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  • 1.
    Benedict, Catherine
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Skinner, Jeffrey S
    Meng, Rengong
    Chang, Yongjian
    Bhalerao, Rishikesh
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huner, Norman P A
    Finn, Chad E
    Chen, Tony H H
    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).
    The CBF1-dependent low temperature signalling pathway, regulon and increase in freeze tolerance are conserved in Populus spp2006In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 29, no 7, p. 1259-1272Article in journal (Refereed)
    Abstract [en]

    The meristematic tissues of temperate woody perennials must acclimate to freezing temperatures to survive the winter and resume growth the following year. To determine whether the C-repeat binding factor (CBF) family of transcription factors contributing to this process in annual herbaceous species also functions in woody perennials, we investigated the changes in phenotype and transcript profile of transgenic Populus constitutively expressing CBF1 from Arabidopsis (AtCBF1). Ectopic expression of AtCBF1 was sufficient to significantly increase the freezing tolerance of non-acclimated leaves and stems relative to wild-type plants. cDNA microarray experiments identified genes up-regulated by ectopic AtCBF1 expression in Populus, demonstrated a strong conservation of the CBF regulon between Populus and Arabidopsis and identified differences between leaf and stem regulons. We studied the induction kinetics and tissue specificity of four CBF paralogues identified from the Populus balsamifera subsp. trichocarpa genome sequence (PtCBFs). All four PtCBFs are cold-inducible in leaves, but only PtCBF1 and PtCBF3 show significant induction in stems. Our results suggest that the central role played by the CBF family of transcriptional activators in cold acclimation of Arabidopsis has been maintained in Populus. However, the differential expression of the PtCBFs and differing clusters of CBF-responsive genes in annual (leaf) and perennial (stem) tissues suggest that the perennial-driven evolution of winter dormancy may have given rise to specific roles for these 'master-switches' in the different annual and perennial tissues of woody species.

  • 2.
    Brouwer, Bastiaan
    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).
    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).
    Bagard, Matthieu
    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).
    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).
    The impact of light intensity on shade-induced leaf senescence2012In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 35, no 6, p. 1084-1098Article in journal (Refereed)
    Abstract [en]

    Plants often have to cope with altered light conditions, which in leaves induce various physiological responses ranging from photosynthetic acclimation to leaf senescence. However, our knowledge of the regulatory pathways by which shade and darkness induce leaf senescence remains incomplete. To determine to what extent reduced light intensities regulate the induction of leaf senescence, we performed a functional comparison between Arabidopsis leaves subjected to a range of shading treatments. Individually covered leaves, which remained attached to the plant, were compared with respect to chlorophyll, protein, histology, expression of senescence-associated genes, capacity for photosynthesis and respiration, and light compensation point (LCP). Mild shading induced photosynthetic acclimation and resource partitioning, which, together with a decreased respiration, lowered the LCP. Leaf senescence was induced only under strong shade, coinciding with a negative carbon balance and independent of the red/far-red ratio. Interestingly, while senescence was significantly delayed at very low light compared with darkness, phytochrome A mutant plants showed enhanced chlorophyll degradation under all shading treatments except complete darkness. Taken together, our results suggest that the induction of leaf senescence during shading depends on the efficiency of carbon fixation, which in turn appears to be modulated via light receptors such as phytochrome A.

  • 3. Cooke, Janice E. K.
    et al.
    Eriksson, Maria E.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Junttila, Olavi
    The dynamic nature of bud dormancy in trees: environmental control and molecular mechanisms2012In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 35, no 10, p. 1707-1728Article in journal (Refereed)
    Abstract [en]

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

  • 4.
    Edlund, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Novak, Ondrej
    Karady, Michael
    Ljung, Karin
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Contrasting patterns of cytokinins between years in senescing aspen leaves2017In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 40, p. 622-634Article in journal (Refereed)
    Abstract [en]

    Cytokinins are plant hormones that typically block or delay leaf senescence. We profiled 34 different cytokinins/cytokinin metabolites (including precursors, conjugates and degradation products) in leaves of a free-growing mature aspen (Populus tremula) before and after the initiation of autumnal senescence over three consecutive years. The levels and profiles of individual cytokinin species, or classes/groups, varied greatly between years, despite the fact that the onset of autumn senescence was at the same time each year, and senescence was not associated with depletion of either active or total cytokinin levels. Levels of aromatic cytokinins (topolins) were low and changed little over the autumn period. Diurnal variations and weather-dependent variations in cytokinin content were relatively limited. We also followed the expression patterns of all aspen genes implicated as having roles in cytokinin metabolism or signaling, but neither the pattern of regulation of any group of genes nor the expression of any particular gene supported the notion that decreased cytokinin signaling could explain the onset of senescence. Based on the results from this tree, we therefore suggest that cytokinin depletion is unlikely to explain the onset of autumn leaf senescence in aspen.

  • 5. Edwards, Kieron D.
    et al.
    Takata, Naoki
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Johansson, Mikael
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). RNA Biology and Molecular Physiology, Bielefeld University, Bielefeld, Germany.
    Jurca, Manuela
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Novak, Ondrej
    Henykova, Eva
    Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Liverani, Silvia
    Kozarewa, Iwanka
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Strnad, Miroslav
    Millar, Andrew J.
    Ljung, Karin
    Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Umeå, Sweden.
    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).
    Circadian clock components control daily growth activities by modulating cytokinin levels and cell division-associated gene expression in Populus trees2018In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 41, no 6, p. 1468-1482Article in journal (Refereed)
    Abstract [en]

