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  • 51.
    Bandau, Franziska
    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.
    Decker, Vicki Huizu Guo
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Gundale, Michael J.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE 90183 Umeå, Sweden.
    Albrectsen, Benedicte Riber
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK 1871 Frederiksberg C, Denmark.
    Genotypic tannin levels in Populus tremula impact the way nitrogen enrichment affects growth and allocation responses for some traits and not for others2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 10, article id e0140971Article in journal (Refereed)
    Abstract [en]

    Plant intraspecific variability has been proposed as a key mechanism by which plants adapt to environmental change. In boreal forests where nitrogen availability is strongly limited, nitrogen addition happens indirectly through atmospheric N deposition and directly through industrial forest fertilization. These anthropogenic inputs of N have numerous environmental consequences, including shifts in plant species composition and reductions in plant species diversity. However, we know less about how genetic differences within plant populations determine how species respond to eutrophication in boreal forests. According to plant defense theories, nitrogen addition will cause plants to shift carbon allocation more towards growth and less to chemical defense, potentially enhancing vulnerability to antagonists. Aspens are keystone species in boreal forests that produce condensed tannins to serve as chemical defense. We conducted an experiment using ten Populus tremula genotypes from the Swedish Aspen Collection that express extreme levels of baseline investment into foliar condensed tannins. We investigated whether investment into growth and phenolic defense compounds in young plants varied in response to two nitrogen addition levels, corresponding to atmospheric N deposition and industrial forest fertilization. Nitrogen addition generally caused growth to increase, and tannin levels to decrease; however, individualistic responses among genotypes were found for height growth, biomass of specific tissues, root: shoot ratios, and tissue lignin and N concentrations. A genotype's baseline ability to produce and store condensed tannins also influenced plant responses to N, although this effect was relatively minor. High-tannin genotypes tended to grow less biomass under low nitrogen levels and more at the highest fertilization level. Thus, the ability in aspen to produce foliar tannins is likely associated with a steeper reaction norm of growth responses, which suggests a higher plasticity to nitrogen addition, and potentially an advantage when adapting to higher concentrations of soil nitrogen.

  • 52.
    Barajas-Lopez, Juan de Dios
    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).
    Kremnev, Dmitry
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Shaikhali, Jehad
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Pinas-Fernandez, Aurora
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Strand, Åsa
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    PAPP5 is involved in the tetrapyrrole mediated plastid signalling during chloroplast development2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 3, article id e60305Article in journal (Refereed)
    Abstract [en]

    The initiation of chloroplast development in the light is dependent on nuclear encoded components. The nuclear genes encoding key components in the photosynthetic machinery are regulated by signals originating in the plastids. These plastid signals play an essential role in the regulation of photosynthesis associated nuclear genes (PhANGs) when proplastids develop into chloroplasts. One of the plastid signals is linked to the tetrapyrrole biosynthesis and accumulation of the intermediates the Mg-ProtoIX and its methyl ester Mg-ProtoIX-ME. Phytochrome-Associated Protein Phosphatase 5 (PAPP5) was isolated in a previous study as a putative Mg-ProtoIX interacting protein. In order to elucidate if there is a biological link between PAPP5 and the tetrapyrrole mediated signal we generated double mutants between the Arabidopsis papp5 and the crd mutants. The crd mutant over-accumulates Mg-ProtoIX and Mg-ProtoIX-ME and the tetrapyrrole accumulation triggers retrograde signalling. The crd mutant exhibits repression of PhANG expression, altered chloroplast morphology and a pale phenotype. However, in the papp5crd double mutant, the crd phenotype is restored and papp5crd accumulated wild type levels of chlorophyll, developed proper chloroplasts and showed normal induction of PhANG expression in response to light. Tetrapyrrole feeding experiments showed that PAPP5 is required to respond correctly to accumulation of tetrapyrroles in the cell and that PAPP5 is most likely a component in the plastid signalling pathway down stream of the tetrapyrrole Mg-ProtoIX/Mg-ProtoIX-ME. Inhibition of phosphatase activity phenocopied the papp5crd phenotype in the crd single mutant demonstrating that PAPP5 phosphatase activity is essential to mediate the retrograde signal and to suppress PhANG expression in the crd mutant. Thus, our results suggest that PAPP5 receives an inbalance in the tetrapyrrole biosynthesis through the accumulation of Mg-ProtoIX and acts as a negative regulator of PhANG expression during chloroplast biogenesis and development.

  • 53. Barker-Åström, Kara
    et al.
    Schelin, Jenny
    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).
    Clarke, Adrian K
    Campbell, Douglas A
    Chlorosis during nitrogen starvation is altered by carbon dioxide and temperature status and is mediated by the ClpP1 protease in Synechococcus elongatus.2005In: Archives of Microbiology, ISSN 0302-8933, Vol. 183, no 1, p. 66-9Article in journal (Refereed)
    Abstract [en]

    The interactive effects of inorganic carbon status, temperature and light on chlorosis induced by nitrogen deficiency, and the roles of Clp proteases in this process were investigated. In wild-type cultures grown in high or ambient CO2, following transfer to media lacking combined nitrogen, phycocyanin per cell dropped primarily through dilution of the pigment through cell division, and also suffered variable degrees of net degradation. When grown at high CO2 (5%), chlorophyll (Chl) suffered net degradation to a greater extent than phycocyanin. In marked contrast, growth at ambient CO2 resulted in Chl per cell dropping through dilution. Conditions that drove net Chl degradation in the wild-type resulted in little or no net Chl degradation in a clpPI inactivation mutant, with Chl content dropping largely through growth dilution in the mutant. The chlorotic response of a clpPII inactivation strain was nearly the same as that of wild-type, although phycocyanin degradation may have been slightly accelerated in the former.

  • 54.
    Barros, Jaime
    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).
    Serk, Henrik
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Granlund, Irene
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Pesquet, Edouard
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    The cell biology of lignification in higher plants2015In: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 115, no 7, p. 1053-1074Article, review/survey (Refereed)
    Abstract [en]

    Background Lignin is a polyphenolic polymer that strengthens and waterproofs the cell wall of specialized plant cell types. Lignification is part of the normal differentiation programme and functioning of specific cell types, but can also be triggered as a response to various biotic and abiotic stresses in cells that would not otherwise be lignifying.

    Scope Cell wall lignification exhibits specific characteristics depending on the cell type being considered. These characteristics include the timing of lignification during cell differentiation, the palette of associated enzymes and substrates, the sub-cellular deposition sites, the monomeric composition and the cellular autonomy for lignin monomer production. This review provides an overview of the current understanding of lignin biosynthesis and polymerization at the cell biology level.

    Conclusions The lignification process ranges from full autonomy to complete co-operation depending on the cell type. The different roles of lignin for the function of each specific plant cell type are clearly illustrated by the multiple phenotypic defects exhibited by knock-out mutants in lignin synthesis, which may explain why no general mechanism for lignification has yet been defined. The range of phenotypic effects observed include altered xylem sap transport, loss of mechanical support, reduced seed protection and dispersion, and/or increased pest and disease susceptibility.

  • 55.
    Bashar Shafiul, Shamrat
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Characterization of cell wall in transgenic aspen with modified xylan acetylation2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    ABSTRACT

    Mature plant cells are enclosed by inflexible wall made up of cellulose microfibrils, pectins, hemicelluloses and in some cases lignin. This cell wall provides the structure and the defense for plant cells. In secondary cell walls of dicotyledons, major hemicellulose is xylan consisting of β-(1, 4)-linked xylose units. Xylan is synthesized in Golgi apparatus by several enzymes activities. REDUCED WALL ACETYLATION (RWA) genes are involved in xylan acetylation. These genes were downregulated in hybrid aspen in order to reduce xylan acetylation activity during its biosynthesis. In addition, acetyl xylan esterase (FC2) from the fungus Aspergillus niger was expressed in hybrid aspen to modify xylan acetylation post-synthetically. In this work, I have studied effects of these modifications on wood cell wall composition.

    The cell wall components were sequentially extracted by using the small scale method and the weight of extractives, lignin, hemicelluloses and celluloses per weight of dry wood were determined. In addition, the Updegraff cellulose, Klason lignin contents per weight of extractive free wood were determined and monosugar compositions of non-cellulosic components were analyzed by methanolysis and Trimethylsilyl derivatisation (TMS). 

