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  • 51. KROL, M
    et al.
    SPANGFORT, MD
    HUNER, NPA
    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).
    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).
    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).
    CHLOROPHYLL A/B-BINDING PROTEINS, PIGMENT CONVERSIONS, AND EARLY LIGHT-INDUCED PROTEINS IN A CHLOROPHYLL B-LESS BARLEY MUTANT1995In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 107, no 3, p. 873-883Article in journal (Refereed)
    Abstract [en]

    Monospecific polyclonal antibodies have been raised against synthetic peptides derived from the primary sequences from different plant light-harvesting Chl a/b-binding (LHC) proteins. Together with other monospecific antibodies, these were used to quantify the levels of the 10 different LHC proteins in wild-type and chlorina 12 barley (Hordeum vulgare L.), grown under normal and intermittent light (ImL). Chlorina 12, grown under normal light, lacked Lhcb1 (type I LHC II) and Lhcb6 (CP24) and had reduced amounts of Lhcb2, Lhcb3 (types II and III LHC II), and Lhcb4 (CP 29). Chlorina f2 grown under ImL lacked all LHC proteins, whereas wild-type ImL plants contained Lhcb5 (CP 26) and a small amount of Lhcb2. The chlorina f2 ImL thylakoids were organized in large parallel arrays, but wild-type ImL thylakoids had appressed regions, indicating a possible role for Lhcb5 in grana stacking. Chlorina f2 grown under ImL contained considerable amounts of violaxanthin (2-3/reaction center), representing a pool of phototransformable xanthophyll cycle pigments not associated with LHC proteins. Chlorina f2 and the plants grown under ImL also contained early light-induced proteins (ELIPs) as monitored by western blotting. The levels of both ELIPs and xanthophyll cycle pigments increased during a 1 h of high light treatment, without accumulation of LHC proteins. These data are consistent with the hypothesis that ELIPs are pigment-binding proteins, and we suggest that ELIPs bind photoconvertible xanthophylls and replace ''normal'' LHC proteins under conditions of light stress.

  • 52. KROMER, S
    et al.
    MALMBERG, G
    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).
    MITOCHONDRIAL CONTRIBUTION TO PHOTOSYNTHETIC METABOLISM - A STUDY WITH BARLEY (HORDEUM-VULGARE L) LEAF PROTOPLASTS AT DIFFERENT LIGHT INTENSITIES AND CO2 CONCENTRATIONS1993In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 102, no 3, p. 947-955Article in journal (Refereed)
    Abstract [en]

    An oligomycin concentration that specifically inhibits oxidative Phosphorylation was added to isolated barley (Hordeum vulgare L.) leaf protoplasts at various irradiances and carbon dioxide concentrations. At saturating as well as low light intensities, photosynthetic oxygen evolution was decreased as a result of the oligomycin treatment, whereas no effect was observed at intermediate light intensities. This was the same for photorespiratory and nonphotorespiratory conditions. These results were confirmed by measurements of fluorescence quenching under the same conditions. Metabolite analysis in the presence of oligomycin revealed a drastic decrease in the mitochondrial and cytosolic ATP/ADP ratios, whereas there was little or no effect on the chloroplastic ratio. Concomitantly, sucrose phosphate synthase activity was reduced. Under high irradiances, this inhibition of sucrose synthesis by oligomycin apparently caused a feedback inhibition on the Calvin cycle and the photosynthetic activity. Under low irradiances, a feedback regulation compensated, indicating that light was more limiting than the activity of regulative enzymes. Thus, the importance of mitochondrial respiratory activity might be different in different metabolic situations. At saturating light, the oxidation of excess photosynthetic redox equivalents is required to sustain a high rate of photosynthesis. At low light, the supply of ATP to the cytosol might be required to support biosynthetic reactions.

  • 53. KRUPA, Z
    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).
    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).
    PHOTOINHIBITION AND RECOVERY OF PHOTOSYNTHESIS IN PSBA GENE-INACTIVATED STRAINS OF CYANOBACTERIUM ANACYSTIS-NIDULANS1990In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 93, no 1, p. 1-6Article in journal (Refereed)
  • 54. Laitinen, Teresa
    et al.
    Morreel, Kris
    Delhomme, Nicolas
    Gauthier, Adrien
    Schiffthaler, Bastian
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Nickolov, Kaloian
    Brader, Günter
    Lim, Kean-Jin
    Teeri, Teemu H.
    Street, Nathaniel R.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Boerjan, Wout
    Kärkönen, Anna
    A Key Role for Apoplastic H2O2 in Norway Spruce Phenolic Metabolism2017In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 174, no 3, p. 1449-1475Article in journal (Refereed)
    Abstract [en]

    Apoplastic events such as monolignol oxidation and lignin polymerization are difficult to study in intact trees. To investigate the role of apoplastic hydrogen peroxide (H2O2) in gymnosperm phenolic metabolism, an extracellular lignin-forming cell culture of Norway spruce (Picea abies) was used as a research model. Scavenging of apoplastic H2O2 by potassium iodide repressed lignin formation, in line with peroxidases activating monolignols for lignin polymerization. Time-course analyses coupled to candidate substrate-product pair network propagation revealed differential accumulation of low-molecular-weight phenolics, including (glycosylated) oligolignols, (glycosylated) flavonoids, and proanthocyanidins, in lignin-forming and H2O2-scavenging cultures and supported that monolignols are oxidatively coupled not only in the cell wall but also in the cytoplasm, where they are coupled to other monolignols and proanthocyanidins. Dilignol glycoconjugates with reduced structures were found in the culture medium, suggesting that cells are able to transport glycosylated dilignols to the apoplast. Transcriptomic analyses revealed that scavenging of apoplastic H2O2 resulted in remodulation of the transcriptome, with reduced carbon flux into the shikimate pathway propagating down to monolignol biosynthesis. Aggregated coexpression network analysis identified candidate enzymes and transcription factors for monolignol oxidation and apoplastic H2O2 production in addition to potential H2O2 receptors. The results presented indicate that the redox state of the apoplast has a profound influence on cellular metabolism.

  • 55.
    Lapointe, Line
    et al.
    Dep of Plant sciences, University of Wetern Ontario, Canada.
    Huner, Norman
    Dep of Plant sciences, University of Western Ontario, Canada.
    Carpentier, R
    Dep of Plant sciences, University of Western Ontario, Canada.
    Ottander, Christina
    Umeå University, Faculty of Science and Technology, Umeå Mathematics Education Research Centre (UMERC).
    Resistance to low temperature photoinhibition is not associated with isolated thylakoid membranes of winter rye.1991In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 97, no 2, p. 804-810Article in journal (Refereed)
    Abstract [en]

    In vivo measurements of chlorophyll a fluorescence indicate that cold-hardened winter rye (Secale cereale L. cv Musketeer) develops a resistance to low temperature-induced photoinhibition compared with nonhardened rye. After 7.2 hours at 5 degrees C and 1550 micromoles per square meter per second, the ratio of variable fluorescence/maximum fluorescence was depressed by only 23% in cold-hardened rye compared with 46% in nonhardened rye. We have tested the hypothesis that the principal site of this resistance to photoinhibition resides at the level of rye thylakoid membranes. Thylakoids were isolated from cold-hardened and nonhardened rye and exposed to high irradiance (1000-2600 micromoles per square meter per second) at either 5 or 20 degrees C. The photoinhibitory response measured by room temperature fluorescence induction, photosystem II electron transport, photoacoustic spectroscopy, or [(14)C]atrazine binding indicates that the differential resistance to low temperature-induced photoinhibition in vivo is not observed in isolated thylakoids. Similar results were obtained whether isolated rye thylakoids were photoinhibited or thylakoids were isolated from rye leaves preexposed to a photoinhibitory treatment. Thus, we conclude that increased resistance to low temperature-induced photoinhibition is not a property of thylakoid membranes but is associated with a higher level of cellular organization.

