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  • 1001. Zamioudis, Christos
    et al.
    Korteland, Jolanda
    Van Pelt, Johan A.
    van Hamersveld, Muriel
    Dombrowski, Nina
    Bai, Yang
    Hanson, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Molecular Plant Physiology, Department of Biology, Faculty of Science, Utrecht University, The Netherlands.
    Van Verk, Marcel C.
    Ling, Hong-Qing
    Schulze-Lefert, Paul
    Pieterse, Corne M. J.
    Rhizobacterial volatiles and photosynthesis-related signals coordinate MYB72 expression in Arabidopsis roots during onset of induced systemic resistance and iron-deficiency responses2015Inngår i: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 84, nr 2, s. 309-322Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In Arabidopsis roots, the transcription factor MYB72 plays a dual role in the onset of rhizobacteria-induced systemic resistance (ISR) and plant survival under conditions of limited iron availability. Previously, it was shown that MYB72 coordinates the expression of a gene module that promotes synthesis and excretion of iron-mobilizing phenolic compounds in the rhizosphere, a process that is involved in both iron acquisition and ISR signaling. Here, we show that volatile organic compounds (VOCs) from ISR-inducing Pseudomonas bacteria are important elicitors of MYB72. In response to VOC treatment, MYB72 is co-expressed with the iron uptake-related genes FERRIC REDUCTION OXIDASE2 (FRO2) and IRON-REGULATED TRANSPORTER1 (IRT1) in a manner that is dependent on FER-LIKE IRON DEFICIENCY TRANSCRIPTION FACTOR (FIT), indicating that MYB72 is an intrinsic part of the plant's iron-acquisition response that is typically activated upon iron starvation. However, VOC-induced MYB72 expression is activated independently of iron availability in the root vicinity. Moreover, rhizobacterial VOC-mediated induction of MYB72 requires photosynthesis-related signals, while iron deficiency in the rhizosphere activates MYB72 in the absence of shoot-derived signals. Together, these results show that the ISR- and iron acquisition-related transcription factor MYB72 in Arabidopsis roots is activated by rhizobacterial volatiles and photosynthesis-related signals, and enhances the iron-acquisition capacity of roots independently of the iron availability in the rhizosphere. This work highlights the role of MYB72 in plant processes by which root microbiota simultaneously stimulate systemic immunity and activate the iron-uptake machinery in their host plants. Significance Statement Plant roots intimately interact with plant growth-promoting rhizobacteria that prime the plant immune system and aid in iron uptake two functions facilitated by the root-specific transcription factor MYB72. Here we show how MYB72 and iron uptake responses are systemically activated by photosynthesis-related signals and volatiles produced by plant growth-promoting rhizobacteria, highlighting the important role of beneficial root microbiota in supporting plant growth and health.

  • 1002. Zang, Hong
    et al.
    Moritz, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Norstedt, Gunnar
    Hirschberg, Angelica L.
    Tollet-Egnell, Petra
    Effects of oestrogen and testosterone therapy on serum metabolites in postmenopausal women2012Inngår i: Clinical Endocrinology, ISSN 0300-0664, E-ISSN 1365-2265, Vol. 77, nr 2, s. 288-295Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Objectives Metabolite profiles of body fluids or tissue extracts can be regarded as important indicators of physiological or pathological states. Whether hormone-specific alterations of the serum metabolome can be identified using this technique has not been tested yet. The aim of this study was to investigate metabolic responses during hormone therapy in postmenopausal women by a nontargeted metabolomics approach. Methods Sixty naturally postmenopausal women were randomly assigned to treatment with testosterone undecanoate 40 similar to mg every second day; estradiol valerate 2 similar to mg daily; or the combination of both. Serum metabolites were determined by gas chromatography-mass spectrometry (GC-MS) before and after 3 similar to months of treatment. Metabolites affected by the treatment were identified and correlated with changes in insulin sensitivity and lipid profiles. Results Treatment-dependent and hormone-specific effects on serum metabolites were observed, ranging between 69% reduction and 184% increase, but the metabolites that best explained the differences could not be structurally identified. Effects on annotated metabolites were less associated with clinical parameters as compared to established serum markers for adverse lipid and carbohydrate metabolism, such as cholesterol and triglycerides. However, cystine, lysine and tyrosine were shown to change in correlation with insulin sensitivity and high-density lipoprotein cholesterol levels in response to testosterone, indicating that those responses were somehow related to each other. Conclusions Oestrogen- and androgen-specific alterations in the serum metabolome could be identified using GC-MS, reflecting hormone-specific effects on whole body metabolism. New knowledge regarding steroid-mediated metabolic responses within different tissues might be obtained using a similar approach on tissue extracts.

