phosphorylation of LHCII was increased in the koLhcb3 plants compared with wild-type plants in both State 1 and State 2. The relative increase in phosphorylation upon transition from State 1 to State 2 was also significantly higher in koLhcb3. It is suggested that the main function of Lhcb3 is to modulate the rate of state transitions.

  • 175.
    De Bleser, Helena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Crosstalk of ethylene and gibberellins during wood formation in hybridaspen2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Both gibberellins (GAs) and ethylene (ET) or its in planta precursor 1‐Aminocyclopropane-1‐carboxylic acid (ACC) stimulate cambial cell division and modify wood development when exogenously applied to wood forming tissues of trees. Furthermore both hormones are involved in tension wood (TW) formation in leaned trees. In Arabidopsis a cross‐talk of ET and GA on a molecular level has been demonstrated. We have examined here the effects of GA and ACC, alone and in combination, on wood development in hybrid aspen (Populus tremula x tremuloides) to investigate their potential of cross-talk during wood development. The response of selected transcripts involved in GA, ET and auxin signaling, biosynthesis and transport was inspected in the total stem of T89 trees after 10 hours of treatment with quantitative real‐time PCR (qPCR). Analysis of the phenotype, anatomy and chemistry of wild-type, ethylene-insensitive and GA‐deficient trees after 2 weeks of treatment emphasized that a cross‐talk between GA and ACC is plausible. Based on primary growth characteristics, GA and ACC seemed to be partially redundant. Lignin stainings suggest antagonistic interactions, while fiber to vessel ratios and the distribution of G‐layers put forward a collaborating action. Diffuse reflectance FT‐IR demonstrates that functional GA and ACC signalling are needed to induce differences in chemical composition.

     

  • 176.
    De La Torre, Amanda
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Vancouver, BC, Canada.
    Ingvarsson, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Aitken, S. N.
    Vancouver, BC, Canada.
    Genetic architecture and genomic patterns of gene flow between hybridizing species of Picea2015Inngår i: Heredity, ISSN 0018-067X, E-ISSN 1365-2540, Vol. 115, nr 2, s. 153-164Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hybrid zones provide an opportunity to study the effects of selection and gene flow in natural settings. We employed nuclear microsatellites (single sequence repeat (SSR)) and candidate gene single-nucleotide polymorphism markers (SNPs) to characterize the genetic architecture and patterns of interspecific gene flow in the Picea glauca x P. engelmannii hybrid zone across a broad latitudinal (40-60 degrees) and elevational (350-3500 m) range in western North America. Our results revealed a wide and complex hybrid zone with broad ancestry levels and low interspecific heterozygosity, shaped by asymmetric advanced-generation introgression, and low reproductive barriers between parental species. The clinal variation based on geographic variables, lack of concordance in clines among loci and the width of the hybrid zone points towards the maintenance of species integrity through environmental selection. Congruency between geographic and genomic clines suggests that loci with narrow clines are under strong selection, favoring either one parental species (directional selection) or their hybrids (overdominance) as a result of strong associations with climatic variables such as precipitation as snow and mean annual temperature. Cline movement due to past demographic events (evidenced by allelic richness and heterozygosity shifts from the average cline center) may explain the asymmetry in introgression and predominance of P. engelmannii found in this study. These results provide insights into the genetic architecture and fine-scale patterns of admixture, and identify loci that may be involved in reproductive barriers between the species.

  • 177.
    de La Torre, Amanda R
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Birol, Inanc
    Bousquet, Jean
    Ingvarsson, Pär K
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Jones, Steven J. M
    Keeling, Christopher I
    MacKay, John
    Nilsson, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Ritland, Kermit
    Street, Nathaniel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Yanchuk, Alvin
    Zerbe, Philipp
    Bohlmann, Jörg
    Insights into conifer giga-genomes2014Inngår i: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 166, nr 4, s. 1724-1732Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Insights from sequenced genomes of major land plant lineages have advanced research in almost every aspect of plant biology. Until recently, however, assembled genome sequences of gymnosperms have been missing from this picture. Conifers of the pine family (Pinaceae) are a group of gymnosperms that dominate large parts of the world's forests. Despite their ecological and economic importance, conifers seemed long out of reach for complete genome sequencing, due in part to their enormous genome size (20-30 Gb) and the highly repetitive nature of their genomes. Technological advances in genome sequencing and assembly enabled the recent publication of three conifer genomes: white spruce (Picea glauca), Norway spruce (Picea abies), and loblolly pine (Pinus taeda). These genome sequences revealed distinctive features compared with other plant genomes and may represent a window into the past of seed plant genomes. This Update highlights recent advances, remaining challenges, and opportunities in light of the publication of the first conifer and gymnosperm genomes.