    Trees are carbon dioxide sinks and major producers of terrestrial biomass with distinct seasonal growth patterns. Circadian clocks enable the coordination of physiological and biochemical temporal activities, optimally regulating multiple traits including growth. To dissect the clock's role in growth, we analysed Populus tremula x P. tremuloides trees with impaired clock function due to down-regulation of central clock components. late elongated hypocotyl (lhy-10) trees, in which expression of LHY1 and LHY2 is reduced by RNAi, have a short free-running period and show disrupted temporal regulation of gene expression and reduced growth, producing 30-40% less biomass than wild-type trees. Genes important in growth regulation were expressed with an earlier phase in lhy-10, and CYCLIN D3 expression was misaligned and arrhythmic. Levels of cytokinins were lower in lhy-10 trees, which also showed a change in the time of peak expression of genes associated with cell division and growth. However, auxin levels were not altered in lhy-10 trees, and the size of the lignification zone in the stem showed a relative increase. The reduced growth rate and anatomical features of lhy-10 trees were mainly caused by misregulation of cell division, which may have resulted from impaired clock function.

  • 6. Granado-Yela, C
    et al.
    García-Verdugo, C
    Carrillo, K
    Rubio DE Casas, R
    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).
    Balaguer, L
    Temporal matching among diurnal photosynthetic patterns within the crown of the evergreen sclerophyll Olea europaea L2011In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 34, no 5, p. 800-810Article in journal (Refereed)
    Abstract [en]

    Trees are modular organisms that adjust their within-crown morphology and physiology in response to within-crown light gradients. However, whether within-plant variation represents a strategy for optimizing light absorption has not been formally tested. We investigated the arrangement of the photosynthetic surface throughout one day and its effects on the photosynthetic process, at the most exposed and most sheltered crown layers of a wild olive tree (Olea europaea L.). Similar measurements were made for cuttings taken from this individual and grown in a greenhouse at contrasted irradiance-levels (100 and 20% full sunlight). Diurnal variations in light interception, carbon fixation and carbohydrate accumulation in sun leaves were negatively correlated with those in shade leaves under field conditions when light intensity was not limiting. Despite genetic identity, these complementary patterns were not found in plants grown in the greenhouse. The temporal disparity among crown positions derived from specialization of the photosynthetic behaviour at different functional and spatial scales: architectural structure (crown level) and carbon budget (leaf level). Our results suggest that the profitability of producing a new module may not only respond to construction costs or light availability, but also rely on its spatio-temporal integration within the productive processes at the whole-crown level.

  • 7. HALLGREN, JE
    et al.
    LINDER, S
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    RICHTER, A
    TROENG, E
    GRANAT, L
    UPTAKE OF SO2 IN SHOOTS OF SCOTS PINE - FIELD-MEASUREMENTS OF NET FLUX OF SULFUR IN RELATION TO STOMATAL CONDUCTANCE1982In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 5, no 1, p. 75-83Article in journal (Refereed)
  • 8. Hoffman, Daniel E.
    et al.
    Jonsson, Pär
    Umeå University, Faculty of Science and Technology, Department of Chemistry. SweTree Technologies AB, Umeå, Sweden.
    Bylesjö, Max
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Almac Diagnostics Ltd, Craigavon, UK.
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Eriksson, Maria E.
    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
    Changes in diurnal patterns within the Populus transcriptome and metabolome in response to photoperiod variation2010In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 33, no 8, p. 1298-1313Article in journal (Refereed)
    Abstract [en]

    Changes in seasonal photoperiod provides an important environmental signal that affects the timing of winter dormancy in perennial, deciduous, temperate tree species, such as hybrid aspen (Populus tremula x Populus tremuloides). In this species, growth cessation, cold acclimation and dormancy are induced in the autumn by the detection of day-length shortening that occurs at a given critical day length. Important components in the detection of such day-length changes are photoreceptors and the circadian clock, and many plant responses at both the gene regulation and metabolite levels are expected to be diurnal. To directly examine this expectation and study components in these events, here we report transcriptomic and metabolomic responses to a change in photoperiod from long to short days in hybrid aspen. We found about 16% of genes represented on the arrays to be diurnally regulated, as assessed by our pre-defined criteria. Furthermore, several of these genes were involved in circadian-associated processes, including photosynthesis and primary and secondary metabolism. Metabolites affected by the change in photoperiod were mostly involved in carbon metabolism. Taken together, we have thus established a molecular catalog of events that precede a response to winter.

  • 9. HOFSLAGARE, O
    et al.
    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).
    SJOBERG, S
    INGRI, N
    A PRECISE POTENTIOMETRIC METHOD FOR DETERMINATION OF ALGAL ACTIVITY IN AN OPEN CO2 SYSTEM1983In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 6, no 3, p. 195-201Article in journal (Refereed)
  • 10.
    Hurry, Vaughan
    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).
    Tobiaeson, M
    Kromer, S
    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).
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Mitochondria contribute to increased photosynthetic capacity of leaves of winter rye (Secale-Cereale L) following cold-hardening1995In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 18, no 1, p. 69-76Article in journal (Refereed)
    Abstract [en]

    Cold-hardening of winter rye (Secale cereale L. cv. Musketeer) increased dark respiration from -2.2 to -3.9 mu mol O-2 m(-2)s(-1) and doubled light- and CO2-saturated photosynthesis at 20 degrees C from 18.1 to 37.0 mu mol O-2 m(-2) s(-1). We added oligomycin at a concentration that specifically inhibits oxidative phosphorylation to see whether the observed increase in dark respiration reflected an increase in respiration in the light, and whether this contributed to the enhanced photosynthesis of cold-hardened leaves, Oligomycin inhibited light- and CO2-saturated rates of photosynthesis in non-hardened and cold-hardened leaves by 14 and 25%, respectively, and decreased photochemical quenching of chlorophyll a fluorescence to a greater degree in cold-hardened than in non-hardened leaves, These data indicate an increase both in the rate of respiration in the light, and in the importance of respiration to photosynthesis following cold-hardening, Analysis of metabolite pools indicated that oligomycin inhibited photosynthesis by limiting regeneration of ribulose-1,5-bisphosphate, This limitation was particularly severe in cold-hardened leaves, and the resulting low 3-phosphoglycerate pools led to a feed-forward inhibition of sucrose-phosphate synthase activity, Thus, it does not appear that oxidative phosphorylation supports the increase in photosynthetic O-2 evolution following cold-hardening by increasing the availability of cytosolic ATP, The data instead support the hypothesis that the mitochondria function in the light by using the reducing equivalents generated by nan-cyclic photosynthetic electron transport.