  • 56.
    Law, Simon R.
    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.
    Chrobok, Daria
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Juvany, Marta
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Delhomme, Nicolas
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Lindén, Pernilla
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Department of Forest Genetics and Physiology, Umeå Plant Science Centre, Swedish Agriculture University, Umeå, Sweden.
    Brouwer, Bastiaan
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Ahad, Abdul
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Moritz, Thomas
    Department of Forest Genetics and Physiology, Umeå Plant Science Centre, Swedish Agriculture University, Umeå, Sweden.
    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.
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Keech, Olivier
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Darkened leaves use different metabolic strategies for senescence and survival2018In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 177, no 1, p. 132-150Article in journal (Refereed)
    Abstract [en]

    In plants, an individually darkened leaf initiates senescence much more rapidly than a leaf from a whole darkened plant. Combining transcriptomic and metabolomic approaches in Arabidopsis (Arabidopsis thaliana), we present an overview of the metabolic strategies that are employed in response to different darkening treatments. Under darkened plant conditions, the perception of carbon starvation drove a profound metabolic readjustment in which branched-chain amino acids and potentially monosaccharides released from cell wall loosening became important substrates for maintaining minimal ATP production. Concomitantly, the increased accumulation of amino acids with a high nitrogen-carbon ratio may provide a safety mechanism for the storage of metabolically derived cytotoxic ammonium and a pool of nitrogen for use upon returning to typical growth conditions. Conversely, in individually darkened leaf, the metabolic profiling that followed our 13C-enrichment assays revealed a temporal and differential exchange of metabolites, including sugars and amino acids, between the darkened leaf and the rest of the plant. This active transport could be the basis for a progressive metabolic shift in the substrates fueling mitochondrial activities, which are central to the catabolic reactions facilitating the retrieval of nutrients from the senescing leaf. We propose a model illustrating the specific metabolic strategies employed by leaves in response to these two darkening treatments, which support either rapid senescence or a strong capacity for survival.

  • 57.
    Lernmark, U
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    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).
    Distribution of pyruvate-dehydrogenase complex activities between chloroplasts and mitochondria from leaves of different species1994In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 106, no 4, p. 1633-1638Article in journal (Refereed)
    Abstract [en]

    Protoplasts from barley (Hordeum vulgare), pea (Pisum sativum), wheat (Triticum aestivum), and spinach (Spinacia oleracea) leaves were fractionated into chloroplast- and mitochondrion-enriched fractions. Pyruvate dehydrogenase complex capacities in mitochondria (mtPDC) and chloroplasts (cpPDC) were measured in appropriate fractions under conditions optimal for each isozyme. The total cellular capacity of PDC was similar in barley and pea but about 50% lower in wheat and spinach. in pea a distribution of 87% mtPDC and 13% cpPDC was found on a cellular basis. In barley, wheat, and spinach the subcellular distribution was the opposite, with about 15% mtPDC and 85% cpPDC. cpPDC activity was constant at about 0.1 nmol cell(-1) h(-1) in cells from different regions along the developing barley leaf and showed no correlation with developmental patterns of photosynthetic parameters, such as increasing Chl and NADP-glyceraldehyde-3-phosphate dehydrogenase activity. Similarly, the capacity of the mitochondrial isoform did not change during barley leaf development and had a developmental pattern similar to that of citrate synthase and fumarase. Differences in subcellular distribution of PDCs in barley and pea are proposed to be due to differences in regulation, not to changes in isozyme proportions during leaf development or to species-specific differences in phosphorylation state of mtPDC after organelle separation.

  • 58. Lesniewska, Joanna
    et al.
    Ohman, David
    Krzeslowska, Magdalena
    Kushwah, Sunita
    Barciszewska-Pacak, Maria
    Kleczkowski, Leszek A.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sundberg, Bjorn
    Moritz, Thomas
    Mellerowicz, Ewa J.
    Defense Responses in Aspen with Altered Pectin Methylesterase Activity Reveal the Hormonal Inducers of Tyloses2017In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 173, no 2, p. 1409-1419Article in journal (Refereed)
    Abstract [en]

    Tyloses are ingrowths of parenchyma cells into the lumen of embolized xylem vessels, thereby protecting the remaining xylem from pathogens. They are found in heartwood, sapwood, and in abscission zones and can be induced by various stresses, but their molecular triggers are unknown. Here, we report that down-regulation of PECTIN METHYLESTERASE1 (PtxtPME1) in aspen (Populus tremula 3 tremuloides) triggers the formation of tyloses and activation of oxidative stress. We tested whether any of the oxidative stress-related hormones could induce tyloses in intact plantlets grown in sterile culture. Jasmonates, including jasmonic acid (JA) and methyl jasmonate, induced the formation of tyloses, whereas treatments with salicylic acid (SA) and 1-aminocyclopropane-1carboxylic acid (ACC) were ineffective. SA abolished the induction of tyloses by JA, whereas ACC was synergistic with JA. The ability of ACC to stimulate tyloses formation when combined with JA depended on ethylene (ET) signaling, as shown by a decrease in the response in ET-insensitive plants. Measurements of internal ACC and JA concentrations in wild-type and ET-insensitive plants treated simultaneously with these two compounds indicated that ACC and JA regulate each other's concentration in an ET-dependent manner. The findings indicate that jasmonates acting synergistically with ethylene are the key molecular triggers of tyloses.

  • 59. LONNEBORG, A
    et al.
    LIND, LK
    KALLA, SR
    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).
    ACCLIMATION PROCESSES IN THE LIGHT-HARVESTING SYSTEM OF THE CYANOBACTERIUM ANACYSTIS-NIDULANS FOLLOWING A LIGHT SHIFT FROM WHITE TO RED-LIGHT1985In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 78, no 1, p. 110-114Article in journal (Refereed)
  • 60. Mahboubi, Amir
    et al.
    Linden, Pernilla
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Moritz, Thomas
    Niittyla, Totte
    C-13 Tracking after (CO2)-C-13 Supply Revealed Diurnal Patterns of Wood Formation in Aspen2015In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 168, no 2, p. 478-489Article in journal (Refereed)
    Abstract [en]

    Wood of trees is formed from carbon assimilated in the photosynthetic tissues. Determining the temporal dynamics of carbon assimilation, subsequent transport into developing wood, and incorporation to cell walls would further our understanding of wood formation in particular and tree growth in general. To investigate these questions, we designed a (CO2)-C-13 labeling system to study carbon transport and incorporation to developing wood of hybrid aspen (Populus tremula 3 tremuloides). Tracking of C-13 incorporation to wood over a time course using nuclear magnetic resonance spectroscopy revealed diurnal patterns in wood cell wall biosynthesis. The dark period had a differential effect on C-13 incorporation to lignin and cell wall carbohydrates. No C-13 was incorporated into aromatic amino acids of cell wall proteins in the dark, suggesting that cell wall protein biosynthesis ceased during the night. The results show previously unrecognized temporal patterns in wood cell wall biosynthesis, suggest diurnal cycle as a possible cue in the regulation of carbon incorporation to wood, and establish a unique C-13 labeling method for the analysis of wood formation and secondary growth in trees.

  • 61. Mahboubi, Amir
    et al.
    Ratke, Christine
    Gorzsas, Andras
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kumar, Manoj
    Mellerowicz, Ewa J.
    Niittyla, Totte
    Aspen SUCROSE TRANSPORTER3 Allocates Carbon into Wood Fibers2013In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 163, no 4, p. 1729-1740Article in journal (Refereed)
    Abstract [en]

    Wood formation in trees requires carbon import from the photosynthetic tissues. In several tree species, including Populus species, the majority of this carbon is derived from sucrose (Suc) transported in the phloem. The mechanism of radial Suc transport from phloem to developing wood is not well understood. We investigated the role of active Suc transport during secondary cell wall formation in hybrid aspen (Populus tremula x Populus tremuloides). We show that RNA interference-mediated reduction of PttSUT3 (for Suc/H+ symporter) during secondary cell wall formation in developing wood caused thinner wood fiber walls accompanied by a reduction in cellulose and an increase in lignin. Suc content in the phloem and developing wood was not significantly changed. However, after (CO2)-C-13 assimilation, the SUT3RNAi lines contained more C-13 than the wild type in the Suc-containing extract of developing wood. Hence, Suc was transported into developing wood, but the Suc-derived carbon was not efficiently incorporated to wood fiber walls. A yellow fluorescent protein: PttSUT3 fusion localized to plasma membrane, suggesting that reduced Suc import into developing wood fibers was the cause of the observed cell wall phenotype. The results show the importance of active Suc transport for wood formation in a symplasmically phloem-loading tree species and identify PttSUT3 as a principal transporter for carbon delivery into secondary cell wall-forming wood fibers.