    I have found that content of cellulose determined by sequential extraction method was significantly increased in all constructs as compared to the wild type. Reduction of lignin (as determined by sequential extraction) was found in DFC2 construct and RWA RNAi 35S-AB and CD constructs. Furthermore, RWA RNAi 35S-CD and RWA RNAi WP-ABCD constructs showed decreased hemicellulose as compared to the wild type. Moreover, DFC2 constructs exhibited decrease in non-cellulosic sugars hydrolyzed during TMS. FC2 expressing lines showed a reduction in xylose which is the main building block of xylan. In contrast, glucose and galactose contents were increased. Inhibition of expression of all RWA genes (WP-ABCD) caused similar changes.

    Considering all the data I conclude that, reduced acetylation of xylan can affect extractability, biosynthesis or modification of polysaccharides and lignin in cell wall.

    Keywords: Cellulose microfibrils; pectins; hemicellulose; lignin, xylan; secondary wall; aspen; xylan biosynthesis; biosynthesis of polysaccharides. 

  • 56.
    Bañares de Dios, Guillermo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Elucidating the role of CSK during early light response and chloroplast development2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Elucidating the role of CSK during early light response and chloroplast development

    Chloroplasts of higher plants have evolved from endosymbiotic, ancestor of modern prokaryotic cyanobacteria. During evolution most of the genes from the genome of the endosymbiont have moved to the nucleus of it host. As a consequence the components of the photosynthetic machinery are encoded both in the chloroplastic and in the nuclear genomes. Therefore, expression of both genomes must be tightly coordinated to ensure a simultaneous and stoichiometric biosynthesis of the chloroplast components at different developmental stages and under environmental or metabolic changes. This is achieved by a mechanism referred to as retrograde signalling. During retrograde signalling, signals are emitted from the chloroplast consisting on intracellular pathways emitted by the chloroplast communicating the status of the chloroplast and regulating the expression of nuclear genes encoding plastid components. The aim of this project was to elucidate the role of CSK (Chloroplast Sensor Kinase) in relation to previously described retrograde signalling components PRIN2 (Plastid Redox INsensitive 2) and GUN1 (Genomes UNcoupled 1). CSK is a plastid kinase involved in the long- term, acclimation response to balance the ratio between PSII and PSI by regulating the expression of psaA. The activity of CSK is regulated by the redox state of the plastoquinone pool. My work revealed that CSK is up- regulated upon light exposure. In addition, similarly to the prin2 and gun1 mutants, the csk mutant exhibited lower chlorophyll content, a striking yellow cotyledon tip phenotype, impaired chloroplast development and a down- regulation of PEP dependent genes psaA and psbA during a de- etiolation development and for the establishment of PEP activity in light. Furthermore, the similarity in the mutant phenotypes suggests that CSK is involved in the same signalling pathway as PRIN2 and GUN1.

  • 57.
    Bellini, Catherine
    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). Institut Jean-Pierre Bourgin, UMR 1318 INRA-AgroParisTech, Versailles, France.
    Pacurar, Daniel I
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Perrone, Irene
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Adventitious roots and lateral roots: similarities and differences2014In: Annual Review of Plant Biology, ISSN 1543-5008, E-ISSN 1545-2123, Vol. 65, p. 639-666Article, review/survey (Refereed)
    Abstract [en]

    In addition to its role in water and nutrient uptake, the root system is fundamentally important because it anchors a plant to its substrate. Although a wide variety of root systems exist across different species, all plants have a primary root (derived from an embryonic radicle) and different types of lateral roots. Adventitious roots, by comparison, display the same functions as lateral roots but develop from aerial tissues. In addition, they not only develop as an adaptive response to various stresses, such as wounding or flooding, but also are a key limiting component of vegetative propagation. Lateral and adventitious roots share key elements of the genetic and hormonal regulatory networks but are subject to different regulatory mechanisms. In this review, we discuss the developmental processes that give rise to lateral and adventitious roots and highlight knowledge acquired over the past few years about the mechanisms that regulate adventitious root formation.

  • 58.
    Benedict, Catherine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Geisler, Matt
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Huner, Norman
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Consensus by democracy. Using meta-analyses of microarray and genomic data to model the cold acclimation signaling pathway in Arabidopsis.2006In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 141, no 4, p. 1219-1232Article in journal (Refereed)
    Abstract [en]

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

  • 59.
    Benedict, Catherine
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Skinner, J. S.
    Meng, R.
    Chang, Y.
    Bhalerao, R.
    Finn, C.
    Chen, T. H. H.
    Umeå University, Faculty of Science and Technology.
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    The Role of the CBF-dependent Signalling Pathway in Woody Perennials2006In: Cold Hardiness in Plants: Molecular Genetics, Cell Biology and Physiology / [ed] T Chen, M Uemura, S Fujikawa, Wallingford: CABI Publishing, 2006, p. 167-180Chapter in book (Other academic)
  • 60.
    Benedict, Catherine
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Skinner, Jeffrey S
    Meng, Rengong
    Chang, Yongjian
    Bhalerao, Rishikesh
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huner, Norman P A
    Finn, Chad E
    Chen, Tony H H
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    The CBF1-dependent low temperature signalling pathway, regulon and increase in freeze tolerance are conserved in Populus spp2006In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 29, no 7, p. 1259-1272Article in journal (Refereed)
    Abstract [en]

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

  • 61.
    Benlloch, Reyes
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Kim, Min Chul
    Division of Applied Life Science (BK21 Program), Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 660-701, Korea.
    Sayou, Camille
    Thevenon, Emmanuel
    CEA, iRTSV, Laboratoire Physiologie Cellulaire et Végétale, F-38054 Grenoble, France.
    Parcy, Francois
    CEA, iRTSV, Laboratoire Physiologie Cellulaire et Végétale, F-38054 Grenoble, France.
    Nilsson, Ove
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Integrating long-day flowering signals: a LEAFY binding site is essential for proper photoperiodic activation of APETALA12011In: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 67, no 6, p. 1094-1102Article in journal (Refereed)
    Abstract [en]

    The transition to flowering in Arabidopsis is characterized by the sharp and localized upregulation of APETALA1 (AP1) transcription in the newly formed floral primordia. Both the flower meristem-identity gene LEAFY (LFY) and the photoperiod pathway involving the FLOWERING LOCUS T (FT) and FD genes contribute to this upregulation. These pathways have been proposed to act independently but their respective contributions and mode of interaction have remained elusive. To address these questions, we studied the AP1 regulatory region. Combining in vitro and in vivo approaches, we identified which of the three putative LFY binding sites present in the AP1 promoter is essential for its activation by LFY. Interestingly, we found that this site is also important for the correct photoperiodic-dependent upregulation of AP1. In contrast, a previously proposed putative FD-binding site appears dispensable and unable to bind FD and we found no evidence for FD binding to other sites in the AP1 promoter, suggesting that the FT/FD-dependent activation of AP1 might be indirect. Altogether, our data give new insight into the interaction between the FT and LFY pathways in the upregulation of AP1 transcription under long-day conditions.

  • 62.
    Benlloch, Reyes
    et al.
    Department of Forest Genetics and Plant Physiology, SLU.
    Shevela, Dmitriy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hainzl, Tobias
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Grundström, Christin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shutova, Tatyana
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Crystal structure and functional characterization of Photosystem II-associated carbonic anhydrase CAH3 in Chlamydomonas reinhardtii2015In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 167, no 3, p. 950-962Article in journal (Refereed)
    Abstract [en]

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

  • 63. Benson, Samuel L
    et al.
    Maheswaran, Pratheesh
    Ware, Maxwell A
    Hunter, C Neil
    Horton, Peter
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ruban, Alexander V
    Johnson, Matthew P
    An intact light harvesting complex I antenna system is required for complete state transitions in Arabidopsis2015In: Nature plants, ISSN 2055-026X, Vol. 1, no 12, article id 15176Article in journal (Refereed)
    Abstract [en]

    Efficient photosynthesis depends on maintaining balance between the rate of light-driven electron transport occurring in photosystem I (PSI) and photosystem II (PSII), located in the chloroplast thylakoid membranes. Balance is achieved through a process of 'state transitions' that increases energy transfer towards PSI when PSII is overexcited (state II), and towards PSII when PSI is overexcited (state I). This is achieved through redox control of the phosphorylation state of light-harvesting antenna complex II (LHCII). PSI is served by both LHCII and four light-harvesting antenna complex I (LHCI) subunits, Lhca1, 2, 3 and 4. Here we demonstrate that despite unchanged levels of LHCII phosphorylation, absence of specific Lhca subunits reduces state transitions in Arabidopsis. The severest phenotype-observed in a mutant lacking Lhca4 (Delta Lhca4)-displayed a 69% reduction compared with the wild type. Yet, surprisingly, the amounts of the PSI-LHCI-LHCII supercomplex isolated by blue native polyacrylamide gel electrophoresis (BN-PAGE) from digitonin-solubilized thylakoids were similar in the wild type and Delta Lhca mutants. Fluorescence excitation spectroscopy revealed that in the wild type this PSI-LHCI-LHCII supercomplex is supplemented by energy transfer from additional LHCII trimers in state II, whose binding is sensitive to digitonin, and which are absent in Delta Lhca4. The grana margins of the thylakoid membrane were found to be the primary site of interaction between this 'extra' LHCII and the PSI-LHCI-LHCII supercomplex in state II. The results suggest that the LHCI complexes mediate energetic interactions between LHCII and PSI in the intact membrane.