  • 11.
    Johansson Jänkänpää, Hanna
    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).
    Mishra, Yogesh
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Schröder, Wolfgang P
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    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).
    Metabolic profiling reveals metabolic shifts in Arabidopsis plants grown under different light conditions2012In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 35, no 10, p. 1824-1836Article in journal (Refereed)
    Abstract [en]

    Plants have tremendous capacity to adjust their morphology, physiology and metabolism in response to changes in growing conditions. Thus, analysis solely of plants grown under constant conditions may give partial or misleading indications of their responses to the fluctuating natural conditions in which they evolved. To obtain data on growth-condition dependent differences in metabolite levels we compared leaf metabolite profiles of Arabidopsis thaliana growing under three constant laboratory light conditions: 30 (LL), 300 (NL) and 600 (HL) µmol photons m(-2) s(-1) . We also shifted plants to the field and followed their metabolite composition for three days. Numerous compounds showed light-intensity dependent accumulation, including: many sugars and sugar derivatives (fructose, sucrose, glucose, galactose and raffinose); tricarboxylic acid (TCA) cycle intermediates and amino acids (ca. 30% of which were more abundant under HL and 60% under LL). However, the patterns differed after shifting NL plants to field conditions. Levels of most identified metabolites (mainly amino acids, sugars and TCA cycle intermediates) rose after 2 h and peaked after 73 h, indicative of a "biphasic response" and "circadian" effects. The results provide new insight into metabolomic level mechanisms of plant acclimation, and highlight the role of known protectants under natural conditions.

  • 12.
    Jonsson Čabrajić, Anna V
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Lidén, Marlene
    Sveriges Lantbruksuniversitet, Umeå, Institutionen för Skogens ekologi och skötsel.
    Lundmark, Tomas
    Sveriges Lantbruksuniversitet, Umeå, Enheten för skoglig fältforskning.
    Ottosson-Löfvenius, Mikael
    Sveriges Lantbruksuniversitet, Umeå, Institutionen för Skogens ekologi och skötsel.
    Palmqvist, Kristin
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Modelling hydration and photosystem II activation in relation to in situ rain and humidity patterns: a tool to compare performance of rare an generalist epiphytic lichens2010In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 33, p. 840-850Article in journal (Refereed)
    Abstract [en]

    A dynamic water and activity model was developed to assess how efficiently lichens can exploit in situ rain and humid air. The capacity to rehydrate and activate photosynthesis [i.e. photosystem II (PSII)] by these water sources was compared among four hydrophilic and one generalist epiphytic lichen. Hydration status, potential (instant activation) and realized (delayed activation) day-light activity were simulated using a model based on species-specific hydration, PSII activation characteristics and in situ water content for Platismatia norvegica in three microclimatic scenarios. The results showed that delayed PSII activation could have profound effects on lichens' ability to exploit environmental water sources. During rain, realized activity was reduced by 19, 34 and 56% compared to simulations assuming instant activation for three hydrophilic lichens in the driest microclimate. During humid air, the reduction was 81% for the most extreme species and scenario, because of slow hydration and low equilibrium water content. Many and brief hydration events may thus hamper species with slow activation and fast desiccation kinetics. No evidence of compensation by a 'water-holding' morphology was observed among studied species. The developed model may provide a tool for identifying suitable habitats for long-term persistence of lichens with physiological constraints.

  • 13.
    Keech, Olivier
    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).
    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).
    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).
    Rouhier, Nicolas
    The redox control of photorespiration: from biochemical and physiological aspects to biotechnological considerations2017In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 40, no 4, p. 553-569Article, review/survey (Refereed)
    Abstract [en]

    Photorespiration is a complex and tightly regulated process occurring in photosynthetic organisms. This process can alter the cellular redox balance, notably via the production and consumption of both reducing and oxidizing equivalents. Under certain circumstances, these equivalents, as well as reactive oxygen or nitrogen species, can become prominent in subcellular compartments involved in the photorespiratory process, eventually promoting oxidative post-translational modifications of proteins. Keeping these changes under tight control should therefore be of primary importance. In order to review the current state of knowledge about the redox control of photorespiration, we primarily performed a careful description of the known and potential redox-regulated or oxidation sensitive photorespiratory proteins, and examined in more details two interesting cases: the glycerate kinase and the glycine cleavage system. When possible, the potential impact and subsequent physiological regulations associated with these changes have been discussed. In a second part, we reviewed the extent to which photorespiration contributes to cellular redox homeostasis considering, in particular, the set of peripheral enzymes associated with the canonical photorespiratory pathway. Finally, some recent biotechnological strategies to circumvent photorespiration for future growth improvements are discussed in the light of these redox regulations.