  • 178.
    De La Torre, Amanda R
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lin, Yao-Cheng
    Van de Peer, Yves
    Ingvarsson, Pär K
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Genome-wide analysis reveals diverged patterns of codon bias, gene expression, and rates of sequence evolution in Picea gene families2015Inngår i: Genome Biology and Evolution, ISSN 1759-6653, E-ISSN 1759-6653, Vol. 7, nr 4, s. 1002-1015Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The recent sequencing of several gymnosperm genomes has greatly facilitated studying the evolution of their genes and gene families. In this study, we examine the evidence for expression-mediated selection in the first two fully sequenced representatives of the gymnosperm plant clade (Picea abies and Picea glauca). We use genome-wide estimates of gene expression (> 50,000 expressed genes) to study the relationship between gene expression, codon bias, rates of sequence divergence, protein length, and gene duplication. We found that gene expression is correlated with rates of sequence divergence and codon bias, suggesting that natural selection is acting on Picea protein-coding genes for translational efficiency. Gene expression, rates of sequence divergence, and codon bias are correlated with the size of gene families, with large multicopy gene families having, on average, a lower expression level and breadth, lower codon bias, and higher rates of sequence divergence than single-copy gene families. Tissue-specific patterns of gene expression were more common in large gene families with large gene expression divergence than in single-copy families. Recent family expansions combined with large gene expression variation in paralogs and increased rates of sequence evolution suggest that some Picea gene families are rapidly evolving to cope with biotic and abiotic stress. Our study highlights the importance of gene expression and natural selection in shaping the evolution of protein-coding genes in Picea species, and sets the ground for further studies investigating the evolution of individual gene families in gymnosperms.

  • 179.
    Decker, Daniel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Kleczkowski, Leszek A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    UDP-Sugar Producing Pyrophosphorylases: Distinct and Essential Enzymes With Overlapping Substrate Specificities, Providing de novo Precursors for Glycosylation Reactions2019Inngår i: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 9, artikkel-id 1822Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Nucleotide sugars are the key precursors for all glycosylation reactions and are required both for oligo- and polysaccharides synthesis and protein and lipid glycosylation. Among all nucleotide sugars, UDP-sugars are the most important precursors for biomass production in nature (e.g., synthesis of cellulose, hemicellulose, and pectins for cell wall production). Several recent studies have already suggested a potential role for UDP-Glc in plant growth and development, and UDP-Glc has also been suggested as a signaling molecule, in addition to its precursor function. In this review, we will cover primary mechanisms of formation of UDP-sugars, by focusing on UDP-sugar metabolizing pyrophosphorylases. The pyrophosphorylases can be divided into three families: UDP-Glc pyrophosphorylase (UGPase), UDP-sugar pyrophosphorylase (USPase), and UDP-N-acetyl glucosamine pyrophosphorylase (UAGPase), which can be distinguished both by their amino acid sequences and by differences in substrate specificity. Substrate specificities of these enzymes are discussed, along with structure-function relationships, based on their crystal structures and homology modeling. Earlier studies with transgenic plants have revealed that each of the pyrophosphorylases is essential for plant survival, and their loss or a decrease in activity results in reproductive impairment. This constitutes a problem when studying exact in vivo roles of the enzymes using classical reverse genetics approaches. Thus, strategies involving the use of specific inhibitors (reverse chemical genetics) are also discussed. Further characterization of the properties/roles of pyrophosphorylases should address fundamental questions dealing with mechanisms and control of carbohydrate synthesis and may allow to identify targets for manipulation of biomass production in plants.

  • 180.
    Decker, Daniel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Lindberg, Stina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Eriksson, Jonas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kleczkowski, Leszek A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    A luminescence-based assay of UDP-sugar producing pyrophosphorylases2014Inngår i: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 6, nr 1, s. 57-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A coupled luminescence assay was applied to monitor pyrophosphate (PPi) production by either purified barley UDP-glucose pyrophosphorylase (UGPase) or purified Leishmania UDP-sugar pyrophosphorylase (USPase). In the assay, the PPi produced by the pyrophosphorylases was converted to ATP by ATP-sulfurylase, and the ATP produced was linked to luminescent light formation through the action of firefly luciferase. The assay allowed for a quantitative measurement of UGPase and USPase activities, down to a pmol per min level. The activities were linear with time and proportional to the amount of the enzyme added, and were neither affected by Pi nor by DTT. For UGPase, K-m values with UTP and Glc-1-P were 0.14 and 0.26 mM, respectively, whereas for USPase the respective K-m values with UTP, Glc-1-P and Gal-1-P were 0.4, 2.9 and 3.9 mM. Possible applications of the luminescence-based assay for not only UDP-sugar producing pyrophosphorylases, but also other types of pyrophosphorylases are discussed.