  • 1003. Zaragoza-Castells, Joana
    et al.
    Sánchez-Gómez, David
    Valladares, Fernando
    Hurry, Vaughan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Atkin, Owen K
    Does growth irradiance affect temperature dependence and thermal acclimation of leaf respiration? Insights from a Mediterranean tree with long-lived leaves.2007Inngår i: Plant Cell & Environment, ISSN 0140-7791, Vol. 30, nr 7, s. 820-33Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding the response of leaf respiration (R) to changes in irradiance and temperature is a prerequisite for predicting the impacts of climate change on plant function and future atmospheric CO2 concentrations. Little is known, however, about the interactive effects of irradiance and temperature on leaf R. We investigated whether growth irradiance affects the temperature response of leaf R in darkness (Rdark) and in light (Rlight) in seedlings of a broad-leaved evergreen species, Quercus ilex. Two hypotheses concerning Rdark were tested: (1) the Q10 (i.e. the proportional increase in R per 10 °C rise in temperature) of leaf Rdark is lower in shaded plants than in high-light-grown plants, and (2) shade-grown plants exhibit a lower degree of thermal acclimation of Rdark than plants exposed to higher growth irradiance. We also assessed whether light inhibition of Rlight differs between leaves exposed to contrasting temperatures and growth irradiances, and whether the degree of thermal acclimation of Rlight is dependent on growth irradiance. We showed that while growth irradiance did impact on photosynthesis, it had no effect on the Q10 of leaf Rdark. Growth irradiance had little impact on thermal acclimation when fully expanded, pre-existing leaves were exposed to contrasting temperatures for several weeks. When Rlight was measured at a common irradiance, Rlight/Rdark ratios were higher in shaded plants due to homeostasis of Rlight between growth irradiance treatments and to the lower Rdark in shaded leaves. We also showed that Rlight does not acclimate to the same degree as Rdark, and that Rlight/Rdark decreases with increasing measuring and growth temperatures, irrespective of the growth irradiance. Collectively, we raised the possibility that predictive carbon cycle models can assume that growth irradiance and photosynthesis do not affect the temperature sensitivity of leaf Rdark of long-lived evergreen leaves, thus simplifying incorporation of leaf R into such models.

  • 1004. Zarter, C Ryan
    et al.
    Adams, William W
    Ebbert, Volker
    Adamska, Iwona
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Demmig-Adams, Barbara
    Winter acclimation of PsbS and related proteins in the evergreen Arctostaphylos uva-ursi as influenced by altitude and light environment.2006Inngår i: Plant, Cell & Environment, ISSN 0140-7791, Vol. 29, nr 5, s. 869-78Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The evergreen groundcover bearberry (Arctostaphylos uva-ursi[L.] Sprengel) was characterized over two successive years (2002–2004) from both sun-exposed and shaded sites at a montane ponderosa pine and subalpine forest community of 1900- and 2800-m-high altitudes, respectively. During summer, photosynthetic capacities and pre-dawn photosystem II (PSII) efficiency were similarly high in all four populations, and in winter, only the sun-exposed and shaded populations at 2800 m exhibited complete down-regulation of photosynthetic oxygen evolution capacity and consistent sustained down-regulation of PSII efficiency. This photosynthetic down-regulation at high altitude involved a substantial decrease in PSII components [pheophytin, D1 protein, oxygen evolving complex ([OEC)], a strong up-regulation of several anti-early-light-inducible protein (Elip)- and anti-high-light-inducible protein (Hlip)-reactive bands and a warm-sustained retention of zeaxanthin and antheraxanthin (Z + A). PsbS, the protein modulating the rapid engagement and disengagement of Z + A in energy dissipation, exhibited its most pronounced winter increases in the shade at 1900 m, and thus apparently assumes a greater role in providing rapidly reversible zeaxanthin-dependent photoprotection during winter when light becomes excessive in the shaded population, which remains photosynthetically active. It is attractive to hypothesize that PsbS relatives (Elips/Hlips) may be involved in sustained zeaxanthin-dependent photoprotection under the more extreme winter conditions at 2800 m.

