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  • 1. Adam, Zach
    et al.
    Adamska, Iwona
    Nakabayashi, Kazumi
    Ostersetzer, Oren
    Haussuhl, Kirsten
    Manuell, Andrea
    Zheng, Bo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Vallon, Olivier
    Rodermel, Steven
    Shinozaki, Kazuo
    Chloroplast and mitochondrial proteases in Arabidopsis: a proposed nomenclature2001In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 125, no 4, p. 1912-1918Article in journal (Refereed)
    Abstract [en]

    The identity and scope of chloroplast and mitochondrial proteases in higher plants has only started to become apparent in recent years. Biochemical and molecular studies suggested the existence of Clp, FtsH, and DegP proteases in chloroplasts, and a Lon protease in mitochondria, although currently the full extent of their role in organellar biogenesis and function remains poorly understood. Rapidly accumulating DNA sequence data, especially from Arabidopsis, has revealed that these proteolytic enzymes are found in plant cells in multiple isomeric forms. As a consequence, a systematic approach was taken to catalog all these isomers, to predict their intracellular location and putative processing sites, and to propose a standard nomenclature to avoid confusion and facilitate scientific communication. For the Clp protease most of the ClpP isomers are found in chloroplasts, whereas one is mitochondrial. Of the ATPase subunits, the one ClpD and two ClpC isomers are located in chloroplasts, whereas both ClpX isomers are present in mitochondria. Isomers of the Lon protease are predicted in both compartments, as are the different forms of FtsH protease. DegP, the least characterized protease in plant cells, has the most number of isomers and they are predicted to localize in several cell compartments. These predictions, along with the proposed nomenclature, will serve as a framework for future studies of all four families of proteases and their individual isomers.

  • 2. Anoman, Armand D.
    et al.
    Flores-Tornero, Maria
    Benstein, Ruben M.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Biocenter–Botanical Institute II, University of Cologne, Cologne, Germany.
    Blau, Samira
    Rosa-Tellez, Sara
    Braeutigam, Andrea
    Fernie, Alisdair R.
    Munoz-Bertomeu, Jesus
    Schilasky, Soeren
    Meyer, Andreas J.
    Kopriva, Stanislav
    Segura, Juan
    Krueger, Stephan
    Ros, Roc
    Deficiency in the Phosphorylated Pathway of Serine Biosynthesis Perturbs Sulfur Assimilation2019In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 180, no 1, p. 153-170Article in journal (Refereed)
    Abstract [en]

    Although the plant Phosphorylated Pathway of L-Ser Biosynthesis (PPSB) is essential for embryo and pollen development, and for root growth, its metabolic implications have not been fully investigated. A transcriptomics analysis of Arabidopsis (Arabidopsis thaliana) PPSB-deficient mutants at night, when PPSB activity is thought to be more important, suggested interaction with the sulfate assimilation process. Because sulfate assimilation occurs mainly in the light, we also investigated it in PPSB-deficient lines in the day. Key genes in the sulfate starvation response, such as the adenosine 5'phosphosulfate reductase genes, along with sulfate transporters, especially those involved in sulfate translocation in the plant, were induced in the PPSB-deficient lines. However, sulfate content was not reduced in these lines as compared with wild-type plants; besides the glutathione (GSH) steady-state levels in roots of PPSB-deficient lines were even higher than in wild type. This suggested that PPSB deficiency perturbs the sulfate assimilation process between tissues/organs. Alteration of thiol distribution in leaves from different developmental stages, and between aerial parts and roots in plants with reduced PPSB activity, provided evidence supporting this idea. Diminished PPSB activity caused an enhanced flux of S-35 into thiol biosynthesis, especially in roots. GSH turnover also accelerated in the PPSB-deficient lines, supporting the notion that not only biosynthesis, but also transport and allocation, of thiols were perturbed in the PPSB mutants. Our results suggest that PPSB is required for sulfide assimilation in specific heterotrophic tissues and that a lack of PPSB activity perturbs sulfur homeostasis between photosynthetic and nonphotosynthetic tissues.

  • 3. Arnqvist, L
    et al.
    Dutta, P C
    Jonsson, Lisbeth
    Södertörn University, Avdelning Naturvetenskap.
    Sitbon, F
    Reduction of cholesterol and glycoalkaloid levels in transgenic potato plants by overexpression of a type 1 sterol methyltransferase cDNA2003In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 131, no 4, p. 1792-1799Article in journal (Refereed)
    Abstract [en]

    Transgenic potato (Solanum tuberosum cv Desiree) plants overexpressing a soybean (Glycine max) type 1 sterol methyltransferase (GmSMT1) cDNA were generated and used to study sterol biosynthesis in relation to the production of toxic glycoalkaloids. Transgenic plants displayed an increased total sterol level in both leaves and tubers, mainly due to increased levels of the 24-ethyl sterols isofucosterol and sitosterol. The higher total sterol level was due to increases in both free and esterified sterols. However, the level of free cholesterol, a nonalkylated sterol, was decreased. Associated with this was a decreased glycoalkaloid level in leaves and tubers, down to 41% and 63% of wild-type levels, respectively. The results show that glycoalkaloid biosynthesis can be down-regulated in transgenic potato plants by reducing the content of free nonalkylated sterols, and they support the view of cholesterol as a precursor in glycoalkaloid biosynthesis.

  • 4. Aronsson, Henrik
    et al.
    Schottler, Mark A.
    Kelly, Amelie A.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sundqvist, Christer
    Dormann, Peter
    Karim, Sazzad
    Jarvis, Paul
    Monogalactosyldiacylglycerol deficiency in Arabidopsis affects pigment composition in the prolamellar body and impairs thylakoid membrane energization and photoprotection in leaves2008In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 148, no 1, p. 580-592Article in journal (Refereed)
    Abstract [en]

    Monogalactosyldiacylglycerol (MGDG) is the major lipid constituent of chloroplast membranes and has been proposed to act directly in several important plastidic processes, particularly during photosynthesis. In this study, the effect of MGDG deficiency, as observed in the monogalactosyldiacylglycerol synthase1-1 (mgd1-1) mutant, on chloroplast protein targeting, phototransformation of pigments, and photosynthetic light reactions was analyzed. The targeting of plastid proteins into or across the envelope, or into the thylakoid membrane, was not different from wild-type in the mgd1 mutant, suggesting that the residual amount of MGDG in mgd1 was sufficient to maintain functional targeting mechanisms. In dark-grown plants, the ratio of bound protochlorophyllide (Pchlide, F656) to free Pchlide (F631) was increased in mgd1 compared to the wild type. Increased levels of the photoconvertible pigment-protein complex (F656), which is photoprotective and suppresses photooxidative damage caused by an excess of free Pchlide, may be an adaptive response to the mgd1 mutation. Leaves of mgd1 suffered from a massively impaired capacity for thermal dissipation of excess light due to an inefficient operation of the xanthophyll cycle; the mutant contained less zeaxanthin and more violaxanthin than wild type after 60 min of high-light exposure and suffered from increased photosystem II photoinhibition. This is attributable to an increased conductivity of the thylakoid membrane at high light intensities, so that the proton motive force is reduced and the thylakoid lumen is less acidic than in wild type. Thus, the pH-dependent activation of the violaxanthin de-epoxidase and of the PsbS protein is impaired.

  • 5.
    Askerlund, Per
    Jönköping University, School of Education and Communication, HLK, Disciplinary Research. Department of Plant Biochemistry, Lund University, Lund, Sweden.
    Calmodulin-stimulated Ca2+-ATPases in the vacuolar and plasma membranes in cauliflower1997In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 114, no 3, p. 999-1007Article in journal (Refereed)
    Abstract [en]

    The subcellular locations of Ca2+-ATPases in the membranes of cauliflower (Brassica oleracea L.) inflorescences were investigated. After continuous sucrose gradient centrifugation a 111-kD calmodulin (CaM)-stimulated and CaM-binding Ca2+-ATPase (BCA1; P. Askerlund [1996] Plant Physiol 110: 913–922; S. Malmstrom, P. Askerlund, M.G. Palmgren [1997] FEBS Lett 400: 324–328) comigrated with vacuolar membrane markers, whereas a 116-kD CaM-binding Ca2+-ATPase co-migrated with a marker for the plasma membrane. The 116-kD Ca2+-ATPase was enriched in plasma membranes obtained by aqueous two-phase partitioning, which is in agreement with a plasma membrane location of this Ca2+-ATPase. Countercurrent distribution of a low-density intracellular membrane fraction in an aqueous two-phase system resulted in the separation of the endoplasmic reticulum and vacuolar membranes. The 111-kD Ca2+-ATPase co-migrated with a vacuolar membrane marker after countercurrent distribution but not with markers for the endoplasmic reticulum. A vacuolar membrane location of the 111-kD Ca2+-ATPase was further supported by experiments with isolated vacuoles from cauliflower: (a) Immunoblotting with an antibody against the 111-kD Ca2+-ATPase showed that it was associated with the vacuoles, and (b) ATP-dependent Ca2+ uptake by the intact vacuoles was found to be CaM stimulated and partly protonophore insensitive.