  • 64. Bergman, Alexandra
    et al.
    Hellgren, John
    Moritz, Thomas
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Siewers, Verena
    Nielsen, Jens
    Chen, Yun
    Heterologous phosphoketolase expression redirects flux towards acetate, perturbs sugar phosphate pools and increases respiratory demand in Saccharomyces cerevisiae2019In: Microbial Cell Factories, ISSN 1475-2859, E-ISSN 1475-2859, Vol. 18, article id 25Article in journal (Refereed)
    Abstract [en]

    Introduction: Phosphoketolases (Xfpk) are a non-native group of enzymes in yeast, which can be expressed in combination with other metabolic enzymes to positively influence the yield of acetyl-CoA derived products by reducing carbon losses in the form of CO2. In this study, a yeast strain expressing Xfpk from Bifidobacterium breve, which was previously found to have a growth defect and to increase acetate production, was characterized.

    Results: Xfpk-expression was found to increase respiration and reduce biomass yield during glucose consumption in batch and chemostat cultivations. By cultivating yeast with or without Xfpk in bioreactors at different pHs, we show that certain aspects of the negative growth effects coupled with Xfpk-expression are likely to be explained by proton decoupling. At low pH, this manifests as a reduction in biomass yield and growth rate in the ethanol phase. Secondly, we show that intracellular sugar phosphate pools are significantly altered in the Xfpk-expressing strain. In particular a decrease of the substrates xylulose-5-phosphate and fructose-6-phosphate was detected (26% and 74% of control levels) together with an increase of the products glyceraldehyde-3-phosphate and erythrose-4-phosphate (208% and 542% of control levels), clearly verifying in vivo Xfpk enzymatic activity. Lastly, RNAseq analysis shows that Xfpk expression increases transcription of genes related to the glyoxylate cycle, the TCA cycle and respiration, while expression of genes related to ethanol and acetate formation is reduced. The physiological and transcriptional changes clearly demonstrate that a heterologous phosphoketolase flux in combination with endogenous hydrolysis of acetyl-phosphate to acetate increases the cellular demand for acetate assimilation and respiratory ATP-generation, leading to carbon losses.

    Conclusion: Our study shows that expression of Xfpk in yeast diverts a relatively small part of its glycolytic flux towards acetate formation, which has a significant impact on intracellular sugar phosphate levels and on cell energetics. The elevated acetate flux increases the ATP-requirement for ion homeostasis and need for respiratory assimilation, which leads to an increased production of CO2. A majority of the negative growth effects coupled to Xfpk expression could likely be counteracted by preventing acetate accumulation via direct channeling of acetyl-phosphate towards acetyl-CoA.

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

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

  • 66.
    Bernhardsson, Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ingvarsson, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Geographic structure and adaptive population differentiation in herbivore defence genes in European aspen (Populus tremula L., Salicaceae)2012In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 21, no 9, p. 2197-2207Article in journal (Refereed)
    Abstract [en]

    When a phenotypic trait is subjected to spatially variable selection and local adaptation, the underlying genes controlling the trait are also expected to show strong patterns of genetic differentiation since alternative alleles are favored in different geographical locations. Here we study 71 SNPs from seven genes associated with inducible defense responses in a sample of P. tremula collected from across Sweden. Four of these genes (PPO2, TI2, TI4 and TI5) show substantial population differentiation and a PCA conducted on the defense SNPs divides the Swedish population into three distinct clusters. Several defense SNPs show latitudinal clines, although these were not robust to multiple testing. However, five SNPs (located within TI4 and TI5) show strong longitudinal clines that remain significant after multiple test correction. Genetic geographical variation, supporting local adaptation, has earlier been confirmed in genes involved in the photoperiod pathway in P. tremula, but this is, to our knowledge, one of the first times that geographic variation has been found in genes involved in plant defense against antagonists.

  • 67.
    Bernhardsson, Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ingvarsson, Pär K
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Molecular population genetics of elicitor-induced resistance genes in European aspen (Populus tremula L., Salicaceae)2011In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 9, p. e24867-Article in journal (Refereed)
    Abstract [en]

    Owing to their long life span and ecological dominance in many communities, forest trees are subject to attack from a diverse array of herbivores throughout their range, and have therefore developed a large number of both constitutive and inducible defenses. We used molecular population genetics methods to examine the evolution of eight genes in European aspen, Populus tremula, that are all associated with defensive responses against pests and/or pathogens, and have earlier been shown to become strongly up-regulated in poplars as a response to wounding and insect herbivory. Our results show that the majority of these defense genes show patterns of intraspecific polymorphism and site-frequency spectra that are consistent with a neutral model of evolution. However, two of the genes, both belonging to a small gene family of polyphenol oxidases, show multiple deviations from the neutral model. The gene PPO1 has a 600 bp region with a highly elevated K(A)/K(S) ratio and reduced synonymous diversity. PPO1 also shows a skew toward intermediate frequency variants in the SFS, and a pronounced fixation of non-synonymous mutations, all pointing to the fact that PPO1 has been subjected to recurrent selective sweeps. The gene PPO2 shows a marked excess of high frequency, derived variants and shows many of the same trends as PPO1 does, even though the pattern is less pronounced, suggesting that PPO2 might have been the target of a recent selective sweep. Our results supports data from both Populus and other species which have found that the the majority of defense-associated genes show few signs of selection but that a number of genes involved in mediating defense against herbivores show signs of adaptive evolution.

  • 68.
    Bernhardsson, Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Robinson, Kathryn M.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Abreu, Ilka N.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Albrectsen, Benedicte R.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Univ Copenhagen, Sect Plant Biochem, Dept Plant & Environm Sci, DK-1871 Frederiksberg, Denmark.
    Ingvarsson, Pär K.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Geographic structure in metabolome and herbivore community co-occurs with genetic structure in plant defence genes2013In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 16, no 6, p. 791-798Article in journal (Refereed)
    Abstract [en]

    Plantherbivore interactions vary across the landscape and have been hypothesised to promote local adaption in plants to the prevailing herbivore regime. Herbivores that feed on European aspen (Populus tremula) change across regional scales and selection on host defence genes may thus change at comparable scales. We have previously observed strong population differentiation in a set of inducible defence genes in Swedish P. tremula. Here, we study the geographic patterns of abundance and diversity of herbivorous insects, the untargeted metabolome of the foliage and genetic variation in a set of wound-induced genes and show that the geographic structure co-occurs in all three data sets. In response to this structure, we observe local maladaptation of herbivores, with fewer herbivores on local trees than on trees originated from more distant localities. Finally, we also identify 28 significant associations between single nucleotide polymorphisms SNPs from defence genes and a number of the herbivore traits and metabolic profiles.

  • 69.
    Bernhardsson, Carolina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Science, Umeå, Sweden; Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Science, Uppsala, Sweden.
    Vidalis, Amaryllis
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Population Genetics, Center of Life and Food Sciences Weihenstephan, Technische Universität München.
    Wang, Xi
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Science, Uppsala, Sweden.
    Scofield, Douglas
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Uppsala Multidisciplinary Center for Advanced Computational Science; Department of Ecology and Genetics: Evolutionary Biology, Uppsala University, Uppsala, Sweden.
    Schiffthaler, Bastian
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Baison, John
    Street, Nathaniel
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Garcia-Gil, M. Rosario
    Ingvarsson, Pär K.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Science, Uppsala, Sweden.
    An Ultra-Dense Haploid Genetic Map for Evaluating the Highly Fragmented Genome Assembly of Norway Spruce (Picea abies)2019In: G3: Genes, Genomes, Genetics, ISSN 2160-1836, E-ISSN 2160-1836, Vol. 9, no 5, p. 1623-1632Article in journal (Refereed)
    Abstract [en]

    Norway spruce (Picea abies (L.) Karst.) is a conifer species of substanital economic and ecological importance. In common with most conifers, the P. abies genome is very large (similar to 20 Gbp) and contains a high fraction of repetitive DNA. The current P. abies genome assembly (v1.0) covers approximately 60% of the total genome size but is highly fragmented, consisting of >10 million scaffolds. The genome annotation contains 66,632 gene models that are at least partially validated (), however, the fragmented nature of the assembly means that there is currently little information available on how these genes are physically distributed over the 12 P. abies chromosomes. By creating an ultra-dense genetic linkage map, we anchored and ordered scaffolds into linkage groups, which complements the fine-scale information available in assembly contigs. Our ultra-dense haploid consensus genetic map consists of 21,056 markers derived from 14,336 scaffolds that contain 17,079 gene models (25.6% of the validated gene models) that we have anchored to the 12 linkage groups. We used data from three independent component maps, as well as comparisons with previously published Picea maps to evaluate the accuracy and marker ordering of the linkage groups. We demonstrate that approximately 3.8% of the anchored scaffolds and 1.6% of the gene models covered by the consensus map have likely assembly errors as they contain genetic markers that map to different regions within or between linkage groups. We further evaluate the utility of the genetic map for the conifer research community by using an independent data set of unrelated individuals to assess genome-wide variation in genetic diversity using the genomic regions anchored to linkage groups. The results show that our map is sufficiently dense to enable detailed evolutionary analyses across the P. abies genome.