  • 14.
    Keech, Olivier
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Pesquet, Edouard
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ahad, Abdul
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Askne, Anna
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Norvall, Dag
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Vodnala, Sharvani Munender
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Tuominen, Hannele
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Dizengremel, Pierre
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    The different fate of mitochondria and chloroplasts during dark-induced senescence in Arabidopsis leaves2007In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 30, no 12, p. 1523-1534Article in journal (Refereed)
    Abstract [en]

    Senescence is an active process allowing the reallocation of valuable nutrients from the senescing organ towards storage and/or growing tissues. Using Arabidopsis thaliana leaves from both whole darkened plants (DPs) and individually darkened leaves (IDLs), we investigated the fate of mitochondria and chloroplasts during dark-induced leaf senescence. Combining in vivo visualization of fates of the two organelles by three-dimensional reconstructions of abaxial parts of leaves with functional measurements of photosynthesis and respiration, we showed that the two experimental systems displayed major differences during 6 d of dark treatment. In whole DPs, organelles were largely retained in both epidermal and mesophyll cells. However, while the photosynthetic capacity was maintained, the capacity of mitochondrial respiration decreased. In contrast, IDLs showed a rapid decline in photosynthetic capacity while maintaining a high capacity for mitochondrial respiration throughout the treatment. In addition, we noticed an unequal degradation of organelles in the different cell types of the senescing leaf. From these data, we suggest that metabolism in leaves of the whole DPs enters a ‘stand-by mode’ to preserve the photosynthetic machinery for as long as possible. However, in IDLs, mitochondria actively provide energy and carbon skeletons for the degradation of cell constituents, facilitating the retrieval of nutrients. Finally, the heterogeneity of the degradation processes involved during senescence is discussed with regard to the fate of mitochondria and chloroplasts in the different cell types.

  • 15.
    Kurepin, Leonid V.
    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). Department of Biology and the Biotron Center for Experimental Climate Change Research, University of Western Ontario, London, Ontario, Canada.
    Stangl, Zsofia R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ivanov, Alexander G.
    Bui, Vi
    Mema, Marin
    Huner, Norman P. A.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Way, Danielle
    Hurry, Vaughan
    Contrasting acclimation abilities of two dominant boreal conifers to elevated CO2 and temperature2018In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 41, no 6, p. 1331-1345Article in journal (Refereed)
    Abstract [en]

    High latitude forests will experience large changes in temperature and CO2 concentrations this century. We evaluated the effects of future climate conditions on 2 dominant boreal tree species, Pinus sylvestris L. and Picea abies (L.) H. Karst, exposing seedlings to 3 seasons of ambient (430 ppm) or elevated CO2 (750 ppm) and ambient temperatures, a + 4 degrees C warming or a + 8 degrees C warming. Pinus sylvestris responded positively to warming: seedlings developed a larger canopy, maintained high net CO2 assimilation rates (Anet), and acclimated dark respiration (Rdark). In contrast, carbon fluxes in Picea abies were negatively impacted by warming: maximum rates of Anet decreased, electron transport was redirected to alternative electron acceptors, and thermal acclimation of Rdark was weak. Elevated CO2 tended to exacerbate these effects in warm-grown Picea abies, and by the end of the experiment Picea abies from the +8 degrees C, high CO2 treatment produced fewer buds than they had 3 years earlier. Treatments had little effect on leaf and wood anatomy. Our results highlight that species within the same plant functional type may show opposite responses to warming and imply that Picea abies may be particularly vulnerable to warming due to low plasticity in photosynthetic and respiratory metabolism.

  • 16. LEVERENZ, JW
    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).
    QUANTUM YIELDS OF PHOTOSYNTHESIS AT TEMPERATURES BETWEEN -2-DEGREES C AND 35-DEGREES C IN A COLD-TOLERANT C-3 PLANT (PINUS-SYLVESTRIS) DURING THE COURSE OF ONE YEAR1987In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 10, no 4, p. 287-295Article in journal (Refereed)
  • 17. Lidén, Marlene
    et al.
    Jonsson Čabrajić, Anna V
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Ottosson-Löfvenius, Mikael
    Palmqvist, Kristin
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Lundmark, Tomas
    Species-specific activation time-lags can explain habitat restrictions in hydrophiclic lichens2010In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 33, p. 851-862Article in journal (Refereed)
    Abstract [en]

    Photosystem II (PSII) activation after hydration with water or humid air was measured in four hydrophilic and a generalist lichen to test the hypothesis that slow activation might explain habitat restriction in the former group. For the hydrophilic species, activation was after 4 h nearly completed in Lobaria amplissima and Platismatia norvegica, while only c. 50% for Bryoria bicolor and Usnea longissima. The generalist Platismatia glauca was activated instantaneously. The effect of this on lichen field performance was investigated using a dynamic model separating the two water sources rain and humid air. Model simulations were made using the species-specific characteristics and climate data from 12 stream microhabitats. For U. longissima, slow PSII activation could reduce realized photosynthesis by a factor of five. Bryoria bicolor was almost as severely affected, while P. norvegica displayed moderate reductions. Lobaria amplissima displayed longer realized activity periods even in unfavourable microclimates, possibly because of a higher water loss resistance. Both close proximity to streams and presence of turbulent water had a positive impact on realized activity among the slowly activated species, coinciding with observed distribution patterns of hydrophilic species. The results presented here may thus partly explain observed habitat restrictions of rare hydrophilic lichens.