  • 62.
    Mao, Hailiang
    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.
    Nakamura, Moritaka
    Viotti, Corrado
    Grebe, Markus
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Institute of Biochemistry and Biology, Plant Physiology, University of Potsdam, Germany.
    A Framework for Lateral Membrane Trafficking and Polar Tethering of the PEN3 ATP-Binding Cassette Transporter2016In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 172, no 4, p. 2245-2260Article in journal (Refereed)
    Abstract [en]

    The outermost cell layer of plants, the epidermis, and its outer (lateral) membrane domain facing the environment are continuously challenged by biotic and abiotic stresses. Therefore, the epidermis and the outer membrane domain provide important selective and protective barriers. However, only a small number of specifically outer membrane-localized proteins are known. Similarly, molecular mechanisms underlying the trafficking and the polar placement of outer membrane domain proteins require further exploration. Here, we demonstrate that ACTIN7 (ACT7) mediates trafficking of the PENETRATION3 (PEN3) outer membrane protein from the trans-Golgi network (TGN) to the plasma membrane in the root epidermis of Arabidopsis (Arabidopsis thaliana) and that actin function contributes to PEN3 endocytic recycling. In contrast to such generic ACT7-dependent trafficking from the TGN, the EXOCYST84b (EXO84b) tethering factor mediates PEN3 outer-membrane polarity. Moreover, precise EXO84b placement at the outer membrane domain itself requires ACT7 function. Hence, our results uncover spatially and mechanistically distinct requirements for ACT7 function during outer lateral membrane cargo trafficking and polarity establishment. They further identify an exocyst tethering complex mediator of outer lateral membrane cargo polarity.

  • 63. Mateo, Alfonso
    et al.
    Mühlenbock, Per
    Rustérucci, Christine
    Chang, Christine Chi-Chen
    Miszalski, Zbigniew
    Karpinska, Barbara
    Parker, Jane E
    Mullineaux, Philip M
    Karpinski, Stanislaw
    Umeå University, Faculty of Science and Technology, Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre.
    LESION SIMULATING DISEASE 1 is required for acclimation to conditions that promote excess excitation energy.2004In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 136, no 1, p. 2818-30Article in journal (Refereed)
    Abstract [en]

    The lsd1 mutant of Arabidopsis fails to limit the boundaries of hypersensitive cell death response during avirulent pathogen infection and initiates unchecked lesions in long day photoperiod giving rise to the runaway cell death (rcd) phenotype. We link here the initiation and propagation of rcd to the activity of photosystem II, stomatal conductance and ultimately to photorespiratory H(2)O(2). A cross of lsd1 with the chlorophyll a/b binding harvesting-organelle specific (designated cao) mutant, which has a reduced photosystem II antenna, led to reduced lesion formation in the lsd1/cao double mutant. This lsd1 mutant also had reduced stomatal conductance and catalase activity in short-day permissive conditions and induced H(2)O(2) accumulation followed by rcd when stomatal gas exchange was further impeded. All of these traits depended on the defense regulators EDS1 and PAD4. Furthermore, nonphotorespiratory conditions retarded propagation of lesions in lsd1. These data suggest that lsd1 failed to acclimate to light conditions that promote excess excitation energy (EEE) and that LSD1 function was required for optimal catalase activity. Through this regulation LSD1 can influence the effectiveness of photorespiration in dissipating EEE and consequently may be a key determinant of acclimatory processes. Salicylic acid, which induces stomatal closure, inhibits catalase activity and triggers the rcd phenotype in lsd1, also impaired acclimation of wild-type plants to conditions that promote EEE. We propose that the roles of LSD1 in light acclimation and in restricting pathogen-induced cell death are functionally linked.

  • 64. Mikami, Koji
    et al.
    Saavedra, Laura
    Hiwatashi, Yuji
    Uji, Toshiki
    Hasebe, Mitsuyasu
    Sommarin, Marianne
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    A dibasic amino acid pair conserved in the activation loop directs plasma membrane localization and is necessary for activity of plant type I/II Phosphatidylinositol Phosphate Kinase2010In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 153, no 3, p. 1004-1015Article in journal (Refereed)
    Abstract [en]

    Phosphatidylinositol phosphate kinase (PIPK) is an enzyme involved in the regulation of cellular levels of phosphoinositides involved in various physiological processes, such as cytoskeletal organization, ion channel activation, and vesicle trafficking. In animals, research has focused on the modes of activation and function of PIPKs, providing an understanding of the importance of plasma membrane localization. However, it still remains unclear how this issue is regulated in plant PIPKs. Here, we demonstrate that the carboxyl-terminal catalytic domain, which contains the activation loop, is sufficient for plasma membrane localization of PpPIPK1, a type I/II B PIPK from the moss Physcomitrella patens. The importance of the carboxyl-terminal catalytic domain for plasma membrane localization was confirmed with Arabidopsis (Arabidopsis thaliana) AtPIP5K1. Our findings, in which substitution of a conserved dibasic amino acid pair in the activation loop of PpPIPK1 completely prevented plasma membrane targeting and abolished enzymatic activity, demonstrate its critical role in these processes. Placing our results in the context of studies of eukaryotic PIPKs led us to conclude that the function of the dibasic amino acid pair in the activation loop in type I/II PIPKs is plant specific.

  • 65. Mirjam, Esther
    et al.
    Dohmann, Natascha
    Levesque, Mitchell Paul
    Isono, Erika
    Schmid, Markus
    Department of Developmental Genetics, Center for Plant Molecular Biology, Tübingen University, 72076 Tuebingen, Germany.
    Schwechheimer, Claus
    Auxin responses in mutants of the Arabidopsis CONSTITUTIVE PHOTOMORPHOGENIC9 signalosome2008In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 147, no 3, p. 1369-1379Article in journal (Refereed)
  • 66. Myouga, Fumiyoshi
    et al.
    Takahashi, Kaori
    Tanaka, Ryoichi
    Nagata, Noriko
    Kiss, Anett Z.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nomura, Yuko
    Nakagami, Hirofumi
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Shinozaki, Kazuo
    Stable accumulation of photosystem II requires one-helix protein1 (OHP1) of the light harvesting-like family2018In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 176, no 3, p. 2277-2291Article in journal (Refereed)
    Abstract [en]

    The cellular functions of two Arabidopsis (Arabidopsis thaliana) one-helix proteins, OHP1 and OHP2 (also named LIGH-THARVESTING-LIKE2 [LIL2] and LIL6, respectively, because they have sequence similarity to light-harvesting chlorophyll a/b-binding proteins), remain unclear. Tagged null mutants of OHP1 and OHP2 (ohp1 and ohp2) showed stunted growth with pale-green leaves on agar plates, and these mutants were unable to grow on soil. Leaf chlorophyll fluorescence and the composition of thylakoid membrane proteins revealed that ohp1 deletion substantially affected photosystem II (PSII) core protein function and led to reduced levels of photosystem I core proteins; however, it did not affect LHC accumulation. Transgenic ohp1 plants rescued with OHP1-HA or OHP1-Myc proteins developed a normal phenotype. Using these tagged OHP1 proteins in transgenic plants, we localized OHP1 to thylakoid membranes, where it formed protein complexes with both OHP2 and High Chlorophyll Fluorescence244 (HCF244). We also found PSII core proteins D1/D2, HCF136, and HCF173 and a few other plant-specific proteins associated with the OHP1/OHP2-HCF244 complex, suggesting that these complexes are early intermediates in PSII assembly. OHP1 interacted directly with HCF244 in the complex. Therefore, OHP1 and HCF244 play important roles in the stable accumulation of PSII.