  • 70.
    Besya, Azim-Berdy
    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.
    Grönlund, Andreas
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Intrinsic phenotypic stability of a bi-stable auto regulatory gene2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 22951Article in journal (Refereed)
    Abstract [en]

    Even under homogenous conditions clonal cells can assume different distinct states for generations to follow, also known as epigenetic inheritance. Such long periods of different phenotypic states can be formed due to the existence of more than one stable state in the molecule concentration, where the different states are explored through molecular fluctuations. By formulating a single reaction variable representing the birth and death of molecules, including transcription, translation and decay, we calculate the escape time from the phenotypic states attained from autocatalytic synthesis through a Fokker-Planck formulation and integration of an effective pseudo-potential. We calculate the stability of the phenotypic states both for cooperative binding feedback and dimer binding feedback, resulting in non-linear decay.

  • 71.
    Betson, Tatiana R
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Augusti, Angela
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Schleucher, Jürgen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Quantification of deuterium isotopomers of tree-ring cellulose using nuclear magnetic resonance.2006In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 78, no 24, p. 8406-8411Article in journal (Refereed)
    Abstract [en]

    Stable isotopes in tree rings are important tools for reconstruction of past climate. Deuterium (D) is of particular interest since it may contain climate signals and report on tree physiology. Measurements of the D/H ratio of tree-ring cellulose have proven difficult to interpret, presumably because the D/H ratio of the whole molecule blends the abundances of the seven D isotopomers of cellulose. Here we present a method to measure the abundance of the D isotopomers of tree-ring cellulose by nuclear magnetic resonance spectroscopy (NMR). The method transforms tree-ring cellulose into a glucose derivative that gives highly resolved, quantifiable deuterium NMR spectra. General guidelines for measurement of D isotopomers by NMR are described. The transformation was optimized for yield and did not alter the original D isotopomer abundances, thus, conserving the original signals recorded in wood cellulose. In the tree-ring samples tested, the abundances of D isotopomers varied by approximately ±10% (2% standard error). This large variability can only be caused by biochemistry processes and shows that more information is present in D isotopomer abundances, compared to the D/H ratio. Therefore, measurements of the D isotopomer distribution of tree rings may be used to obtain information on long-term adaptations to environmental changes and past climate change.

  • 72. Betson, Tatiana R.
    et al.
    Augusti, Angela
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Schleucher, Jürgen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Quantifying deuterium isotopomers of cellulose using Nuclear Magnetic Resonance2006In: Analytical Chemistry, Vol. 78, no 24, p. 8406-8411Article in journal (Refereed)
  • 73. Betti, Marco
    et al.
    Bauwe, Hermann
    Busch, Florian A.
    Fernie, Alisdair R.
    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).
    Levey, Myles
    Ort, Donald R.
    Parry, Martin A. J.
    Sage, Rowan
    Timm, Stefan
    Walker, Berkley
    Weber, Andreas P. M.
    Manipulating photorespiration to increase plant productivity: recent advances and perspectives for crop improvement2016In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 67, no 10, p. 2977-2988Article, review/survey (Refereed)
    Abstract [en]

    Recycling of the 2-phosphoglycolate generated by the oxygenase reaction of Rubisco requires a complex and energy-consuming set of reactions collectively known as the photorespiratory cycle. Several approaches aimed at reducing the rates of photorespiratory energy or carbon loss have been proposed, based either on screening for natural variation or by means of genetic engineering. Recent work indicates that plant yield can be substantially improved by the alteration of photorespiratory fluxes or by engineering artificial bypasses to photorespiration. However, there is also evidence indicating that, under certain environmental and/or nutritional conditions, reduced photorespiratory capacity may be detrimental to plant performance. Here we summarize recent advances obtained in photorespiratory engineering and discuss prospects for these advances to be transferred to major crops to help address the globally increasing demand for food and biomass production.

  • 74. Bhalerao, RP
    et al.
    Collier, JL
    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).
    Grossman, AR
    The structure of phycobilisomes in mutants of synechococcus sp strain pcc-7942 devoid of specific linker polypeptides1995In: Photochemistry and Photobiology, ISSN 0031-8655, E-ISSN 1751-1097, Vol. 61, no 3, p. 298-302Article in journal (Refereed)
    Abstract [en]

    The effect of elimination of the 30, 33 and 9 kDa phycobilisome rod-linker polypeptides on rod length was examined by electron microscopy of phycobilisomes isolated from wild-type Synechococcus sp. strain PCC 7942 and from genetically engineered mutants with lesions in the genes encoding the rod-linker polypeptides. The maximum rod length in the absence of the 33 kDa linker polypeptide was two phycocyanin hexamers, whereas rods with up to five hexamers were found in the mutant strain lacking the 30 kDa linker polypeptide. Elimination of the 9 kDa linker polypeptide did not have a significant effect on rod length. Finally, mutants lacking either the 30 or 33 kDa rod-associated linker polypeptides had an increased number of rods that terminated with a phycocyanin trimer. These observations are discussed with respect to the role of the linker polypeptides in the biosynthesis of the rod substructure.

  • 75. Bhalerao, RP
    et al.
    Gillbro, T
    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).
    Structure and energy-transfer of the phycobilisome in a linker protein replacement mutant of cyanobacterium synechococcus-79421991In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1060, no 1, p. 59-66Article in journal (Refereed)
    Abstract [en]

    The role of the linker proteins in the biogenesis and energy transfer of the phycobilisome rod was monitored by making insertional inactivation in the cpcI gene coding for the core-proximal 33 kilodalton (kDa) protein in the cyanobacterium Synechococcus 7942. The insertion leaves the cpcH gene coding for the core-distal 30 kDa protein intact and functional. Analysis of the phycobilisome protein composition of the cpcI mutant shows that the 30 kDa protein is present in normal amounts in the rod, indicating that the 30 kDa linker protein can replace the 33 kDa protein in the biogenesis and structural integrity of the rod. The absorption and fluorescence characteristics of the mutated phycobilisome is almost indistinguishable from that of the wild-type of the same rod length. The fluorescence kinetics from the cpcI mutant show that the dominating decay component has a lifetime from phycocyanin of 69 ps as compared to 72 ps found for the wild-type phycobilisome with the same rod length. The results show that replacing the 33 kDa for the 30 kDa linker in the rod does not alter the energy harvesting or the energy transfer characteristics of the rod in contrast to what has been concluded from data obtained from in vitro experiments. We conclude that the linker polypeptides have only a minor influence on the energy transfer characteristics of the rod but are mainly involved in determining the length of the rod in response to changing environmental light conditions.

  • 76. 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.

  • 77. Bhalerao, RP
    et al.
    Lind, LK
    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).
    Cloning of the cpce and cpcf genes from synechococcus sp pcc-6301 and their inactivation in synechococcus sp pcc-79421994In: Plant Molecular Biology, ISSN 0167-4412, E-ISSN 1573-5028, Vol. 26, no 1, p. 313-326Article in journal (Refereed)
    Abstract [en]

    Two open reading frames denoted as cpcE and cpcF were cloned and sequenced from Synechococcus sp. PCC 6301. The cpcE and cpcF genes are located downstream of the cpcB2A2 gene cluster in the phycobilisome rod operon and can be transcribed independently of the upstream cpcB2A2 gene cluster. The cpcE and cpcF genes were separately inactivated by insertion of a kanamycin resistance cassette in Synechococcus sp. PCC 7942 to generate mutants R2EKM and R2FKM, respectively, both of which display a substantial reduction in spectroscopically detectable phycocyanin. The levels of beta- and alpha-phycocyanin polypeptides were reduced in the R2EKM and R2FKM mutants although the phycocyanin and linker genes are transcribed at normal levels in the mutants as in the wild type indicating the requirement of the functional cpcE and cpcF genes for normal accumulation of phycocyanin. Two biliprotein fractions were isolated on sucrose density gradient from the R2EKM/R2FKM mutants. The faster sedimenting fraction consisted of intact phycobilisomes. The slower sedimenting biliprotein fraction was found to lack phycocyanin polypeptides, thus no free phycocyanin was detected in the mutants. Characterization of the phycocyanin from the mutants revealed that it was chromophorylated, had a lambda(max) similar to that from the wild type and could be assembled into the phycobilisome rods. Thus, although phycocyanin levels are reduced in the R2EKM and R2FKM mutants, the remaining phycocyanin seems to be chromophorylated and similar to that in the wild type with respect to phycobilisome rod assembly and energy transfer to the core.

