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  • 1. Bennett, M
    et al.
    Bellini, C
    Van Der Straeten, D
    Integrative biology: dissecting cross talk between plant signaling pathways2005In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 123, p. 109-Article, review/survey (Other (popular science, discussion, etc.))
  • 2. Bhalerao, RP
    et al.
    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).
    Factors influencing the phycobilisome rod composition of the cyanobacterium synechococcus sp pcc-7942: effects of reduced phycocyanin content, lack of rod-linkers, and over-expression of the rod-terminating linker1994In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 90, no 1, p. 187-197Article in journal (Refereed)
    Abstract [en]

    Four novel mutants with altered phycobilisomes were constructed in the cyanobacterium Synechococcus 7942 to study factors influencing the rod length and composition. These mutants show (1) reduced phycocyanin content, (2) reduced phycocyanin content combined with loss of the 33 kDa linker, (3) loss of the 30 kDa rod-linker and (4) overexpression of the 9 kDa rod terminating linker. For these mutants we determined the 33 to 27 kDa and 30 to 27 kDa linker ratios in the isolated phycobilisomes and compared these ratios with those in the wild type. The 30 kDa linker can be incorporated into the rods in absence of the 33 kDa linker. The incorporation of the 30 kDa linker is lower in absence of the 33 kDa linker. When the 30 kDa linker is missing, an increase in the level of the 33 kDa linker is seen, indicating that there could be an excess of the 33 kDa linker in the cells. Our results also show that a reduction in the phycocyanin content causes a decrease in the rod length simultaneously with a reduction of the 30/27 linker ratio, without altering the 33/27 ratio. Reduced phycocyanin content and absence of the 33 kDa linker cause a dramatic reduction in the incorporation of the 30 kDa linker into the rods in the mutant B2SMIKM. Over-expression of the 9 kDa linker results in a decreased incorporation of both the 33 and 30 kDa linkers into the rods, the effect being more pronounced for the 30 kDa linker. This result indicates that the level of the 9 kDa linker relative to those of the 33 and the 30 kDa linkers may be an important determinant of the phycobilisome rod length.

  • 3. Bishop, NI
    et al.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    CORRELATION OF THE PHOTOSYSTEM-I AND PHOTOSYSTEM-II REACTION CENTER CHLOROPHYLL-PROTEIN COMPLEXES, CP-AI AND CP-AII, WITH PHOTOSYSTEM ACTIVITY AND LOW-TEMPERATURE FLUORESCENCE EMISSION PROPERTIES IN MUTANTS OF SCENEDESMUS1980In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 49, no 4, p. 477-486Article in journal (Refereed)
  • 4. BORODIN, V
    et al.
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    THE EFFECT OF LIGHT QUALITY ON THE INDUCTION OF EFFICIENT PHOTOSYNTHESIS UNDER LOW CO2 CONDITIONS IN CHLAMYDOMONAS-REINHARDTII AND CHLORELLA-PYRENOIDOSA1994In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 92, no 2, p. 254-260Article in journal (Refereed)
    Abstract [en]

    The effect of blue and red light on the adaptation to low CO2 conditions was studied in high-CO2 grown cultures of Chlorella pyrenoidosa (82T) and Chlamydomonas reinhardtii (137(+)) by measuring O-2 exchange under various inorganic carbon (C-i) concentrations. At equal photosynthetic photon flux density (PPFD), blue light was more favourable for adaptation in both species, compared to red light. The difference in photosynthetic oxygen evolution between cells adapted to low C-i under blue and red light was more pronounced when oxygen evolution was measured under low C-i compared to high C-i conditions. The effect of light quality on adaptation remained for several hours. The different effects caused by blue and red light was observed in C. pyrenoidosa over a wide range of PPFD with increasing differences at increasing PPFD. The maximal difference was obtained at a PPFD above 1 500 mu mol m(-2) s(-1). We found no difference in the extracellular carbonic anhydrase activity between blue- and red light adapted cells. The light quality effect recorded under C-i-limiting conditions in C. reinhardtii cells adapted to air, was only 37% less when instead of pure blue light red light containing 12.5% of blue light (similar PPFD as blue light) was used during adaptation to low carbon. This indicates that in addition to affecting photosynthesis, blue light affected a sensory system involved in algal adaptation to low C-i conditions. Since the affinity for C-i of C. pyrenoidosa and C. reinhardtii cells adapted to air under blue light was higher than that of cells adapted under red light, we suggest that induction of some component(s) of the C-i accumulating mechanism is regulated by the light quality.

  • 5.
    Brunoni, Federica
    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, Sweden.
    Ljung, Karin
    Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Bellini, Catherine
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Control of root meristem establishment in conifers2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 165, no 1, p. 81-89Article in journal (Refereed)
    Abstract [en]

    The evolution of terrestrial plant life was made possible by the establishment of a root system, which enabled plants to migrate from aquatic to terrestrial habitats. During evolution, root organization has gradually progressed from a very simple to a highly hierarchical architecture. Roots are initiated during embryogenesis and branch afterward through lateral root formation. Additionally, adventitious roots can be formed post-embryonically from aerial organs. Induction of adventitious roots (ARs) forms the basis of the vegetative propagation via cuttings in horticulture, agriculture and forestry. This method, together with somatic embryogenesis, is routinely used to clonally multiply conifers. In addition to being utilized as propagation techniques, adventitious rooting and somatic embryogenesis have emerged as versatile models to study cellular and molecular mechanisms of embryo formation and organogenesis of coniferous species. Both formation of the embryonic root and the AR primordia require the establishment of auxin gradients within cells that coordinate the developmental response. These processes also share key elements of the genetic regulatory networks that, e.g. are triggering cell fate. This minireview gives an overview of the molecular control mechanisms associated with root development in conifers, from initiation in the embryo to post-embryonic formation in cuttings.

  • 6. Campbell, D
    et al.
    Clarke, A K
    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).
    Oxygen-dependent electron flow influences photosystem II function and psbA gene expression in the cyanobacterium Synechococcus sp PCC 79421999In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 105, no 4, p. 746-755Article in journal (Refereed)
    Abstract [en]

    During acclimated growth in Synechococcus sp, PCC 7942 a substantial proportion of the electrons extracted from mater by photosystem II ultimately flow back to oxygen, This flow increases rapidly under high light, which allows Synechococcus to maintain photosystem II centers largely open, even under excessive excitation, The electron flow to oxygen with increasing light accounts for the progressive discrepancy between the light response curve of measured oxygen evolution, and the light response curve of photosystem II activity estimated from fluorescence measures. In cells under anoxia this flexible electron sink is lost and photosystem II centers suffer partial closure at the growth light intensity, with closure becoming more severe under excess light. As predicted from earlier work this PSII closure results in rapid loss of psbAI message, encoding the D1:1 protein of PSII, and induction of psbAII/AIII encoding the alternate D1:2 protein. The changes in the mRNA pool are not, however, reflected at the protein level, and D1:1 remains in the thylakoid membranes. There is no accumulation of D1:2, despite some continued synthesis of other proteins. PSII closure, therefore, results in repression of psbAI and induction psbAII/AIII expression, but D1:1/D1:2 exchange is blocked by anoxia, downstream from transcription. D1:1 protein and PSII activity are quite stable under anoxia and moderate illumination, Nevertheless, upon recovery under oxygenic conditions, the existing D1:1 is lost from the membranes, resulting in a transient drop in PSII activity. This suggests that under normal conditions the cells use oxygen to facilitate preemptive turnover of D1 proteins.