  • 67. Nakamura, Moritaka
    et al.
    Claes, Andrea R.
    Grebe, Tobias
    Hermkes, Rebecca
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Viotti, Corrado
    Ikeda, Yoshihisa
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Grebe, Markus
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Auxin and ROP GTPase Signaling of Polar Nuclear Migration in Root Epidermal Hair Cells2018In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 176, no 1, p. 378-391Article in journal (Refereed)
    Abstract [en]

    Polar nuclear migration is crucial during the development of diverse eukaryotes. In plants, root hair growth requires polar nuclear migration into the outgrowing hair. However, knowledge about the dynamics and the regulatory mechanisms underlying nuclear movements in root epidermal cells remains limited. Here, we show that both auxin and Rho-of-Plant (ROP) signaling modulate polar nuclear position at the inner epidermal plasma membrane domain oriented to the cortical cells during cell elongation as well as subsequent polar nuclear movement to the outer domain into the emerging hair bulge in Arabidopsis (Arabidopsis thaliana). Auxin signaling via the nuclear AUXIN RESPONSE FACTOR7 (ARF7)/ARF19 and INDOLE ACETIC ACID7 pathway ensures correct nuclear placement toward the inner membrane domain. Moreover, precise inner nuclear placement relies on SPIKE1 Rho-GEF, SUPERCENTIPEDE1 Rho-GDI, and ACTIN7 (ACT7) function and to a lesser extent on VTI11 vacuolar SNARE activity. Strikingly, the directionality and/or velocity of outer polar nuclear migration into the hair outgrowth along actin strands also are ACT7 dependent, auxin sensitive, and regulated by ROP signaling. Thus, our findings provide a founding framework revealing auxin and ROP signaling of inner polar nuclear position with some contribution by vacuolar morphology and of actin-dependent outer polar nuclear migration in root epidermal hair cells.

  • 68. NILSSON, O
    et al.
    MORITZ, T
    IMBAULT, N
    SANDBERG, G
    OLSSON, O
    HORMONAL CHARACTERIZATION OF TRANSGENIC TOBACCO PLANTS EXPRESSING THE ROLC GENE OF AGROBACTERIUM-RHIZOGENES TL-DNA1993In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 102, no 2, p. 363-371Article in journal (Refereed)
    Abstract [en]

    Transgenic tobacco (Nicotiana tabacum L. cv Wisconsin 38) plants expressing the Agrobacterium rhizogenes rolC gene under the control of the cauliflower mosaic virus 35S RNA promoter were constructed. These plants displayed several morphological alterations reminiscent of changes in indole-3-acetic acid (IAA), cytokinin, and gibberellin (GA) content. However, investigations showed that neither the IAA pool size nor its rate of turnover were altered significantly in the rolC plants. The biggest difference between rolC and wild-type plants was in the concentrations of the cytokinin, isopentenyladenosine (iPA) and the gibberellin GA19. Radioimmunoassay and liquid chromatography-mass spectrometry measurements revealed a drastic reduction in rolC plants of iPA as well as in several other cytokinins tested, suggesting a possible reduction in the synthesis rate of cytokinins. Furthermore, gas chromatography-mass spectrometry quantifications of GA19 showed a 5- to 6-fold increase in rolC plants compared with wild-type plants, indicating a reduced activity of the GA19 oxidase, a proposed regulatory step in the gibberellin biosynthesis. Thus, we conclude that RolC activity in transgenic plants leads to major alterations in the metabolism of cytokinins and gibberellins.

  • 69.
    Norén, Louise
    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).
    Kindgren, Peter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Copenhagen Plant Science Centre, University of Copenhagen.
    Stachula, Paulina
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Rühl, Mark
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Eriksson, Maria E.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    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).
    Strand, Åsa
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Circadian and Plastid Signaling Pathways Are Integrated to Ensure Correct Expression of the CBF and COR Genes during Photoperiodic Growth2016In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 171, no 2, p. 1392-1406Article in journal (Refereed)
    Abstract [en]

    The circadian clock synchronizes a wide range of biological processes with the day/night cycle, and correct circadian regulation is essential for photosynthetic activity and plant growth. We describe here a mechanism where a plastid signal converges with the circadian clock to fine-tune the regulation of nuclear gene expression in Arabidopsis (Arabidopsis thaliana). Diurnal oscillations of tetrapyrrole levels in the chloroplasts contribute to the regulation of the nucleus-encoded transcription factors C-REPEAT BINDING FACTORS (CBFs). The plastid signal triggered by tetrapyrrole accumulation inhibits the activity of cytosolic HEAT SHOCK PROTEIN90 and, as a consequence, the maturation and stability of the clock component ZEITLUPE (ZTL). ZTL negatively regulates the transcription factor LONG HYPOCOTYL5 (HY5) and PSEUDO-RESPONSE REGULATOR5 (PRR5). Thus, low levels of ZTL result in a HY5- and PRR5-mediated repression of CBF3 and PRR5-mediated repression of CBF1 and CBF2 expression. The plastid signal thereby contributes to the rhythm of CBF expression and the downstream COLD RESPONSIVE expression during day/night cycles. These findings provide insight into how plastid signals converge with, and impact upon, the activity of well-defined clock components involved in circadian regulation.

  • 70.
    OQUIST, G
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    SEASONALLY INDUCED CHANGES IN ACYL LIPIDS AND FATTY-ACIDS OF CHLOROPLAST THYLAKOIDS OF PINUS-SILVESTRIS - A CORRELATION BETWEEN THE LEVEL OF UNSATURATION OF MONOGALACTOSYLDIGLYCERIDE AND THE RATE OF ELECTRON-TRANSPORT1982In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 69, no 4, p. 869-875Article in journal (Refereed)
  • 71.
    Oquist, Gunnar
    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).
    HURRY, VM
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    HUNER, NPA
    LOW-TEMPERATURE EFFECTS ON PHOTOSYNTHESIS AND CORRELATION WITH FREEZING TOLERANCE IN SPRING AND WINTER CULTIVARS OF WHEAT AND RYE1993In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 101, no 1, p. 245-250Article in journal (Refereed)
    Abstract [en]

    Winter cultivars of rye (Secale cereale L., cv Musketeer) and wheat (Triticum aestivum L. cvs Kharkov and Monopol), but not a spring cultivar of wheat (Glenlea), grown at cold-hardening temperatures showed, at high irradiances, a higher proportion of oxidized to reduced primary, stable quinone receptor (Q(A)) than did the same cultivars grown under nonhardening conditions. In addition, there was a positive correlation between the effects of low-growth temperature on this increased proportion of oxidized Q(A), and a concomitant increase in the capacity for photosynthesis, and LT50, the temperature at which 50% of the seedlings are killed, in cultivars showing different freezing tolerances. This suggests that low-temperature modulation of the photosynthetic apparatus may be an important factor during the induction of freezing resistance in cereals. Finally, the control of photosystem II photochemistry by nonphotochemical quenching of excitation energy was identical for nonhardened and cold-hardened winter rye. However, examination of measuring temperature effects per se revealed that, irrespective of growth temperature, nonphotochemical quenching exerted a stronger control on photosystem II photochemistry at 10-degrees-C rather than at 20-degrees-C.

  • 72. PALMQVIST, K
    et al.
    SJOBERG, S
    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 OF INORGANIC CARBON ACCUMULATION IN THE UNICELLULAR GREEN-ALGAE SCENEDESMUS-OBLIQUUS AND CHLAMYDOMONAS-REINHARDTII1988In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 87, no 2, p. 437-442Article in journal (Refereed)
  • 73. PALMQVIST, K
    et al.
    SUNDBLAD, LG
    WINGSLE, G
    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).
    ACCLIMATION OF PHOTOSYNTHETIC LIGHT REACTIONS DURING INDUCTION OF INORGANIC CARBON ACCUMULATION IN THE GREEN-ALGA CHLAMYDOMONAS-REINHARDTII1990In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 94, no 1, p. 357-366Article in journal (Refereed)
  • 74.
    Papazian, Stefano
    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.
    Khaling, Eliezer
    Bonnet, Christelle
    Lassueur, Steve
    Reymond, Philippe
    Moritz, Thomas
    Blande, James D.
    Albrectsen, Benedicte R.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Central Metabolic Responses to Ozone and Herbivory Affect Photosynthesis and Stomatal Closure2016In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 172, no 3, p. 2057-2078Article in journal (Refereed)
    Abstract [en]

    Plants have evolved adaptive mechanisms that allow them to tolerate a continuous range of abiotic and biotic stressors. Tropospheric ozone (O-3), a global anthropogenic pollutant, directly affects living organisms and ecosystems, including plant-herbivore interactions. In this study, we investigate the stress responses of Brassica nigra (wild black mustard) exposed consecutively to O-3 and the specialist herbivore Pieris brassicae. Transcriptomics and metabolomics data were evaluated using multivariate, correlation, and network analyses for the O-3 and herbivory responses. O-3 stress symptoms resembled those of senescence and phosphate starvation, while a sequential shift from O-3 to herbivory induced characteristic plant defense responses, including a decrease in central metabolism, induction of the jasmonic acid/ethylene pathways, and emission of volatiles. Omics network and pathway analyses predicted a link between glycerol and central energy metabolism that influences the osmotic stress response and stomatal closure. Further physiological measurements confirmed that while O-3 stress inhibited photosynthesis and carbon assimilation, sequential herbivory counteracted the initial responses induced by O-3, resulting in a phenotype similar to that observed after herbivory alone. This study clarifies the consequences of multiple stress interactions on a plant metabolic system and also illustrates how omics data can be integrated to generate new hypotheses in ecology and plant physiology.