  • 1005. Zas, Rafael
    et al.
    Björklund, Niklas
    Sampedro, Luis
    Hellqvist, Claes
    Karlsson, Bo
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Nordlander, Göran
    Genetic variation in resistance of Norway spruce seedlings to damage by the pine weevil Hylobius abietis2017Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 13, nr 5, artikkel-id 111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Regeneration of northern conifer forests is commonly performed by reforestation with genetically improved materials obtained from long-term breeding programs focused on productivity and timber quality. Sanitary threats can, however, compromise the realization of the expected genetic gain. Including pest resistance traits in the breeding programs may contribute to a sustainable protection. Here we quantified the variation in different components of resistance of Norway spruce to its main pest, the pine weevil Hylobius abietis. We followed insect damage in two large progeny trials (52 open-pollinated families with 100-200 individuals per family and trial) naturally infested by the pine weevil. Pine weevils damaged between 17 and 48% of the planted seedlings depending on the trial and year, and mortality due to weevil damage was up to 11.4%. The results indicate significant genetic variation in resistance to the pine weevil, and importantly, the variation was highly consistent across trials irrespective of contrasting incidence levels. Individual heritability estimates for the different components of seedling resistance were consistently low, but family heritabilities were moderate (0.53 to 0.81). While forward selections and breeding for higher resistance seem not feasible, backwards selections of the best parent trees emerge as a putative alternative to reduce weevil damage. A positive genetic correlation between early growth potential and probability of being attacked by the weevil was also observed, but the relationship was weak and appeared only in one of the trials. Overall, results presented here open the door to a new attractive way for reducing damage caused by this harmful pest.

  • 1006. Zelent, B
    et al.
    Yano, T
    Ohlsson, P-I
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Smith, ML
    Paul, J
    Vanderkooi, JM
    Optical spectra of lactoperoxidase as a function of solvent2005Inngår i: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 44, nr 48, s. 15953-15959Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The iron of lactoperoxidase is predominantly high-spin at ambient temperature. Optical spectra of lactoperoxidase indicate that the iron changes from high-spin to low-spin in the temperature range from room temperature to 20 K. The transformation is independent of whether the enzyme is in glycerol/water or solid sugar glass. Addition of the inhibitor benzohydroxamic acid increases the amount of the low-spin form, and again the transformation is independent of whether the protein is in an aqueous solution or a nearly anhydrous sugar. In contrast to lactoperoxidase, horseradish peroxidase remains high-spin over the temperature excursion in both solvents and with addition of benzohydroxamic acid. We conclude that details of the heme pocket of lactoperoxidase allow ligation changes with temperature that are dependent upon the apoprotein but independent of solvent fluctuations. At low pH, lactoperoxidase shows a solvent-dependent transition; the high-spin form is predominant in anhydrous sugar glass, but in the presence of water, the low-spin form is also present in abundance. The active site of lactoperoxidase is not as tightly constrained at low pH as at neutrality, though the enzyme is active over a wide pH range.

  • 1007. Zelisko, Agnieszka
    et al.
    García-Lorenzo, Maribel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Jackowski, Grzegorz
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Funk, Christiane
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    AtFtsH6 is involved in the degradation of the light-harvesting complex II during high-light acclimation and senescence2005Inngår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 1091-6490, Vol. 102, nr 39, s. 13699-704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Degradation of the most abundant membrane protein on earth, the light-harvesting complex of Photosystem II (LHC II), is highly regulated under various environmental conditions, e.g., light stress, to prevent photochemical damage to the reaction center. We identified the LHC II degrading protease in Arabidopsis thaliana as a Zn2+-dependent metalloprotease, activated by the removal of unknown extrinsic factors, similar to the proteolytic activity directed against Lhcb3 in barley. By using a reversed genetic approach, the chloroplast-targeted protease FtsH6 was identified as being responsible for the degradation. T-DNA KO A. thaliana mutants, lacking ftsH6, were unable to degrade either Lhcb3 during dark-induced senescence or Lhcb1 and Lhcb3 during highlight acclimation. The A. thaliana ftsH6 gene has a clear orthologue in the genome of Populus trichocarpa. It is likely that FtsH6 is a general LHC II protease and that FtsH6-dependent LHC II proteolysis is a feature of all higher plants.