  • 6.
    Askerlund, Per
    Jönköping University, School of Education and Communication, HLK, Disciplinary Research. Department of Plant Biochemistry, Lund University, Lund, Sweden.
    Modulation of an Intracellular Calmodulin-Stimulated Ca2+-Pumping ATPase in Cauliflower by Trypsin (The Use of Calcium Green-5N to Measure Ca2+ Transport in Membrane Vesicles)1996In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 110, no 3, p. 913-922Article in journal (Refereed)
    Abstract [en]

    The effect of controlled trypsin digestion of a calmodulin-stimulated Ca2+-ATPase in low-density intracellular membranes from cauliflower (Brassica oleracea L.) inflorescences was investigated. Ca2+ uptake into vesicles was measured either continuously with the fluorescent Ca2+ indicator Calcium Green-5N or with a radio-active filter technique. Trypsin treatment of vesicles resulted in a 3-fold activation of Ca2+ uptake and loss of calmodulin sensitivity. Immunoblotting experiments with an antiserum raised against the Ca2+-ATPase showed that the trypsin activation was accompanied by a decrease in the amount of intact Ca2+-ATPase (111 kD) and by successive appearances of polypeptides of 102 and 99 to 84 kD. 125I-Calmodulin overlays showed that only the intact Ca2+-ATPase bound calmodulin. Removal of the calmodulin-binding domain (about 9 kD) was not enough to obtain full activation. Trypsin proteolysis resulted in a Ca2+ concentration necessary for half-maximal activity of 0.5 [mu]M, whereas a value of about 2 [mu]M was obtained with untreated membranes in the presence of calmodulin. Without trypsin treatment or calmodulin the activity was not saturated even at 57 [mu]M free Ca2+. The data suggest that trypsin digestion and calmodulin activate the cauliflower Ca2+-ATPase by at least partly different mechanisms.

  • 7.
    Askerlund, Per
    et al.
    Jönköping University, School of Education and Communication, HLK, Disciplinary Research. Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.
    Evans, David E.
    Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.
    Reconstitution and Characterization of a Calmodulin-Stimulated Ca-Pumping ATPase Purified from Brassica oleracea L1992In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 100, no 4, p. 1670-1681Article in journal (Refereed)
    Abstract [en]

    Purification and functional reconstitution of a calmodulin-stimulated Ca(2+)-ATPase from cauliflower (Brassica oleracea L.) is described. Activity was purified about 120-fold from a microsomal fraction using calmodulin-affinity chromatography. The purified fraction showed a polypeptide at 115 kD, which formed a phosphorylated intermediate in the presence of Ca(2+), together with a few polypeptides with lower molecular masses that were not phosphorylated. The ATPase was reconstituted into liposomes by 3-([cholamidopropyl]-dimethylammonio-)1-propanesulfonate (CHAPS) dialysis. The proteoliposomes showed ATP-dependent Ca(2+) uptake and ATPase activity, both of which were stimulated about 4-fold by calmodulin. Specific ATPase activity was about 5 mumol min(-1) (mg protein)(-1), and the Ca(2+)/ATP ratio was 0.1 to 0.5 when the ATPase was reconstituted with entrapped oxalate. The purified, reconstituted Ca(2+)-ATPase was inhibited by vanadate and erythrosin B, but not by cyclopiazonic acid and thapsigargin. Activity was supported by ATP (100%) and GTP (50%) and had a pH optimum of about 7.0. The effect of monovalent and divalent cations (including Ca(2+)) on activity is described. Assay of membranes purified by two-phase partitioning indicated that approximately 95% of the activity was associated with intracellular membranes, but only about 5% with plasma membranes. Sucrose gradient centrifugation suggests that the endoplasmic reticulum is the major cellular location of calmodulin-stimulated Ca(2+)-pumping ATPase in Brassica oleracea inflorescences.

  • 8.
    Askerlund, Per
    et al.
    Jönköping University, School of Education and Communication, HLK, Disciplinary Research. Department of Plant Biochemistry, University of Lund, Lund, Sweden.
    Larsson, Christer
    Department of Plant Biochemistry, University of Lund, Lund, Sweden.
    Transmembrane Electron Transport in Plasma Membrane Vesicles Loaded with an NADH-Generating System or Ascorbate1991In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 96, no 4, p. 1178-1184Article in journal (Refereed)
    Abstract [en]

    Sugar beet (Beta vulgaris L.) leaf plasma membrane vesicles were loaded with an NADH-generating system (or with ascorbate) and were tested spectrophotometrically for their ability to reduce external, membrane-impermeable electron acceptors. Either alcohol dehydrogenase plus NAD+ or 100 millimolar ascorbate was included in the homogenization medium, and right-side-out (apoplastic side-out) plasma membrane vesicles were subsequently prepared using two-phase partitioning. Addition of ethanol to plasma membrane vesicles loaded with the NADH-generating system led to a production of NADH inside the vesicles which could be recorded at 340 nanometers. This system was able to reduce 2,6-dichlorophenolindophenol-3′-sulfonate (DCIP-sulfonate), a strongly hydrophilic electron acceptor. The reduction of DCIP-sulfonate was stimulated severalfold by the K+ ionophore valinomycin, included to abolish membrane potential (outside negative) generated by electrogenic transmembrane electron flow. Fe3+-chelates, such as ferricyanide and ferric citrate, as well as cytochrome c, were not reduced by vesicles loaded with the NADH-generating system. In contrast, right-side-out plasma membrane vesicles loaded with ascorbate supported the reduction of both ferric citrate and DCIP-sulfonate, suggesting that ascorbate also may serve as electron donor for transplasma membrane electron transport. Differences in substrate specificity and inhibitor sensitivity indicate that the electrons from ascorbate and NADH were channelled to external acceptors via different electron transport chains. Transplasma membrane electron transport constituted only about 10% of total plasma membrane electron transport activity, but should still be sufficient to be of physiological significance in, e.g. reduction of Fe3+ to Fe2+ for uptake.

  • 9.
    Askerlund, Per
    et al.
    Jönköping University, School of Education and Communication, HLK, Disciplinary Research. Department of Plant Biochemistry, University of Lund, Lund, Sweden.
    Laurent, Pascal
    Laboratoire de Biomembranes Vegetales, Unité de Recherche Associé 1180, Université Pierre et Marie Curie, Paris, France.
    Nakagawa, Hiroki
    Faculty of Horticulture, Chiba University, Matsudo, Chiba, Japan.
    Kader, Jean-Claude
    Laboratoire de Biomembranes Vegetales, Unité de Recherche Associé 1180, Université Pierre et Marie Curie, Paris, France.
    NADH-Ferricyanide Reductase of Leaf Plasma Membranes: Partial Purification and Immunological Relation to Potato Tuber Microsomal NADH-Ferricyanide Reductase and Spinach Leaf NADH-Nitrate Reductase1991In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 95, no 1, p. 6-13Article in journal (Refereed)
    Abstract [en]

    Plasma membranes obtained by two-phase partitioning of microsomal fractions from spinach (Spinacea oleracea L. cv Medania) and sugar beet leaves (Beta vulgaris L.) contained relatively high NADH-ferricyanide reductase and NADH-nitrate reductase (NR; EC 1.6.6.1) activities. Both of these activities were latent. To investigate whether these activities were due to the same enzyme, plasma membrane polypeptides were separated with SDS-PAGE and analyzed with immunoblotting methods. Antibodies raised against microsomal NADH-ferricyanide reductase (tentatively identified as NADH-cytochrome b5 reductase, EC 1.6.2.2), purified from potato (Solanum tuberosum L. cv Bintje) tuber microsomes, displayed one single band at 43 kilodaltons when reacted with spinach plasma membranes, whereas lgG produced against NR from spinach leaves gave a major band at 110 kilodaltons together with a few fainter bands of lower molecular mass. Immunoblotting analysis using inside-out and right-side-out plasma membrane vesicles strongly indicated that NR was not an integral protein but probably trapped inside the plasma membrane vesicles during homogenization. Proteins from spinach plasma membranes were solubilized with the zwitterionic detergent 3-[(3-cholamidopropyl) dimethylammonio] 1-propane-sulfonate and separated on a Mono Q anion exchange column at pH 5.6 with fast protein liquid chromatography. One major peak of NADH-ferricyanide reductase activity was found after separation. The peak fraction was enriched about 70-fold in this activity compared to the plasma membrane. When the peak fractions were analyzed with SDS-PAGE the NADH-ferricyanide reductase activity strongly correlated with a 43 kilodalton polypeptide which reacted with the antibodies against potato microsomal NADH-ferricyanide reductase. Thus, our data indicate that most, if not all, of the truly membrane-bound NADH-ferricyanide reductase activity of leaf plasma membranes is due to an enzyme very similar to potato tuber microsomal NADH-ferricyanide reductase (NADH-cytochrome b5 reductase).

  • 10.
    Aspeborg, Henrik
    et al.
    KTH, School of Biotechnology (BIO).
    Schrader, J.
    Coutinho, P. M.
    Stam, M.
    Kallas, A.
    Djerbi, S.
    Nilsson, Peter
    KTH, School of Biotechnology (BIO), Proteomics (closed 20130101).
    Denman, S.
    Amini, B.
    Sterky, Fredrik
    KTH, School of Biotechnology (BIO), Proteomics (closed 20130101).
    Master, E.
    Sandberg, G.
    Mellerowicz, E.
    Sundberg, B.
    Henrissat, B.
    Teeri, Tuula T.
    KTH, School of Biotechnology (BIO), Glycoscience.
    Carbohydrate-active enzymes involved in the secondary cell wall biogenesis in hybrid aspen2005In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 137, no 3, p. 983-997Article in journal (Refereed)
    Abstract [en]

    Wood formation is a fundamental biological process with significant economic interest. While lignin biosynthesis is currently relatively well understood, the pathways leading to the synthesis of the key structural carbohydrates in wood fibers remain obscure. We have used a functional genomics approach to identify enzymes involved in carbohydrate biosynthesis and remodeling during xylem development in the hybrid aspen Populus tremula x tremuloides. Microarrays containing cDNA clones from different tissue-specific libraries were hybridized with probes obtained from narrow tissue sections prepared by cryosectioning of the developing xylem. Bioinformatic analyses using the sensitive tools developed for carbohydrate-active enzymes allowed the identification of 25 xylem-specific glycosyltransferases belonging to the Carbohydrate-Active EnZYme families GT2, GT8, GT14, GT31, GT43, GT47, and GT61 and nine glycosidases (or transglycosidases) belonging to the Carbohydrate-Active EnZYme families GH9, GH10, GH16, GH17, GH19, GH28, GH35, and GH51. While no genes encoding either polysaccharide lyases or carbohydrate esterases were found among the secondary wall-specific genes, one putative O-acetyltransferase was identified. These wood-specific enzyme genes constitute a valuable resource for future development of engineered fibers with improved performance in different applications.