  • 7.
    Carius, Anke B.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Rogne, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Duchoslav, Miloš
    Charles University, Prague, Czech Republic.
    Wolf-Watz, Magnus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Shutova, Tatiana
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Dynamic pH‐induced conformational changes of the PsbO protein in the fluctuating acidity of the thylakoid lumen2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 166, no 1, p. 288-299Article in journal (Refereed)
    Abstract [en]

    The PsbO protein is an essential extrinsic subunit of photosystem II, the pigment–protein complex responsible for light‐driven water splitting. Water oxidation in photosystem II supplies electrons to the photosynthetic electron transfer chain and is accompanied by proton release and oxygen evolution. While the electron transfer steps in this process are well defined and characterized, the driving forces acting on the liberated protons, their dynamics and their destiny are all largely unknown. It was suggested that PsbO undergoes proton‐induced conformational changes and forms hydrogen bond networks that ensure prompt proton removal from the catalytic site of water oxidation, i.e. the Mn4CaO5 cluster. This work reports the purification and characterization of heterologously expressed PsbO from green algae Chlamydomonas reinhardtii and two isoforms from the higher plant Solanum tuberosum (PsbO1 and PsbO2). A comparison to the spinach PsbO reveals striking similarities in intrinsic protein fluorescence and CD spectra, reflecting the near‐identical secondary structure of the proteins from algae and higher plants. Titration experiments using the hydrophobic fluorescence probe ANS revealed that eukaryotic PsbO proteins exhibit acid–base hysteresis. This hysteresis is a dynamic effect accompanied by changes in the accessibility of the protein's hydrophobic core and is not due to reversible oligomerization or unfolding of the PsbO protein. These results confirm the hypothesis that pH‐dependent dynamic behavior at physiological pH ranges is a common feature of PsbO proteins and causes reversible opening and closing of their β‐barrel domain in response to the fluctuating acidity of the thylakoid lumen.

  • 8. Castelain, Mathieu
    et al.
    Le Hir, Rozenn
    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).
    The non-DNA-binding bHLH transcription factor PRE3/bHLH135/ATBS1/TMO7 is involved in the regulation of light signaling pathway in Arabidopsis2012In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 145, no 3, p. 450-460Article in journal (Refereed)
    Abstract [en]

    Plant basic Helix-loop-helix (bHLH) proteins are transcription factors that are involved in many developmental mechanisms, including light signaling and hormone homeostasis. Some of them are non-DNA-binding proteins and could act as dominant negative regulators of other bHLH proteins by forming heterodimers, in a similar way to animal inhibitor of DNA-binding proteins. It has been recently reported that several non-DNA-binding bHLHs are involved in light signaling (KDR/PRE6), gibberellic acid signaling (PRE1/BNQ1/bHLH136) or brassinosteroid signaling (ATBS1). Here we report that Arabidopsis lines overexpressing the PRE3/bHLH135/ATBS1/TMO7 gene are less responsive to red, far-red and blue light than wild-type which is likely to explain the light hyposensitive phenotype displayed when grown under white light conditions. Using quantitative polymerase chain reaction, we show that the expression of PRE3 and KDR/PRE6 genes is regulated by light and that light-related genes are deregulated in the PRE3-ox lines. We show that PRE3 is expressed in the shoot and root meristems and that PRE3-ox lines also have a defect in lateral root development. Our results not only suggest that PRE3 is involved in the regulation of light signaling, but also support the hypothesis that non-DNA-binding bHLH genes are promiscuous genes regulating a wide range of both overlapping and specific regulatory pathways.

  • 9. Chatterjee, Ruchira
    et al.
    Lassalle, Louise
    Gul, Sheraz
    Fuller, Franklin D.
    Young, Iris D.
    Ibrahim, Mohamed
    de Lichtenberg, Casper
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry – Ångström, Molecular Biomimetics, Uppsala University, Uppsala 75237, Sweden.
    Cheah, Mun Hon
    Zouni, Athina
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry – Ångström, Molecular Biomimetics, Uppsala University, Uppsala 75237, Sweden.
    Yachandra, Vittal K.
    Kern, Jan
    Yano, Junko
    Structural isomers of the S-2 state in photosystem II: do they exist at room temperature and are they important for function?2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 166, no 1, p. 60-72Article in journal (Refereed)
    Abstract [en]

    In nature, an oxo‐bridged Mn4CaO5 cluster embedded in photosystem II (PSII), a membrane‐bound multi‐subunit pigment protein complex, catalyzes the water oxidation reaction that is driven by light‐induced charge separations in the reaction center of PSII. The Mn4CaO5 cluster accumulates four oxidizing equivalents to enable the four‐electron four‐proton catalysis of two water molecules to one dioxygen molecule and cycles through five intermediate S‐states, S0 – S4 in the Kok cycle. One important question related to the catalytic mechanism of the oxygen‐evolving complex (OEC) that remains is, whether structural isomers are present in some of the intermediate S‐states and if such equilibria are essential for the mechanism of the O‐O bond formation. Here we compare results from electron paramagnetic resonance (EPR) and X‐ray absorption spectroscopy (XAS) obtained at cryogenic temperatures for the S2state of PSII with structural data collected of the S1, S2 and S3 states by serial crystallography at neutral pH (∼6.5) using an X‐ray free electron laser at room temperature. While the cryogenic data show the presence of at least two structural forms of the S2 state, the room temperature crystallography data can be well‐described by just one S2 structure. We discuss the deviating results and outline experimental strategies for clarifying this mechanistically important question.

  • 10.
    Chen, Yang-Er
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. College of Life Sciences, Sichuan Agricultural University, Ya'an, China.
    Yuan, Shu
    Schröder, Wolfgang P.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Comparison of methods for extracting thylakoid membranes of Arabidopsis plants2016In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 156, no 1, p. 3-12Article in journal (Refereed)
    Abstract [en]

    Robust and reproducible methods for extracting thylakoid membranes are required for the analysis of photosynthetic processes in higher plants such as Arabidopsis. Here, we compare three methods for thylakoid extraction using two different buffers. Method I involves homogenizing the plant material witha metal/glass blender; method II involves manually grinding the plant materialin ice-cold grinding buffer with a mortar and method III entails snap-freezing followed by manual grinding with a mortar, after which the frozen powder is thawed in isolation buffer. Thylakoid membrane samples extracted using each method were analyzed with respect to protein and chlorophyll content, yields relative to starting material, oxygen-evolving activity, protein complex content and phosphorylation. We also examined how the use of fresh and frozen thylakoid material affected the extracts’ contents of protein complexes. The use of different extraction buffers did not significantly alter the protein contentof the extracts in any case. Method I yielded thylakoid membranes with the highest purity and oxygen-evolving activity. Method III used low amounts of starting material and was capable of capturing rapid phosphorylation changes in the sample at the cost of higher levels of contamination. Method II yielded thylakoid membrane extracts with properties intermediate between those obtained with the other two methods. Finally, frozen and freshly isolated thylakoid membranes performed identically in blue native-polyacrylamide gel electrophoresis experiments conducted in order to separate multimeric protein supracomplexes.