  • 1008. Zhang, Bo
    et al.
    Holmlund, Mattias
    Lorrain, Severine
    Norberg, Mikael
    Bakó, László
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Fankhauser, Christian
    Nilsson, Ove
    BLADE-ON-PETIOLE proteins act in an E3 ubiquitin ligase complex to regulate PHYTOCHROME INTERACTING FACTOR 4 abundance2017Inngår i: eLIFE, E-ISSN 2050-084X, Vol. 6, artikkel-id e26759Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Both light and temperature have dramatic effects on plant development. Phytochrome photoreceptors regulate plant responses to the environment in large part by controlling the abundance of PHYTOCHROME INTERACTING FACTOR (PIF) transcription factors. However, the molecular determinants of this essential signaling mechanism still remain largely unknown. Here, we present evidence that the BLADE-ON-PETIOLE (BOP) genes, which have previously been shown to control leaf and flower development in Arabidopsis, are involved in controlling the abundance of PIF4. Genetic analysis shows that BOP2 promotes photo-morphogenesis and modulates thermomorphogenesis by suppressing PIF4 activity, through a reduction in PIF4 protein level. In red-light-grown seedlings PIF4 ubiquitination was reduced in the bop2 mutant. Moreover, we found that BOP proteins physically interact with both PIF4 and CULLIN3A and that a CULLIN3-BOP2 complex ubiquitinates PIF4 in vitro. This shows that BOP proteins act as substrate adaptors in a CUL3BOP1/BOP2 E3 ubiquitin ligase complex, targeting PIF4 proteins for ubiquitination and subsequent degradation.

  • 1009.
    Zhang, Bo
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Tremousaygue, Dominique
    Denancé, Nicolas
    van Esse, H. Peter
    Hörger, Anja C.
    Dabos, Patrick
    Goffner, Deborah
    Thomma, Bart P. H. J.
    van der Hoorn, Renier A. L.
    Tuominen, Hannele
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    PIRIN2 stabilizes cysteine protease XCP2 and increases susceptibility to the vascular pathogen Ralstonia solanacearum in Arabidopsis2014Inngår i: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 79, nr 6, s. 1009-1019Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    PIRIN (PRN) is a member of the functionally diverse cupin protein superfamily. There are four members of the Arabidopsis thaliana PRN family, but the roles of these proteins are largely unknown. Here we describe a function of the Arabidopsis PIRIN2 (PRN2) that is related to susceptibility to the bacterial plant pathogen Ralstonia solanacearum. Two prn2 mutant alleles displayed decreased disease development and bacterial growth in response to R. solanacearum infection. We elucidated the underlying molecular mechanism by analyzing PRN2 interactions with the papain-like cysteine proteases (PLCPs) XCP2, RD21A, and RD21B, all of which bound to PRN2 in yeast two-hybrid assays and in Arabidopsis protoplast co-immunoprecipitation assays. We show that XCP2 is stabilized by PRN2 through inhibition of its autolysis on the basis of PLCP activity profiling assays and enzymatic assays with recombinant protein. The stabilization of XCP2 by PRN2 was also confirmed in planta. Like prn2 mutants, an xcp2 single knockout mutant and xcp2 prn2 double knockout mutant displayed decreased susceptibility to R.solanacearum, suggesting that stabilization of XCP2 by PRN2 underlies susceptibility to R.solanacearum in Arabidopsis.