  • 75. Pribil, Mathias
    et al.
    Sandoval-Ibanez, Omar
    Xu, Wenteng
    Sharma, Anurag
    Labs, Mathias
    Liu, Qiuping
    Galgenmueller, Carolina
    Schneider, Trang
    Wessels, Malgorzata
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Matsubara, Shizue
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Wanner, Gerhard
    Leister, Dario
    Fine-Tuning of Photosynthesis Requires CURVATURE THYLAKOID1-Mediated Thylakoid Plasticity2018In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 176, no 3, p. 2351-2364Article in journal (Refereed)
    Abstract [en]

    The thylakoid membrane system of higher plant chloroplasts consists of interconnected subdomains of appressed and nonappressed membrane bilayers, known as grana and stroma lamellae, respectively. CURVATURE THYLAKOID1 (CURT1) protein complexes mediate the shape of grana stacks in a dosage-dependent manner and facilitate membrane curvature at the grana margins, the interface between grana and stroma lamellae. Although grana stacks are highly conserved among land plants, the functional relevance of grana stacking remains unclear. Here, we show that inhibiting CURT1-mediated alteration of thylakoid ultrastructure in Arabidopsis (Arabidopsis thaliana) reduces photosynthetic efficiency and plant fitness under adverse, controlled, and natural light conditions. Plants that lack CURT1 show less adjustment of grana diameter, which compromises regulatory mechanisms like the photosystem II repair cycle and state transitions. Interestingly, CURT1A suffices to induce thylakoid membrane curvature in planta and thylakoid hyperbending in plants overexpressing CURT1A. We suggest that CURT1 oligomerization is regulated at the posttranslational level in a light-dependent fashion and that CURT1-mediated thylakoid plasticity plays an important role in fine-tuning photosynthesis and plant fitness during challenging growth conditions.

  • 76.
    Rahmani, Fatemeh
    et al.
    Molecular Plant Physiology, Utrecht University, Utrecht, The Netherlands; Centre for BioSystems Genomics, Wageningen, The Netherlands.
    Hummel, Maureen
    Molecular Plant Physiology, Utrecht University, Utrecht, The Netherlands; Centre for BioSystems Genomics, Wageningen, The Netherlands.
    Schuurmans, Jolanda
    Molecular Plant Physiology, Utrecht University, Utrecht, The Netherlands; Centre for BioSystems Genomics, Wageningen, The Netherlands.
    Wiese-Klinkenberg, Anika
    Molecular Plant Physiology, Utrecht University, Utrecht, The Netherlands; Centre for BioSystems Genomics, Wageningen, The Netherlands.
    Smeekens, Sjef
    Molecular Plant Physiology, Utrecht University, Utrecht, The Netherlands; Centre for BioSystems Genomics, Wageningen, The Netherlands.
    Hanson, Johannes
    Molecular Plant Physiology, Utrecht University, Utrecht, The Netherlands; Centre for BioSystems Genomics, Wageningen, The Netherlands.
    Sucrose control of translation mediated by an upstream open reading frame-encoded peptide2009In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 150, no 3, p. 1356-1367Article in journal (Refereed)
    Abstract [en]

    Regulation of gene expression through translational control is common in many organisms. The Arabidopsis (Arabidopsis thaliana) transcription factor bZIP11 is translational repressed in response to sucrose (Suc), resulting in Suc-regulated changes in amino acid metabolism. The 5' leader of the bZIP11 mRNA harbors several upstream open reading frames (uORFs), of which the second uORF is well conserved among bZIP11 homologous genes. The uORF2 element encodes a Suc control peptide (SC-peptide) of 28 residues that is sufficient for imposing Suc-induced repression of translation (SIRT) on a heterologous mRNA. Detailed analysis of the SC-peptide suggests that it functions as an attenuator peptide. Results suggest that the SC-peptide inhibits bZIP11 translation in response to high Suc levels by stalling the ribosome on the mRNA. The conserved noncanonical AUG contexts of bZIP11 uORFs allow inefficient translational initiation of the uORF, resulting in translation initiation of the scanning ribosome at the AUG codon of the bZIP11 main ORF. The results presented show that Suc-dependent signaling mediates differential translation of mRNAs containing SC-peptides encoding uORFs.

  • 77.
    Renberg, Linda
    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.
    Johansson, Annika I.
    Shutova, Tatiana
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Stenlund, Hans
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Aksmann, Anna
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Raven, John A.
    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).
    Moritz, Thomas
    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).
    A metabolomic approach to study major metabolite changes during acclimation to limiting CO2 in chlamydomonas reinhardtii2010In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 154, no 1, p. 187-196Article in journal (Refereed)
    Abstract [en]

    Using a gas chromatography-mass spectrometry-time of flight technique, we determined major metabolite changes during induction of the carbon-concentrating mechanism in the unicellular green alga Chlamydomonas reinhardtii. In total, 128 metabolites with significant differences between high-and low-CO2-grown cells were detected, of which 82 were wholly or partially identified, including amino acids, lipids, and carbohydrates. In a 24-h time course experiment, we show that the amino acids serine and phenylalanine increase transiently while aspartate and glutamate decrease after transfer to low CO2. The biggest differences were typically observed 3 h after transfer to low-CO2 conditions. Therefore, we made a careful metabolomic examination at the 3-h time point, comparing low-CO2 treatment to high-CO2 control. Five metabolites involved in photorespiration, 11 amino acids, and one lipid were increased, while six amino acids and, interestingly, 21 lipids were significantly lower. Our conclusion is that the metabolic pattern during early induction of the carbon-concentrating mechanism fit a model where photorespiration is increasing.

  • 78. Resman, Lars
    et al.
    Howe, Glenn
    Jonsen, David
    Englund, Madeleine
    Druart, Nathalie
    Schrader, Jarmo
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Skinner, Jeff
    Sjödin, Andreas
    Chen, Tony
    Bhalerao, Rishikesh P
    Components acting downstream of short day perception regulate differential cessation of cambial activity and associated responses in early and late clones of hybrid poplar2010In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 154, no 3, p. 1294-1303Article in journal (Refereed)
    Abstract [en]

    Short days (SDs) in autumn induce growth cessation, bud set, cold acclimation, and dormancy in trees of boreal and temperate forests, and these responses occur earlier in northern than in southern genotypes. Nevertheless, we know little about whether this variation results from differential perception of SDs or differential downstream responses to the SD signal or a combination of the two. We compared global patterns of SD-regulated gene expression in the stems of hybrid poplar (Populus trichocarpa × Populus deltoides) clones that differ in their SD-induced growth cessation in order to address this question. The timing of cessation of cambial cell division caused by SDs differed between the clones and was coincident with the change in the pattern of expression of the auxin-regulated genes. The clones also differed in the timing of their SD-regulated changes in the transcript abundance of genes associated with cold tolerance, starch breakdown, and storage protein accumulation. By analyzing the expression of homologs of FLOWERING LOCUS T, we demonstrated that the clones differed little in their perception of SDs under the growth conditions applied but differed substantially in the downstream responses manifested in the timing and magnitude of gene expression after SD treatment. These results demonstrate the existence of factors that act downstream of SD perception and can contribute to variation in SD-regulated adaptive photoperiodic responses in trees.