  • 11.
    Bai, Bing
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    van der Horst, Sjors
    Cordewener, Jan H. G.
    America, Twan A. H. P.
    Hanson, Johannes
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Bentsink, Leonie
    Seed-Stored mRNAs that Are Specifically Associated to Monosomes Are Translationally Regulated during Germination2020In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 182, no 1, p. 378-392Article in journal (Refereed)
    Abstract [en]

    The life cycle of many organisms includes a quiescent stage, such as bacterial or fungal spores, insect larvae, or plant seeds. Common to these stages is their low water content and high survivability during harsh conditions. Upon rehydration, organisms need to reactivate metabolism and protein synthesis. Plant seeds contain many mRNAs that are transcribed during seed development. Translation of these mRNAs occurs during early seed germination, even before the requirement of transcription. Therefore, stored mRNAs are postulated to be important for germination. How these mRNAs are stored and protected during long-term storage is unknown. The aim of this study was to investigate how mRNAs are stored in dry seeds and whether they are indeed translated during seed germination. We investigated seed polysome profiles and the mRNAs and protein complexes that are associated with these ribosomes in seeds of the model organism Arabidopsis (Arabidopsis thaliana). We showed that most stored mRNAs are associated with monosomes in dry seeds; therefore, we focus on monosomes in this study. Seed ribosome complexes are associated with mRNA-binding proteins, stress granule, and P-body proteins, which suggests regulated packing of seed mRNAs. Interestingly, similar to 17% of the mRNAs that are specifically associated with monosomes are translationally up-regulated during seed germination. These mRNAs are transcribed during seed maturation, suggesting a role for this developmental stage in determining the translational fate of mRNAs during early germination.

  • 12.
    Bajhaiya, Amit K.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Univ Manchester, Fac Life Sci, Manchester, Lancs, England.
    Dean, Andrew P.
    Zeef, Leo A. H.
    Webster, Rachel E.
    Pittman, Jon K.
    PSR1 Is a Global Transcriptional Regulator of Phosphorus Deficiency Responses and Carbon Storage Metabolism in Chlamydomonas reinhardtii2016In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 170, no 3, p. 1216-1234Article in journal (Refereed)
    Abstract [en]

    Many eukaryotic microalgae modify their metabolism in response to nutrient stresses such as phosphorus (P) starvation, which substantially induces storage metabolite biosynthesis, but the genetic mechanisms regulating this response are poorly understood. Here, we show that P starvation-induced lipid and starch accumulation is inhibited in a Chlamydomonas reinhardtii mutant lacking the transcription factor Pi Starvation Response1 (PSR1). Transcriptomic analysis identified specific metabolism transcripts that are induced by P starvation but misregulated in the psr1 mutant. These include transcripts for starch and triacylglycerol synthesis but also transcripts for photosynthesis-, redox-, and stress signaling-related proteins. To further examine the role of PSR1 in regulating lipid and starch metabolism, PSR1 complementation lines in the psr1 strain and PSR1 overexpression lines in a cell wall-deficient strain were generated. PSR1 expression in the psr1 lines was shown to be functional due to rescue of the psr1 phenotype. PSR1 overexpression lines exhibited increased starch content and number of starch granules per cell, which correlated with a higher expression of specific starch metabolism genes but reduced neutral lipid content. Furthermore, this phenotype was consistent in the presence and absence of acetate. Together, these results identify a key transcriptional regulator in global metabolism and demonstrate transcriptional engineering in microalgae to modulate starch biosynthesis.

  • 13.
    Baxter, Charles J
    et al.
    Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.
    Redestig, Henning
    Max-Planck Institute for Molecular Plant Physiology, Potsdam-Golm, Germany.
    Schauer, Nicolas
    Max-Planck Institute for Molecular Plant Physiology, Potsdam-Golm, Germany.
    Repsilber, Dirk
    ax-Planck Institute for Molecular Plant Physiology, Potsdam-Golm, Germany.
    Patil, Kiran R
    Center for Microbial Biotechnology, BioCentrum Technical University of Denmark, Kongens Lyngby, Denmark.
    Nielsen, Jens
    Max-Planck Institute for Molecular Plant Physiology, Potsdam-Golm, Germany.
    Selbig, Joachim
    Max-Planck Institute for Molecular Plant Physiology, Potsdam-Golm, Germany.
    Liu, Junli
    Genetics Programme, Scottish Crop Research Institute, Dundee, United Kingdom .
    Fernie, Alisdair R
    Max-Planck Institute for Molecular Plant Physiology, Potsdam-Golm, Germany.
    Sweetlove, Lee J
    Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.
    The metabolic response of heterotrophic Arabidopsis cells to oxidative stress2007In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 143, no 1, p. 312-25Article in journal (Refereed)
    Abstract [en]

    To cope with oxidative stress, the metabolic network of plant cells must be reconfigured either to bypass damaged enzymes or to support adaptive responses. To characterize the dynamics of metabolic change during oxidative stress, heterotrophic Arabidopsis (Arabidopsis thaliana) cells were treated with menadione and changes in metabolite abundance and (13)C-labeling kinetics were quantified in a time series of samples taken over a 6 h period. Oxidative stress had a profound effect on the central metabolic pathways with extensive metabolic inhibition radiating from the tricarboxylic acid cycle and including large sectors of amino acid metabolism. Sequential accumulation of metabolites in specific pathways indicated a subsequent backing up of glycolysis and a diversion of carbon into the oxidative pentose phosphate pathway. Microarray analysis revealed a coordinated transcriptomic response that represents an emergency coping strategy allowing the cell to survive the metabolic hiatus. Rather than attempt to replace inhibited enzymes, transcripts encoding these enzymes are in fact down-regulated while an antioxidant defense response is mounted. In addition, a major switch from anabolic to catabolic metabolism is signaled. Metabolism is also reconfigured to bypass damaged steps (e.g. induction of an external NADH dehydrogenase of the mitochondrial respiratory chain). The overall metabolic response of Arabidopsis cells to oxidative stress is remarkably similar to the superoxide and hydrogen peroxide stimulons of bacteria and yeast (Saccharomyces cerevisiae), suggesting that the stress regulatory and signaling pathways of plants and microbes may share common elements.

  • 14.
    Benedict, Catherine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Geisler, Matt
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Huner, Norman
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Consensus by democracy. Using meta-analyses of microarray and genomic data to model the cold acclimation signaling pathway in Arabidopsis.2006In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 141, no 4, p. 1219-1232Article in journal (Refereed)
    Abstract [en]

    The whole-genome response of Arabidopsis (Arabidopsis thaliana) exposed to different types and durations of abiotic stress has now been described by a wealth of publicly available microarray data. When combined with studies of how gene expression is affected in mutant and transgenic Arabidopsis with altered ability to transduce the low temperature signal, these data can be used to test the interactions between various low temperature-associated transcription factors and their regulons. We quantized a collection of Affymetrix microarray data so that each gene in a particular regulon could vote on whether a cis-element found in its promoter conferred induction (+1), repression (–1), or no transcriptional change (0) during cold stress. By statistically comparing these election results with the voting behavior of all genes on the same gene chip, we verified the bioactivity of novel cis-elements and defined whether they were inductive or repressive. Using in silico mutagenesis we identified functional binding consensus variants for the transcription factors studied. Our results suggest that the previously identified ICEr1 (induction of CBF expression region 1) consensus does not correlate with cold gene induction, while the ICEr3/ICEr4 consensuses identified using our algorithms are present in regulons of genes that were induced coordinate with observed ICE1 transcript accumulation and temporally preceding genes containing the dehydration response element. Statistical analysis of overlap and cis-element enrichment in the ICE1, CBF2, ZAT12, HOS9, and PHYA regulons enabled us to construct a regulatory network supported by multiple lines of evidence that can be used for future hypothesis testing.

  • 15.
    Benlloch, Reyes
    et al.
    Department of Forest Genetics and Plant Physiology, SLU.
    Shevela, Dmitriy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hainzl, Tobias
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Grundström, Christin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shutova, Tatyana
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Crystal structure and functional characterization of Photosystem II-associated carbonic anhydrase CAH3 in Chlamydomonas reinhardtii2015In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 167, no 3, p. 950-962Article in journal (Refereed)
    Abstract [en]

    In oxygenic photosynthesis, light energy is stored in the form of chemical energy by converting CO2 and water into carbohydrates.The light-driven oxidation of water that provides the electrons and protons for the subsequent CO2 fixation takes place inphotosystem II (PSII). Recent studies show that in higher plants, HCO3– increases PSII activity by acting as a mobile acceptor ofthe protons produced by PSII. In the green alga Chlamydomonas reinhardtii, a luminal carbonic anhydrase, CrCAH3, was suggested toimprove proton removal from PSII, possibly by rapid reformation of HCO3– from CO2. In this study, we investigated the interplaybetween PSII and CrCAH3 by membrane inlet mass spectrometry and x-ray crystallography. Membrane inlet mass spectrometrymeasurements showed that CrCAH3 was most active at the slightly acidic pH values prevalent in the thylakoid lumen underillumination. Two crystal structures of CrCAH3 in complex with either acetazolamide or phosphate ions were determined at 2.6- and2.7-Å resolution, respectively. CrCAH3 is a dimer at pH 4.1 that is stabilized by swapping of the N-terminal arms, a feature notpreviously observed in a-type carbonic anhydrases. The structure contains a disulfide bond, and redox titration of CrCAH3 functionwith dithiothreitol suggested a possible redox regulation of the enzyme. The stimulating effect of CrCAH3 and CO2/HCO3– on PSIIactivity was demonstrated by comparing the flash-induced oxygen evolution pattern of wild-type and CrCAH3-less PSIIpreparations. We showed that CrCAH3 has unique structural features that allow this enzyme to maximize PSII activity at lowpH and CO2 concentration.