  • 11. Delarue, M.
    et al.
    Muller, P.
    Bellini, C.
    Delbarre, A.
    Increased auxin efflux in the IAA-overproducing sur1 mutant of Arabidopsis thaliana: A mechanism for reducing auxin levels?1999In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 107, no 1, p. 120-127Article in journal (Refereed)
    Abstract [en]

    With the aim of investigating the mechanisms that maintain auxin homeostasis in plants, we have monitored the net uptake and metabolism of exogenously supplied indole-3-acetic acid (IAA) and naphthalene-1-acetic acid (NAA) in seedlings of wild type and the IAA-overproducing mutant sur1 of Arabidopsis thaliana. Tritiated IAA and NAA entered the seedling tissues within minutes and were mostly accumulated as metabolites, probably amino acid and sugar conjugates, The mutant seedlings were marked by a strong increase of [H-3]IAA metabolism and a reduction of the accumulation levels of both free [H-3]IAA and [H-3]NAA. The same characteristics were observed in wild-type seedlings grown on 5 mu M picloram. We measured [H-3]NAA uptake in the presence of high concentrations of unlabeled NAA or the auxin efflux carrier inhibitor naphthylphthalamic acid (NPA). This abolished the difference in free [H-3]NAA accumulation between the mutant or picloram-treated seedlings and wild-type seedlings. These data indicated that active auxin efflux carriers were present in Arabidopsis seedling tissues. Picloram-treated seedlings and seedlings of the IAA-overproducing mutant sur1 displayed increased auxin efflux carrier activity as well as elevated conjugation of IAA. There is previous evidence to suggest that conjugation is a means to remove excess IAA in plant cells. Here, we discuss the possibility of efflux constituting an additional mechanism for regulating free IAA levels in the face of an excess auxin supply.

  • 12.
    ELIASSON, L
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    FACTORS AFFECTING THE INHIBITORY EFFECT OF INDOLYLACETIC ACID ON ROOT-FORMATION IN PEA CUTTINGS1981In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 51, no 1, p. 23-26Article in journal (Refereed)
  • 13. FALK, S
    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).
    RECOVERY OF PHOTOSYNTHESIS AND PHOTOSYSTEM-II FLUORESCENCE IN CHLAMYDOMONAS-REINHARDTII AFTER EXPOSURE TO 3 LEVELS OF HIGH LIGHT1992In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 85, no 1, p. 61-68Article in journal (Refereed)
    Abstract [en]

    Recovery from 60 min of photoinhibitory treatment at photosynthetic photon flux densities of 500, 1400 and 2200-mu-mol m-2 s-1 was followed in cells of the green alga Chlamydomonas reinhardtii grown at 125-mu-mol m-2 s-1. These light treatments re resent photoregulation, moderate photoinhibition and strong photoinhibition, respectively. Treatment in photoregulatory light resulted in an increased maximal rate of oxygen evolution (P(max)) and an increased quantum yield (PHI), but a 15% decrease in F(V)/F(M). Treatment at moderately photoinhibitory light resulted in a 30% decrease in F(V)/F(M) and an approximately equal decrease in PHI. Recovery in dim light restored F(V)/F(M) within 15 and 45 min after high light treatment at 500 and 1 400-mu-mol m-2 s-1 respectively. Convexity (THETA), a measure of the extent of co-limitation between PS II turnover and whole-chain electron transport, and PHI approached, but did not reach the control level during recovery after exposure to 1 400-mu-mol m 2 s-1, whereas P(max) increased above the control. Treatment at 2200-mu-mol m-2 s-1 resulted in a strong reduction of the modeled parameters PHI, THETA and P(max). Subsequent recovery was initially rapid but the rate decreased, and a complete recovery was not reached within 120 min. Based on the results, it is hypothesized that exposure to high light results in two phenomena. The first, expressed at all three light intensities, involves redistribution within the different aspects of PS II heterogeneity rather than a photoinhibitory destruction of PS II reaction centers. The second, most strongly expressed at 2200-mu-mol m-2 s-1, is a physical damage to PS II shown as an almost total loss of PS II(alpha) and PS II Q(B)-reducing centers. Thus recovery displayed two phases, the first was rapid and the only visible phase in algae exposed to 500 and 1 400-mu-mol m-2 s-1. The second phase was slow and visible only in the later part of recovery in cells exposed to 2 200-mu-mol m-2 s-1.

  • 14. FALK, S
    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).
    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).
    TEMPERATURE-DEPENDENT PHOTOINHIBITION AND RECOVERY OF PHOTOSYNTHESIS IN THE GREEN-ALGA CHLAMYDOMONAS-REINHARDTII ACCLIMATED TO 12 AND 27-DEGREES-C1990In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 78, no 2, p. 173-180Article in journal (Refereed)
  • 15. Gama, Filipe
    et al.
    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).
    Eymery, Francoise
    Finkemeier, Iris
    Gelhaye, Eric
    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).
    Dietz, Karl Josef
    Rey, Pascal
    Jacquot, Jean-Pierre
    Rouhier, Nicolas
    The mitochondrial type II peroxiredoxin from poplar2007In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 129, no 1, p. 196-206Article in journal (Refereed)
    Abstract [en]

    Mitochondria are a major site of reactive oxygen species production and controlling the peroxide levels in this compartment is essential. Peroxiredoxins (Prx) are heme-free peroxidases, which use reactive cysteines for their catalysis and reducing systems for their regeneration. One of the two Prxs present in poplar mitochondria, Prx IIF, expressed as a recombinant protein, was found to reduce a broad range of peroxides with electrons provided preferentially by glutaredoxin and to a lesser extent by glutathione, all the thioredoxins tested being inefficient. This protein is constitutively expressed because it is found in all tissues analyzed. Its expression is modified during a biotic interaction between poplar and the rust fungus Melampsora laricii populina. On the other hand, Prx IIF expression does not substantially vary under abiotic stress conditions. Nevertheless, water deficit or chilling and probably induced senescence, but not photooxidative conditions or heavy metal treatment, also led to a small increase in PrxIIF abundance in Arabidopsis thaliana plants.

  • 16.
    Gardeström, Per
    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).
    EDWARDS, GE
    HENRICSON, D
    ERICSON, I
    THE LOCALIZATION OF SERINE HYDROXYMETHYLTRANSFERASE IN LEAVES OF C-3 AND C-4 SPECIES1985In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 64, no 1, p. 29-33Article in journal (Refereed)
  • 17.
    Gardeström, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Igamberdiev, Abir U.
    The origin of cytosolic ATP in photosynthetic cells2016In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 157, no 3, p. 367-379Article, review/survey (Refereed)
    Abstract [en]

    In photosynthetically active cells, both chloroplasts and mitochondria have the capacity to produce ATP via photophosphorylation and oxidative phosphorylation, respectively. Thus, theoretically, both organelles could provide ATP for the cytosol, but the extent, to which they actually do this, and how the process is regulated, both remain unclear. Most of the evidence discussed comes from experiments with rapid fractionation of isolated protoplasts subjected to different treatments in combination with application of specific inhibitors. The results obtained indicate that, under conditions where ATP demand for photosynthetic CO2 fixation is sufficiently high, the mitochondria supply the bulk of ATP for the cytosol. In contrast, under stress conditions where CO2 fixation is severely limited, ATP will build up in chloroplasts and it can then be exported to the cytosol, by metabolite shuttle mechanisms. Thus, depending on the conditions, either mitochondria or chloroplasts can supply the bulk of ATP for the cytosol. This supply of ATP is discussed in relation to the idea that mitochondrial functions may be tuned to provide an optimal environment for the chloroplast. By balancing cellular redox states, mitochondria can contribute to an optimal photosynthetic capacity.