  • 78. Bhalerao, RP
    et al.
    Lind, LK
    Persson, CE
    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).
    Cloning of the phycobilisome rod linker genes from the cyanobacterium synechococcus sp pcc-6301 och their inactivation in synechococcus sp pcc-79421993In: Molecular General Genetics, ISSN 0026-8925, E-ISSN 1432-1874, Vol. 237, no 1-2, p. 89-96Article in journal (Refereed)
    Abstract [en]

    The phycobilisome rod linker genes in the two closely related cyanobacteria Synechococcus sp. PCC 6301 and Synechococcus sp. PCC 7942 were studied. Southern blot analysis showed that the genetic organization of the phycobilisome rod operon is very similar in the two strains. The phycocyanin gene pair is duplicated and separated by a region of about 2.5 kb. The intervening region between the duplicated phycocyanin gene pair was cloned from Synechococcus sp. PCC 6301 and sequenced. Analysis of this DNA sequence revealed the presence of three open reading frames corresponding to 273, 289 and 81 amino acids, respectively. Insertion of a kanamycin resistance cassette into these open reading frames indicated that they corresponded to the genes encoding the 30, 33 and 9 kDa rod linkers, respectively, as judged by the loss of specific linkers from the phycobilisomes of the insertional mutants. Amino acid compositions of the 30 and 33 kDa linkers derived from the DNA sequence were found to deviate from those of purified 33 and 30 kDa linkers in the amounts of glutamic acid/glutamine residues. On the basis of similarity of the amino acid sequence of the rod linkers between Synechococcus sp. PCC 6301 and Calothrix sp. PCC 7601 we name the genes encoding the 30, 33 and 9 kDa linkers cpcH, cpcI and cpcD, respectively. The three linker genes were found to be co-transcribed on an mRNA of 3700 nucleotides. However, we also detected a smaller species of mRNA, of 3400 nucleotides, which would encode only the cpcH and cpcI genes. The 30 kDa linker was still found in phycobilisome rods lacking the 33 kDa linker and the 9 kDa linker was detected in mutants lacking the 33 or the 30 kDa linkers. Free phycocyanin was found in the mutants lacking the 33 or the 30 kDa linkers, whereas no free phycocyanin could be found in the mutant lacking the 9 kDa linker.

  • 79.
    Bhalerao, Rupali
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Keskitalo, Johanna
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sterky, Fredrik
    Erlandsson, Rikard
    Björkbacka, Harry
    Birve, Simon Jonsson
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gardeström, Per
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gustafsson, Petter
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Lundeberg, Joakim
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Gene expression in autumn leaves2003In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 131, no 2, p. 430-442Article in journal (Refereed)
    Abstract [en]

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

  • 80.
    Birve, Simon
    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).
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Johansson, L B A
    Secondary structure of NADPH: protochlorophyllide oxidoreductase examined by circular dichroism and prediction methods1996In: Biochemical Journal, ISSN 0264-6021, E-ISSN 1470-8728, Vol. 317, no 2, p. 549-555Article in journal (Refereed)
    Abstract [en]

    To study the secondary structure of the enzyme NADPH:protochlorophyllide oxidoreductase (PCOR), a novel method of enzyme isolation was developed. The detergent isotridecyl poly(ethylene glycol) ether (Genapol X-080) selectively solubilizes the enzyme from a prolamellar-body fraction isolated from wheat (Triticum aestivum L.). The solubilized fraction was further purified by ion-exchange chromatography. The isolated enzyme was studied by fluorescence spectroscopy at 77 K, and by CD spectroscopy. The fluorescence-emission spectra revealed that the binding properties of the substrate and co-substrate were preserved and that photo-reduction occurred. The CD spectra of PCOR were analysed for the relative amounts of the secondary structures, alpha-helix, beta-sheet, turn and random coil. The secondary structure composition was estimated to be 33% alpha-helix, 19% beta-sheet, 20% turn and 28% random coil. These values are in agreement with those predicted by the Predict Heidelberg Deutschland and self-optimized prediction method from alignments methods. The enzyme has some amino acid identity with other NADPH-binding enzymes containing the Rossmann fold. The Rossmann-fold fingerprint motif is localized in the N-terminal region and at the expected positions in the predicted secondary structure. It is suggested that PCOR is anchored to the interfacial region of the membrane by either a beta-sheet or an alpha-helical region containing tryptophan residues. A hydrophobic loop-region could also be involved in membrane anchoring.

  • 81. Bitocchi, Elena
    et al.
    Rau, Domenico
    Benazzo, Andrea
    Bellucci, Elisa
    Goretti, Daniela
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Biagetti, Eleonora
    Panziera, Alex
    Laido, Giovanni
    Rodriguez, Monica
    Gioia, Tania
    Attene, Giovanna
    McClean, Phillip
    Lee, Rian K.
    Jackson, Scott A.
    Bertorelle, Giorgio
    Papa, Roberto
    High Level of Nonsynonymous Changes in Common Bean Suggests That Selection under Domestication Increased Functional Diversity at Target Traits2017In: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 7, article id 2005Article in journal (Refereed)
    Abstract [en]

    Crop species have been deeply affected by the domestication process, and there have been many efforts to identify selection signatures at the genome level. This knowledge will help geneticists to better understand the evolution of organisms, and at the same time, help breeders to implement successful breeding strategies. Here, we focused on domestication in the Mesoamerican gene pool of Phaseolus vulgaris by sequencing 49 gene fragments from a sample of 45 P. vulgaris wild and domesticated accessions, and as controls, two accessions each of the closely related species Phaseolus coccineus and Phaseolus dumosus. An excess of nonsynonymous mutations within the domesticated germplasm was found. Our data suggest that the cost of domestication alone cannot explain fully this finding. Indeed, the significantly higher frequency of polymorphisms in the coding regions observed only in the domesticated plants (compared to noncoding regions), the fact that these mutations were mostly nonsynonymous and appear to be recently derived mutations, and the investigations into the functions of their relative genes (responses to biotic and abiotic stresses), support a scenario that involves new functional mutations selected for adaptation during domestication. Moreover, consistent with this hypothesis, selection analysis and the possibility to compare data obtained for the same genes in different studies of varying sizes, data types, and methodologies allowed us to identify four genes that were strongly selected during domestication. Each selection candidate is involved in plant resistance/tolerance to abiotic stresses, such as heat, drought, and salinity. Overall, our study suggests that domestication acted to increase functional diversity at target loci, which probably controlled traits related to expansion and adaptation to new agro-ecological growing conditions.

  • 82.
    Björkholm, Patrik
    et al.
    The Linnaeus Centre for Bioinformatics, Uppsala University, Uppsala.
    Daniluk, Pawel
    Department of Biophysics, Faculty of Physics, University of Warsaw, Warsaw, Poland.
    Kryshtafovych, Andriy
    UC Davis Genome Centre, UC Davis, USA.
    Fidelis, Krzysztof
    UC Davis Genome Centre, UC Davis, USA.
    Andersson, Robin
    The Linnaeus Centre for Bioinformatics, Uppsala University, Uppsala.
    Hvidsten, Torgeir
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Using multi-data hidden Markov models trained on local neighborhoods of protein structure to predict residue-residue contacts.2009In: Bioinformatics, ISSN 1367-4803, E-ISSN 1367-4811, Vol. 25, no 10, p. 1264-1270Article in journal (Refereed)
    Abstract [en]

    MOTIVATION: Correct prediction of residue-residue contacts in proteins that lack good templates with known structure would take ab initio protein structure prediction a large step forward. The lack of correct contacts, and in particular long-range contacts, is considered the main reason why these methods often fail. RESULTS: We propose a novel hidden Markov model (HMM)-based method for predicting residue-residue contacts from protein sequences using as training data homologous sequences, predicted secondary structure and a library of local neighborhoods (local descriptors of protein structure). The library consists of recurring structural entities incorporating short-, medium- and long-range interactions and is general enough to reassemble the cores of nearly all proteins in the PDB. The method is tested on an external test set of 606 domains with no significant sequence similarity to the training set as well as 151 domains with SCOP folds not present in the training set. Considering the top 0.2 x L predictions (L = sequence length), our HMMs obtained an accuracy of 22.8% for long-range interactions in new fold targets, and an average accuracy of 28.6% for long-, medium- and short-range contacts. This is a significant performance increase over currently available methods when comparing against results published in the literature.