  • 16. Bergman, Anders
    et al.
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ericson, Ingemar
    Method to Obtain a Chlorophyll-free Preparation of Intact Mitochondria from Spinach Leaves.1980In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 66, no 3, p. 442-445Article in journal (Refereed)
    Abstract [en]

    Mitochondria from green leaves of spinach have been prepared using a three-step procedure involving differential centrifugation, partition in an aqueous dextran polyethylene glycol two-phase system and Percoll gradient centrifugation. The mitochondrial fractions after the different steps of purification were compared. The final mitochondrial preparation was totally free from chloroplast material measured as chlorophyll content. The enrichment of mitochondria in relation to peroxisomes and microsomes was approximately 12 and 33 times, respectively, based on NAD:isocitrate dehydrogenase activity, glycolate oxidase activity, and NADPH:cytochrome c oxidoreductase activity. The apparent intactness of the inner and the outer mitochondrial membranes was higher than 90% as measured by latency of enzyme activities. The mitochondria showed high respiratory rates with respiratory control and the ADP/O ratios approached the theoretical limits.

  • 17.
    Beste, Lisa
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Nahar, Nurun
    Dalman, Kerstin
    Fujioka, Shozo
    Jonsson, Lisbeth
    Stockholm University, Faculty of Science, Department of Botany.
    Dutta, Paresh C.
    Sitbon, Folke
    Synthesis of Hydroxylated Sterols in Transgenic Arabidopsis Plants Alters Growth and Steroid Metabolism2011In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 157, no 1, p. 426-440Article in journal (Refereed)
    Abstract [en]

    To explore mechanisms in plant sterol homeostasis, we have here increased the turnover of sterols in Arabidopsis (Arabidopsis thaliana) and potato (Solanum tuberosum) plants by overexpressing four mouse cDNA encoding cholesterol hydroxylases (CHs), hydroxylating cholesterol at the C-7, C-24, C-25, or C-27 positions. Compared to the wild type, the four types of Arabidopsis transformant showed varying degrees of phenotypic alteration, the strongest one being in CH25 lines, which were dark-green dwarfs resembling brassinosteroid-related mutants. Gas chromatography-mass spectrometry analysis of extracts from wild-type Arabidopsis plants revealed trace levels of alpha and beta forms of 7-hydroxycholesterol, 7-hydroxycampesterol, and 7-hydroxysitosterol. The expected hydroxycholesterol metabolites in CH7-, CH24-, and CH25 transformants were identified and quantified using gas chromatography-mass spectrometry. Additional hydroxysterol forms were also observed, particularly in CH25 plants. In CH24 and CH25 lines, but not in CH7 ones, the presence of hydroxysterols was correlated with a considerable alteration of the sterol profile and an increased sterol methyltransferase activity in microsomes. Moreover, CH25 lines contained clearly reduced levels of brassinosteroids, and displayed an enhanced drought tolerance. Equivalent transformations of potato plants with the CH25 construct increased hydroxysterol levels, but without the concomitant alteration of growth and sterol profiles observed in Arabidopsis. The results suggest that an increased hydroxylation of cholesterol and/or other sterols in Arabidopsis triggers compensatory processes, acting to maintain sterols at adequate levels.

  • 18. Bhalerao, R.
    et al.
    Keskitalo, J.
    Sterky, Fredrik
    KTH, Superseded Departments, Biotechnology.
    Erlandsson, R.
    Bjorkbacka, H.
    Birve, S. J.
    Karlsson, J.
    Gardestrom, P.
    Gustafsson, P.
    Lundeberg, Joakim
    KTH, Superseded Departments, Biotechnology.
    Jansson, S.
    Gene expression in autumn leaves2003In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 131, no 2, p. 430-442Article in journal (Refereed)
    Abstract [en]

    Two cDNA libraries were prepared, one from leaves of a field-grown aspen (Populus tremula) tree, harvested just before any visible sign of leaf senescence in the autumn, and one from young but fully expanded leaves of greenhouse-grown aspen (Populus tremula X tremuloides). Expressed sequence tags (ESTs; 5,128 and 4,841, respectively) were obtained from the two libraries. A semiautomatic method of annotation and functional classification of the ESTs, according to a modified Munich Institute of Protein Sequences classification scheme, was developed, utilizing information from three different databases. The patterns of gene expression in the two libraries were strikingly different. In the autumn leaf library, ESTs encoding metallothionein, early light-inducible proteins, and cysteine proteases were most abundant. Clones encoding other proteases and proteins involved in respiration and breakdown of lipids and pigments, as well as stress-related genes, were also well represented. We identified homologs to many known senescence-associated genes, as well as seven different genes encoding cysteine proteases, two encoding aspartic proteases, five encoding metallothioneins, and 35 additional genes that were up-regulated in autumn leaves. We also indirectly estimated the rate of plastid protein synthesis in the autumn leaves to be less that 10% of that in young leaves.

  • 19.
    Bhalerao, Rupali
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Keskitalo, Johanna
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sterky, Fredrik
    Erlandsson, Rikard
    Björkbacka, Harry
    Birve, Simon Jonsson
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Lundeberg, Joakim
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gene expression in autumn leaves2003In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 131, no 2, p. 430-442Article in journal (Refereed)
    Abstract [en]

    Two cDNA libraries were prepared, one from leaves of a field-grown aspen (Populus tremula) tree, harvested just before any visible sign of leaf senescence in the autumn, and one from young but fully expanded leaves of greenhouse-grown aspen (Populus tremula x tremuloides). Expressed sequence tags (ESTs; 5,128 and 4,841, respectively) were obtained from the two libraries. A semiautomatic method of annotation and functional classification of the ESTs, according to a modified Munich Institute of Protein Sequences classification scheme, was developed, utilizing information from three different databases. The patterns of gene expression in the two libraries were strikingly different. In the autumn leaf library, ESTs encoding metallothionein, early light-inducible proteins, and cysteine proteases were most abundant. Clones encoding other proteases and proteins involved in respiration and breakdown of lipids and pigments, as well as stress-related genes, were also well represented. We identified homologs to many known senescence-associated genes, as well as seven different genes encoding cysteine proteases, two encoding aspartic proteases, five encoding metallothioneins, and 35 additional genes that were up-regulated in autumn leaves. We also indirectly estimated the rate of plastid protein synthesis in the autumn leaves to be less that 10% of that in young leaves.

  • 20.
    Blanco, Nicolas E.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ceccoli, Romina D.
    Dalla Via, Maria V.
    Voss, Ingo
    Segretin, Maria E.
    Bravo-Almonacid, Fernando F.
    Melzer, Michael
    Hajirezaei, Mohammad-Reza
    Scheibe, Renate
    Hanke, Guy T.
    Expression of the Minor Isoform Pea Ferredoxin in Tobacco Alters Photosynthetic Electron Partitioning and Enhances Cyclic Electron Flow2013In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 161, no 2, p. 866-879Article in journal (Refereed)
    Abstract [en]

    Ferredoxins (Fds) are ferrosulfoproteins that function as low-potential electron carriers in plants. The Fd family is composed of several isoforms that share high sequence homology but differ in functional characteristics. In leaves, at least two isoforms conduct linear and cyclic photosynthetic electron transport around photosystem I, and mounting evidence suggests the existence of at least partial division of duties between these isoforms. To evaluate the contribution of different kinds of Fds to the control of electron fluxes along the photosynthetic electron transport chain, we overexpressed a minor pea (Pisum sativum) Fd isoform (PsFd1) in tobacco (Nicotiana tabacum) plants. The transplastomic OeFd1 plants exhibited variegated leaves and retarded growth and developmental rates. Photosynthetic studies of these plants indicated a reduction in carbon dioxide assimilation rates, photosystem II photochemistry, and linear electron flow. However, the plants showed an increase in nonphotochemical quenching, better control of excitation pressure at photosystem II, and no evidence of photoinhibition, implying a better dynamic regulation to remove excess energy from the photosynthetic electron transport chain. Finally, analysis of P700 redox status during illumination confirmed that the minor pea Fd isoform promotes enhanced cyclic flow around photosystem I. The two novel features of this work are: (1) that Fd levels achieved in transplastomic plants promote an alternative electron partitioning even under greenhouse light growth conditions, a situation that is exacerbated at higher light intensity measurements; and (2) that an alternative, minor Fd isoform has been overexpressed in plants, giving new evidence of labor division among Fd isoforms.

  • 21. Blokhina, Olga
    et al.
    Laitinen, Teresa
    Hatakeyama, Yuto
    Delhomme, Nicolas
    Paasela, Tanja
    Zhao, Lei
    Street, Nathaniel
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Wada, Hiroshi
    Karkonen, Anna
    Fagerstedt, Kurt
    Ray Parenchymal Cells Contribute to Lignification of Tracheids in Developing Xylem of Norway Spruce1[OPEN]2019In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 181, no 4, p. 1552-1572Article in journal (Refereed)
    Abstract [en]

    A comparative transcriptomic study and a single-cell metabolome analysis were combined to determine whether parenchymal ray cells contribute to the biosynthesis of monolignols in the lignifying xylem of Norway spruce (Picea abies). Ray parenchymal cells may function in the lignification of upright tracheids by supplying monolignols. To test this hypothesis, parenchymal ray cells and upright tracheids were dissected with laser-capture microdissection from tangential cryosections of developing xylem of spruce trees. The transcriptome analysis revealed that among the genes involved in processes typical for vascular tissues, genes encoding cell wall biogenesis-related enzymes were highly expressed in both developing tracheids and ray cells. Interestingly, most of the shikimate and monolignol biosynthesis pathway-related genes were equally expressed in both cell types. Nonetheless, 1,073 differentially expressed genes were detected between developing ray cells and tracheids, among which a set of genes expressed only in ray cells was identified. In situ single cell metabolomics of semi-intact plants by picoliter pressure probe-electrospray ionization-mass spectrometry detected monolignols and their glycoconjugates in both cell types, indicating that the biosynthetic route for monolignols is active in both upright tracheids and parenchymal ray cells. The data strongly support the hypothesis that in developing xylem, ray cells produce monolignols that contribute to lignification of tracheid cell walls. Transcriptomics combined with single-cell metabolomics give new information on the role of rays in lignification of developing xylem in Norway spruce.