  • 18.
    GEZEILUS, K
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    HALLGREN, JE
    EFFECT OF SO32- ON THE ACTIVITY OF RIBULOSE BISPHOSPHATE CARBOXYLASE FROM SEEDLINGS OF PINUS-SILVESTRIS1980In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 49, no 4, p. 354-358Article in journal (Refereed)
  • 19.
    GEZELIUS, K
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    ERICSSON, A
    HALLGREN, JE
    BRUNES, L
    EFFECTS OF BUD REMOVAL IN SCOTS PINE (PINUS-SILVESTRIS) SEEDLINGS1981In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 51, no 2, p. 181-188Article in journal (Refereed)
  • 20. Greer, DH
    et al.
    Ottander, Christina
    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).
    Photoinhibition and recovery of photosynthesis in intact barley leaves at 5 and 20°C1991In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 81, no 2, p. 203-210Article in journal (Refereed)
    Abstract [en]

    Photoinhibition of photosynthesis and its recovery were studied in intact barley (Hordeum vulgare L. cv. Gunilla) leaves grown in a controlled environment by exposing them to two temperatures, 5 and 20-degrees-C, and a range of photon flux densities in excess of that during growth. Additionally, photoinhibition was examined in the presence of chloramphenicol (CAP, an inhibitor of chloroplast protein synthesis) and of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Susceptibility to photoinhibition was much higher at 5 than at 20-degrees-C. Furthermore, at 20-degrees-C CAP exacerbated photoinhibition strongly, whereas CAP had little additional effect (10%) at 5-degrees-C. These results support the model that net photoinhibition is the difference between the inactivation and repair of photosystem II (PSII); i.e. the degradation and synthesis of the reaction centre protein, D1. Furthermore, the steady-state extent of photoinhibition was strongly dependent on temperature and the results indicated this was manifested through the effects of temperature on the repair process of PSII. We propose that the continuous repair of PSII at 20-degrees-C conferred at least some protection from photoinhibition. At 5-degrees-C the repair process was largely inhibited, with increased photoinhibition as a consequence. However, we suggest where repair is inhibited by low temperature, some protection is alternatively conferred by the photoinhibited reaction centres. Providing they are not degraded, such centres could still dissipate excitation energy non-radiatively, thereby conferring protection of remaining photochemically active centres under steady-state conditions. A fraction of PS II centres were capable of resisting photoinhibition when the repair process was inhibited by CAP. This is discussed in relation to PS II heterogeneity. Furthermore, the repair process was not apparently activated within 3 h when barley leaves were transferred to photoinhibitory light conditions at 20-degrees-C.

  • 21.
    HALLGREN, JE
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    GEZELIUS, K
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    EFFECTS OF SO2 ON PHOTOSYNTHESIS AND RIBULOSE BISPHOSPHATE CARBOXYLASE IN PINE TREE SEEDLINGS1982In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 54, no 2, p. 153-161Article in journal (Refereed)
  • 22.
    HALLGREN, JE
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    SUNDBOM, E
    STRAND, M
    PHOTOSYNTHETIC RESPONSES TO LOW-TEMPERATURE IN BETULA-PUBESCENS AND BETULA-TORTUOSA1982In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 54, no 3, p. 275-282Article in journal (Refereed)
  • 23.
    Hansson, Andreas
    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).
    Jensen, Poul E
    Chlorophyll limitation in plants remodels and balances the photosynthetic apparatus by changing the accumulation of photosystems I and II through two different approaches.2009In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 135, no 2, p. 214-228Article in journal (Refereed)
    Abstract [en]

    Arabidopsis plants with a reduced expression of CHL27 (chl27), an enzyme (EC 1.14.13.81) required for the synthesis of Pchlide, are chlorotic and have a Chl a/b ratio two times higher than wild-type (WT). Knockdown plants transformed with a construct constitutively expressing CHL27 recovered regarding Chl level, a/b ratio and 77K fluorescence. A negative correlation was found between total Chl and Chl a/b ratio in the examined plants. The chl27 plants fail to assemble WT amounts of complete PSI and PSII, leading to an elevated PSII/PSI ratio. The PSI remaining in chl27 is fully functional with a quantum yield higher than for WT. Despite a severe reduction of photosystem II antennae protein (LHCII) and an increased proportion of stroma lammella, the chl27 plants are able to perform state transitions. No major differences were found regarding PSII quantum yield, qN and 1 - qp whereas non-photochemical quenching was decreased by a factor two in chl27 plants. The PSII quantum yield for dark-adapted plants and plants given 10 min recovery after high light treatment were similar for both WT and chl27 showing that chl27 plants are not more susceptible to photoinhibition than WT. Taken together the plant manage to acclimate and to balance the two photosystems well even when it is severely limited in Chl. The way to achieve this differs for the two photosystems: regarding PSI a general reduction of core and antenna subunits occurs with no apparent change in the antenna composition; whereas for PSII there is a preferential loss of antenna proteins.

  • 24. Henriksson, Nils
    et al.
    Marshall, John
    Lundholm, Jonas
    Boily, Asa
    Boily, Jean-Francois
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nasholm, Torgny
    Improved in vivo measurement of alternative oxidase respiration in field-collected pine roots2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 167, no 1, p. 34-47Article in journal (Refereed)
    Abstract [en]

    Cellular respiration via the alternative oxidase pathway (AOP) leads to a considerable loss in efficiency. Compared to the cytochrome pathway (COP), AOP produces 0-50% as much ATP per carbon (C) respired. Relative partitioning between the pathways can be measured in vivo based on their differing isotopic discriminations against O-18 in O-2. Starting from published methods, we have refined and tested a new protocol to improve measurement precision and efficiency. The refinements detect an effect of tissue water content (P < 0.0001), which we have removed, and yield precise discrimination endpoints in the presence of pathway-specific respiratory inhibitors [CN- and salicylhydroxamic acid (SHAM)], which improves estimates of AOP/COP partitioning. Fresh roots of Pinus sylvestris were sealed in vials with a CO2 trap. The air was replaced to ensure identical starting conditions. Headspace air was repeatedly sampled and isotopically analyzed using isotope-ratio mass spectrometry. The method allows high-precision measurement of the discrimination against O-18 in O-2 because of repeated measurements of the same incubation vial. COP and AOP respiration discriminated against O-18 by 15.1 +/- 0.3 parts per thousand and 23.8 +/- 0.4 parts per thousand, respectively. AOP contributed to root respiration by 23 +/- 0.2% of the total in an unfertilized stand. In a second, nitrogen-fertilized, stand AOP contribution was only 14 +/- 0.2% of the total. These results suggest the improved method can be used to assess the relative importance of COP and AOP activities in ecosystems, potentially yielding information on the role of each pathway for the carbon use efficiency of organisms.