  • 181.
    Decker, Daniel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Meng, Meng
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Gornicka, Agnieszka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Hofer, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Wilczynska, Malgorzata
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Kleczkowski, Leszek A
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Substrate kinetics and substrate effects on the quaternary structure of barley UDP-glucose pyrophosphorylase2012Inngår i: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 79, s. 39-45Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    UDP-Glc pyrophosphorylase (UGPase) is an essential enzyme responsible for production of UDP-Glc, which is used in hundreds of glycosylation reactions involving addition of Glc to a variety of compounds. In this study, barley UGPase was characterized with respect to effects of its substrates on activity and quaternary structure of the protein. Its K(m) values with Glc-1-P and UTP were 0.33 and 0.25 mM, respectively. Besides using Glc-1-P as a substrate, the enzyme had also considerable activity with Gal-1-P; however, the K(m) for Gal-1-P was very high (>10 mM), rendering this reaction unlikely under physiological conditions. UGPase had a relatively broad pH optimum of 6.5-8.5, regardless of the direction of reaction. The enzyme equilibrium constant was 0.4, suggesting slight preference for the Glc-1-P synthesis direction of the reaction. The quaternary structure of the enzyme, studied by Gas-phase Electrophoretic Mobility Macromolecule Analysis (GEMMA), was affected by addition of either single or both substrates in either direction of the reaction, resulting in a shift from UGPase dimers toward monomers, the active form of the enzyme. The substrate-induced changes in quaternary structure of the enzyme may have a regulatory role to assure maximal activity. Kinetics and factors affecting the oligomerization status of UGPase are discussed.

  • 182.
    Decker, Daniel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Öberg, Christopher
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kleczkowski, Leszek A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Identification and characterization of inhibitors of UDP-glucose and UDP-sugar pyrophosphorylases for in vivo studies2017Inngår i: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 90, nr 6, s. 1093-1107Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    UDP-sugars serve as ultimate precursors in hundreds of glycosylation reactions (e.g. for protein and lipid glycosylation, synthesis of sucrose, cell wall polysaccharides, etc.), underlying an important role of UDP-sugar-producing enzymes in cellular metabolism. However, genetic studies on mechanisms of UDP-sugar formation were frequently hampered by reproductive impairment of the resulting mutants, making it difficult to assess an in vivo role of a given enzyme. Here, a chemical library containing 17 500 compounds was separately screened against purified UDP-glucose pyrophosphorylase (UGPase) and UDP-sugar pyrophosphorylase (USPase), both enzymes representing the primary mechanisms of UDP-sugar formation. Several compounds have been identified which, at 50 μm, exerted at least 50% inhibition of the pyrophosphorylase activity. In all cases, both UGPase and USPase activities were inhibited, probably reflecting common structural features of active sites of these enzymes. One of these compounds (cmp #6), a salicylamide derivative, was found as effective inhibitor of Arabidopsis pollen germination and Arabidopsis cell culture growth. Hit optimization on cmp #6 yielded two analogs (cmp #6D and cmp #6D2), which acted as uncompetitive inhibitors against both UGPase and USPase, and were strong inhibitors in the pollen test, with apparent inhibition constants of less than 1 μm. Their effects on pollen germination were relieved by addition of UDP-glucose and UDP-galactose, suggesting that the inhibitors targeted UDP-sugar formation. The results suggest that cmp #6 and its analogs may represent useful tools to study in vivo roles of the pyrophosphorylases, helping to overcome the limitations of genetic approaches.

  • 183.
    Decker, Daniel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Öberg, Christopher
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kleczkowski, Leszek A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    The structure-activity relationship of the salicylimide derived inhibitors of UDP-sugar producing pyrophosphorylases2018Inngår i: Plant Signalling & Behavior, ISSN 1559-2316, E-ISSN 1559-2324, Vol. 13, nr 8, artikkel-id e1507406Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    UDP-sugars are key precursors for biomass production in nature (synthesis of cellulose, hemicellulose, etc.). They are produced de novo by distinct UDP-sugar producing pyrophosphorylases. Studies on the roles of these enzymes using genetic knockouts were hampered by sterility of the mutants and by functional-complementation from related enzyme(s), hindering clear interpretation of the results. In an attempt to override these difficulties, we turned to the reverse chemical genetics approaches to identify compounds which interfere with the activity of those enzymes in vivo. Hit expansion on one of such compounds, a salicylimide derivative, allowed us to identify several inhibitors with a range of activities. The present study provides a structure-activity relationship for these compounds.

  • 184.
    Decker, Vicki Huizu
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Phenolics, Nitrogen, and Biotic Interactions: A Study of Phenylpropanoid Metabolites and Gene Expression in the Leaves of Populus tremula.2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    European aspen (Populus tremula) is a fast growing tree species, rich in phenolic compounds. Defense theories suggest that soil nitrogen greatly influence plant allocation togrowth and defense; however, the allocation priorities are not well understood. Further,although foliar phenolic compounds are considered defensive, specialist organisms may positively associate with and alter them. There are two classes of phenolics in aspen,condensed tannins (CTs) and salicinoids. They are likely to shape the interactions of themany organisms, for example, herbivorous insects and endophytic fungi and three-way interactions among host genotype, specialist herbivores and endophytic fungi could be greatly altered by aspen geno- and chemotypes’ responses to soil nitrogen.

    Firstly, I focused on the allocation of carbon to growth and defense in aspen genotypes with varied tannin content in response to nutrient addition. Nitrogen promoted plant growth and suppressed foliar CT levels. At the molecular level expression of genes of the phenylpropanoid pathway (PPP) decreased under low additions of N (equivalent to 15kg/ha), whereas genes at the beginning and at the end of the pathway increased in response to high levels of N (~150 kg/ha). Aspens high in CTs displayed consistently stronger PPP gene expressions compared to CT-low aspens, and correlations between PPP genes and phenolic products varied with tannin content, as an effect of leaf age, in response to N enrichment, and individually with genotype. More negative correlations (indicative of allocation trade-offs) between PPP gene expressions and phenolic products were found in aspen genets with low tannin levels compared to aspens with inherently high tannin levels.