  • 22. BRUNES, L
    et al.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    ELIASSON, L
    ON THE REASON FOR THE DIFFERENT PHOTOSYNTHETIC RATES OF SEEDLINGS OF PINUS-SILVESTRIS AND BETULA-VERRUCOSA1980In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 66, no 5, p. 940-944Article in journal (Refereed)
  • 23. Campbell, D
    et al.
    Eriksson, Mats-Jerry
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Oquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Clarke, A K
    A cyanobacterium resists UV-B by exchanging Photosystem II D1 proteins.1997In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 114, no 3, p. 30004-30004Article in journal (Refereed)
  • 24. Campbell, D
    et al.
    OQUIST, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Predicting light acclimation in cyanobacteria from nonphotochemical quenching of photosystem II fluorescence, which reflects state transitions in these organisms1996In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 111, no 4, p. 1293-1298Article in journal (Refereed)
    Abstract [en]

    An important factor in photosynthetic ecophysiology is the light regime that a photobiont is acclimated to exploit. In a wide range of cyanobacteria and cyano-lichens, the easily measured fluorescence parameters, coefficient of nonphotochemical quenching of photosystem II variable fluorescence (q(N)) and nonphotochemical quenching, decline to a minimum near the acclimated growth light intensity. This characteristic pattern predicts the integrated light regime to which populations are acclimated, information that is particularly useful for cyanobacteria or cyano-lichens from habitats with highly variable light intensities. q(N) reflects processes that compete with photosystem II photochemistry for absorbed excitation energy. In cyanobacteria, we find no evidence for energy-dependent quenching mechanisms, which are the predominant components of q(N) in higher plants. Instead, in cyanobacteria, q(N) correlates closely with the excitation flow from the phycobilisome to photosystem I, indicating that q(N) reflects the state transition mechanism for equilibration of excitation from the phycobilisome to the two photosystems.

  • 25. Carlenor, E
    et al.
    Persson, Bengt L.
    Department of Biochemistry, Arrhenius Laboratory, University of Stockholm.
    Glaser, E
    Andersson, B
    Rydström, J
    On the presence of a nicotinamide nucleotide transhydrogenase in mitochondria from potato tuber1988In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 88, p. 303-308Article in journal (Refereed)
    Abstract [en]

    Mitochondria isolated from potato (Solanum tuberosum L.) tuber wereinvestigated for the presence of a nicotinamide nucleotide transhydrogenaseactivity. Submitochondrial particles derived from these mitochondriaby sonication catalyzed a reduction of NAD' or 3-acetylpyridine-NAD'by NADPH, which showed a maximum of about 50 to 150 nanomoles/minute. milligram protein at pH 5 to 6. The Km values for 3-acetylpyridine-NAD' and NADPH were about 24 and 55 micromolar, respectively.Intact mitochondria showed a negligible activity in the absence of detergents.However, in the presence of detergents the specific activity approachedabout 30% of that seen with submitochondrial particles. Thepotato mitochondria transhydrogenase activity was sensitive to trypsinand phenylarsine oxide, both agents that are known to inhibit the mammaliantranshydrogenase. Antibodies raised against rat liver transhydrogenasecrossreacted with two peptides in potato tuber mitochondrialmembranes with a molecular mass of 100 to 115 kilodaltons. Theobserved transhydrogenase activities may be due to an unspecific activityof dehydrogenases and/or to a genuine transhydrogenase. The activitycontributions by NADH dehydrogenases and transhydrogenase to thetotal transhydrogenase activity were investigated by determining theirrelative sensitivities to trypsin. It is concluded that, at high or neutralpH, the observed transhydrogenase activity in potato tuber submitochondrialparticles is due to the presence of a genuine and specific highmolecular weight transhydrogenase. At low pH an unspecific reaction ofan NADH dehydrogenase with NADPH contributes to the total transhydrogenaseactivity. 

  • 26.
    Carr, Herman
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Axelsson, Lennart
    Photosynthetic utilization of bicarbonate in Zostera marina is reduced by inhibitors of mitochondrial ATPase and electron transport2008In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 147, no 2, p. 879-885Article in journal (Refereed)
    Abstract [en]

    When Zostera marina was irradiated after a period of darkness, initiation of photosynthetic O-2 evolution occurred in two phases. During a lag phase, lasting 4 to 5 min, photosynthesis was supported by a diffusive entry of CO2. Photosynthesis then rapidly increased to its full rate. Tris buffer, at a concentration of 50 mM, completely inhibited this increase without affecting CO2-supported photosynthesis during the lag phase. These results verify that the increase in photosynthesis after the lag phase depended on an activation of bicarbonate (HCO3-) utilization through acid zones generated by proton pumps located to the outer cell membrane. In similar experiments, 6.25 mu M of the mitochondrial ATPase blocker oligomycin inhibited photosynthetic HCO3- utilization by more than 60%. Antimycin A, a selective blocker of mitochondrial electron transport, caused a similar inhibition of HCO3- utilization. Measurements at elevated CO2 concentrations verified that neither oligomycin nor antimycin interfered with linear photosynthetic electron transport or with CO2 fixation. Thus, a major part of the ATP used for the generation of acid zones involved in HCO3- utilization in Z. marina was derived from mitochondrial respiration.

  • 27.
    Cañas, Rafael A
    et al.
    University of Malaga.
    Villalobos, David P
    University of Malaga.
    Díaz-Moreno, Sara
    University of Malaga.
    Cánovas, Francisco M
    University of Malaga.
    Cantón, Francisco R
    University of Malaga.
    Molecular and functional analyses support a role of Ornithine-{delta}-aminotransferase in the provision of glutamate for glutamine biosynthesis during pine germination2008In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 148, no 1, p. 77-88Article in journal (Refereed)
    Abstract [en]

    We report the molecular characterization and functional analysis of a gene (PsdeltaOAT) from Scots pine (Pinus sylvestris) encoding Orn-delta-aminotransferase (delta-OAT; EC 2.6.1.13), an enzyme of arginine metabolism. The deduced amino acid sequence contains a putative N-terminal signal peptide for mitochondrial targeting. The polypeptide is similar to other delta-OATs from plants, yeast, and mammals and encoded by a single-copy gene in pine. PsdeltaOAT encodes a functional delta-OAT as determined by expression of the recombinant protein in Escherichia coli and analysis of the active enzyme. The expression of PsdeltaOAT was undetectable in the embryo, but highly induced at early stages of germination and seedling development in all different organs. Transcript levels decreased in later developmental stages, although an increase was observed in lignified stems of 90-d-old plants. An increase of delta-OAT activity was observed in germinating embryos and seedlings and appears to mirror the observed alterations in PsdeltaOAT transcript levels. Similar expression patterns were also observed for genes encoding arginase and isocitrate dehydrogenase. Transcripts of PsdeltaOAT and the arginase gene were found widely distributed in different cell types of pine organs. Consistent with these results a metabolic pathway is proposed for the nitrogen flow from the megagametophyte to the developing seedling, which is also supported by the relative abundance of free amino acids in embryos and seedlings. Taken together, our data support that delta-OAT plays an important role in this process providing glutamate for glutamine biosynthesis during early pine growth.

  • 28.
    Chang, Christine
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Slesak, Ireneusz
    Jorda, Lucia
    Sotnikov, Alexey
    Stockholm University, Faculty of Science, Department of Botany.
    Melzer, Michael
    Miszalski, Zbigniew
    Mullineaux, Philip M.
    Parker, Jane E.
    Karpinska, Barbara
    Karpinski, Stanislaw
    Arabidopsis Chloroplastic Glutathione Peroxidases Play a Role in Cross Talk between Photooxidative Stress and Immune Responses2009In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 150, no 2, p. 670-683Article in journal (Refereed)
    Abstract [en]

    Glutathione peroxidases (GPXs; EC 1.11.1.9) are key enzymes of the antioxidant network in plants and animals. In order to investigate the role of antioxidant systems in plant chloroplasts, we generated Arabidopsis (Arabidopsis thaliana) transgenic lines that are depleted specifically in chloroplastic (cp) forms of GPX1 and GPX7. We show that reduced cpGPX expression, either in transgenic lines with lower total cpGPX expression (GPX1 and GPX7) or in a gpx7 insertion mutant, leads to compromised photooxidative stress tolerance but increased basal resistance to virulent bacteria. Depletion of both GPX1 and GPX7 expression also caused alterations in leaf cell and chloroplast morphology. Leaf tissues were characterized by shorter and more rounded palisade cells, irregular spongy mesophyll cells, and larger intercellular air spaces compared with the wild type. Chloroplasts had larger and more abundant starch grains than in wild-type and gpx7 mutant plants. Constitutively reduced cpGPX expression also led to higher foliar ascorbic acid, glutathione, and salicylic acid levels in plants exposed to higher light intensities. Our results suggest partially overlapping functions of GPX1 and GPX7. The data further point to specific changes in the chloroplast ascorbate-glutathione cycle due to reduced cpGPX expression, initiating reactive oxygen species and salicylic acid pathways that affect leaf development, light acclimation, basal defense, and cell death programs. Thus, cpGPXs regulate cellular photooxidative tolerance and immune responses.