  • 1010. Zhang, H
    et al.
    Goodman, H M
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Antisense inhibition of the photosystem I antenna protein Lhca4 in Arabidopsis thaliana1997Inngår i: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 115, nr 4, s. 1525-1531Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 1011. Zhang, Lifang
    et al.
    Selao, Tiago Toscano
    Selstam, Eva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Norling, Birgitta
    Subcellular Localization of Carotenoid Biosynthesis in Synechocystis sp PCC 68032015Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, nr 6, artikkel-id e0130904Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The biosynthesis pathway of carotenoids in cyanobacteria is partly described. However, the subcellular localization of individual steps is so far unknown. Carotenoid analysis of different membrane subfractions in Synechocystis sp. PCC6803 shows that "light" plasma membranes have a high carotenoid/protein ratio, when compared to "heavier" plasma membranes or thylakoids. The localization of CrtQ and CrtO, two well-defined carotenoid synthesis pathway enzymes in Synechocystis, was studied by epitope tagging and western blots. Both enzymes are locally more abundant in plasma membranes than in thylakoids, implying that the plasma membrane has higher synthesis rates of beta-carotene precursor molecules and echinenone.

  • 1012. Zhao, Chengsong
    et al.
    Lasses, Theres
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Bako, Laszlo
    Kong, Danyu
    Zhao, Bingyu
    Chanda, Bidisha
    Bombarely, Aureliano
    Cruz-Ramírez, Alfredo
    Scheres, Ben
    Brunner, Amy M.
    Beers, Eric P.
    XYLEM NAC DOMAIN1, an angiosperm NAC transcription factor, inhibits xylem differentiation through conserved motifs that interact with RETINOBLASTOMA-RELATED2017Inngår i: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 216, nr 1, s. 76-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Arabidopsis thaliana gene XYLEM NAC DOMAIN1 (XND1) is upregulated in xylem tracheary elements. Yet overexpression of XND1 blocks differentiation of tracheary elements. The molecular mechanism of XND1 action was investigated. Phylogenetic and motif analyses indicated that XND1 and its homologs are present only in angiosperms and possess a highly conserved C-terminal region containing linear motifs (CKII-acidic, LXCXE, E2F(TD)-like and LXCXE-mimic) predicted to interact with the cell cycle and differentiation regulator RETINOBLASTOMA-RELATED (RBR). Protein-protein interaction and functional analyses of XND1 deletion mutants were used to test the importance of RBR-interaction motifs. Deletion of either the LXCXE or the LXCXE-mimic motif reduced both the XND1-RBR interaction and XND1 efficacy as a repressor of differentiation, with loss of the LXCXE motif having the strongest negative impacts. The function of the XND1 C-terminal domain could be partially replaced by RBR fused to the N-terminal domain of XND1. XND1 also transactivated gene expression in yeast and plants. The properties of XND1, a transactivator that depends on multiple linear RBR-interaction motifs to inhibit differentiation, have not previously been described for a plant protein. XND1 harbors an apparently angiosperm-specific combination of interaction motifs potentially linking the general differentiation regulator RBR with a xylem-specific pathway for inhibition of differentiation.

  • 1013.
    Zheng, Bo
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Halperin, Tami
    Hruskova-Heidingsfeldovac, Olga
    Adam, Zach
    Clarke, Adrian
    Characterization of Chloroplast Clp proteins in Arabidopsis: Localization, tissue specificity and stress responses2002Inngår i: PHYSIOLOGIA PLANTARUM, Vol. 114, s. 92-101Artikkel i tidsskrift (Fagfellevurdert)
  • 1014.
    Zheng, Bo
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    MacDonald, Tara M
    Sutinen, Sirkka
    Hurry, Vaughan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Clarke, Adrian K
    A nuclear-encoded ClpP subunit of the chloroplast ATP-dependent Clp protease is essential for early development in Arabidopsis thaliana.2006Inngår i: Planta, ISSN 0032-0935, Vol. 224, nr 5, s. 1103-15Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ClpP4 is a nuclear-encoded plastid protein that functions as a proteolytic subunit of the ATP-dependent Clp protease of higher plants. Given the lack of viable clpP4 knockout mutants, antisense clpP4 repression lines were prepared to study the functional importance of ClpP4 in Arabidopsis thaliana. Screening of transformants revealed viable lines with up to 90% loss of wild type levels of ClpP4 protein, while those with > 90% were severely bleached and strongly retarded in vegetative growth, failing to reach reproductive maturity. Of the viable antisense plants, repression of clpP4 expression produced a pleiotropic phenotype, of which slow growth and leaf variegation were most prominent. Chlorosis was most severe in younger leaves, with the affected regions localized around the mid-vein and exhibiting impaired chloroplast development and mesophyll cell differentiation. Chlorosis lessened during leaf expansion until all had regained the wild type appearance upon maturity. This change in phenotype correlated with the developmental expression of ClpP4 in the wild type, in which ClpP4 was less abundant in mature leaves due to post-transcriptional/translational regulation. Repression of ClpP4 caused a concomitant down-regulation of other nuclear-encoded ClpP paralogs in the antisense lines, but no change in other chloroplast-localized Clp proteins. Greening of the young chlorotic antisense plants upon maturation was accelerated by increased light, either by longer photoperiod or by higher growth irradiance; conditions that both raised levels of ClpP4 in wild type leaves. In contrast, shift to low growth irradiance decreased the relative amount of ClpP4 in wild type leaves, and caused newly developed leaves of fully greened antisense lines to regain the chlorotic phenotype.