  • 79. Rigal, Adeline
    et al.
    Yordanov, Yordan S.
    Perrone, Irene
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Karlberg, Anna
    Tisserant, Emilie
    Bellini, Catherine
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Busov, Victor B.
    Martin, Francis
    Kohler, Annegret
    Bhalerao, Rishi
    Legue, Valerie
    The AINTEGUMENTA LIKE1 Homeotic Transcription Factor PtAIL1 controls the formation of Adventitious Root Primordia in Poplar2012In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 160, no 4, p. 1996-2006Article in journal (Refereed)
    Abstract [en]

    Adventitious rooting is an essential but sometimes rate-limiting step in the clonal multiplication of elite tree germplasm, because the ability to form roots declines rapidly with age in mature adult plant tissues. In spite of the importance of adventitious rooting, the mechanism behind this developmental process remains poorly understood. We have described the transcriptional profiles that are associated with the developmental stages of adventitious root formation in the model tree poplar (Populus trichocarpa). Transcriptome analyses indicate a highly specific temporal induction of the AINTEGUMENTA LIKE1 (PtAIL1) transcription factor of the AP2 family during adventitious root formation. Transgenic poplar samples that overexpressed PtAIL1 were able to grow an increased number of adventitious roots, whereas RNA interference mediated the down-expression of PtAIL1 expression, which led to a delay in adventitious root formation. Microarray analysis showed that the expression of 15 genes, including the transcription factors AGAMOUS-Like6 and MYB36, was overexpressed in the stem tissues that generated root primordia in PtAIL1-overexpressing plants, whereas their expression was reduced in the RNA interference lines. These results demonstrate that PtAIL1 is a positive regulator of poplar rooting that acts early in the development of adventitious roots.

  • 80.
    Samuelsson, Göran
    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).
    LONNEBORG, A
    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).
    THE SUSCEPTIBILITY OF PHOTOSYNTHESIS TO PHOTOINHIBITION AND THE CAPACITY OF RECOVERY IN HIGH AND LOW LIGHT GROWN CYANOBACTERIA, ANACYSTIS-NIDULANS1987In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 83, no 2, p. 438-441Article in journal (Refereed)
  • 81. SANDELIUS, AS
    et al.
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    LOCALIZATION OF GALACTOLIPID BIOSYNTHESIS IN ETIOPLASTS ISOLATED FROM DARK-GROWN WHEAT (TRITICUM-AESTIVUM L)1984In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 76, no 4, p. 1041-1046Article in journal (Refereed)
  • 82. Sane, P V
    et al.
    Ivanov, A G
    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).
    Huner, N P A
    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).
    Changes in the redox potential of primary and secondary electron-accepting quinones in photosystem II confer increased resistance to photoinhibition in low-temperature-acclimated arabidopsis2003In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 132, no 4, p. 2144-2151Article in journal (Refereed)
    Abstract [en]

    Exposure of control (non-hardened) Arabidopsis leaves for 2 h at high irradiance at 5 degreesC resulted in a 55% decrease in photosystem II (PSII) photochemical efficiency as indicated by FcFm. In contrast, cold-acclimated leaves exposed to the same conditions showed only a 22degreesC decrease in FupsilonFm. Thermoluminescence was used to assess the possible role(s) of PSII recombination events in this differential resistance to photoinhibition. Thermoluminescence measurements of PSH revealed that S(2)QA(-) recombination was shifted to higher temperatures, whereas the characteristic temperature of the S(2)Q(B)(-) recombination was shifted to lower temperatures in cold-acclimated plants. These shifts in recombination temperatures indicate higher activation energy for the S(2)Q(A)(-) redox, pair and lower activation energy for the S(2)Q(B) redoxpair. This results in an increase in the free-energy gap between P680(+)Q(A)(-) and P680(+)Pheo(-) and a narrowing of the free energy gap between primary and secondary electron-accepting quinones in PSH electron acceptors. We propose that these effects result in an increased population of reduced primary electron-accepting quinone in PSII, facilitating non-radiative P680(+)QA(-) radical pair recombination. Enhanced reaction center quenching was confirmed using in vivo chlorophyll fluorescence-quenching analysis. The enhanced dissipation of excess light energy within the reaction center of PSII, in part, accounts for the observed increase in resistance to high-light stress in cold-acclimated Arabidopsis plants.

  • 83. Schubert, Marian
    et al.
    Gronvold, Lars
    Sandve, Simen R.
    Hvidsten, Torgeir R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Fjellheim, Siri
    Evolution of Cold Acclimation and Its Role in Niche Transition in the Temperate Grass Subfamily Pooideae2019In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 180, no 1, p. 404-419Article in journal (Refereed)
    Abstract [en]

    The grass subfamily Pooideae dominates the grass floras in cold temperate regions and has evolved complex physiological adaptations to cope with extreme environmental conditions like frost, winter, and seasonality. One such adaptation is cold acclimation, wherein plants increase their frost tolerance in response to gradually falling temperatures and shorter days in the autumn. However, understanding how complex traits like cold acclimation evolve remains a major challenge in evolutionary biology. Here, we investigated the evolution of cold acclimation in Pooideae and found that a phylogenetically diverse set of Pooideae species displayed cold acclimation capacity. However, comparing differential gene expression after cold treatment in transcriptomes of five phylogenetically diverse species revealed widespread species-specific responses of genes with conserved sequences. Furthermore, we studied the correlation between gene family size and number of cold-responsive genes as well as between selection pressure on coding sequences of genes and their cold responsiveness. We saw evidence of protein-coding and regulatory sequence evolution as well as the origin of novel genes and functions contributing toward evolution of a cold response in Pooideae. Our results reflect that selection pressure resulting from global cooling must have acted on already diverged lineages. Nevertheless, conservation of cold-induced gene expression of certain genes indicates that the Pooideae ancestor may have possessed some molecular machinery to mitigate cold stress. Evolution of adaptations to seasonally cold climates is regarded as particularly difficult. How Pooideae evolved to transition from tropical to temperate biomes sheds light on how complex traits evolve in the light of climate changes.

  • 84.
    Sellstedt, Anita
    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).
    LINDBLAD, P
    ACTIVITIES, OCCURRENCE, AND LOCALIZATION OF HYDROGENASE IN FREE-LIVING AND SYMBIOTIC FRANKIA1990In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 92, no 3, p. 809-815Article in journal (Refereed)
  • 85.
    Sellstedt, Anita
    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).
    WINSHIP, LJ
    ACETYLENE, NOT ETHYLENE, INACTIVATES THE UPTAKE HYDROGENASE OF ACTINORHIZAL NODULES DURING ACETYLENE-REDUCTION ASSAYS1990In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 94, no 1, p. 91-94Article in journal (Refereed)
  • 86.
    Selstam, Eva
    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).
    SANDELIUS, AS
    A COMPARISON BETWEEN PROLAMELLAR BODIES AND PROTHYLAKOID MEMBRANES OF ETIOPLASTS OF DARK-GROWN WHEAT CONCERNING LIPID AND POLYPEPTIDE COMPOSITION1984In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 76, no 4, p. 1036-1040Article in journal (Refereed)
  • 87. Seo, M
    et al.
    Akaba, S
    Delarue, M
    Bellini, C
    Caboche, M
    Koshiba, T
    Higher expression of an aldehyde oxydase in the auxin overproducing superroot mutant of arabidopsis thaliana1998In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 116, p. 687-693Article in journal (Refereed)
  • 88. Seo, M.
    et al.
    Akaba, S.
    Oritani, T.
    Delarue, M.
    Bellini, C.
    Caboche, M.
    Koshiba, T.
    Higher activity of an aldehyde oxidase in the auxin-overproducing superroot1 mutant of Arabidopsis thaliana1998In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 116, no 2, p. 687-693Article in journal (Refereed)
    Abstract [en]

    Aldehyde oxidase (AO; EC 1.2.3.1) activity was measured in seedlings of wild type or an auxin-overproducing mutant, superroot1 (sur1), of Arabidopsis thaliana. Activity staining for AO after native polyacrylamide gel electrophoresis separation of seedling extracts revealed that there were three major bands with AO activity (AO1-3) in wild-type and mutant seedlings. One of them (AO1) had a higher substrate preference for indole-3-aldehyde. This AO activity was significantly higher in sur1 mutant seedlings than in the wild type. The difference in activity was most apparent 7 d after germination, the same time required for the appearance of the remarkable sur1 phenotype, which includes epinastic cotyledons, elongated hypocotyls, and enhanced root development. Higher activity was observed in the root and hypocotyl region of the mutant seedlings. We also assayed the indole-3-acetaldehyde oxidase activity in extracts by high-performance liquid chromatography detection of indole-3-acetic acid (IAA). The activity was about 5 times higher in the extract of the sur1 seedlings, indicating that AO1 also has a substrate preference for abscisic aldehyde. Treatment of the wild-type seedlings with picloram or IAA caused no significant increase in AO1 activity. This result suggested that the higher activity of AO1 in sur1 mutant seedlings was not induced by IAA accumulation and, thus, strongly supports the possible role of AO1 in IAA biosynthesis in Arabidopsis seedlings.