    Secondly, I studied the connection between foliar phenolic compounds and endophytic fungi in the presence and absence of a specialist herbivorous beetle (Chrysomela tremula) and as an effect of soil nitrogen addition. Richness and abundance of fungal endophytes associated with aspen genotypes and phenolic profile, however this specificity disappeared in the presence of the leaf beetles. Herbivory both enhanced endophyte richness andabundance in the leaves and it also increased in response to nitrogen addition.

  • 185.
    Decker, Vicki Huizu
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Agostinelli, A
    Chen, SS
    Cleary, M
    Witzell, J
    Albrectsen, Benedicte
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Foliar fungal endophytes respond to nitrogen fertilization and herbivory in aspen genotypesManuskript (preprint) (Annet vitenskapelig)
  • 186.
    Decker, Vicki Huizu
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Bandau, Franziska
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Gundale, Michael J.
    Cole, Christopher T.
    Albrectsen, Benedicte R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Aspen phenylpropanoid genes’ expression levels correlate with genets’ tannin richness and vary both in responses to soil nitrogen and associations with phenolic profiles2017Inngår i: Tree Physiology, ISSN 0829-318X, E-ISSN 1758-4469, Vol. 37, nr 2, s. 270-279Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Condensed tannin (CT) contents of European aspen (Populus tremula L.) vary among genotypes, and increases in nitrogen (N) availability generally reduce plants’ tannin production in favor of growth, through poorly understood mechanisms. We hypothesized that intrinsic tannin production rates may co-vary with gene expression responses to soil N and resource allocation within the phenylpropanoid pathway (PPP). Thus, we examined correlations between soil N levels and both expression patterns of eight PPP genes (measured by quantitative-reverse transcription PCR) and foliar phenolic compounds (measured by liquid chromatography–mass spectrometry) in young aspen genets with intrinsically extreme CT levels. Monitored phenolics included salicinoids, lignins, flavones, flavonols, CT precursors and CTs. The PPP genes were consistently expressed more strongly in high-CT trees. Low N supplements reduced expression of genes throughout the PPP in all genets, while high N doses restored expression of genes at the beginning and end of the pathway. These PPP changes were not reflected in pools of tannin precursors, but varying correlations between gene expression and foliar phenolic pools were detected in young and mature leaves, suggesting that processes linking gene expression and the resulting phenolics vary spatially and temporally. Precursor fluxes suggested that CT-related metabolic rate or sink controls are linked to intrinsic carbon allocation strategies associated with N responses. Overall, we found more negative correlations (indicative of allocation trade-offs) between PPP gene expression and phenolic products following N additions in low-CT plants than in high-CT plants. The tannin-related expression dynamics suggest that, in addition to defense, relative tannin levels may also be indicative of intraspecific variations in the way aspen genets respond to soil fertility. 

  • 187.
    Decker, Vicki Huizu
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Siddique, A
    Albrectsen, Benedicte
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Specialist Leaf Beetles Enrich Diversity of Endophytic Fungi in Aspen Leaves, and Mask Intra-specific Host SpecificityManuskript (preprint) (Annet vitenskapelig)
  • 188. Dejardin, A
    et al.
    Sokolov, L N
    Kleczkowski, Leszek A
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Sugar/osmoticum levels modulate differential abscisic acid-independent expression of two stress-responsive sucrose synthase genes in Arabidopsis1999Inngår i: Biochemical Journal, ISSN 0264-6021, E-ISSN 1470-8728, Vol. 344, s. 503-509Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sucrose synthase (Sus) is a key enzyme of sucrose metabolism. Two Sus-encoding genes (Sus1 and Sus2) from Arabidopsis thaliana were found to be profoundly and differentially regulated in leaves exposed to environmental stresses (cold stress, drought or O-2 deficiency). Transcript levels of Sus1 increased on exposure to cold and drought, whereas Sus2 mRNA was induced specifically by O-2 deficiency. Both cold and drought exposures induced the accumulation of soluble sugars and caused a decrease in leaf osmotic potential, whereas O-2 deficiency was characterized by a nearly complete depletion in sugars. Feeding abscisic acid (ABA) to detached leaves or subjecting Arabidopsis ABA-deficient mutants to cold stress conditions had no effect on the expression profiles of Sus1 or Sus2, whereas feeding metabolizable sugars (sucrose or glucose) or non-metabolizable osmotica [poly(ethylene glycol), sorbitol or mannitol] mimicked the effects of osmotic stress on Sus1 expression in detached leaves. By using various sucrose/mannitol solutions, we demonstrated that Sus1 was up-regulated by a decrease in leaf osmotic potential rather than an increase in sucrose concentration itself. We suggest that Sus1 expression is regulated via an ABA-independent signal transduction pathway that is related to the perception of a decrease in leaf osmotic potential during stresses. In contrast, the expression of Sus2 was independent of sugar/osmoticum effects, suggesting the involvement of a signal transduction mechanism distinct from that regulating Sus1 expression. The differential stress-responsive regulation of Sus genes in leaves might represent part of a general cellular response to the allocation of carbohydrates during acclimation processes.