  • 25. HETHERINGTON, SE
    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).
    MONITORING CHILLING INJURY - A COMPARISON OF CHLOROPHYLL FLUORESCENCE MEASUREMENTS, POST-CHILLING GROWTH AND VISIBLE SYMPTOMS OF INJURY IN ZEA-MAYS1988In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 72, no 2, p. 241-247Article in journal (Refereed)
  • 26. HODGINS, RRW
    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).
    PORPHYRIN METABOLISM IN CHILL-STRESSED SEEDLINGS OF SCOTS PINE (PINUS-SYLVESTRIS)1989In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 77, no 4, p. 620-624Article in journal (Refereed)
  • 27.
    HUSSDANELL, K
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    ELIASSON, L
    OHBERG, I
    CONDITIONS FOR ROOTING OF LEAFY CUTTINGS OF ALNUS-INCANA1980In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 49, no 2, p. 113-116Article in journal (Refereed)
  • 28.
    HUSSDANELL, K
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    ROELOFSEN, W
    AKKERMANS, ADL
    MEIJER, P
    CARBON METABOLISM OF FRANKIA SPP IN ROOT-NODULES OF ALNUS-GLUTINOSA AND HIPPOPHAE-RHAMNOIDES1982In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 54, no 4, p. 461-466Article in journal (Refereed)
  • 29. Igamberdiev, A U
    et al.
    Bykova, N V
    Lea, P J
    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 role of photorespiration in redox and energy balance of photosynthetic plant cells: A study with a barley mutant deficient in glycine decarboxylase2001In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 111, no 4, p. 427-438Article in journal (Refereed)
    Abstract [en]

    Protoplasts and mitochondria were isolated from leaves of homozygous barley (Hordeum vulgare L,) mutant deficient in glycine decarboxylase complex (GDC, EC 2.1.2.10) and wild-type plants. The photosynthetic rates of isolated protoplasts from the mutant and wild-type plants under saturating CO, were similar, but the respiratory rate of the mutant was two-fold higher. Respiration in the mutant plants was much more strongly inhibited by antimycin A than in wild-type plants and a low level of the alternative oxidase protein was found in mitochondria, The activities of NADP- and NAD-dependent malate dehydrogenases were also increased in mutant plants, suggesting an activation of the malate-oxaloacetate exchange for redox transfer between organelles. Mutant plants had elevated activities of NADH- and NADPH-dependent glyoxylate/hydroxypruvate reductases, which may be involved in oxidizing excess NAD(P)H and the scavenging of glyoxylate. We estimated distribution of pools of adenylates, NAD(H) and NADP(H) between chloroplasts, cytosol and mitochondria. Under photorespiratory conditions, ATP/ADP and NADPH/NADP ratios in the mutant were higher in chloroplasts as compared to wild-type plants. The cytosolic NADH/NAD ratio was increased, whereas the ratio in mitochondria decreased. It is concluded that photorespiration serves as an effective redox transfer mechanism from the chloroplast, Plants with a lowered GDC content are deficient in this mechanism, which leads to over-reduction and over-energization of the chloroplasts.

  • 30.
    Igamberdiev, Abir U
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    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).
    Krömer, Silke
    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).
    The role of mitochondrial electron transport during photosynthetic induction. A study with barley (Hordeum vulgare) protoplasts incubated with rotenone and oligomycin1998In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 104, no 3, p. 431-439Article in journal (Refereed)
    Abstract [en]

    Mitochondrial contribution to photosynthetic metabolism during photosynthetic induction was investigated in protoplasts from barley leaves (Hordeum vulgare L. cv. Gunilla, Svalof) by using an inhibitor of mitochondrial Complex I (rotenone) and an inhibitor of the mitochondrial ATPase (oligomycin). Both inhibitors increased the lag phase of photosynthetic induction after the transition of protoplasts from darkness to light. This effect was not observed with broken protoplasts or isolated chloroplasts. Using the method of rapid fractionation of protoplasts it was shown that the delay in photosynthetic induction was accompanied by a decrease in ATP/ADP ratios of the cytosol and mitochondria, whereas the ratio in chloroplasts was not affected. A delay in activation of chloroplastidic NADP-dependent malate dehydrogenase (EC 1.1.1.82) was observed in the presence of either inhibitor. A delay was also observed in the rise of photochemical quenching of chlorophyll fluorescence in the presence of rotenone or oligomycin during photosynthetic induction. The results indicate that during the transition from dark to light the mitochondrial electron transport chain and its Complex I participate in the reoxidation of excessive redox equivalents from photosynthetic electron transport.

  • 31.
    Igamberdiev, Abir U
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Zhou, Guoquing
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Malmberg, Gunilla
    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).
    Respiration of barley protoplasts before and after illumination1997In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 99, no 1, p. 15-22Article in journal (Refereed)
    Abstract [en]

    Respiratory O-2 consumption was investigated in dark-adapted barley (Hordeum vulgare L. cv. Gunilla) protoplasts and after illumination for 10 min at high and very low CO2 in the presence of respiratory and photorespiratory inhibitors. In dark-adapted protoplasts no difference was observed between inhibitor treatments in high and very low CO2. The respiratory rate increased somewhat after illumination and a difference in responce to inhibitors was in some cases observed between high and very low CO2. Thus, the operation of the mitochondrial electron transport chain is affected following a period of active photosynthesis. In all situations tested, oligomycin inhibited respiratiory O-2 uptake indicating that respiration of mitochondria in protoplasts is not strictly ADP limited. Antimycin A inhibited respiration more in dark-adapted protoplasts than after illumination whereas SHAM gave the opposite response. Rotenone inhibited respiration both in dark adapted protoplasts (about 30%) and after illumination where the inhibition was much greater in very low CO2 (50%) than in high CO2 (10%). After iilumination in very low CO2, SHAM + rotenone inhibited respiration almost completely (70%). Photorespiratory inhibitors had very small effect on O-2 consumption in darkness. After illumination the effect of aminoacetonitrile (AAN) was also very low whereas a-hydroxypyridine-2-methane sulphonate (HPMS) in photorespiratory conditions inhibited O-2 uptake much stronger (35%). The addition of glyoxylate enhanced respiration in the presence of HPMS up to the control level suggesting that alternative pathways of glyoxylate conversion might be operating. The differences in inhibitor responses may reflect fine mechanisms for the regulation of energetic balance in the plant cell which consists of switching from electron transport coupled to ATP production to non-coupled transport. Photorespiratory flux is also very flexible, and the suppression of glycine decarboxylation can induce bypass reactions of glyoxylate metabolism.