  • 89. Smakowska, Elwira
    et al.
    Skibior-Blaszczyk, Renata
    Czarna, Malgorzata
    Kolodziejczak, Marta
    Kwasniak-Owczarek, Malgorzata
    Parys, Katarzyna
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Janska, Hanna
    Lack of FTSH4 protease affects protein carbonylation, mitochondrial morphology and phospholipid content in mitochondria of Arabidopsis: new insights into a complex interplay2016In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 17, no 4, p. 2516-2535Article in journal (Refereed)
    Abstract [en]

    FTSH4 is one of the inner membrane-embedded ATP-dependent metalloproteases in mitochondria of Arabidopsis (Arabidopsis thaliana). In mutants impaired to express FTSH4, carbonylated proteins accumulated and leaf morphology was altered when grown under a short-day photoperiod, at 22°C, and a long-day photoperiod, at 30°C. To provide better insight into the function of FTSH4, we compared the mitochondrial proteomes and oxyproteomes of two ftsh4 mutants and wild-type plants grown under conditions inducing the phenotypic alterations. Numerous proteins from various submitochondrial compartments were observed to be carbonylated in the ftsh4 mutants, indicating a widespread oxidative stress. One of the reasons for the accumulation of carbonylated proteins in ftsh4 was the limited ATP-dependent proteolytic capacity of ftsh4 mitochondria, arising from insufficient ATP amount, probably as a result of an impaired oxidative phosphorylation (OXPHOS), especially complex V. In ftsh4, we further observed giant, spherical mitochondria coexisting among normal ones. Both effects, the increased number of abnormal mitochondria and the decreased stability/activity of the OXPHOS complexes, were probably caused by the lower amount of the mitochondrial membrane phospholipid cardiolipin. We postulate that the reduced cardiolipin content in ftsh4 mitochondria leads to perturbations within the OXPHOS complexes, generating more reactive oxygen species and less ATP, and to the deregulation of mitochondrial dynamics, causing in consequence the accumulation of oxidative damage.

  • 90.
    Sorin, Céline
    et al.
    Versailles cedex, France; Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Negroni, Luc
    Gif-sur-Yvette, France.
    Balliau, Thierry
    Gif-sur-Yvette, France.
    Corti, Hélène
    Gif-sur-Yvette, France.
    Jacquemot, Marie-Pierre
    Gif-sur-Yvette, France.
    Davanture, Marléne
    Gif-sur-Yvette, France.
    Sandberg, Göran
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Zivy, Michel
    Gif-sur-Yvette, France.
    Bellini, Catherine
    Versailles Cedex, France; Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Proteomic analysis of different mutant genotypes of Arabidopsis led to the identification of 11 proteins correlating with adventitious root development2006In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 140, no 1, p. 349-364Article in journal (Refereed)
    Abstract [en]

    A lack of competence to form adventitious roots by cuttings or explants in vitro occurs routinely and is an obstacle for the clonal propagation and rapid fixation of elite genotypes. Adventitious rooting is known to be a quantitative genetic trait. We performed a proteomic analysis of Arabidopsis ( Arabidopsis thaliana) mutants affected in their ability to develop adventitious roots in order to identify associated molecular markers that could be used to select genotypes for their rooting ability and/or to get further insight into the molecular mechanisms controlling adventitious rooting. Comparison of two-dimensional gel electrophoresis protein profiles resulted in the identification of 11 proteins whose abundance could be either positively or negatively correlated with endogenous auxin content, the number of adventitious root primordia, and/or the number of mature adventitious roots. One protein was negatively correlated only to the number of root primordia and two were negatively correlated to the number of mature adventitious roots. Two putative chaperone proteins were positively correlated only to the number of primordia, and, interestingly, three auxin-inducible GH3-like proteins were positively correlated with the number of mature adventitious roots. The others were correlated with more than one parameter. The 11 proteins are predicted to be involved in different biological processes, including the regulation of auxin homeostasis and light-associated metabolic pathways. The results identify regulatory pathways associated with adventitious root formation and represent valuable markers that might be used for the future identification of genotypes with better rooting abilities.

  • 91.
    Strand, Åsa
    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).
    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).
    Henkes, S
    Huner, N
    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).
    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).
    Stitt, M
    Acclimation of Arabidopsis leaves developing at low temperatures. Increasing cytoplasmic volume accompanies increased activities of enzymes in the Calvin cycle and in the sucrose-biosynthesis pathway1999In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 119, no 4, p. 1387-1397Article in journal (Refereed)
    Abstract [en]

    Photosynthetic and metabolic acclimation to low growth temperatures were studied in Arabidopsis (Heynh.). Plants were grown at 23 degrees C and then shifted to 5 degrees C. We compared the leaves shifted to 5 degrees C for 10 d and the new leaves developed at 5 degrees C with the control leaves on plants that had been left at 23 degrees C. Leaf development at 5 degrees C resulted in the recovery of photosynthesis to rates comparable with those achieved by control leaves at 23 degrees C. There was a shift in the partitioning of carbon from starch and toward sucrose (Suc) in leaves that developed at 5 degrees C. The recovery of photosynthetic capacity and the redirection of carbon to Suc in these leaves were associated with coordinated increases in the activity of several Calvin-cycle enzymes, even larger increases in the activity of key enzymes for Suc biosynthesis, and an increase in the phosphate available for metabolism. Development of leaves at 5 degrees C also led to an increase in cytoplasmic volume and a decrease in vacuolar volume, which may provide an important mechanism for increasing the enzymes and metabolites in cold-acclimated leaves. Understanding the mechanisms underlying such structural changes during leaf development in the cold could result in novel approaches to increasing plant yield.

  • 92.
    SUNDBOM, E
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    STRAND, M
    HALLGREN, JE
    TEMPERATURE-INDUCED FLUORESCENCE CHANGES - A SCREENING METHOD FOR FROST TOLERANCE OF POTATO (SOLANUM SP)1982In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 70, no 5, p. 1299-1302Article in journal (Refereed)
  • 93. Tomaz, Tiago
    et al.
    Bagard, Matthieu
    Pracharoenwattana, Itsara
    Lindén, Pernilla
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Lee, Chun Pong
    Carroll, Adam J
    Ströher, Elke
    Smith, Steven M
    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).
    Millar, A Harvey
    Mitochondrial malate dehydrogenase lowers leaf respiration and alters photorespiration and plant growth in Arabidopsis.2010In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 154, no 3, p. 1143-1157Article in journal (Refereed)
    Abstract [en]

    Malate dehydrogenase (MDH) catalyzes a reversible NAD(+)-dependent-dehydrogenase reaction involved in central metabolism and redox homeostasis between organelle compartments. To explore the role of mitochondrial MDH (mMDH) in Arabidopsis (Arabidopsis thaliana), knockout single and double mutants for the highly expressed mMDH1 and lower expressed mMDH2 isoforms were constructed and analyzed. A mmdh1mmdh2 mutant has no detectable mMDH activity but is viable, albeit small and slow growing. Quantitative proteome analysis of mitochondria shows changes in other mitochondrial NAD-linked dehydrogenases, indicating a reorganization of such enzymes in the mitochondrial matrix. The slow-growing mmdh1mmdh2 mutant has elevated leaf respiration rate in the dark and light, without loss of photosynthetic capacity, suggesting that mMDH normally uses NADH to reduce oxaloacetate to malate, which is then exported to the cytosol, rather than to drive mitochondrial respiration. Increased respiratory rate in leaves can account in part for the low net CO(2) assimilation and slow growth rate of mmdh1mmdh2. Loss of mMDH also affects photorespiration, as evidenced by a lower postillumination burst, alterations in CO(2) assimilation/intercellular CO(2) curves at low CO(2), and the light-dependent elevated concentration of photorespiratory metabolites. Complementation of mmdh1mmdh2 with an mMDH cDNA recovered mMDH activity, suppressed respiratory rate, ameliorated changes to photorespiration, and increased plant growth. A previously established inverse correlation between mMDH and ascorbate content in tomato (Solanum lycopersicum) has been consolidated in Arabidopsis and may potentially be linked to decreased galactonolactone dehydrogenase content in mitochondria in the mutant. Overall, a central yet complex role for mMDH emerges in the partitioning of carbon and energy in leaves, providing new directions for bioengineering of plant growth rate and a new insight into the molecular mechanisms linking respiration and photosynthesis in plants.