  • 1015. Zulfugarov, Ismayil S.
    et al.
    Tovuu, Altanzaya
    Eu, Young-Jae
    Dogsom, Bolormaa
    Poudyal, Roshan Sharma
    Nath, Krishna
    Hall, Michael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Banerjee, Mainak
    Yoon, Ung Chan
    Moon, Yong-Hwan
    An, Gynheung
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Lee, Choon-Hwan
    Production of superoxide from Photosystem II in a rice (Oryza sativa L.) mutant lacking PsbS2014Inngår i: BMC Plant Biology, ISSN 1471-2229, E-ISSN 1471-2229, Vol. 14, s. 242-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: PsbS is a 22-kDa Photosystem (PS) II protein involved in non-photochemical quenching (NPQ) of chlorophyll fluorescence. Rice (Oryza sativa L.) has two PsbS genes, PsbS1 and PsbS2. However, only inactivation of PsbS1, through a knockout (PsbS1-KO) or in RNAi transgenic plants, results in plants deficient in qE, the energy-dependent component of NPQ. Results: In studies presented here, under fluctuating high light, growth of young seedlings lacking PsbS is retarded, and PSII in detached leaves of the mutants is more sensitive to photoinhibitory illumination compared with the wild type. Using both histochemical and fluorescent probes, we determined the levels of reactive oxygen species, including singlet oxygen, superoxide, and hydrogen peroxide, in leaves and thylakoids. The PsbS-deficient plants generated more superoxide and hydrogen peroxide in their chloroplasts. PSII complexes isolated from them produced more superoxide compared with the wild type, and PSII-driven superoxide production was higher in the mutants. However, we could not observe such differences either in isolated PSI complexes or through PSI-driven electron transport. Time-course experiments using isolated thylakoids showed that superoxide production was the initial event, and that production of hydrogen peroxide proceeded from that. Conclusion: These results indicate that at least some of the photoprotection provided by PsbS and qE is mediated by preventing production of superoxide released from PSII under conditions of excess excitation energy.

  • 1016. Zulfugarov, Ismayil S.
    et al.
    Tovuu, Altanzaya
    Kim, Chi-Yeol
    Vo, Kieu Thi Xuan
    Ko, Soo Yeon
    Hall, Michael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Seok, Hye-Yeon
    Kim, Yeon-Ki
    Skogström, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Moon, Yong-Hwan
    Jansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Jeon, Jong-Seong
    Lee, Choon-Hwan
    Enhanced resistance of PsbS-deficient rice (Oryza sativa L.) to fungal and bacterial pathogens2016Inngår i: Journal of Plant Biology, ISSN 1226-9239, Vol. 59, nr 6, s. 616-626Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The 22-kDa PsbS protein of Photosystem II is involved in nonphotochemical quenching (NPQ) of chlorophyll fluorescence. Genome-wide analysis of the expression pattern in PsbS knockout (KO) rice plants showed that a lack of this protein led to changes in the transcript levels of 406 genes, presumably a result of superoxide produced in the chloroplasts. The top Gene Ontology categories, in which expression was the most differential, included 'Immune response', 'Response to jasmonic acid', and 'MAPK cascade'. From those genes, we randomly selected nine that were up-regulated. Our microarray results were confirmed by quantitative RT-PCR analysis. The KO and PsbS RNAi (knockdown) plants were more resistant to pathogens Magnaporthe oryzae PO6-6 and Xanthomonas oryzae pv. oryzae than either the wild-type plants or PsbS-overexpressing transgenic line. These findings suggest that superoxide production might be the reason that these plants have greater pathogen resistance to fungal and bacterial pathogens in the absence of energy-dependent NPQ. For example, a high level of cell wall lignification in the KO mutants was possibly due to enhanced superoxide production. Our data indicate that certain abiotic stress-induced reactive oxygen species can promote specific signaling pathways, which then activate a defense mechanism against biotic stress in PsbS-KO rice plants.