  • 83.
    Björklund, Simon
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Uddestrand, Ida
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Moritz, Thomas
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sundberg, Björn
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Cross-talk between gibberellin and auxin in development of Populus wood: gibberellin stimulates polar auxin transport and has a common transcriptome with auxin2007In: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 52, no 3, p. 499-511Article in journal (Refereed)
    Abstract [en]

    Both indole acetic acid (IAA) and gibberellins (GAs) stimulate cell and organ growth. We have examined GA/IAA cross-talk in cambial growth of hybrid aspen (Populus tremulaxtremuloides). Decapitated trees were fed with IAA and GA, alone and in combination. Endogenous hormone levels after feeding were measured, by mass spectrometry, in the stem tissues below the point of application. These stem tissues with defined hormone balances were also used for global transcriptome analysis, and the abundance of selected transcripts was measured by real-time reverse-transcription polymerase chain reaction. By feeding isotope-labeled IAA, we demonstrated that GA increases auxin levels in the stem by stimulating polar auxin transport. This finding adds a new dimension to the concept that the endogenous GA/IAA balance in plants is determined by cross-talk between the two hormones. We also show that GA has a common transcriptome with auxin, including many transcripts related to cell growth. This finding provides molecular support to physiological experiments demonstrating that either hormone can induce growth if the other hormone is absent/deficient because of mutations or experimental treatments. It also highlights the potential for extensive cross-talk between GA- and auxin-induced responses in vegetative growth of the intact plant. The role of endogenous IAA and GA in wood development is discussed.

  • 84. Björn, Lars Olof
    et al.
    Sundqvist, Christer
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Plant Physiology. Umeå Plant Science Centre.
    A tribute to Per Halldal (1922-1986), a Norwegian photobiologist in Sweden.2007In: Photosynthesis Research, ISSN 0166-8595, Vol. 92, no 1, p. 7-11Article in journal (Other academic)
  • 85.
    Blanco, Nicolas E.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ceccoli, Romina D.
    Dalla Via, Maria V.
    Voss, Ingo
    Segretin, Maria E.
    Bravo-Almonacid, Fernando F.
    Melzer, Michael
    Hajirezaei, Mohammad-Reza
    Scheibe, Renate
    Hanke, Guy T.
    Expression of the Minor Isoform Pea Ferredoxin in Tobacco Alters Photosynthetic Electron Partitioning and Enhances Cyclic Electron Flow2013In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 161, no 2, p. 866-879Article in journal (Refereed)
    Abstract [en]

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

  • 86.
    Blanco, Nicolas E.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Guinea-Diaz, Manuel
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Whelan, James
    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).
    Interaction between plastid and mitochondrial retrograde signalling pathways during changes to plastid redox status2014In: Philosophical Transactions of the Royal Society of London. Biological Sciences, ISSN 0962-8436, E-ISSN 1471-2970, Vol. 369, no 1640, article id 20130231Article in journal (Refereed)
    Abstract [en]

    Mitochondria and chloroplasts depend upon each other; photosynthesis provides substrates for mitochondrial respiration and mitochondrial metabolism is essential for sustaining photosynthetic carbon assimilation. In addition, mitochondrial respiration protects photosynthesis against photoinhibition by dissipating excess redox equivalents from the chloroplasts. Genetic defects in mitochondrial function result in an excessive reduction and energization of the chloroplast. Thus, it is clear that the activities of mitochondria and plastids need to be coordinated, but the manner by which the organelles communicate to coordinate their activities is unknown. The regulator of alternative oxidase (rao1) mutant was isolated as a mutant unable to induce AOX1a expression in response to the inhibitor of the mitochondrial cytochrome c reductase (complex III), antimycin A. RAO1 encodes the nuclear localized cyclin-dependent kinase E1 (CDKE1). Interestingly, the rao1 mutant demonstrates a genome uncoupled phenotype also in response to redox changes in the photosynthetic electron transport chain. Thus, CDKE1 was shown to regulate both LIGHT HARVESTING COMPLEX B (LHCB) and ALTERNATIVE OXIDASE 1 (AOX1a) expression in response to retrograde signals. Our results suggest that CDKE1 is a central nuclear component integrating mitochondrial and plastid retrograde signals and plays a role in regulating energy metabolism during the response to stress.

  • 87.
    Blanco, Nicolas E.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Centro de Estudios Fotosintéticos y Bioquímicos, Universidad Nacional de Rosario (CEFOBI-CONICET/UNR), Rosario, Argentina.
    Liebsch, Daniela
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Rosario, Argentina.
    Guinea Diaz, Manuel
    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).
    Whelan, James
    Dual and dynamic intracellular localization of Arabidopsis thaliana SnRK1.12019In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 70, no 8, p. 2325-2338Article in journal (Refereed)
    Abstract [en]

    Sucrose non-fermenting 1 (SNF1)-related protein kinase 1.1 (SnRK1.1; also known as KIN10 or SnRK1 alpha) has been identified as the catalytic subunit of the complex SnRK1, the Arabidopsis thaliana homologue of a central integrator of energy and stress signalling in eukaryotes dubbed AMPK/Snf1/SnRK1. A nuclear localization of SnRK1.1 has been previously described and is in line with its function as an integrator of energy and stress signals. Here, using two biological models (Nicotiana benthamiana and Arabidopsis thaliana), native regulatory sequences, different microscopy techniques, and manipulations of cellular energy status, it was found that SnRK1.1 is localized dynamically between the nucleus and endoplasmic reticulum (ER). This distribution was confirmed at a spatial and temporal level by co-localization studies with two different fluorescent ER markers, one of them being the SnRK1.1 phosphorylation target HMGR. The ER and nuclear localization displayed a dynamic behaviour in response to perturbations of the plastidic electron transport chain. These results suggest that an ER-associated SnRK1.1 fraction might be sensing the cellular energy status, being a point of crosstalk with other ER stress regulatory pathways.

  • 88.
    Blanco-Rivero, A
    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). Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid 28049, Spain .
    Leganés, F
    Fernández-Valiente, E
    Calle, P
    Fernández-Piñas, F
    mrpA, a gene with roles in resistance to Na+ and adaptation to alkaline pH in the cyanobacterium Anabaena sp. PCC71202005In: Microbiology, ISSN 1350-0872, E-ISSN 1465-2080, Vol. 151, no Pt 5, p. 1671-1682Article in journal (Refereed)
    Abstract [en]

    Transposon mutagenesis of Anabaena sp. PCC7120 led to the isolation of a mutant strain, PHB11, which grew poorly at pH values above 10. The mutant strain exhibited pronounced Na+ sensitivity; this sensitivity was higher under basic conditions. Mutant PHB11 also showed an inhibition of photosynthesis that was much more pronounced at alkaline pH. Reconstruction of the transposon mutation of PHB11 in the wild-type strain reproduced the phenotype of the original mutant. The wild-type version of the mutated gene was cloned and the mutation complemented. In mutant strain PHB11, the transposon had inserted within an ORF that is part of a seven-ORF operon with significant sequence similarity to a family of bacterial operons that are believed to code for a novel multiprotein cation/proton antiporter primarily involved in resistance to salt stress and adaptation to alkaline pH. The Anabaena operon was denoted mrp (multiple resistance and pH adaptation) following the nomenclature of the Bacillus subtilis operon; the ORF mutated in PHB11 corresponded to mrpA. Computer analysis suggested that all seven predicted Anabaena Mrp proteins were highly hydrophobic with several transmembrane domains; in fact, the predicted protein sequences encoded by mrpA, mrpB and mrpC showed significant similarity to hydrophobic subunits of the proton pumping NADH : ubiquinone oxidoreductase. In vivo expression studies indicated that mrpA is induced with increasing external Na+ concentrations and alkaline pH; mrpA is also upregulated under inorganic carbon (Ci) limitation. The biological significance of a putative cyanobacterial Mrp complex is discussed.