  • 29.
    Chen, Yang-Er
    et al.
    Univ Umea, Dept Chem, SE-90187 Umea, Sweden;Sichuan Agr Univ, Coll Life Sci, Yaan 625014, Peoples R China.
    Yuan, Shu
    Sichuan Agr Univ, Coll Resources Sci & Technol, Chengdu 611130, Sichuan, Peoples R China.
    Lezhneva, Lina
    Univ Umea, Dept Chem, SE-90187 Umea, Sweden.
    Meurer, Jörg
    Ludwig Maximilians Univ Munchen, Dept Biol 1, Plant Sci, D-82152 Munich, Planegg Martins, Germany.
    Schwenkert, Serena
    Ludwig Maximilians Univ Munchen, Dept Biol 1, Plant Sci, D-82152 Munich, Planegg Martins, Germany.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Schröder, Wolfgang P.
    Univ Umea, Dept Chem, SE-90187 Umea, Sweden.
    The Low Molecular Mass Photosystem II Protein PsbTn Is Important for Light Acclimation2019In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 179, no 4, p. 1739-1753Article in journal (Refereed)
    Abstract [en]

    Photosystem II (PSII) is a supramolecular complex containing over 30 protein subunits and a large set of cofactors, including various pigments and quinones as well as Mn, Ca, Cl, and Fe ions. Eukaryotic PSII complexes contain many subunits not found in their bacterial counterparts, including the proteins PsbP (PSII), PsbQ, PsbS, and PsbW, as well as the highly homologous, low-molecularmass subunits PsbTn1 and PsbTn2 whose function is currently unknown. To determine the function of PsbTn1 and PsbTn2, we generated single and double psbTn1 and psbTn2 knockout mutants in Arabidopsis (Arabidopsis thaliana). Cross linking and reciprocal coimmunoprecipitation experiments revealed that PsbTn is a lumenal PSII protein situated next to the cytochrome b(559 )subunit PsbE. The removal of the PsbTn proteins decreased the oxygen evolution rate and PSII core phosphorylation level but increased the susceptibility of PSII to photoinhibition and the production of reactive oxygen species. The assembly and stability of PSII were unaffected, indicating that the deficiencies of the psbTn1 psbTn2 double mutants are due to structural changes. Double mutants exhibited a higher rate of nonphotochemical quenching of excited states than the wild type and single mutants, as well as slower state transition kinetics and a lower quantum yield of PSII when grown in the field. Based on these results, we propose that the main function of the PsbTn proteins is to enable PSII to acclimate to light shifts or intense illumination.

  • 30.
    Chen, Yang-Er
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. College of Life Sciences, Sichuan Agricultural University, Ya’an, China; .
    Yuan, Shu
    Lezhneva, Lina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Meurer, Jörg
    Schwenkert, Serena
    Mamedov, Fikret
    Schröder, Wolfgang P.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The Low Molecular Mass Photosystem II Protein PsbTn is Important for Light Acclimation2019In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 179, no 4, p. 1739-1753Article in journal (Refereed)
    Abstract [en]

    Photosystem II (PSII) is a supramolecular complex containing over 30 protein subunits and a large set of cofactors including various pigments and quinones as well as Mn, Ca, Cl, and Fe ions. Eukaryotic PSII complexes contain many subunits not found in their bacterial counterparts, including the proteins PsbP, PsbQ, PsbS, and PsbW, as well as the highly homologous, low molecular mass subunits PsbTn1 and PsbTn2 whose function is currently unknown. To determine the function of PsbTn1 and PsbTn2, we generated single and double psbTn1 and psbTn2 knock-out mutants in Arabidopsis thaliana. Cross-linking and reciprocal co-immunoprecipitation experiments revealed that PsbTn is a lumenal PSII protein situated next to the cytochrome b559 subunit PsbE. The removal of the PsbTn proteins decreased the oxygen evolution rate and PSII core phosphorylation level but increased the susceptibility of PSII to photoinhibition and the production of reactive oxygen species. The assembly and stability of PSII were unaffected, indicating that the deficiencies of the psbTn1 psbTn2 double mutants are due to structural changes. Double mutants exhibited a higher rate of non-photochemical quenching of excited states than the wild type and single mutants, as well as slower state transition kinetics and a lower quantum yield of PSII when grown in the field. Based on these results, we propose that the main function of the PsbTn proteins is to enable PSII to acclimate to light shifts or intense illumination.

  • 31. Cho, Sung Hyun
    et al.
    Purushotham, Pallinti
    Fang, Chao
    Maranas, Cassandra
    Diaz-Moreno, Sara M
    KTH, School of Biotechnology (BIO), Glycoscience.
    Bulone, Vincent
    KTH, School of Biotechnology (BIO), Glycoscience.
    Zimmer, Jochen
    Kumar, Manish
    Nixon, B. Tracy
    Synthesis and Self-Assembly of Cellulose Microfibrils from Reconstituted Cellulose Synthase2017In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 175, no 1, p. 146-156Article in journal (Refereed)
    Abstract [en]

    Cellulose, the major component of plant cell walls, can be converted to bioethanol and is thus highly studied. In plants, cellulose is produced by cellulose synthase, a processive family-2 glycosyltransferase. In plant cell walls, individual beta-1,4-glucan chains polymerized by CesA are assembled into microfibrils that are frequently bundled into macrofibrils. An in vitro system in which cellulose is synthesized and assembled into fibrils would facilitate detailed study of this process. Here, we report the heterologous expression and partial purification of His-tagged CesA5 from Physcomitrella patens. Immunoblot analysis and mass spectrometry confirmed enrichment of PpCesA5. The recombinant protein was functional when reconstituted into liposomes made from yeast total lipid extract. The functional studies included incorporation of radiolabeled Glc, linkage analysis, and imaging of cellulose microfibril formation using transmission electron microscopy. Several microfibrils were observed either inside or on the outer surface of proteoliposomes, and strikingly, several thinner fibrils formed ordered bundles that either covered the surfaces of proteoliposomes or were spawned from liposome surfaces. We also report this arrangement of fibrils made by proteoliposomes bearing CesA8 from hybrid aspen. These observations describe minimal systems of membrane-reconstituted CesAs that polymerize beta-1,4-glucan chains that coalesce to form microfibrils and higher-ordered macrofibrils. How these micro-and macrofibrils relate to those found in primary and secondary plant cell walls is uncertain, but their presence enables further study of the mechanisms that govern the formation and assembly of fibrillar cellulosic structures and cell wall composites during or after the polymerization process controlled by CesA proteins.

  • 32.
    Chrobok, Daria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Law, Simon R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Brouwer, Bastiaan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Linden, Pernilla
    Ziolkowska, Agnieszka
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Liebsch, Daniela
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Narsai, Reena
    Szal, Bozena
    Moritz, Thomas
    Rouhier, Nicolas
    Whelan, James
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Keech, Olivier
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Dissecting the Metabolic Role of Mitochondria during Developmental Leaf Senescence2016In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 172, no 4, p. 2132-2153Article in journal (Refereed)
    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.

  • 33.
    Collani, Silvio
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Max Planck Institute for Developmental Biology,Department of Molecular Biology, Tübingen, Germany.
    Neumann, Manuela
    Yant, Levi
    Schmid, Markus
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. 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 FD2019In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 180, no 1, p. 367-380Article in journal (Refereed)
    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.

  • 34. Dauphinee, Adrian N.
    et al.
    Cardoso, Catarina
    Dalman, Kerstin
    Ohlsson, Jonas A.
    Berglund Fick, Stina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Robert, Stephanie
    Hicks, Glenn R.
    Bozhkov, Peter V
    Minina, Elena A.
    Chemical Screening Pipeline for Identification of Specific Plant Autophagy Modulators2019In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 181, no 3, p. 855-866Article in journal (Refereed)
    Abstract [en]

    Autophagy is a major catabolic process in eukaryotes with a key role in homeostasis, programmed cell death, and aging. In plants, autophagy is also known to regulate agronomically important traits such as stress resistance, longevity, vegetative biomass, and seed yield. Despite its significance, there is still a shortage of reliable tools modulating plant autophagy. Here, we describe the first robust pipeline for identification of specific plant autophagy-modulating compounds. Our screening protocol comprises four phases: (1) high-throughput screening of chemical compounds in cell cultures of tobacco (Nicotiana tabacum); (2) confirmation of the identified hits in planta using Arabidopsis (Arabidopsis thaliana); (3) further characterization of the effect using conventional molecular biology methods; and (4) verification of chemical specificity on autophagy in planta. The methods detailed here streamline the identification of specific plant autophagy modulators and aid in unraveling the molecular mechanisms of plant autophagy.

  • 35.
    de La Torre, Amanda R
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Birol, Inanc
    Bousquet, Jean
    Ingvarsson, Pär K
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Jones, Steven J. M
    Keeling, Christopher I
    MacKay, John
    Nilsson, Ove
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Ritland, Kermit
    Street, Nathaniel
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Yanchuk, Alvin
    Zerbe, Philipp
    Bohlmann, Jörg
    Insights into conifer giga-genomes2014In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 166, no 4, p. 1724-1732Article in journal (Refereed)
    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.

  • 36. Dewez, David
    et al.
    Park, Sungsoon
    García Cerdan, Jose Gines
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindberg, Pia
    Melis, Anastasios
    Mechanism of REP27 protein action in the D1 protein turnover and Photosystem II repair from photodamage2009In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 151, no 1, p. 88-99Article in journal (Refereed)
    Abstract [en]

    The function of the REP27 protein (GenBank accession no. EF127650) in the photosystem II (PSII) repair process was elucidated. REP27 is a nucleus-encoded and chloroplast-targeted protein containing two tetratricopeptide repeat (TPR) motifs, two putative transmembrane domains, and an extended carboxyl (C)-terminal region. Cell fractionation and western-blot analysis localized the REP27 protein in the Chlamydomonas reinhardtii chloroplast thylakoids. A folding model for REP27 suggested chloroplast stroma localization for amino- and C-terminal regions as well as the two TPRs. A REP27 gene knockout strain of Chlamydomonas, termed the rep27 mutant, was employed for complementation studies. The rep27 mutant was aberrant in the PSII-repair process and had substantially lower than wild-type levels of D1 protein. Truncated REP27 cDNA constructs were made for complementation of rep27, whereby TPR1, TPR2, TPR1+TPR2, or the C-terminal domains were deleted. rep27-complemented strains minus the TPR motifs showed elevated levels of D1 in thylakoids, comparable to those in the wild type, but the PSII photochemical efficiency of these strains was not restored, suggesting that the functionality of the PSII reaction center could not be recovered in the absence of the TPR motifs. It is suggested that TPR motifs play a role in the functional activation of the newly integrated D1 protein in the PSII reaction center. rep27-complemented strains missing the C-terminal domain showed low levels of D1 protein in thylakoids as well as low PSII photochemical efficiency, comparable to those in the rep27 mutant. Therefore, the C-terminal domain is needed for a de novo biosynthesis and/or assembly of D1 in the photodamaged PSII template. We conclude that REP27 plays a dual role in the regulation of D1 protein turnover by facilitating cotranslational biosynthesis insertion (C-terminal domain) and activation (TPR motifs) of the nascent D1 during the PSII repair process.