  • 18.
    Lundmark, Maria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Cavaco, Ana M.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Trevion, Stephen
    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).
    Carbon partitioning and export in transgenic Arabidopsis thaliana with altered capacity for sucrose synthesisgrown at low temperture: a role for metabolite transporters2006In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 29, no 9, p. 1703-1714Article in journal (Refereed)
    Abstract [en]

    We investigated the role of metabolite transporters in cold acclimation by comparing the responses of wild-type (WT) Arabidopsis thaliana(Heynh.) with that of transgenic plants over-expressing sucrose-phosphate synthase (SPSox) or with that of antisense repression of cytosolic fructose-1,6-bisphosphatase (FBPas). Plants were grown at 23 °C and then shifted to 5 °C. We compared the leaves shifted to 5 °C for 3 and 10 d with new leaves that developed at 5 °C with control leaves on plants at 23 °C. At 23 °C, ectopic expression of SPS resulted in 30% more carbon being fixed per day and an increase in sucrose export from source leaves. This increase in fixation and export was supported by increased expression of the plastidic triose-phosphate transporter AtTPT and, to a lesser extent, the high-affinity Suc transporter AtSUC1. The improved photosynthetic performance of the SPSox plants was maintained after they were shifted to 5 °C and this was associated with further increases in AtSUC1 expression but with a strong repression of AtTPT mRNA abundance. Similar responses were shown by WT plants during acclimation to low temperature and this response was attenuated in the low sucrose producing FBPas plants. These data suggest that a key element in recovering flux through carbohydrate metabolism in the cold is to control the partitioning of metabolites between the chloroplast and the cytosol, and Arabidopsis modulates the expression of AtTPT to maintain balanced carbon flow. Arabidopsis also up-regulates the expression of AtSUC1, and to lesser extent AtSUC2, as down-stream components facilitate sucrose transport in leaves that develop at low temperatures.

  • 19. Moroney, J V
    et al.
    Bartlett, S 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).
    Carbonic anhydrases in plants and algae2001In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 24, no 2, p. 141-153Article, review/survey (Refereed)
    Abstract [en]

    Carbonic anhydrases catalyse the reversible hydration of CO2, increasing the interconversion between CO2 and HCO3- + H+ in living organisms. The three evolutionarily unrelated families of carbonic anhydrases are designated alpha-, beta -and gamma -CA. Animals have only the alpha -carbonic anhydrase type of carbonic anhydrase, but they contain multiple isoforms of this carbonic anhydrase. In contrast, higher plants, algae and cyanobacteria may contain members of all three CA families. Analysis of the Arabidopsis database reveals at least 14 genes potentially encoding carbonic anhydrases. The database also contains expressed sequence tags (ESTs) with homology to most of these genes. Clearly the number of carbonic anhydrases in plants is much greater than previously thought. Chlamydomonas, a unicellular green alga, is not far behind with five carbonic anhydrases already identified and another in the EST database. In algae, carbonic anhydrases have been found in the mitochondria, the chloroplast thylakoid, the cytoplasm and the periplasmic space. In C-3 dicots, only two carbonic anhydrases have been localized, one to the chloroplast stroma and one to the cytoplasm. A challenge for plant scientists is to identify the number, location and physiological roles of the carbonic anhydrases.

  • 20.
    OQUIST, G
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    BRUNES, L
    HALLGREN, JE
    PHOTOSYNTHETIC EFFICIENCY DURING ONTOGENESIS OF LEAVES OF BETULA-PENDULA1982In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 5, no 1, p. 17-21Article in journal (Refereed)
  • 21.
    OQUIST, G
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    BRUNES, L
    HALLGREN, JE
    PHOTOSYNTHETIC EFFICIENCY OF BETULA-PENDULA ACCLIMATED TO DIFFERENT QUANTUM FLUX DENSITIES1982In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 5, no 1, p. 9-15Article in journal (Refereed)
  • 22.
    Ottander, Christina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Department of Science and Mathematics Education.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Recovery of photosynthesis in winter-stressed Scots pine1991In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 14, no 3, p. 345-349Article in journal (Refereed)
    Abstract [en]

    Winter-induced inhibition of photosynthesis in Scots pine (Pinus sylvestris L.) is caused by the combined effects of light and freezing temperatures; light causes photoinhibition of photosystem 11 (Strand & Oquist, 1985b, Physiologia Plantarum, 65, 117-123), whereas frost causes inhibition of enzymatic steps of photosynthesis (Strand & Oquist, 1988, Plant, Cell & Environment, 11, 231-238). To reveal limiting steps during recovery from winter stress, the potential of photosynthesis to recover and the actual recovery outdoors during spring, were studied in Scots pine. Studies of light dependent O2-evolution under saturating CO2 and recordings of room temperature fluorescence induction kinetics were used. When branches of pine, in February and March, were brought into the laboratory and kept at 18-degrees-C and 100-mu-mol m-2 s-1, light saturated rates and apparent quantum yields of photosynthetic O2-evolution recovered fully within approximately 48 h. The photochemical efficiency of photosystem II, as measured by Fv/Fm ratios, recovered fully within 24h after an initial lag-phase of 2-3 h. Under natural winter conditions, the Fv/Fm ratio decreased more in exposed than in shaded pine, whereas the efficiency of photosynthesis was similarly inhibited in exposed and shaded pine. However, when recovery from winter stress occurred during spring, the Fv/Fm ratios of both shaded and exposed pine recovered well before photosynthesis. It is concluded that the light-induced photoinhibition component of winter stress in photosynthesis of pine recovers well before the frost induced component(s) of winter stress. In this context, reversible photoinhibition of photosynthesis in evergreen conifers is considered as a dynamic down-regulation of photosystem II to prevent more severe photodynamic damage of the thylakoid membrane when photosynthesis is inhibited by frost.