  • 189. Dejonghe, Wim
    et al.
    Kuenen, Sabine
    Mylle, Evelien
    Vasileva, Mina
    Keech, Olivier
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Viotti, Corrado
    Swerts, Jef
    Fendrych, Matyas
    Ortiz-Morea, Fausto Andres
    Mishev, Kiril
    Delang, Simon
    Scholl, Stefan
    Zarza, Xavier
    Heilmann, Mareike
    Kourelis, Jiorgos
    Kasprowicz, Jaroslaw
    Nguyen, Le Son Long
    Drozdzecki, Andrzej
    Van Houtte, Isabelle
    Szatmari, Anna-Maria
    Majda, Mateusz
    Baisa, Gary
    Bednarek, Sebastian York
    Robert, Stephanie
    Audenaert, Dominique
    Testerink, Christa
    Munnik, Teun
    Van Damme, Daniel
    Heilmann, Ingo
    Schumacher, Karin
    Winne, Johan
    Friml, Jiri
    Verstreken, Patrik
    Russinova, Eugenia
    Mitochondrial uncouplers inhibit clathrin-mediated endocytosis largely through cytoplasmic acidification2016Inngår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, artikkel-id 11710Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ATP production requires the establishment of an electrochemical proton gradient across the inner mitochondrial membrane. Mitochondrial uncouplers dissipate this proton gradient and disrupt numerous cellular processes, including vesicular trafficking, mainly through energy depletion. Here we show that Endosidin9 (ES9), a novel mitochondrial uncoupler, is a potent inhibitor of clathrin-mediated endocytosis (CME) in different systems and that ES9 induces inhibition of CME not because of its effect on cellular ATP, but rather due to its protonophore activity that leads to cytoplasm acidification. We show that the known tyrosine kinase inhibitor tyrphostinA23, which is routinely used to block CME, displays similar properties, thus questioning its use as a specific inhibitor of cargo recognition by the AP-2 adaptor complex via tyrosine motif-based endocytosis signals. Furthermore, we show that cytoplasm acidification dramatically affects the dynamics and recruitment of clathrin and associated adaptors, and leads to reduction of phosphatidylinositol 4,5-biphosphate from the plasma membrane.

  • 190. Dekkers, Bas J W
    et al.
    He, Hanzi
    Hanson, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Department of Molecular Plant Physiology, Utrecht University, CH, Utrecht, The Netherlands.
    Willems, Leo A J
    Jamar, Diaan C L
    Cueff, Gwendal
    Rajjou, Loïc
    Hilhorst, Henk W M
    Bentsink, Leónie
    The Arabidopsis DELAY OF GERMINATION 1 gene affects ABSCISIC ACID INSENSITIVE 5 (ABI5) expression and genetically interacts with ABI3 during Arabidopsis seed development2016Inngår i: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 85, nr 4, s. 451-465Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The seed expressed gene DELAY OF GERMINATION (DOG) 1 is absolutely required for the induction of dormancy. Next to a non-dormant phenotype, the dog1-1 mutant is also characterized by a reduced seed longevity suggesting that DOG1 may affect additional seed processes as well. This aspect however, has been hardly studied and is poorly understood. To uncover additional roles of DOG1 in seeds we performed a detailed analysis of the dog1 mutant using both transcriptomics and metabolomics to investigate the molecular consequences of a dysfunctional DOG1 gene. Further, we used a genetic approach taking advantage of the weak aba insensitive (abi) 3-1 allele as a sensitized genetic background in a cross with dog1-1. DOG1 affects the expression of hundreds of genes including LATE EMBRYOGENESIS ABUNDANT and HEAT SHOCK PROTEIN genes which are affected by DOG1 partly via control of ABI5 expression. Furthermore, the content of a subset of primary metabolites, which normally accumulate during seed maturation, was found to be affected in the dog1-1 mutant. Surprisingly, the abi3-1 dog1-1 double mutant produced green seeds which are highly ABA insensitive, phenocopying severe abi3 mutants, indicating that dog1-1 acts as an enhancer of the weak abi3-1 allele and thus revealing a genetic interaction between both genes. Analysis of the dog1 and dog1 abi3 mutants revealed additional seed phenotypes and therefore we hypothesize that DOG1 function is not limited to dormancy but that it is required for multiple aspects of seed maturation, in part by interfering with ABA signalling components.