  • 37.
    Dewez, David
    et al.
    Department of Plant and Microbial Biology, University of California, Berkeley.
    Park, Sungsoon
    Department of Plant and Microbial Biology, University of California, Berkeley.
    García-Cerdán, Jose Gines
    Department of Plant and Microbial Biology, University of California, Berkeley.
    Lindberg, Pia
    Department of Plant and Microbial Biology, University of California, Berkeley.
    Melis, Anastasios
    Department of Plant and Microbial Biology, University of California, Berkeley.
    Mechanism of REP27 protein action in the D1 protein turnover and photosystem II repair from photodamage.2009In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 151, no 1, p. 88-99Article in journal (Refereed)
    Abstract [en]

    The function of the REP27 protein (GenBank accession no. EF127650) in the photosystem II (PSII) repair process was elucidated. REP27 is a nucleus-encoded and chloroplast-targeted protein containing two tetratricopeptide repeat (TPR) motifs, two putative transmembrane domains, and an extended carboxyl (C)-terminal region. Cell fractionation and western-blot analysis localized the REP27 protein in the Chlamydomonas reinhardtii chloroplast thylakoids. A folding model for REP27 suggested chloroplast stroma localization for amino- and C-terminal regions as well as the two TPRs. A REP27 gene knockout strain of Chlamydomonas, termed the rep27 mutant, was employed for complementation studies. The rep27 mutant was aberrant in the PSII-repair process and had substantially lower than wild-type levels of D1 protein. Truncated REP27 cDNA constructs were made for complementation of rep27, whereby TPR1, TPR2, TPR1+TPR2, or the C-terminal domains were deleted. rep27-complemented strains minus the TPR motifs showed elevated levels of D1 in thylakoids, comparable to those in the wild type, but the PSII photochemical efficiency of these strains was not restored, suggesting that the functionality of the PSII reaction center could not be recovered in the absence of the TPR motifs. It is suggested that TPR motifs play a role in the functional activation of the newly integrated D1 protein in the PSII reaction center. rep27-complemented strains missing the C-terminal domain showed low levels of D1 protein in thylakoids as well as low PSII photochemical efficiency, comparable to those in the rep27 mutant. Therefore, the C-terminal domain is needed for a de novo biosynthesis and/or assembly of D1 in the photodamaged PSII template. We conclude that REP27 plays a dual role in the regulation of D1 protein turnover by facilitating cotranslational biosynthesis insertion (C-terminal domain) and activation (TPR motifs) of the nascent D1 during the PSII repair process.

  • 38. Dubreuil, Carole
    et al.
    Jin, Xu
    Barajas-López, Juan de Dios
    Hewitt, Timothy C.
    Tanz, Sandra K.
    Dobrenel, Thomas
    Schröder, Wolfgang P.
    Hanson, Johannes
    Pesquet, Edouard
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Umeå University, Sweden.
    Grönlund, Andreas
    Small, Ian
    Strand, Åsa
    Establishment of Photosynthesis through Chloroplast Development Is Controlled by Two Distinct Regulatory Phases2018In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 176, no 2, p. 1199-1214Article in journal (Refereed)
    Abstract [en]

    Chloroplasts develop from undifferentiated proplastids present in meristematic tissue. Thus, chloroplast biogenesis is closely connected to leaf development, which restricts our ability to study the process of chloroplast biogenesis per se. As a consequence, we know relatively little about the regulatory mechanisms behind the establishment of the photosynthetic reactions and how the activities of the two genomes involved are coordinated during chloroplast development. We developed a single cell-based experimental system from Arabidopsis (Arabidopsis thaliana) with high temporal resolution allowing for investigations of the transition from proplastids to functional chloroplasts. Using this unique cell line, we could show that the establishment of photosynthesis is dependent on a regulatory mechanism involving two distinct phases. The first phase is triggered by rapid light-induced changes in gene expression and the metabolome. The second phase is dependent on the activation of the chloroplast and generates massive changes in the nuclear gene expression required for the transition to photosynthetically functional chloroplasts. The second phase also is associated with a spatial transition of the chloroplasts from clusters around the nucleus to the final position at the cell cortex. Thus, the establishment of photosynthesis is a two-phase process with a clear checkpoint associated with the second regulatory phase allowing coordination of the activities of the nuclear and plastid genomes.

  • 39.
    Dubreuil, Carole
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Jin, Xu
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Barajas-López, Juan de Dios
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Hewitt, Timothy C.
    Tanz, Sandra K.
    Dobrenel, Thomas
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Schröder, Wolfgang P.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hanson, Johannes
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Pesquet, Edouard
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Arrhenius Laboratory, Department of Ecology, Environment, and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
    Grönlund, Andreas
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Small, Ian
    Strand, Åsa
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Establishment of Photosynthesis through Chloroplast Development Is Controlled by Two Distinct Regulatory Phases2018In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 176, no 2, p. 1199-1214Article in journal (Refereed)
    Abstract [en]

    Chloroplasts develop from undifferentiated proplastids present in meristematic tissue. Thus, chloroplast biogenesis is closely connected to leaf development, which restricts our ability to study the process of chloroplast biogenesis per se. As a consequence, we know relatively little about the regulatory mechanisms behind the establishment of the photosynthetic reactions and how the activities of the two genomes involved are coordinated during chloroplast development. We developed a single cell-based experimental system from Arabidopsis (Arabidopsis thaliana) with high temporal resolution allowing for investigations of the transition from proplastids to functional chloroplasts. Using this unique cell line, we could show that the establishment of photosynthesis is dependent on a regulatory mechanism involving two distinct phases. The first phase is triggered by rapid light-induced changes in gene expression and the metabolome. The second phase is dependent on the activation of the chloroplast and generates massive changes in the nuclear gene expression required for the transition to photosynthetically functional chloroplasts. The second phase also is associated with a spatial transition of the chloroplasts from clusters around the nucleus to the final position at the cell cortex. Thus, the establishment of photosynthesis is a two-phase process with a clear checkpoint associated with the second regulatory phase allowing coordination of the activities of the nuclear and plastid genomes.

  • 40. Dun, Xiaoling
    et al.
    Shen, Wenhao
    Hu, Kaining
    Zhou, Zhengfu
    Xia, Shengqian
    Wen, Jing
    Yi, Bin
    Shen, Jinxiong
    Ma, Chaozhi
    Tu, Jinxing
    Fu, Tingdong
    Lagercrantz, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Neofunctionalization of Duplicated Tic40 Genes Caused a Gain-of-Function Variation Related to Male Fertility in Brassica oleracea Lineages2014In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 166, no 3, p. 1403-1419Article in journal (Refereed)
    Abstract [en]

    Gene duplication followed by functional divergence in the event of polyploidization is a major contributor to evolutionary novelties. The Brassica genus evolved from a common ancestor after whole-genome triplication. Here, we studied the evolutionary and functional features of Brassica spp. homologs to Tic40 (for translocon at the inner membrane of chloroplasts with 40 kDa). Four Tic40 loci were identified in allotetraploid Brassica napus and two loci in each of three basic diploid Brassica spp. Although these Tic40 homologs share high sequence identities and similar expression patterns, they exhibit altered functional features. Complementation assays conducted on Arabidopsis thaliana tic40 and the B. napus male-sterile line 7365A suggested that all Brassica spp. Tic40 homologs retain an ancestral function similar to that of AtTic40, whereas BolC9.Tic40 in Brassica oleracea and its ortholog in B. napus, BnaC9.Tic40, in addition, evolved a novel function that can rescue the fertility of 7365A. A homologous chromosomal rearrangement placed bnac9.tic40 originating from the A genome (BraA10.Tic40) as an allele of BnaC9.Tic40 in the C genome, resulting in phenotypic variation for male sterility in the B. napus near-isogenic two-type line 7365AB. Assessment of the complementation activity of chimeric B. napus Tic40 domain-swapping constructs in 7365A suggested that amino acid replacements in the carboxyl terminus of BnaC9.Tic40 cause this functional divergence. The distribution of these amino acid replacements in 59 diverse Brassica spp. accessions demonstrated that the neofunctionalization of Tic40 is restricted to B. oleracea and its derivatives and thus occurred after the divergence of the Brassica spp. A, B, and C genomes.