  • 23.
    Pin, P. A.
    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.
    Nilsson, Ove
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    The multifaceted roles of FLOWERING LOCUS T in plant development2012In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 35, no 10, p. 1742-1755Article in journal (Refereed)
    Abstract [en]

    One of the key developmental processes in flowering plants is the differentiation of the shoot apical meristem into a floral meristem. This transition is regulated through the integration of environmental and endogenous stimuli, involving a complex, hierarchical signalling network. In arabidopsis, the FLOWERING LOCUS T (FT) protein, a mobile signal recognized as a major component of florigen, has a central position in mediating the onset of flowering. FT-like genes seem to be involved in regulating the floral transition in all angiosperms examined to date. Evidence from molecular evolution studies suggests that the emergence of FT-like genes coincided with the evolution of the flowering plants. Hence, the role of FT in floral promotion is conserved, but appears to be restricted to the angiosperms. Besides flowering, FT-like proteins have also been identified as major regulatory factors in a wide range of developmental processes including fruit set, vegetative growth, stomatal control and tuberization. These multifaceted roles of FT-like proteins have resulted from extensive gene duplication events, which occurred independently in nearly all modern angiosperm lineages, followed by sub- or neo-functionalization. This review assesses the plethora of roles that FT-like genes have acquired during evolution and their implications in plant diversity, adaptation and domestication.

  • 24. Podgorska, Anna
    et al.
    Gieczewska, Katarzyna
    Lukawska-Kuzma, Katarzyna
    Rasmusson, Allan 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).
    Szal, Bozena
    Long-term ammonium nutrition of Arabidopsis increases the extrachloroplastic NAD(P)H/NAD(P)(+) ratio and mitochondrial reactive oxygen species level in leaves but does not impair photosynthetic capacity2013In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 36, no 11, p. 2034-2045Article in journal (Refereed)
    Abstract [en]

    Ammonium nutrition has been suggested to be associated with alterations in the oxidation-reduction state of leaf cells. Herein, we show that ammonium nutrition in Arabidopsis thaliana increases leaf NAD(P)H/NAD(P)(+) ratio, reactive oxygen species content and accumulation of biomolecules oxidized by free radicals. We used the method of rapid fractionation of protoplasts to analyse which cellular compartments were over-reduced under ammonium supply and revealed that observed changes in NAD(P)H/NAD(P)(+) ratio involved only the extrachloroplastic fraction. We also showed that ammonium nutrition changes mitochondrial electron transport chain activity, increasing mitochondrial reactive oxygen species production. Our results indicate that the functional impairment associated with ammonium nutrition is mainly associated with redox reactions outside the chloroplast.

  • 25. Podgorska, Anna
    et al.
    Ostaszewska, Monika
    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).
    Rasmusson, Allan G.
    Szal, Bozena
    In comparison with nitrate nutrition, ammonium nutrition increases growth of the frostbite1 Arabidopsis mutant2015In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 38, no 1, p. 224-237Article in journal (Refereed)
    Abstract [en]

    Ammonium nutrition inhibits the growth of many plant species, including Arabidopsis thaliana. The toxicity of ammonium is associated with changes in the cellular redox state. The cellular oxidant/antioxidant balance is controlled by mitochondrial electron transport chain. In this study, we analysed the redox metabolism of frostbite1 (fro1) plants, which lack mitochondrial respiratory chain complex I. Surprisingly, the growth of fro1 plants increased under ammonium nutrition. Ammonium nutrition increased the reduction level of pyridine nucleotides in the leaves of wild-type plants, but not in the leaves of fro1 mutant plants. The observed higher activities of type II NADH dehydrogenases and cytochrome c oxidase in the mitochondrial electron transport chain may improve the energy metabolism of fro1 plants grown on ammonium. Additionally, the observed changes in reactive oxygen species (ROS) metabolism in the apoplast may be important for determining the growth of fro1 under ammonium nutrition. Moreover, bioinformatic analyses showed that the gene expression changes in fro1 plants significantly overlap with the changes previously observed in plants with a modified apoplastic pH. Overall, the results suggest a pronounced connection between the mitochondrial redox system and the apoplastic pH and ROS levels, which may modify cell wall plasticity and influence growth. In this paper, we analysed the redox metabolism of frostbite1 (fro1) plants lacking Complex I under ammonium nutrition. We showed that, although ammonium leads to stress in wild type plants, ammonium does not cause reductive stress in fro1 plants. Our experimental and bioinformatic analyses indicated that mtETC dysfunction strongly influences apoplastic reactive oxygen species content and pH, and suggested that the faster growth of fro1 plants under ammonium nutrition probably results from modification of the cell wall.

  • 26. Ponzio, Camille
    et al.
    Papazian, Stefano
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Albrectsen, Benedicte R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Dicke, Marcel
    Gols, Rieta
    Dual herbivore attack and herbivore density affect metabolic profiles of Brassica nigra leaves2017In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 40, no 8, p. 1356-1367Article in journal (Refereed)
    Abstract [en]

    Plant responses to dual herbivore attack are increasingly studied, but effects on the metabolome have largely been restricted to volatile metabolites and defence-related non-volatile metabolites. However, plants subjected to stress, such as herbivory, undergo major changes in both primary and secondary metabolism. Using a naturally occurring system, we investigated metabolome-wide effects of single or dual herbivory on Brassica nigra plants by Brevicoryne brassicae aphids and Pieris brassicae caterpillars, while also considering the effect of aphid density. Metabolomic analysis of leaf material showed that single and dual herbivory had strong effects on the plant metabolome, with caterpillar feeding having the strongest influence. Additionally, aphid-density-dependent effects were found in both the single and dual infestation scenarios. Multivariate analysis revealed treatment-specific metabolomic profiles, and effects were largely driven by alterations in the glucosinolate and sugar pools. Our work shows that analysing the plant metabolome as a single entity rather than as individual metabolites provides new insights into the subcellular processes underlying plant defence against multiple herbivore attackers. These processes appear to be importantly influenced by insect density.