  • 191.
    Delhomme, Nicolas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Sundström, Görel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Uppsala Univ, Dept Med Biochem & Microbiol, Sci Life Lab, Uppsala, Sweden.
    Zamani, Neda
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Uppsala Univ, Dept Med Biochem & Microbiol, Sci Life Lab, Uppsala, Sweden.
    Lantz, Henrik
    Lin, Yao-Cheng
    Hvidsten, Torgeir R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Norwegian Univ Life Sci, Dept Chem Biotechnol & Food Sci, As, Norway.
    Hoppner, Marc P.
    Jern, Patric
    Van de Peer, Yves
    Lundeberg, Joakim
    Grabherr, Manfred G.
    Street, Nathaniel R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Serendipitous Meta-Transcriptomics: The Fungal Community of Norway Spruce (Picea abies)2015Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, nr 9, artikkel-id e0139080Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    After performing de novo transcript assembly of >1 billion RNA-Sequencing reads obtained from 22 samples of different Norway spruce (Picea abies) tissues that were not surface sterilized, we found that assembled sequences captured a mix of plant, lichen, and fungal transcripts. The latter were likely expressed by endophytic and epiphytic symbionts, indicating that these organisms were present, alive, and metabolically active. Here, we show that these serendipitously sequenced transcripts need not be considered merely as contamination, as is common, but that they provide insight into the plant's phyllosphere. Notably, we could classify these transcripts as originating predominantly from Dothideomycetes and Leotiomycetes species, with functional annotation of gene families indicating active growth and metabolism, with particular regards to glucose intake and processing, as well as gene regulation.

  • 192. DeLuca, T H
    et al.
    Zackrisson, O
    Nilsson, M C
    Sellstedt, Anita
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Quantifying nitrogen-fixation in feather moss carpets of boreal forests2002Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 419, nr 6910, s. 917-920Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biological nitrogen (N) fixation is the primary source of N within natural ecosystems(1), yet the origin of boreal forest N has remained elusive. The boreal forests of Eurasia and North America lack any significant, widespread symbiotic N-fixing plants(1-6). With the exception of scattered stands of alder in early primary successional forests(7), N-fixation in boreal forests is considered to be extremely limited. Nitrogen-fixation in northern European boreal forests has been estimated(2) at only 0.5 kg Nha(-1) yr(-1); however, organic N is accumulated in these ecosystems at a rate of 3 kg N ha(-1) yr(-1) (ref. 8). Our limited understanding of the origin of boreal N is unacceptable given the extent of the boreal forest region, but predictable given our imperfect knowledge of N-fixation(1,9). Herein we report on a N-fixing symbiosis between a cyanobacterium (Nostoc sp.) and the ubiquitous feather moss, Pleurozium schreberi (Bird) Mitt. that alone fixes between 1.5 and 2.0 kg N ha(-1) yr(-1) in mid- to late-successional forests of northern Scandinavia and Finland. Previous efforts have probably underestimated N-fixation potential in boreal forests.

  • 193. DeLuca, Thomas H
    et al.
    Zackrisson, Olle
    Gentili, Francesco
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Sellstedt, Anita
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Nilsson, Marie-Charlotte
    Ecosystem controls on nitrogen fixation in boreal feather moss communities.2007Inngår i: Oecologia, ISSN 0029-8549, Vol. 152, nr 1, s. 121-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    N fixation in feather moss carpets is maximized in late secondary successional boreal forests; however, there is limited understanding of the ecosystem factors that drive cyanobacterial N fixation in feather mosses with successional stage. We conducted a reciprocal transplant experiment to assess factors in both early and late succession that control N fixation in feather moss carpets dominated by Pleurozium schreberi. In 2003, intact microplots of moss carpets (30 cm × 30 cm × 10–20 cm deep) were excavated from three early secondary successional (41–101 years since last fire) forest sites and either replanted within the same stand or transplanted into one of three late successional (241–356 years since last fire) forest sites and the transverse was done for late successional layers of moss. Moss plots were monitored for changes in N-fixation rates by acetylene reduction (June 2003–September 2005) and changes in the presence of cyanobacteria on moss shoots by microscopy (2004). Forest nutrient status was measured using ionic resin capsules buried in the humus layer. Late successional forests exhibit high rates of N fixation and consistently high numbers of cyanobacteria on moss shoots, but low levels of available N. Conversely, early successional forests have higher N availability and have low rates of N fixation and limited presence of cyanobacteria on moss shoots. Transplantation of moss carpets resulted in a significant shift in presence and activity of cyanobacteria 1 year after initiation of the experiment responding to N fertility differences in early versus late successional forests.

  • 194. DELUCIA, EH
    et al.
    DAY, TA
    Oquist, Gunnar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    THE POTENTIAL FOR PHOTOINHIBITION OF PINUS-SYLVESTRIS L SEEDLINGS EXPOSED TO HIGH LIGHT AND LOW SOIL-TEMPERATURE1991Inngår i: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 42, nr 238, s. 611-617Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of high light and root chilling on gas exchange, chlorophyll fluorescence, and bulk shoot water potential (PSI-shoot) was examined for Pinus sylvestris seedlings. Transferring plants from low light (200-mu-mol m-2 s-1, PAR) and a soil temperature of 15-degrees-C to high light (850-mu-mol m-2 S-1) and 1-degrees-C caused > 90% decrease in net photosynthesis and leaf conductance measured at 350 mm3 dm-3 CO2, and a decrease in the ratio of variable to maximum fluorescence (F(v)/F(m)) from 0.83 to 0.63. The decrease in F(v)/F(m) was, however, only marginally greater than when seedlings were transferred from low to high light but kept at a soil temperature of 15-degrees-C. Thus, photoinhibition was a minor component of the substantial decrease observed for net photosynthesis at 1-degrees-C soil temperature. The decrease in net photosynthesis and PSI-shoot at 1-degrees-C was associated with an increased in calculated intracellular CO2 concentration, suggesting that non-stomatal factors related to water stress were involved in inhibiting carbon assimilation. Measurements at saturating external CO2 concentration, however, indicate that stomatal closure was the dominant factor limiting net photosynthesis at low soil temperature. This interpretation was confirmed with additional experiments using Pinus taeda and Picea engelmannii seedlings. Decreases in gas-exchange variables at 5-degrees-C soil temperature were not associated with changes in PSI-shoot. Thus, hormonal factors, localized decreases in PSI-needle, or changes in xylem flux may mediate the response to moderate root chilling.