  • 89.
    Blanco-Rivero, Amaya
    et al.
    Madrid, Spain.
    Shutova, Tatiana
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    José Román, María
    Madrid, Spain.
    Villarejo, Arsenio
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Department of Biology, Universidad Autónoma de Madrid, Madrid, Spain.
    Martinez, Flor
    Madrid, Spain.
    Phosphorylation Controls the Localization and Activation of the Lumenal Carbonic Anhydrase in Chlamydomonas reinhardtii2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 11, article id e49063Article in journal (Refereed)
    Abstract [en]

    Background: Cah3 is the only carbonic anhydrase (CA) isoform located in the thylakoid lumen of Chlamydomonas reinhardtii. Previous studies demonstrated its association with the donor side of the photosystem II (PSII) where it is required for the optimal function of the water oxidizing complex. However this enzyme has also been frequently proposed to perform a critical function in inorganic carbon acquisition and CO2 fixation and all mutants lacking Cah3 exhibit very poor growth after transfer to low CO2 conditions. Results/Conclusions: In the present work we demonstrate that after transfer to low CO2, Cah3 is phosphorylated and that phosphorylation is correlated to changes in its localization and its increase in activity. When C. reinhardtii wild-type cells were acclimated to limiting CO2 conditions, the Cah3 activity increased about 5-6 fold. Under these conditions, there were no detectable changes in the level of the Cah3 polypeptide. The increase in activity was specifically inhibited in the presence of Staurosporine, a protein kinase inhibitor, suggesting that the Cah3 protein was post-translationally regulated via phosphorylation. Immunoprecipitation and in vitro dephosphorylation experiments confirm this hypothesis. In vivo phosphorylation analysis of thylakoid polypeptides indicates that there was a 3-fold increase in the phosphorylation signal of the Cah3 polypeptide within the first two hours after transfer to low CO2 conditions. The increase in the phosphorylation signal was correlated with changes in the intracellular localization of the Cah3 protein. Under high CO2 conditions, the Cah3 protein was only associated with the donor side of PSII in the stroma thylakoids. In contrast, in cells grown at limiting CO2 the protein was partly concentrated in the thylakoids crossing the pyrenoid, which did not contain PSII and were surrounded by Rubisco molecules. Significance: This is the first report of a CA being post-translationally regulated and describing phosphorylation events in the thylakoid lumen.

  • 90. Blumenstein, Kathrin
    et al.
    Albrectsen, Benedicte R.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Martin, Juan A.
    Hultberg, Malin
    Sieber, Thomas N.
    Helander, Marjo
    Witzell, Johanna
    Nutritional niche overlap potentiates the use of endophytes in biocontrol of a tree disease2015In: BioControl (Dordrecht), ISSN 1386-6141, E-ISSN 1573-8248, Vol. 60, no 5, p. 655-667Article in journal (Refereed)
    Abstract [en]

    Asymptomatic endophytic fungi are often regarded as potent biocontrol agents in plants, but the competitive interactions between endophytes and other microbes within the same host plant are poorly understood. We tested a hypothesis that as compared to asymptomatic endophytes, an aggressive pathogen inhabiting the same host is able to utilize carbon substrates more efficiently. Using phenotype microarray, we determined the carbon utilization profiles of the highly virulent Dutch elm disease (DED) pathogen Ophiostoma novo-ulmi, and four asymptomatic elm (Ulmus spp.) endophyte isolates that were selected based on their differential association to the DED-susceptibility pattern of the host elms. The competitive interactions between isolates were evaluated using a niche overlap index. In contrast to our hypothesis, the studied endophytes exhibited extensive niche overlap with the pathogen, suggesting that some endophyte strains might protect elms against DED-pathogen through competition for substrates and provide new tools for biocontrol of DED.

  • 91.
    Bollhoner, Benjamin
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Prestele, Jakob
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Tuominen, Hannele
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Xylem cell death: emerging understanding of regulation and function2012In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 63, no 3, p. 1081-1094Article, review/survey (Refereed)
    Abstract [en]

    Evolutionary, as well as genetic, evidence suggests that vascular development evolved originally as a cell death programme that allowed enhanced movement of water in the extinct protracheophytes, and that secondary wall formation in the water-conducting cells evolved afterwards, providing mechanical support for effective long-distance transport of water. The extant vascular plants possess a common regulatory network to coordinate the different phases of xylem maturation, including secondary wall formation, cell death, and finally autolysis of the cell contents, by the action of recently identified NAC domain transcription factors. Consequently, xylem cell death is an inseparable part of the xylem maturation programme, making it difficult to uncouple cell death mechanistically from secondary wall formation, and thus identify the key factors specifically involved in regulation of cell death. Current knowledge suggests that the necessary components for xylem cell death are produced early during xylem differentiation, and cell death is prevented through the action of inhibitors and storage of hydrolytic enzymes in inactive forms in compartments such as the vacuole. Bursting of the central vacuole triggers autolytic hydrolysis of the cell contents, which ultimately leads to cell death. This cascade of events varies between the different xylem cell types. The water-transporting tracheary elements rely on a rapid cell death programme, with hydrolysis of cell contents taking place for the most part, if not entirely, after vacuolar bursting, while the xylem fibres disintegrate cellular contents at a slower pace, well before cell death. This review includes a detailed description of cell morphology, function of plant growth regulators, such as ethylene and thermospermine, and the action of hydrolytic nucleases and proteases during cell death of the different xylem cell types.

  • 92.
    Bollhöner, Benjamin
    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).
    Jokipii-Lukkari, Soile
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Bygdell, Joakim
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stael, Simon
    Adriasola, Mathilda
    Muñiz, Luis
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Van Breusegem, Frank
    Ezcurra, Inés
    Wingsle, Gunnar
    Tuominen, Hannele
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    The function of two type II metacaspases in woody tissues of Populus trees2018In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 217, no 4, p. 1551-1565Article in journal (Refereed)
    Abstract [en]

    Metacaspases (MCs) are cysteine proteases that are implicated in programmed cell death of plants. AtMC9 (Arabidopsis thaliana Metacaspase9) is a member of the Arabidopsis MC family that controls the rapid autolysis of the xylem vessel elements, but its downstream targets in xylem remain uncharacterized. PttMC13 and PttMC14 were identified as AtMC9 homologs in hybrid aspen (Populustremulaxtremuloides). A proteomic analysis was conducted in xylem tissues of transgenic hybrid aspen trees which carried either an overexpression or an RNA interference construct for PttMC13 and PttMC14. The proteomic analysis revealed modulation of levels of both previously known targets of metacaspases, such as Tudor staphylococcal nuclease, heat shock proteins and 14-3-3 proteins, as well as novel proteins, such as homologs of the PUTATIVE ASPARTIC PROTEASE3 (PASPA3) and the cysteine protease RD21 by PttMC13 and PttMC14. We identified here the pathways and processes that are modulated by PttMC13 and PttMC14 in xylem tissues. In particular, the results indicate involvement of PttMC13 and/or PttMC14 in downstream proteolytic processes and cell death of xylem elements. This work provides a valuable reference dataset on xylem-specific metacaspase functions for future functional and biochemical analyses.

  • 93.
    Bollhöner, Benjamin
    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).
    Zhang, Bo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Stael, Simon
    Denancé, Nicolas
    Overmyer, Kirk
    Goffner, Deborah
    Van Breusegem, Frank
    Tuominen, Hannele
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Post mortem function of AtMC9 in xylem vessel elements2013In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 200, no 2, p. 498-510Article in journal (Refereed)
    Abstract [en]

    Cell death of xylem elements is manifested by rupture of the tonoplast and subsequent autolysis of the cellular contents. Metacaspases have been implicated in various forms of plant cell death but regulation and execution of xylem cell death by metacaspases remains unknown. Analysis of the type II metacaspase gene family in Arabidopsis thaliana supported the function of METACASPASE 9 (AtMC9) in xylem cell death. Progression of xylem cell death was analysed in protoxylem vessel elements of 3-d-old atmc9 mutant roots using reporter gene analysis and electron microscopy. Protoxylem cell death was normally initiated in atmc9 mutant lines, but detailed electron microscopic analyses revealed a role for AtMC9 in clearance of the cell contents post mortem, that is after tonoplast rupture. Subcellular localization of fluorescent AtMC9 reporter fusions supported a post mortem role for AtMC9. Further, probe-based activity profiling suggested a function of AtMC9 on activities of papain-like cysteine proteases. Our data demonstrate that the function of AtMC9 in xylem cell death is to degrade vessel cell contents after vacuolar rupture. We further provide evidence on a proteolytic cascade in post mortem autolysis of xylem vessel elements and suggest that AtMC9 is part of this cascade.