  • 32. Ivanov, A G
    et al.
    Sane, P
    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).
    Krol, M
    Sveshnikov, D
    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).
    Low-temperature modulation of the redox properties of the acceptor side of photosystem II: photoprotection through reaction centre quenching of excess energy2003In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 119, no 3, p. 376-383Article in journal (Refereed)
    Abstract [en]

    Although it has been well established that acclimation to low growth temperatures is strongly correlated with an increased proportion of reduced Q(A) in all photosynthetic groups, the precise mechanism controlling the redox state of Q(A) and its physiological significance in developing cold tolerance in photoautotrophs has not been fully elucidated. Our recent thermoluminescence (TL) measurements of the acceptor site of PSII have revealed that short-term exposure of the cyanobacterium Synechococcus sp. PCC 7942 to cold stress, overwintering of Scots pine (Pinus sylvestris L.), and acclimation of Arabidopsis plants to low growth temperatures, all caused a substantial shift in the characteristic T-M of S(2)Q(B)(-) recombination to lower temperatures. These changes were accompanied by much lower overall TL emission, restricted electron transfer between Q(A) and Q(B), and in Arabidopsis by a shift of the S(2)Q(A)(-)-related peak to higher temperatures. The shifts in recombination temperatures are indicative of a lower activation energy for the S(2)Q(B)(-) redox pair and a higher activation energy for the S(2)Q(A)(-) redox pair. 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 Q(A) and Q(B) electron acceptors. We propose that these effects result in an increased population of reduced Q(A) (Q(A)(-)), facilitating non-radiative P680(+)Q(A)(-) radical pair recombination within the PSII reaction centre. The proposed reaction centre quenching could be an important protective mechanism in cyanobacteria in which antenna and zeaxanthin cycle-dependent quenching are not present. In herbaceous plants, the enhanced capacity for dissipation of excess light energy via PSII reaction centre quenching following cold acclimation may complement their capacity for increased utilization of absorbed light through CO2 assimilation and carbon metabolism. During overwintering of evergreens, when photosynthesis is inhibited, PSII reaction centre quenching may complement non-photochemical quenching within the light-harvesting antenna when zeaxanthin cycle-dependent energy quenching is thermodynamically restricted by low temperatures. We suggest that PSII reaction centre quenching is a significant mechanism enabling cold-acclimated organisms to acquire increased resistance to high light.

  • 33.
    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.
    Gene-edited plants on the plate: the 'CRISPR cabbage story'2018In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 164, no 4, p. 396-405Article in journal (Refereed)
    Abstract [en]

    The European Union (EU) has very strict regulations for genetically modified plants, but gene editing challenges the basis of the legislation. Genome editied plants with no foreign DNA added were according to the Swedish competent authority Jordbruksverket falling outside of the EU definition of genetically modified plants, and should hence not be regulated. This article describes the background to this interpretation and also how plants gene edited using CRISPR-Cas9 (a Brassica deletion mutant) for the first (?) time were grown in a garden, cooked and eaten, and the subsequent media attention. Furthermore, it also adresses the troubles authorities in other European countries have to handle these plants.

  • 34.
    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.
    Gene-edited plants: What is happening now?2018In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 164, no 4, p. 370-371Article in journal (Other academic)
  • 35.
    Jansson, Stefan
    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).
    VIRGIN, I
    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).
    ANDERSSON, B
    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).
    LIGHT-INDUCED-CHANGES OF PHOTOSYSTEM-II ACTIVITY IN DARK-GROWN SCOTS PINE-SEEDLINGS1992In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 84, no 1, p. 6-12Article in journal (Refereed)
    Abstract [en]

    Both chlorophyll a and b and polypeptides of the photosynthetic apparatus are found in gymnosperm seedlings germinated and grown in absolute darkness. The photosystem II (PSII) activity is, however, limited, probably due to an inactive oxygen evolving system. In the present study dark-grown seedlings of Scots pine (Pinus sylvestris I..) were transferred to light and changes in antenna size and the activation process of PSII were investigated using fluorescence measurements and quantitative western blotting. It was found that the activation process is rapid, requires very little light and that strong light inhibits the process. It takes place without any changes in the primary reactions of PSII. Furthermore, all polypeptides except the major light-harvesting chlorophyll alb-binding protein complex of PSII (LHCII) were present in dark-grown seedlings in amounts comparable to the light treated control. The dark-grown seedlings had the same LHCII polypeptide composition as light treated seedlings, and the LHCII present seemed to be fully connected to the reaction centre. The results indicate that activation of PSII in dark-grown conifer seedlings resembles the photoactivation process of angiosperms. This implies that the fundamental processes in the assembly of the photosystem II complex is the same in all plants, but that the regulation differs between different taxa.

  • 36.
    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).
    Dizengremel, Pierre
    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).
    Preparation of leaf mitochondria from Arabidopsis thaliana2005In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 124, no 4, p. 403-409Article in journal (Refereed)
    Abstract [en]

    Arabidopsis thaliana is, perhaps, the most important model species in modern plant biology. However, the isolation of organelles from leaves of this plant has been difficult. Here, we present two different protocols for the isolation of mitochondria, yielding either highly functional crude mitochondria or highly purified mitochondria. The crude mitochondria were well coupled with the substrates tested (malate + glutamate, glycine and NADH), exhibiting respiratory control ratios of 2.1–3.9. Purified mitochondria with very low levels of chlorophyll contamination were obtained by Percoll gradient centrifugation, yielding 1.2 mg of mitochondrial protein from 50 g of leaves.

  • 37.
    Kindgren, Peter
    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).
    Eriksson, Mats-Jerry
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Benedict, Catherine
    Mohapatra, Anasuya
    Gough, Simon P
    Carlsberg Laboratory, 2500 Copenhagen Valby, Denmark.
    Hansson, Mats
    Carlsberg Laboratory, 2500 Copenhagen Valby, Denmark.
    Kieselbach, Thomas
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    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).
    A novel proteomic approach reveals a role for Mg-protoporphyrin IX in response to oxidative stress2011In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 141, no 4, p. 310-320Article in journal (Refereed)
    Abstract [en]

    The presence of genes encoding organellar proteins in different cellular compartments necessitates a tight coordination of expression by the different genomes of the eukaryotic cell. This coordination of gene expression is achieved by organelle-to-nucleus communication. Stress-induced perturbations of the tetrapyrrole pathway trigger large changes in nuclear gene expression. In order to investigate whether the tetrapyrrole Mg-ProtoIX itself is an important part of plastid-to-nucleus communication, we used an affinity column containing Mg-ProtoIX covalently linked to an Affi-Gel matrix. The proteins that bound to Mg-ProtoIX were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis combined with nano liquid chromatography–mass spectrometry (MS)/MS. Thus, we present a novel proteomic approach to address the mechanisms involved in cellular signaling and we identified interactions between Mg-ProtoIX and a large number of proteins associated with oxidative stress responses. Our approach revealed an interaction between Mg-ProtoIX and the heat shock protein 90-type protein, HSP81-2 suggesting that a regulatory complex including HSP90 proteins and tetrapyrroles controlling gene expression is evolutionarily conserved between yeast and plants. In addition, our list of putative Mg-ProtoIX-binding proteins demonstrated that binding of tetrapyrroles does not depend on a specific amino acid motif but possibly on a specific fold of the protein.