  • 195. Demmig-Adams, Barbara
    et al.
    Ebbert, Volker
    Mellman, David L
    Mueh, Kristine E
    Schaffer, Lisa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Funk, Christiane
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Zarter, C Ryan
    Adamska, Iwona
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Adams III, William W
    Modulation of PsbS and flexible vs sustained energy dissipation by light environment in different species2006Inngår i: Physiologia Plantarum, Vol. 127, s. 670-80Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Contrasting acclimation strategies of photosynthesis and photoprotection were identified for annual mesophytes (spinach, pumpkin, and Arabidopsis) vs the tropical evergreen Monstera deliciosa. The annual species utilized full sunlight for photosynthesis to a much greater extent than the evergreen species. Conversely, the evergreen species exhibited a greater capacity for photoprotective thermal energy dissipation as well as a greater expression of the PsbS protein in full sun than the annual species. In all species, the majority of thermal energy dissipation [assessed as non-photochemical fluorescence quenching (NPQ)] was the flexible, ΔpH-dependent form of NPQ over the entire range of growth light environments. However, in response to a transfer of shade-grown plants to high light, the evergreen species exhibited a high level of sustained thermal dissipation (qI), but the annual species did not. This sustained energy dissipation in the evergreen species was not ΔpH-dependent nor did the low level of PsbS in shade leaves increase upon transfer to high light for several days. Sustained ΔpH-independent NPQ was correlated (a) initially, with sustained D1 protein phosphorylation and xanthophyll cycle arrest and (b) subsequently, with an accumulation over several days of PsbS-related one-helix proteins and newly synthesized zeaxanthin and lutein.

  • 196. Deng, Xiaodong
    et al.
    Eriksson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Two iron-responsive promoter elements control expression of FOX1 in Chlamydomonas reinhardtii.2007Inngår i: Eukaryotic Cell, ISSN 1535-9778, Vol. 6, nr 11, s. 2163-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    FOX1 encodes an iron deficiency-induced ferroxidase involved in a high-affinity iron uptake system. Mutagenesis analysis of the FOX1 promoter identified two separate iron-responsive elements, FeRE1 (CACACG) and FeRE2 (CACGCG), between positions –87 and –82 and between positions –65 and –60, respectively, and both are needed for induced FOX1 expression under conditions of iron deficiency.

  • 197. Derbyshire, Paul
    et al.
    Menard, Delphine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Green, Porntip
    Saalbach, Gerhard
    Buschmann, Henrik
    Lloyd, Clive W.
    Pesquet, Edouard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). John Innes Ctr, Norwich NR4 7UH, Norfolk, England.
    Proteomic Analysis of Microtubule Interacting Proteins over the Course of Xylem Tracheary Element Formation in Arabidopsis2015Inngår i: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 27, nr 10, s. 2709-2726Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Plant vascular cells, or tracheary elements (TEs), rely on circumferential secondary cell wall thickenings to maintain sap flow. The patterns in which TE thickenings are organized vary according to the underlying microtubule bundles that guide wall deposition. To identify microtubule interacting proteins present at defined stages of TE differentiation, we exploited the synchronous differentiation of TEs in Arabidopsis thaliana suspension cultures. Quantitative proteomic analysis of microtubule pull-downs, using ratiometric N-14/N-15 labeling, revealed 605 proteins exhibiting differential accumulation during TE differentiation. Microtubule interacting proteins associated with membrane trafficking, protein synthesis, DNA/RNA binding, and signal transduction peaked during secondary cell wall formation, while proteins associated with stress peaked when approaching TE cell death. In particular, CELLULOSE SYNTHASE-INTERACTING PROTEIN1, already associated with primary wall synthesis, was enriched during secondary cell wall formation. RNAi knockdown of genes encoding several of the identified proteins showed that secondary wall formation depends on the coordinated presence of microtubule interacting proteins with nonoverlapping functions: cell wall thickness, cell wall homogeneity, and the pattern and cortical location of the wall are dependent on different proteins. Altogether, proteins linking microtubules to a range of metabolic compartments vary specifically during TE differentiation and regulate different aspects of wall patterning.