  • 94. Borodich, A
    et al.
    Rojdestvenski, I
    Cottam, M
    Anderson, J
    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).
    Segregation of the photosystems in higher plant thylakoids and short- and long-term regulation by a mesoscopic approach2003In: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 225, no 4, p. 431-441Article in journal (Refereed)
    Abstract [en]

    In this paper we consider the relationship between the lateral segregation of photosystems I and II in the grana and characteristics of the short- and long-term regulation in thylakoids following the mesoscopic approach. Our study is thermodynamic; it is based on the Flory-Huggins theory for binary mixtures and the McMillan-Mayer theory of heterogeneous solutions. We demonstrate that state transitions promote rearrangement of photosystems by either favoring their mixing after LHCII phosphorylation or enhancing their segregation after LHCII dephosphorylation. This regulation influences the entire system properties locally. We also demonstrate that the variations of the photosystem ratio promote rearrangement of the photosystems preserving their segregation. This regulation influences the entire system properties globally. The studies presented are another indication of the importance of the segregation of the photosystems in the grana thylakoids of higher plants. Segregation of PSIs and PSIIs is a signature of the spinodal decomposition, which is a fine regulatory mechanism, related to both the short- and long-term adaptations of the photosynthetic apparatus in higher plant thylakoids. (C) 2003 Elsevier Ltd. All rights reserved.

  • 95. Borodich, A
    et al.
    Rojdestvenski, I
    Cottam, M
    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).
    Segregation of the photosystems in thylakoids depends on their size2003In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1606, no 1-3, p. 73-82Article in journal (Refereed)
    Abstract [en]

    Lateral segregation of two types of photosystems in thylakoid membranes of green plants is one of the key factors that provide the stability and fine-tuning of the light quanta supply by pigment proteins and non-cyclic electron transport. Due to this specific feature of the membrane structural organization, the photosynthetic units function in the green plants with optimal performance. In this report a mesoscopic theory is outlined to address the physical aspects of segregation phenomenon. Results of theoretical studies and computer simulations suggest that charge mismatch and the size difference between two photosystems in grana are most responsible for their lateral segregation, which is driven by the screened electrostatic and lipid-induced interactions. Comparative simulations of photosystems of different sizes show the crucial dependence of their ordering on a geometrical parameter. It seems that the size effect alone may prevent photosystems from segregated arrangement in cyanobacterial thylakoids. (C) 2003 Elsevier B.V. All rights reserved.

  • 96. 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.

  • 97. Bossmann, B
    et al.
    Knoetzel, J
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Screening of chlorina mutants of barley (Hordeum vulgare L.) with antibodies against light-harvesting proteins of PS I and PS II: Absence of specific antenna proteins1997In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 52, no 2, p. 127-136Article in journal (Refereed)
    Abstract [en]

    Twenty-three chlorina (clo) mutants from the barley mutant collection of the Carlsberg Laboratory, Copenhagen, were tested for the presence of the four light-harvesting chlorophyll (Chl) a/b-binding proteins (LHC) of Photosystem I (Lhcal-4) and the PS II antenna proteins Lhcb1-3 (LHC II), Lhcb4-6 (CP29, CP26, CP24) and PsbS (CP22) using monospecific and monoclonal antibodies. Mutants allelic to barley mutant clo-f2, impaired in Chi b synthesis, provided evidence that Lhca4, Lhcb1 and Lhcb6 are unstable in the absence of Chi b, and the accumulation of Lhcb2, Lhcb3 and Lhcb4 is also impaired. Mutants at the locus chlorina-a (clo-a(117), clo-a(126) and clo-a(134)) lack or have only trace amounts of Lhca1, Lhca4, Lhcb1 and Lhcb3, whereas a mutant at the locus chlorina-b (clo-b(125)) had reduced amounts of all Lhca proteins. These two mutations could have an effect in protein import or assembly. Evidence is presented that Lhcb5 is the innermost LHC protein of PS II, and that Lhca1 and Lhca4, which have been supposed to be intimately associated in the LHCI-730 complex, can accumulate independently of each other. 77 K fluorescence emission spectra taken from leaves of clo-f2(101), clo-a(126) and clo-b(125) indicate that chlorophyll(s) emitting at 742 nm are coupled to the presence of Lhca4 that is bound to the reaction centre, and those emitting around 730 nm are located on Lhca1.

  • 98. Bourque, S.
    et al.
    Jeandroz, S.
    Grandperret, V.
    Lehotai, Nora
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Agroécologie, AgroSup Dijon, Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique (INRA), Université Bourgogne Franche-Comté, Dijon, France.
    Aime, S.
    Soltis, D. E.
    Miles, N. W.
    Melkonian, M.
    Deyholos, M. K.
    Leebens-Mack, J. H.
    Chase, M. W.
    Rothfels, C. J.
    Stevenson, D. W.
    Graham, S. W.
    Wang, X.
    Wu, S.
    Pires, J. C.
    Edger, P. P.
    Yan, Z.
    Xie, Y.
    Carpenter, E. J.
    Wong, G. K. S.
    Wendehenne, D.
    Nicolas-Frances, V.
    The Evolution of HD2 Proteins in Green Plants2016In: Trends in Plant Science, ISSN 1360-1385, E-ISSN 1878-4372, Vol. 21, no 12, p. 1008-1016Article, review/survey (Refereed)
    Abstract [en]

    In eukaryotes, protein deacetylation is carried out by two well-conserved his tone deacetylase (HDAC) families: RPD3/HDA1 and SIR2. Intriguingly, model plants such as Arabidopsis express an additional plant-specific HDAC family, termed type-2 HDACs (HD2s). Transcriptomic analyses from more than 1300 green plants generated by the 1000 plants (1KP) consortium showed that HD2s appeared early in green plant evolution, the first members being detected in several streptophyte green alga. The HD2 family has expanded via several rounds of successive duplication; members are expressed in all major green plant clades. Interestingly, angiosperm species express new HD2 genes devoid of a zinc-finger domain, one of the main structural features of HD2s. These variants may have been associated with the origin and/or the biology of the ovule/seed.

  • 99.
    Boutté, Yohann
    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).
    Frescatada-Rosa, Márcia
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Men, Shuzhen
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Chow, Cheung-Ming
    Ebine, Kazuo
    Gustavsson, Anna
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Johansson, Lenore
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ueda, Takashi
    Moore, Ian
    Jürgens, Gerd
    Grebe, Markus
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Endocytosis restricts Arabidopsis KNOLLE syntaxin to the cell division plane during late cytokinesis2010In: EMBO Journal, ISSN 0261-4189, E-ISSN 1460-2075, Vol. 29, no 3, p. 546-58Article in journal (Refereed)
    Abstract [en]

    Cytokinesis represents the final stage of eukaryotic cell division during which the cytoplasm becomes partitioned between daughter cells. The process differs to some extent between animal and plant cells, but proteins of the syntaxin family mediate membrane fusion in the plane of cell division in diverse organisms. How syntaxin localization is kept in check remains elusive. Here, we report that localization of the Arabidopsis KNOLLE syntaxin in the plane of cell division is maintained by sterol-dependent endocytosis involving a clathrin- and DYNAMIN-RELATED PROTEIN1A-dependent mechanism. On genetic or pharmacological interference with endocytosis, KNOLLE mis-localizes to lateral plasma membranes after cell-plate fusion. Fluorescence-loss-in-photo-bleaching and fluorescence-recovery-after-photo-bleaching experiments reveal lateral diffusion of GFP-KNOLLE from the plane of division to lateral membranes. In an endocytosis-defective sterol biosynthesis mutant displaying lateral KNOLLE diffusion, KNOLLE secretory trafficking remains unaffected. Thus, restriction of lateral diffusion by endocytosis may serve to maintain specificity of syntaxin localization during late cytokinesis.

  • 100.
    Boutté, Yohann
    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).
    Grebe, Markus
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Cellular processes relying on sterol function in plants2009In: Current opinion in plant biology, ISSN 1369-5266, E-ISSN 1879-0356, Vol. 12, no 6, p. 705-713Article in journal (Refereed)
    Abstract [en]

    Sterols are lipophilic membrane components essential for diverse cellular functions. The plant sterol biosynthesis pathway has largely been defined by biochemical approaches. Sterol function has been investigated by the pharmacological and genetic manipulation of sterol biosynthesis. However, mechanisms by which sterols influence cellular processes and targets of sterol function remain largely unknown. During the last two years, new Arabidopsis sterol biosynthesis mutants have been characterized. Their analysis has revealed the contributions of known and alternative routes of sterol biosynthesis to various cellular processes. Subcellular localization and trafficking of a sterol-binding protein have been investigated and first steps towards in vivo characterization of sterol-enriched membrane domains have been taken. Finally, mechanistic insight into the role of plant sterols during endocytosis and the establishment of cell polarity has been obtained.

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