  • 1017. Ögren, Erling
    et al.
    Öquist, Gunnar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Photoinhibition of photosynthesis in Lemna gibba as induced by the interaction between light and temperature. II. Photosynthetic electron transport1984Inngår i: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 62, nr 2, s. 187-192Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Photoinhibition of photosynthesis in Lemna gibba L. was induced by exposing intact plants to a high photosynthetic photon flux density of 1 750 μmol m−2 s−1 at a low temperature of 3°C. Subsequently isolated chloroplasts showed pronounced reductions in the capacity of whole chain electron transport, measured as Hill activity, and in the efficiency of electron transport to the primary electron acceptor Q of photosystem II, measured as variable chlorophyll fluorescence at 20°C. These changes proceeded with similar kinetics (probably of the first-order reaction), suggesting that the site of photoinhibition is in the electron transfer to Q. A partial uncoupling of the whole chain electron transport also occured. The capacity of electron transport mediated by photosystem I was unaffected. The extent of photoinhibition of photosynthetic electron transport, as produced by a 2 h exposure of L. gibba to three different combinations of photon flux density and temperature was studied. It was shown that intrinsically similar states of photoinhibition, on the evidence of their time courses of recovery, were induced by either a high photon flux density and 25°C or by a moderate photon flux density and 3°C.

  • 1018. Ögren, Erling
    et al.
    Öquist, Gunnar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Photoinhibition of photosynthesis in lemna-gibba as induced by the interaction between light and temperature .3. Chlorophyll fluorescence at 77-K1984Inngår i: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 62, nr 2, s. 193-200Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Photoinhibition in Lemna gibba L. was studied by interpreting chlorophyll fluorescence characteristics at 77 K on the basis of the bipartite model of Butler and co-workers (Butler 1978). Application of this analysis to chloroplasts (isolated from plants before and after exposure to a photosynthetic photon flux density of 1 750 μmol m−2 s−1 at 3°C for 2 h) revealed that photoinhibition had the following effect on primary events in photosynthesis. Firstly, the fluorescence of PS II increased (44%) in the state of open traps (Fo) and decreased (32%) in the state of closed traps (Fm). It is suggested, that the Fo-decrease reflects increased quenching by radiationless decay, both effects occurring at PS II reaction centers. Secondly, the rate constant for transfer of excitation energy from PS II to PS I (kT(μ→J)) increased by 34%. However, in the state of closed traps, the flux of excitation energy via this transfer process decreased, most likely because of increased quenching by radiationless decay at PS II reaction centers. Thirdly, the probability for fluorescence from PS I decreased (19%). This indicates increased quenching by radiationless decay.

  • 1019.
    Öhberg, Helena
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Bång, Ulla
    Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Biological control of clover rot and red clover by Coniothyrium minitans under natural and controlled climatic conditions2010Inngår i: Biocontrol science and technology (Print), ISSN 0958-3157, E-ISSN 1360-0478, Vol. 20, nr 1, s. 25-36Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability of Coniothyrium minitans, contained in the commercial product Contans®WG, to control the development of clover rot in red clover, Trifolium pratense, was for the first time investigated in the field. Studies were performed on an established ley with a grass-clover mixture and on a newly sown pure red clover ley, both at a field site naturally infested with Sclerotinia trifoliorum. In the latter experiment the biocontrol agent was applied either prior to sowing or to growing seedlings. In addition, the ability of sclerotia of two S. trifoliorum isolates to cause disease in detached leaves was studied in a controlled environment. The effect of Contans®WG treatments at temperatures between +5 and +15°C and incubation periods of up to 7 weeks were included. Application of the biocontrol agent to the established ley during early summer, significantly reduced the number of groups of apothecia that developed during autumn in the following year in treated plots, compared to untreated plots. Twice as many red clover plants of the cultivar SW Torun survived in the pure red clover stand experiment the year after Contans®WG application as in the untreated plots, irrespective of how the agent was applied. In the laboratory studies, administering biocontrol treatments to sclerotia significantly reduced disease scores in the detached leaves at all temperatures at an exposure time of 7 weeks. Shorter incubation periods did not always negatively affect sclerotial viability.