  • 38. Krieger-Liszkay, Anja
    et al.
    Spetea, Cornelia
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry – Ångström Laboratory, Uppsala University, Molecular Biomimetic, Uppsala, Sweden.
    Photosynthesis - European Congress on Photosynthesis Research2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 166, no 1, p. 4-6Article in journal (Other academic)
  • 39. 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 OF PHOTOSYNTHESIS AND GROWTH-RESPONSES AT DIFFERENT LIGHT LEVELS IN PSBA GENE MUTANTS OF THE CYANOBACTERIUM SYNECHOCOCCUS1991In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 82, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Photoinhibition of photosynthesis and growth responses at different light levels (10, 120 and 250-mu-mol m-2 s-1) were studied in psbA gene mutants R2S2C3 (psbAI gene present) and R2K1 (psbAII/psbAIII genes present) of the cyanobacterium Synechococcus sp. PCC 7942 (Anacystis nidulans R2). Mutant R2K1 (possessing form II of the D1 protein of photosystem II) was much more resistant to photoinhibition than the mutant R2S2C3 (possessing form I of the D1 protein). At moderate inhibitory light levels (100 to 300-mu-mol m-2 s-1) this was largely ascribed to an increased resistance of the photosystem II reaction centres possessing form II of the D1 protein. However, at higher light levels the higher resistance of mutant R2K1 was assigned to a higher rate of photosystem II repair, i.e. turnover of the D1 protein. Moreover, our results support the hypothesis that photoinhibition of photosystem II and photoinhibitory induced quenching are due to separate processes. Results from growth experiments show that the R2K1 mutant has a slower growth rate than the R2S2C3 mutant but shows an increased survival under high light stress conditions. It is hypothesized that high resistance to photoinhibition, though allowing a better survival under high light, is not advantageous for optimal growth.

  • 40. 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).
    HUNER, NPA
    THE EFFECTS OF CADMIUM ON PHOTOSYNTHESIS OF PHASEOLUS-VULGARIS - A FLUORESCENCE ANALYSIS1993In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 88, no 4, p. 626-630Article in journal (Refereed)
    Abstract [en]

    Bean plants (Phaseolus vulgaris L. cv. Scarlett), germinated in darkness for 1 week, were transferred to light (200 mumol m-2 s-1) and cultivated for 1 week in a complete nutrient solution. After this period, cadmium ions in the form of CdSO4 were added at the concentrations of 0, 10, 20 and 50 muM. The effects of this metal on the properties of photosystem II photochemistry were studied by means of modulated fluorescence analysis. Steady state photochemical quenching, non-photochemical quenching and terminal fluorescence were determined in control and cadmium-treated plants. We postulate that, during short term exposure of plants to cadmium in the early stages of growth, the Calvin cycle reactions are more likely than photosystem II to be the primary target of the toxic influence of cadmium. The reduced demand for ATP and NADPH upon Calvin cycle inhibition causes a down-regulation of photosystem II photochemistry and of the yield of linear electron transport.

  • 41.
    Law, Simon R
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Differences in pH influence the fate of CO2 in plants2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 165, no 3, p. 445-447Article in journal (Refereed)
    Abstract [en]

    Soils represent the largest and most stable carbon pools on Earth, exceeding even the carbon aggregate found in the atmosphere and global phytomass. However, our understanding of how CO2 travels from the soil to the atmosphere, and the role of plants in this journey, is not fully understood. An article in this issue of Physiologia Plantarum (Shimono et al. 2019) sheds light on this process and unearths the dramatic effect pH can have on the fate of CO2 in plants.

  • 42.
    Law, Simon R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Eucalypt seedlings are aided by phosphorus in the face of drought2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 166, no 4, p. 892-893Article in journal (Other academic)
    Abstract [en]

    Drought is an increasingly common climatic event that can devastate ecosystems, as well as surrounding agricultural and forestry industries. Few places face this challenge more than Australia, where millennia of droughts linked to geography and climatic drivers, such as El Niño, have shaped the flora and fauna into forms predicated on resilience and economy. How an organism responds to these cyclic challenges is a combination of the inherent tolerance mechanisms encoded in their genome and outside influences, such as the effect of nutrients and symbiotic interactions. In this issue of Physiologia Plantarum, Tariq et al. (2019) describes how the presence of the element phosphorus can bolster the physiological and biochemical response of eucalypt seedlings to severe drought conditions.

  • 43.
    Law, Simon R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    New tools for engineering tomorrow's forests2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 165, no 4, p. 671-672Article in journal (Other academic)
    Abstract [en]

    It is difficult to overstate the role of wood in the story of humanity. In times that predate recorded history it provided shelter from the elements, light and warmth when burned, and a supple material with which early humans could craft their first tools. Today, it is still one of our chief building materials and an emerging industry is extending its applications through the development of novel biomaterials, such as cellulose fiber-derived nanocomposites. An article in this issue of Physiologia Plantarum (Johnsson et al. 2019) describes the influence the phytohormones auxin and gibberellic acid (GA) have on the process of wood formation, and reveals possible targets for optimizing cell wall properties in fiber cells.

  • 44.
    Law, Simon R
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    The genetic program at the root of the biological stock exchange2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 166, no 3, p. 709-711Article in journal (Refereed)
    Abstract [en]

    Beneath the gardens, farmlands and forest floors that surround us, a hidden world blooms in careful cooperation and intense competition. The mutualistic symbiosis of the thread-like hyphae of fungi and plant roots (collectively termed mycorrhizae from the Greek mykes - meaning 'fungus', and rhiza - for 'root') is present in the vast majority of plant species. As with most intimate relationships, this symbiosis functions on a principle of 'give and take'. As an autotroph, the plant is able to synthesize all the sugars it requires through photosynthesis; however, its immobility hinders its capacity to forage for nutrients vital for its growth and survival. With an expansive network of hyphae, the heterotrophic fungus is able to locate and remobilize water and nutrients, such as phosphorus (P) and nitrogen (N), and barter them for precious sugars with the plant. An article in this issue of Physiologia Plantarum (Zhao et al. 2019) describes alterations in the genetic programming that takes place in the plant root upon the establishment of this fascinating relationship, which has profound implications for plant productivity and soil management methods.

  • 45. Le Hir, Rozenn
    et al.
    Castelain, Mathieu
    Chakraborti, Dipankar
    Moritz, Thomas
    Dinant, Sylvie
    Bellini, Catherine
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, Versailles, France.
    AtbHLH68 transcription factor contributes to the regulation of ABA homeostasis and drought stress tolerance in Arabidopsis thaliana2017In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 160, no 3, p. 312-327Article in journal (Refereed)
    Abstract [en]

    Basic helix-loop-helix (bHLH) transcription factors are involved in a wide range of developmental processes and in response to biotic and abiotic stresses. They represent one of the biggest families of transcription factors but only few of them have been functionally characterized. Here we report the characterization of AtbHLH68 and show that, although the knock out mutant did not have an obvious development phenotype, it was slightly more sensitive to drought stress than the Col-0, and AtbHLH68 overexpressing lines displayed defects in lateral root (LR) formation and a significant increased tolerance to drought stress, likely related to an enhanced sensitivity to abscisic acid (ABA) and/or increased ABA content. AtbHLH68 was expressed in the vascular system of Arabidopsis and its expression was modulated by exogenously applied ABA in an organ-specific manner. We showed that the expression of genes involved in ABA metabolism [AtAAO3 (AtALDEHYDE OXIDASE 3) and AtCYP707A3 (AtABSCISIC ACID 8HYDROXYLASE 3)], in ABA-related response to drought-stress (AtMYC2, AtbHLH122 and AtRD29A) or during LRs development (AtMYC2 and AtABI3) was de-regulated in the overexpressing lines. We propose that AtbHLH68 has a function in the regulation of LR elongation, and in the response to drought stress, likely through an ABA-dependent pathway by regulating directly or indirectly components of ABA signaling and/or metabolism.