  • 41. Eisenhut, Marion
    et al.
    Kahlon, Shira
    Hasse, Dirk
    University of Rostock, Germany.
    Ewald, Ralph
    Lieman-Hurwitz, Judy
    Ogawa, Teruo
    Ruth, Wolfgang
    Bauwe, Hermann
    Kaplan, Aaron
    Hagemann, Martin
    The plant-like C2 glycolate cycle and the bacterial-like glycerate pathway cooperate in phosphoglycolate metabolism in cyanobacteria.2006In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 142, no 1Article in journal (Refereed)
    Abstract [en]

    The occurrence of a photorespiratory 2-phosphoglycolate metabolism in cyanobacteria is not clear. In the genome of the cyanobacterium Synechocystis sp. strain PCC 6803, we have identified open reading frames encoding enzymes homologous to those forming the plant-like C2 cycle and the bacterial-type glycerate pathway. To study the route and importance of 2-phosphoglycolate metabolism, the identified genes were systematically inactivated by mutagenesis. With a few exceptions, most of these genes could be inactivated without leading to a high-CO(2)-requiring phenotype. Biochemical characterization of recombinant proteins verified that Synechocystis harbors an active serine hydroxymethyltransferase, and, contrary to higher plants, expresses a glycolate dehydrogenase instead of an oxidase to convert glycolate to glyoxylate. The mutation of this enzymatic step, located prior to the branching of phosphoglycolate metabolism into the plant-like C2 cycle and the bacterial-like glycerate pathway, resulted in glycolate accumulation and a growth depression already at high CO(2). Similar growth inhibitions were found for a single mutant in the plant-type C2 cycle and more pronounced for a double mutant affected in both the C2 cycle and the glycerate pathway after cultivation at low CO(2). These results suggested that cyanobacteria metabolize phosphoglycolate by the cooperative action of the C2 cycle and the glycerate pathway. When exposed to low CO(2), glycine decarboxylase knockout mutants accumulated far more glycine and lysine than wild-type cells or mutants with inactivated glycerate pathway. This finding and the growth data imply a dominant, although not exclusive, role of the C2 route in cyanobacterial phosphoglycolate metabolism.

  • 42.
    Eklöf, Jens M.
    et al.
    KTH, School of Biotechnology (BIO), Glycoscience.
    Brumer, Harry
    KTH, School of Biotechnology (BIO), Glycoscience.
    The XTH Gene Family: An Update on Enzyme Structure, Function, and Phylogeny in Xyloglucan Remodeling2010In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 153, no 2, p. 456-466Article in journal (Refereed)
  • 43. Eriksson, M
    et al.
    Villand, P
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Induction and regulation of expression of a low-CO2-induced mitochondrial carbonic anhydrase in Chlamydomonas reinhardtii1998In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 116, no 2, p. 637-641Article in journal (Refereed)
    Abstract [en]

    The time course of and the influence of light intensity and light quality on the induction of a mitochondrial carbonic anhydrase (CA) in the unicellular green alga Chlamydomonas reinhardtii was characterized using western and northern blots. This CA was expressed only under low-CO2 conditions (ambient air). In asynchronously grown cells, the mRNA was detected 15 min after transfer from air containing 5% CO2 to ambient air, and the 21-kD polypeptide was detected on western blots after 1 h. When transferred back to air containing 5% CO2, the mRNA disappeared within 1 h and the polypeptide was degraded within 3 d. Photosynthesis was required for the induction in asynchronous cultures. The induction increased with light up to 500 mu mol m(-2) s(-1), where saturation occurred. In cells grown synchronously, however, expression of the mitochondrial CA was also detected in darkness. Under such conditions the expression followed a circadian rhythm, with mRNA appearing in the dark 30 min before the light was turned on. Algae left in darkness continued this rhythm for several days.

  • 44. Eriksson, Mats
    et al.
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    ISOLATION, PURIFICATION, AND CHARACTERIZATION OF MITOCHONDRIA FROM CHLAMYDOMONAS-REINHARDTII1995In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 107, no 2, p. 479-483Article in journal (Refereed)
    Abstract [en]

    Mitochondria were isolated from autotrophically grown Chlamydomonas reinhardtii cell-wall-less mutant CW 92. The cells were broken by vortexing with glass beads, and the mitochondria were collected by differential centrifugation and purified on a Percoll gradient. The isolated mitochondria oxidized malate, pyruvate, succinate, NADH, and a-ketoglutarate. Respiratory control was obtained with malate (2.0) and pyruvate (2.2) but not with the other substrates. From experiments with KCN and salicylhydroxamic acid, it was estimated that the capacity of the cytochrome pathway was at least 100 nmol O-2 mg(-1) protein min(-1) and the capacity of the alternative oxidase was at least 50 nmol O-2 mg(-1) protein min(-1). A low sensitivity to oligomycin indicates some difference in the properties of the mitochondrial ATPase from Chlamydomonas as compared to higher plants.

  • 45.
    Eriksson, Sylvia
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Eremina, Nadejda
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Barth, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Danielsson, Jens
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Harryson, Pia
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Membrane-Induced Folding of the Plant Stress Dehydrin Lti302016In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 171, no 2, p. 932-943Article in journal (Refereed)
    Abstract [en]

    Dehydrins are disordered proteins that are expressed in plants as a response to embryogenesis and water-related stress. The molecular function and structural action of the dehydrins are yet elusive, but increasing evidence points to a role in protecting the structure and functional dynamics of cell membranes. An intriguing example is the cold-induced dehydrin Lti30 that binds to membranes by its conserved K segments. Moreover, this binding can be regulated by pH and phosphorylation and shifts the membrane phase transition to lower temperatures, consistent with the protein's postulated function in cold stress. In this study, we reveal how the Lti30-membrane interplay works structurally at atomic level resolution in Arabidopsis (Arabidopsis thaliana). Nuclear magnetic resonance analysis suggests that negatively charged lipid head groups electrostatically capture the protein's disordered K segments, which locally fold up into a-helical segments on the membrane surface. Thus, Lti30 conforms to the general theme of structure-function relationships by folding upon binding, in spite of its disordered, atypically hydrophilic and repetitive sequence signatures. Moreover, the fixed and well-defined structure of the membrane-bound K segments suggests that dehydrins have the molecular prerequisites for higher level binding specificity and regulation, raising new questions about the complexity of their biological function.

  • 46. Erling Tjus, Staffan
    et al.
    Vibe Scheller, Henrik
    Andersson, Bertil
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Biomedicine and Surgery, Cell biology.
    Lindberg Möller, Birger
    Active oxygen produced during selective excitation of photosystem I is damaging not only to photosystem I, but also to photosystem II.2001In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 125, p. 2007-2015Article in journal (Refereed)
  • 47. Felten, Judith
    et al.
    Kohler, Annegret
    Morin, Emmanuelle
    Bhalerao, Rishikesh P
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Palme, Klaus
    Martin, Francis
    Ditengou, Franck A
    Legue, Valerie
    The ectomycorrhizal fungus laccaria bicolor stimulates lateral root formation in poplar and arabidopsis through auxin transport and signaling2009In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 151, no 4, p. 1991-2005Article in journal (Refereed)
    Abstract [en]

    The early phase of the interaction between tree roots and ectomycorrhizal fungi, prior to symbiosis establishment, is accompanied by a stimulation of lateral root (LR) development. We aimed to identify gene networks that regulate LR development during the early signal exchanges between poplar (Populus tremula x Populus alba) and the ectomycorrhizal fungus Laccaria bicolor with a focus on auxin transport and signaling pathways. Our data demonstrated that increased LR development in poplar and Arabidopsis (Arabidopsis thaliana) interacting with L. bicolor is not dependent on the ability of the plant to form ectomycorrhizae. LR stimulation paralleled an increase in auxin accumulation at root apices. Blocking plant polar auxin transport with 1-naphthylphthalamic acid inhibited LR development and auxin accumulation. An oligoarray-based transcript profile of poplar roots exposed to molecules released by L. bicolor revealed the differential expression of 2,945 genes, including several components of polar auxin transport (PtaPIN and PtaAUX genes), auxin conjugation (PtaGH3 genes), and auxin signaling (PtaIAA genes). Transcripts of PtaPIN9, the homolog of Arabidopsis AtPIN2, and several PtaIAAs accumulated specifically during the early interaction phase. Expression of these rapidly induced genes was repressed by 1-naphthylphthalamic acid. Accordingly, LR stimulation upon contact with L. bicolor in Arabidopsis transgenic plants defective in homologs of these genes was decreased or absent. Furthermore, in Arabidopsis pin2, the root apical auxin increase during contact with the fungus was modified. We propose a model in which fungus-induced auxin accumulation at the root apex stimulates LR formation through a mechanism involving PtaPIN9-dependent auxin redistribution together with PtaIAA-based auxin signaling.

  • 48. Forslund, Karin
    Biosynthesis of the Nitrile Glucosides Rhodiocyanoside A and D and the Cyanogenic Glucosides Lotaustralin and Linamarin in Lotus japonicus.2004In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 135, p. 71-84Article in journal (Refereed)
  • 49. Forslund, Karin
    et al.
    Bak, Soren
    Plant-Insect Interactions as a Response to Metabolic Engineering of Natural Product Synthesis studied by Functional Genomics in Lotus japonicus2003In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 131, p. 844-846Article in journal (Refereed)
  • 50. Fracheboud, Yvan
    et al.
    Luquez, Virginia
    Björkén, Lars
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sjödin, Andreas
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Tuominen, Hannele
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    The control of autumn senescence in European aspen2009In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 149, no 4, p. 1982-1991Article in journal (Refereed)
    Abstract [en]

    The initiation, progression, and natural variation of autumn senescence in European aspen (Populus tremula) was investigated by monitoring chlorophyll degradation in (1) trees growing in natural stands and (2) cloned trees growing in a greenhouse under various light regimes. The main trigger for the initiation of autumn senescence in aspen is the shortening photoperiod, but there was a large degree of variation in the onset of senescence, both within local populations and among trees originating from different populations, where it correlated with the latitude of their respective origins. The variation for onset of senescence with a population was much larger than the variation of bud set. Once started, autumn senescence was accelerated by low temperature and longer nights, and clones that started to senescence late had a faster senescence. Bud set and autumn senescence appeared to be under the control of two independent critical photoperiods, but senescence could not be initiated until a certain time after bud set, suggesting that bud set and growth arrest are important for the trees to acquire competence to respond to the photoperiodic trigger to undergo autumn senescence. A timetable of events related to bud set and autumn senescence is presented.

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