  • 1020.
    Öquist, Gunnar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Benner, M.
    Why are some nations more successful than others in research impact?: a comparison between Denmark and Sweden2015Inngår i: Incentives and Performance: Governance of Research Organizations / [ed] Isabell M. Welpe, Jutta Wollersheim, Stefanie Ringelhan, Margit Osterloh, Springer, 2015, s. 241-257Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    Bibliometric impact analyses show that Swedish research has less international visibility than Danish research. When taking a global view on all subject fields and selecting publications cited higher than the 90th percentile, i.e., the Top 10 %—publications, the Swedish Research Council shows that although Sweden ranks 15 % above world average, Denmark, the Netherlands and Switzerland rank 35–40 % above. To explain these different performances, The Royal Swedish Academy of Sciences asked us to compare the national research systems on three levels: priority setting at national level, governance of universities and direction and funding of research. There are of course many similarities between the Danish and Swedish research systems but there are still subtle differences that have developed over time, which may explain the different international visibility. First of all, it does not depend on different levels of public spending on research and development. However, the core funding of universities relative external funding is higher in Denmark than in Sweden. The academic leadership of Danish universities in terms of board, vice-chancellor, faculty dean and department chair is also more coherent and focused on priority setting, recruitment, organization and deployment of resources to establish research environments that operate at the forefront of international research. On all these points we see a weaker leadership in Sweden. Furthermore, over the last 20 years, public funding of research in Sweden has become more and more unpredictable and program oriented with many new actors, while the Danish funding system, although it also has developed over time, shows more consistency with strong actors to fund individuals with novel ideas. The research policy in Sweden has also developed multiple, sometimes even conflicting goals, which have undermined conditions for high-impact research, while in Denmark a policy to support excellence in research has been more coherent.

  • 1021.
    Öquist, Gunnar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Huner, Norman P.A.
    Department of Plant Sciences, University of Western Ontario, London, Canada.
    Photosynthesis of overwintering evergreen plants2003Inngår i: Annual Review of Plant Physiology and Plant Molecular Biology, ISSN 1040-2519, E-ISSN 2331-0960, Vol. 54, s. 329-355Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    In this review we focus on photosynthetic behavior of overwintering evergreens with an emphasis on both the acclimative responses of photosynthesis to cold and the winter behavior of photosynthesis in conifers. Photosynthetic acclimation is discussed in terms of the requirement for a balance between the energy absorbed through largely temperature-insensitive photochemical processes and the energy used for temperature-sensitive biochemical processes and growth. Cold acclimation transforms the xanthophyll-mediated nonphotochemical antenna quenching of absorbed light from a short-term dynamic response to a long-term sustained quenching for the whole winter period. This acclimative response helps protect the evergreen foliage from photooxidative damage during the winter when photosynthesis is restricted or prevented by low temperatures. Although the molecular mechanisms behind the sustained winter excitation quenching are largely unknown, it does involve major alterations in the organization and composition of the photosystem II antenna. In addition, photosystem I may play an important role in overwintering evergreens not only by quenching absorbed light photochemically via its support of cyclic electron transport at low temperatures, but also by nonphotochemical quenching of absorbed light irrespective of temperature. The possible role of photosystem II reaction centers in nonphotochemical quenching of absorbed energy in overwintering evergreens is also discussed. Processes like chlororespiration and cyclic electron transport may also be important for maintaining the functional integrity of the photosynthetic apparatus of overwintering evergreens both during periods of thawing in winter and during recovery from winter stress in spring. We suggest that the photosynthetic acclimation responses of overwintering evergreens represent specific evolutionary adaptations for plant species that invest in the long-term maintenance of leaf structure in cold climatic zones as exemplified by the boreal forests of the Northern Hemisphere.

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