  • 94. Van Aken, Olivier
    et al.
    De Clercq, Inge
    Ivanova, Aneta
    Law, Simon R
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Van Breusegem, Frank
    Millar, A. Harvey
    Whelan, James
    Mitochondrial and Chloroplast Stress Responses Are Modulated in Distinct Touch and Chemical Inhibition Phases2016In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 171, no 3, p. 2150-2165Article in journal (Refereed)
    Abstract [en]

    Previous studies have identified a range of transcription factors that modulate retrograde regulation of mitochondrial and chloroplast functions in Arabidopsis (Arabidopsis thaliana). However, the relative importance of these regulators and whether they act downstream of separate or overlapping signaling cascades is still unclear. Here, we demonstrate that multiple stress-related signaling pathways, with distinct kinetic signatures, converge on overlapping gene sets involved in energy organelle function. The transcription factor ANAC017 is almost solely responsible for transcript induction of marker genes around 3 to 6 h after chemical inhibition of organelle function and is a key regulator of mitochondrial and specific types of chloroplast retrograde signaling. However, an independent and highly transient gene expression phase, initiated within 10 to 30 min after treatment, also targets energy organelle functions, and is related to touch and wounding responses. Metabolite analysis demonstrates that this early response is concurrent with rapid changes in tricarboxylic acid cycle intermediates and large changes in transcript abundance of genes encoding mitochondrial dicarboxylate carrier proteins. It was further demonstrated that transcription factors AtWRKY15 and AtWRKY40 have repressive regulatory roles in this touch-responsive gene expression. Together, our results show that several regulatory systems can independently affect energy organelle function in response to stress, providing different means to exert operational control.

  • 95. Van de Wouwer, Dorien
    et al.
    Vanholme, Ruben
    Decou, Raphaël
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Goeminne, Geert
    Audenaert, Dominique
    Nguyen, Long
    Höfer, René
    Pesquet, Edouard
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Arrhenius Laboratories, Department of Ecology, Environment, and Plant Sciences, Stockholm University, Sweden.
    Vanholme, Bartel
    Boerjan, Wout
    Chemical Genetics Uncovers Novel Inhibitors of Lignification, Including p-Iodobenzoic Acid Targeting CINNAMATE-4-HYDROXYLASE2016In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 172, no 1, p. 198-220Article in journal (Refereed)
    Abstract [en]

    Plant secondary-thickened cell walls are characterized by the presence of lignin, a recalcitrant and hydrophobic polymer that provides mechanical strength and ensures long-distance water transport. Exactly the recalcitrance and hydrophobicity of lignin put a burden on the industrial processing efficiency of lignocellulosic biomass. Both forward and reverse genetic strategies have been used intensively to unravel the molecular mechanism of lignin deposition. As an alternative strategy, we introduce here a forward chemical genetic approach to find candidate inhibitors of lignification. A high-throughput assay to assess lignification in Arabidopsis (Arabidopsis thaliana) seedlings was developed and used to screen a 10-k library of structurally diverse, synthetic molecules. Of the 73 compounds that reduced lignin deposition, 39 that had a major impact were retained and classified into five clusters based on the shift they induced in the phenolic profile of Arabidopsis seedlings. One representative compound of each cluster was selected for further lignin-specific assays, leading to the identification of an aromatic compound that is processed in the plant into two fragments, both having inhibitory activity against lignification. One fragment, p-iodobenzoic acid, was further characterized as a new inhibitor of CINNAMATE 4-HYDROXYLASE, a key enzyme of the phenylpropanoid pathway synthesizing the building blocks of the lignin polymer. As such, we provide proof of concept of this chemical biology approach to screen for inhibitors of lignification and present a broad array of putative inhibitors of lignin deposition for further characterization.

  • 96.
    Wingsle, Gunnar
    et al.
    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).
    HALLGREN, JE
    KARPINSKI, S
    ISOLATION, PURIFICATION, AND SUBCELLULAR-LOCALIZATION OF ISOZYMES OF SUPEROXIDE-DISMUTASE FROM SCOTS PINE (PINUS-SYLVESTRIS L) NEEDLES1991In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 95, no 1, p. 21-28Article in journal (Refereed)
    Abstract [en]

    Two of four isozymes of superoxide dismutase (SOD) (EC 1.15.1.1) were purified from Scots pine (Pinus sylvestris L.) needles. One form was cytosolic (SOD-1) and the other was associated with chloroplasts (SOD-3). The holoenzyme molecular masses was estimated at approximately 35 kilodaltons by gel filtration. The subunit molecular weight of the dimeric enzymes was estimated to 16.5 kilodaltons (SOD-1) and 20.4 kilodaltons (SOD-3) on sodium dodecyl sulfatepolyacrylamide gels. The NH2-terminal sequence of the pine enzymes showed similarities to other purified superoxide dismutases located in the corresponding compartment. The cytosolic form revealed two additional amino acids at position 1 and 2 at the NH2-terminal. Both forms were cyanide- and hydrogenperoxide-sensitive and SOD-3 was found to contain approximately one copper atom per subunit, indicating that they belong to the cupro-zinc SODs. The isoelectric point was 4.9 and 4.5 for SOD-1 and SOD-3, respectively.

  • 97. Zhang, H
    et al.
    Goodman, H M
    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).
    Antisense inhibition of the photosystem I antenna protein Lhca4 in Arabidopsis thaliana1997In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 115, no 4, p. 1525-1531Article in journal (Refereed)
    Abstract [en]

    The function of Lhca4, a gene encoding the photosystem I type IV chlorophyll a/b-binding protein complex in Arabidopsis, was investigated using antisense technology. Lhca4 protein was reduced in a number of mutant lines and abolished in one. The inhibition of protein was not correlated with the inhibition of mRNA. No depletion of Lhca1 was observed, but the low-temperature fluorescence emission spectrum was drastically altered in the mutants. The emission maximum was blue-shifted by 6 nm, showing that chlorophyll molecules bound to Lhca4 are responsible for most of the long-wavelength fluorescence emission. Some mutants also showed an unexplainable delay in flowering time and an increase in seed weight.

  • 98. Zhurov, Vladimir
    et al.
    Navarro, Marie
    Bruinsma, Kristie A.
    Arbona, Vicent
    Estrella Santamaria, M.
    Cazaux, Marc
    Wybouw, Nicky
    Osborne, Edward J.
    Ens, Cherise
    Rioja, Cristina
    Vermeirssen, Vanessa
    Rubio-Somoza, Ignacio
    Krishna, Priti
    Diaz, Isabel
    Schmid, Markus
    Max Planck Institute for Developmental Biology, Department of Molecular Biology, Spemannstrasse 35, 72076 Tübingen, Germany.
    Gomez-Cadenas, Aurelio
    Van de Peer, Yves
    Grbic, Miodrag
    Clark, Richard M.
    Van Leeuwen, Thomas
    Grbic, Vojislava
    Reciprocal Responses in the Interaction between Arabidopsis and the Cell-Content-Feeding Chelicerate Herbivore Spider Mite2014In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 164, no 1, p. 384-399Article in journal (Refereed)
12 51 - 98 of 98
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