  • 27.
    Razzak, Abdur
    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. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå SE-901 87, Sweden.
    Ranade, Sonali Sachin
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå SE-901 87, Sweden.
    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.
    Garcia-Gil, M. R.
    Differential response of Scots pine seedlings to variable intensity and ratio of red and far-red light2017In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 40, no 8, p. 1332-1340Article in journal (Refereed)
    Abstract [en]

    We investigated the response to increasing intensity of red (R) and far-R (FR) light and to a decrease in R: FR ratio in Pinus sylvestris L. (Scots pine) seedling. The results showed that FR high-irradiance response for hypocotyl elongation may be present in Scots pine and that this response is enhanced by increasing light intensity. However, both hypocotyl inhibition and pigment accumulation were more strongly affected by the R light compared with FR light. This is in contrast to previous reports in Arabidopsis thaliana (L.) Heynh. In the angio-sperm, A. thaliana R light shows an overall milder effect on inhibition of hypocotyl elongation and on pigment biosynthesis compared with FR suggesting conifers and angiosperms respond very differently to the different light regimes. Scots pine shade avoidance syndrome with longer hypocotyls, shorter cotyledons and lower chlorophyll content in response to shade conditions resembles the response observed in A. thaliana. However, anthocyanin accumulation increased with shade in Scots pine, which again differs from what is known in angiosperms. Overall, the response of seedling development and physiology to R and FR light in Scots pine indicates that the regulatory mechanism for light response may differ between gymnosperms and angiosperms.

  • 28. Savitch, L V
    et al.
    Leonardos, E D
    Krol, 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).
    Grodzinski, B
    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).
    Two different strategies for light utilization in photosynthesis in relation to growth and cold acclimation2002In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 25, no 6, p. 761-771Article in journal (Refereed)
    Abstract [en]

    Seedlings of Lodgepole pine (Pinus contorta L.) and winter wheat (Triticum aestivum L. cv. Monopol) were cold acclimated under controlled conditions to induce frost hardiness. Lodgepole pine responded to cold acclimation by partial inhibition of photosynthesis with an associated partial loss of photosystem II reaction centres, and a reduction in needle chlorophyll content. This was accompanied by a low daily carbon gain, and the development of a high and sustained capacity for non-photochemical quenching of absorbed light. This sustained dissipation of absorbed light as heat correlated with an increased de-epoxidation of the xanthophyll cycle pigments forming the quenching forms antheraxanthin and zeaxanthin. In addition, the PsbS protein known to bind chlorophyll and the xanthophyll cycle pigments increased strongly during cold acclimation of pine. In contrast, winter wheat maintained high photosynthetic rates, showed no loss of chlorophyll content per leaf area, and exhibited a high daily carbon gain and a minimal non-photochemical quenching after cold acclimation. In accordance, cold acclimation of wheat neither increased the de-epoxidation of the xanthophylls nor the content of the PsbS protein. These different responses of photosynthesis to cold acclimation are correlated with pine, reducing its need for assimilates when entering dormancy associated with termination of primary growth, whereas winter wheat maintains a high need for assimilates as it continues to grow and develop throughout the cold-acclimation period. It appears that without evolving a sustained ability for controlled dissipation of absorbed light as heat throughout the winter, winter green conifers would not have managed to adapt and establish themselves so successfully in the cold climatic zones of the northern hemisphere.

  • 29.
    Schleucher, Jürgen
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Vanderveer, Peter
    Department of Botany, University of Wisconsin-Madison.
    Markley, John L
    Department of Biochemistry, University of Wisconsin-Madison.
    Sharkey, Thomas D
    Department of Botany, University of Wisconsin-Madison.
    Intramolecular deuterium distributions of glucose reveal disequilibrium of chloroplast phosphoglucose isomerase1999In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 22, no 5, p. 525-533Article in journal (Refereed)
    Abstract [en]

    D, deuterium δD(NMR), chemical shift axis in a deuterium NMR spectrum F6P, fructose-6-phosphate G6P, glucose-6-phosphate IRMS, isotope ratio mass spectrometry NMR, nuclear magnetic resonance PGI, phosphoglucose isomerase Intramolecular deuterium distributions of the carbon-bound hydrogens of glucose were measured using deuterium nuclear magnetic resonance. Glucose isolated from leaf starch of common bean (Phaseolus vulgaris cv. Linden) or spinach (Spinacia oleracea cv. Giant nobel) was depleted in deuterium in the C(2) position, compared with glucose isolated from leaf sucrose or bean endosperm starch. In beans, the depletion of C(2) was independent of the light intensity during growth (150 or 700 μmol photons s–1 m–2). The ratio of glucose-6-phosphate to fructose-6-phosphate ([G6P]/[F6P]) in bean chloroplasts was 0·9 in high light, indicating that the phosphoglucose isomerase reaction was not in equilibrium ([G6P]/[F6P]) ≈ 3). This implies that the kinetic isotope effect of phosphoglucose isomerase depleted deuterium in the C(2) position of G6P. Because the depletion was the same, the chloroplastic ([G6P]/[F6P]) ratio was in disequilibrium irrespective of the light intensity. If the ([G6P]/[F6P]) ratio was in equilibrium, a large chloroplastic pool of G6P would be unavailable for regeneration of ribulose-1,5-bisphospate. We argue that chloroplast phosphoglucose isomerase activity is regulated to avoid this. The deuterium depletion of C(2) explains the known low overall deuterium abundance of leaf starch. This example shows that measurements of intramolecular deuterium distributions can be essential to understand overall deuterium abundances of plant material.