  • 198.
    Devadas, Arun
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Characterization of fungual strains for bioethanol production and sugar utilization2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Bioethanol production from cellulose based sources is currently in focus in several research projects and the need of the hour is a versatile fermenting organism that can utilize both 5C and 6C sugars effectively. Several naturally occurring fungi have the property of fermenting both types of sugars more efficiently than the traditionally used Saccharomyces cerevisiae which only can ferment hexose sugars. In this study, six different fungi were grown on a media with sugar concentrations similar to the spent sulphite liquor (SSL) from the paper pulp industry. Known fungi such as S. cerevisiae and T. versicolor as well as 4 unidentified wood rot species were grown in sealed bottles with media containing mixture of 6C and 5C. Comparison was made between ethanol fermentation, sugar consumption and enzyme activities (ALDH and PDC). The fermentation experiment was run for 21 days and ethanol concentrations up to 18g/L were achieved. We conclude that two of the fungi produce sufficient amount of ethanol and could be used in large-scale fermentation processes.

  • 199.
    Dimotakis, Charilaos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Understanding of the role of CAD4, CAD5 and CAD6 gene redundancy during the lignification of Arabidopsis xylem.2015Independent thesis Advanced level (degree of Master (Two Years)), 40 poäng / 60 hpOppgave
    Abstract [en]

    Abstract

     

    Lignin is a cell wall polyphenolic polymer constituting the second most abundant bio-polymer on earth. This polymer is mostly accumulated in wood or xylem where it covers the other cell wall polysaccharides. Thus the removal of lignin allows accessing the polysaccharidic cell wall polymers which can then be converted into bio-fuels, textile or paper. Understanding lignin biosynthesis is therefore important to improve the industrial processing of the woody biomass. Lignin derives from the oxidative polymerization of different types of monomers called monolignols including 4-hydroxyphenylpropene alcohols as the most common monomers. Monolignols derive from the amino acid phenylalanine which is converted by a biosynthetic pathway known as the phenylpropanoid pathway. The last step of the multiple enzymatic process use the enzyme cinnamyl alcohol dehydrogenase (CAD) to convert 4-hydroxyphenylpropene aldehydes into 4-hydroxyphenylpropene alcohols. CAD is encoded by a small multigenic family in Arabidopsis thaliana comprising 17 genes.

    The aim of this master thesis is to understand the role of cinnamyl alcohol dehydrogenase gene redundancy during xylem lignification. CAD4, CAD5 and CAD6 have been associated in previous studies with xylem lignification and the main aim is to decipher if these genes are redundant or if they exhibit specificity in their expression (level, time and/or localization) and/or protein activity and structure. To do so, a genetic analysis of the single and double T-DNA insertional loss-of-function mutants in each of these genes were studied to compare their morphological characteristics, their biochemical structure (for both lignin quantification and composition) as well as their gene expression levels.

    Although minor changes in the lignin quantity and composition were observed for all of the single mutants, double mutants exhibited significant reductions and changes. Gene expression analysis moreover showed that the loss-of-function in any one of the three CADs caused a reduction ranging from 48% to 95% of the expression of the other CADs independently of the gene mutated. CAD4 and CAD5 both catalyzed the reduction of classical 4-hydroxyphenylpropene aldehydes into their corresponding alcohols: CAD5 catalytic activity is more specific to doubly methoxylated 4-hydroxyphenylpropene aldehydes than CAD4. In contrast, CAD6 did not affect the classical monolignols incorporation into lignin, but instead appeared to assist the function of CAD4 and CAD5. A clear synergetic effect of the double mutants suggested that a potential interaction could occur between these CAD proteins. Overall, our analysis showed that these three CAD genes were not redundant, but instead exhibited distinct function during xylem lignin biosynthesis.

  • 200. Dinant, S.
    et al.
    Wolff, N.
    De Marco, F.
    Vilaine, F.
    Gissot, L.
    Aubry, E.
    Sandt, C.
    Bellini, C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, Versailles, France.
    Le Hir, R.
    Synchrotron FTIR and Raman spectroscopy provide unique spectral fingerprints for Arabidopsis floral stem vascular tissues2019Inngår i: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 70, nr 3, s. 871-883Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cell walls are highly complex structures that are modified during plant growth and development. For example, the development of phloem and xylem vascular cells, which participate in the transport of sugars and water as well as providing support, can be influenced by cell-specific wall composition. Here, we used synchrotron radiation-based Fourier-transform infrared (SR-FTIR) and Raman spectroscopy to analyse the cell wall composition of floral stem vascular tissues of wild-type Arabidopsis and the double-mutant sweet11-1 sweet12-1, which has impaired sugar transport. The SR-FTIR spectra showed that in addition to modified xylem cell wall composition, phloem cell walls in the double-mutant line were characterized by modified hemicellulose composition. Combining Raman spectroscopy with a classification and regression tree (CART) method identified combinations of Raman shifts that could distinguish xylem vessels and fibers. In addition, the disruption of the SWEET11 and SWEET12 genes impacted on xylem wall composition in a cell-specific manner, with changes in hemicelluloses and cellulose observed at the xylem vessel interface. These results suggest that the facilitated transport of sugars by transporters that exist between vascular parenchyma cells and conducting cells is important in ensuring correct phloem and xylem cell wall composition.

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