  • 46. Leonardos, E D
    et al.
    Savitch, L V
    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).
    Grodzinski, B
    Daily photosynthetic and C-export patterns in winter wheat leaves during cold stress and acclimation2003In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 117, no 4, p. 521-531Article in journal (Refereed)
    Abstract [en]

    Diurnal patterns of whole-plant and leaf gas exchange and (14) C-export of winter wheat acclimated at 20 and 5degreesC were determined. The 5degreesC-acclimated plants had lower relative growth rates, smaller biomass and leaf area, but larger specific leaf weight than 20degreesC plants. Photosynthetic rates in 20degreesC and 5degreesC-acclimated leaves were similar; however, daytime export from 5degreesC-acclimated leaves was 45% lower. Photosynthesis and export remained steady in 20degreesC and 5degreesC-acclimated leaves during the daytime. By comparison, photosynthesis in 5degreesC-stressed leaves (20degreesC-acclimated plants exposed to 5degreesC 12 h before and during measurements) declined from 70 to 50% of the 20degreesC-acclimated leaves during the daytime, while export remained constant at 35% of the 20degreesC-acclimated and 60% of the 5degreesC-acclimated leaves. At high light and CO2 , photosynthesis and export increased in both 20degreesC and 5degreesC-acclimated leaves, but rates in 5degreesC-stressed leaves remained unchanged. At all conditions daytime export was greater than nighttime export. Taken together, during cold acclimation photosynthesis was upregulated, whereas export was only partially increased. We suggest that this reflects a requirement of cold-acclimated plants to both sustain an increased leaf metabolic demand while concomitantly supporting translocation of photoassimilates to overwintering sinks.

  • 47. LERNMARK, U
    et al.
    HENRICSON, D
    WIGGE, B
    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).
    GLYCINE OXIDATION IN MITOCHONDRIA ISOLATED FROM LIGHT GROWN AND ETIOLATED PLANT-TISSUE1991In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 82, no 3, p. 339-344Article in journal (Refereed)
    Abstract [en]

    Mitochondria were isolated from light grown and dark grown monocotyledonous (wheat-Triticum aestivum and barley-Hordeum vulgare) and dicotyledonous (pea-Pisum sativum) plants and their capacity to oxidize glycine was measured. In all of the studied plant species the rate of mitochondrial glycine oxidation was high in light grown leaves. Glycine oxidation in mitochondria from etiolated leaves was also very substantial; the rate of glycine oxidation relative to the oxidation of other substrates was about half as compared to green tissue. In etiolated non-photosynthetic tissues the relative glycine oxidation was only ca 20% of that measured in green leaves. The effect of light on the development of glycine oxidation capacity was studied using etiolated barley which was transferred to light for 6 to 24 h. During this time the rate of glycine oxidation as compared to the oxidation of NADH and malate increased, approaching the ratio observed in light grown leaves. It is concluded that the synthesis of proteins involved in glycine oxidation is regulated both in a light dependent and in a tissue specific manner. Monocotyledonous plants should be very useful for further studies of this aspect due to the relatively small developmental difference between etiolated and light grown leaf tissue.

  • 48.
    Leul, Melakeselam
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Normand, Philippe
    Université de Lyon, Lyon, France .
    Sellstedt, Anita
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    The organization, regulation and phylogeny of uptake hydrogenase genes in Frankia2007In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 130, no 3, p. 464-470Article in journal (Refereed)
    Abstract [en]

    Frankia alni ACN14a, Frankia sp. CcI3 and Frankia sp. EAN1pec, which have different host specificity and geographical distribution, have two uptake hydrogenase syntons in their genome: hydrogenase synton#1 and hydrogenase synton#2. The organization of hydrogenase genes on these syntons also varies. Phylogenetic analysis of the structural genes of these syntons showed that they were significantly divergent and that hydrogenase synton#1 subunits of these Frankia strains were probably ancestral among the actinobacteria. Hydrogenase gene duplication might have occurred long before emergence of the three Frankia lineages. The structural subunits of hydrogenase HupS2 and HupL2 (synton#2) of F. alni ACN14a and Frankia sp. CcI3, which belong to phylogenetic Frankia cluster 1, were grouped closely together but away from Frankia sp. EAN1pec, which belongs to Frankia cluster 3. Phylogenetic analysis showed the occurrence of lateral transfer of hupL2 in Frankia sp. EAN1pec to or from Geobacter sulfurreducens. The transcript levels of hupS1 and hupL1 relative to hupS2 and hupL2 were higher in F. alni ACN14a grown under free-living conditions. Under symbiotic conditions, transcript levels of hupS2 and hupL2 were higher than those of hupS1 and hupL1. Hydrogenase subunits of synton#1 are more expressed under free-living conditions, whereas those of synton#2 are mainly involved in symbiotic interactions.

  • 49. 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).
    WINGSLE, G
    PHOTOSYNTHESIS AND PHOTOINHIBITION IN LEAVES OF CHLOROPHYLL-B-LESS BARLEY IN RELATION TO ABSORBED LIGHT1992In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 85, no 3, p. 495-502Article in journal (Refereed)
    Abstract [en]

    The response of photosynthesis to absorbed light by intact leaves of wild-type (Hordeum vulgare L. cv. Gunilla) and chlorophyll b-less barley (H. vulgare L. cv. Dornaria, chlorina-f2(2800)) was measured in a light integrating sphere. Up to the section where the light response curve bends most sharply the responses of the b-less and wild-type barley were similar but not identical. Average quantum yield and convexity for the mutant light response curves were 0.89 and 0.90, respectively times those of the wild-type barley. The maximum quantum yield for PSII photochemistry was also 10% lower as indicated by fluorescence induction kinetics (F(v)/F(m)). Just above the region where the light curve bends most sharply, photosynthesis decreased with time in thc mutant but not in the wild-type barley. This decrease was associated with a decrease in F(v)/F(m) indicating photoinhibition of PSII. This photoinhibition occurred in the same region of the light response curve where zeaxanthin formation occurs. Zeaxanthin formation occurred in both the chlorophyll b-less and wild-type leaves. However, the epoxidation state was lower in the mutant than in the wild-type barley. The results indicate that chlorophyll b-less mutants will have reduced photosynthetic production as a result of an increased sensitivity to photoinhibition and possibly a lowered quantum yield and convexity in the absence of photoinhibition.

  • 50.
    Mahboubi, Amir
    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).
    Niittylä, Totte
    Sucrose transport and carbon fluxes during wood formation2018In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 164, no 1, p. 67-81Article in journal (Refereed)
    Abstract [en]

    Wood biosynthesis defines the chemical and structural properties of wood. The metabolic pathways that produce the precursors of wood cell wall polymers have a central role in defining wood properties. To make rational design of wood properties feasible, we need not only to understand the cell wall biosynthetic machinery, but also how sucrose transport and metabolism in developing wood connect to cell wall biosynthesis and how they respond to genetic and environmental cues. Here, we review the current understanding of the sucrose transport and primary metabolism pathways leading to the precursors of cell wall biosynthesis in woody plant tissues. We present both old, persistent questions and new emerging themes with a focus on wood formation in trees and draw upon evidence from the xylem tissues of herbaceous plants when it is relevant.

12 1 - 50 of 92
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