  • 30.
    Shevela, Dmitriy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Stavanger, Norway.
    Arnold, Janine
    Reisinger, Veronika
    Berends, Hans-Martin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kmiec, Karol
    Koroidov, Sergey
    Umeå University, Faculty of Science and Technology, Department of Chemistry. PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA, USA.
    Bue, Ann Kristin
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Eichacker, Lutz A.
    Biogenesis of water splitting by photosystem II during de-etiolation of barley (Hordeum vulgare L.)2016In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 39, no 7, p. 1524-1536Article in journal (Refereed)
    Abstract [en]

    Etioplasts lack thylakoid membranes and photosystem complexes. Light triggers differentiation of etioplasts into mature chloroplasts, and photosystem complexes assemble in parallel with thylakoid membrane development. Plastids isolated at various time points of de-etiolation are ideal to study the kinetic biogenesis of photosystem complexes during chloroplast development. Here, we investigated the chronology of photosystem II (PSII) biogenesis by monitoring assembly status of chlorophyll-binding protein complexes and development of water splitting via O2 production in plastids (etiochloroplasts) isolated during de-etiolation of barley (Hordeum vulgare L.). Assembly of PSII monomers, dimers and complexes binding outer light-harvesting antenna [PSII-light-harvesting complex II (LHCII) supercomplexes] was identified after 1, 2 and 4 h of de-etiolation, respectively. Water splitting was detected in parallel with assembly of PSII monomers, and its development correlated with an increase of bound Mn in the samples. After 4 h of de-etiolation, etiochloroplasts revealed the same water-splitting efficiency as mature chloroplasts. We conclude that the capability of PSII to split water during de-etiolation precedes assembly of the PSII-LHCII supercomplexes. Taken together, data show a rapid establishment of water-splitting activity during etioplast-to-chloroplast transition and emphasize that assembly of the functional water-splitting site of PSII is not the rate-limiting step in the formation of photoactive thylakoid membranes.

  • 31. STRAND, M
    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).
    EFFECTS OF FROST HARDENING, DEHARDENING AND FREEZING STRESS ON INVIVO CHLOROPHYLL FLUORESCENCE OF SEEDLINGS OF SCOTS PINE (PINUS-SYLVESTRIS L)1988In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 11, no 4, p. 231-238Article in journal (Refereed)
  • 32.
    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).
    Foyer, C H
    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).
    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).
    Altering flux through the sucrose biosynthesis pathway in transgenic Arabidopsis thaliana modifies photosynthetic acclimation at low temperatures and the development of freezing tolerance2003In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 26, no 4, p. 523-535Article in journal (Refereed)
    Abstract [en]

    To test the hypothesis that the up-regulation of sucrose biosynthesis during cold acclimation is essential for the development of freezing tolerance, the acclimation responses of wild-type (WT) Arabidopsis thaliana (Heynh.) were compared with transgenic plants over-expressing sucrose phosphate synthase (over-sps) or with antisense repression of either cytosolic fructose-1,6-bisphosphatase (antifbp) or sucrose phosphate synthase (antisps). Plants were grown at 23 degreesC and then shifted to 5 degreesC. The leaves shifted to 5 degreesC for 10 d and the new leaves that developed at 5 degreesC were compared with control leaves on plants at 23 degreesC. Plants over-expressing sucrose phosphate synthase showed improved photosynthesis and increased flux of fixed carbon into sucrose when shifted to 5 degreesC, whereas both antisense lines showed reduced flux into soluble sugars relative to WT. The improved photosynthetic performance by the over-sps plants shifted to 5 degreesC was associated with an increase in freezing tolerance relative to WT (-9.1 and -7.2 degreesC, respectively). In contrast, both antisense lines showed impaired development of freezing tolerance (- 5.2 and -5.8 degreesC for antifbp and antisps, respectively) when shifted to 5 degreesC. In the new leaves developed at 5 degreesC the recovery of photosynthesis as typically seen in WT was strongly inhibited in both antisense lines and this inhibition was associated with a further failure of both antisense lines to cold acclimate. Thus, functional sucrose biosynthesis at low temperature in the over-sps plants reduced the inhibition of photosynthesis, maintained the mobilization of carbohydrates from source leaves to sinks and increased the rate at which freezing tolerance developed. Modification of sucrose metabolism therefore represents an additional approach that will have benefits both for the development of freezing tolerance and over-wintering, and for the supply of exportable carbohydrate to support growth at low temperatures.

  • 33.
    Wagner, Raik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Von Sydow, Lotta
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Aigner, Harald
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Netotea, Sergiu
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Bioinformatics Infrastructure for Life Sciences (BILS), Linköping, Sweden.
    Brugière, Sabine
    Sjögren, Lars
    Ferro, Myriam
    Clarke, Adrian
    Funk, Christiane
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Deletion of FtsH11 protease has impact on chloroplast structure and function in Arabidopsis thaliana when grown under continuous light2016In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 39, no 11, p. 2530-2544Article in journal (Refereed)
    Abstract [en]

    The membrane-integrated metallo-protease FtsH11 of Arabidopsis thaliana is proposed to be dual targeted to mitochondria and chloroplasts. A bleached phenotype was observed in ftsh11 grown at long days or continuous light, pointing to disturbances in the chloroplast. Within the chloroplast FtsH11 was found to be located exclusively in the envelope. Two chloroplast-located proteins of unknown function (Tic22-like protein and YGGT-A) showed significantly higher abundance in envelope membranes and intact chloroplasts of ftsH11, and therefore qualify as potential substrates for the FtsH11 protease. No proteomic changes were observed in the mitochondria of 6 weeks old ftsH11 compared to wild type and FtsH11 was not immunodetected in these organelles. The abundance of plastidic proteins, especially of photosynthetic proteins, was altered even during standard growth conditions in total leaves of ftsh11. At continuous light the amount of PSI decreased relative to PSII, accompanied by a drastic change of the chloroplast morphology and a drop of NPQ. FtsH11 is crucial for chloroplast structure and function during growth in prolonged photoperiod.

  • 34.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Effects of low temperature on photosynthesis1983In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 6, no 4, p. 281-300Article, review/survey (Refereed)
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