Book of Abstracts - Geyseco

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P - Posters tructural rearrangements in cell organelles during adaptation to temperature stresses are discussed. P11-026: VESICLE DELIVERY IN POLLEN TUBES: PER- FECTLY COORDINATED INTRACELLULAR LOGIS- TICS Van Oostende, C. 1 *- Guillet, D. 2 - Juillot, S. 1 - Geitmann, A. 1 1 Institut de recherche en biologie végétale-Universite de Montreal 2 Mc Gill University *Corresponding author, e-mail: chloevanoostende@gmail.com Cellular growth in plants implies the continuous assembly of new cell wall surface to prevent the expanding wall from rupturing. Most plant cells are characterized by diffuse growth that requires cell wall assembly over large surfaces. In contrast, the generation of complex cell shapes necessitates spatially confined growth and assembly processes. An example for this is the pollen tube, which displays tip-growth, where the expansion occurs solely at the extreme end of the cell. Pollen tube growth plays a crucial function during sexual plant reproduction since it ensures the delivery of the male gametes to the ovules which are nestled deep in the pistillar tissues of the receiving flower. Pollen tube growth is extremely fast and, therefore, cell wall assembly is the principal metabolic activity. The spatial confinement of the cell wall assembly requires an intracellular transport system that is precisely controlled in space and time. Hence, trafficking of vesicles and other elements of the endomembrane system (Golgi, endoplasmic reticulum, endosomes) must be subject to a sophisticated system of cellular transport logistics mediated by the cytoskeleton. By combining high temporal and spatial resolution laser scanning microscopy with advanced imaging techniques originally developed for molecular movements (STICS, spatio-temporal image correlation spectroscopy), we monitored the delivery of vesicles towards the tube apex, the movements of organelles and the dynamics of the cytoskeleton. We used these motion profiles to generate a mathematical model of intracellular trafficking that will help us to understand the logistic transport principles employed by growing plant cells. P11-027: GENERATION OF ACETOLACTATE SYNTHA- SE INHIBITORS - TOLERANT ALFALFA Feuillebois, P 1 * - Schaller, A. 2 - Hain, R. 1 1 Bayer CropScience, Herbicide Research 2 University of Hohenheim, Institute of Plant Physiology and Biotechnology *Corresponding author, e-mail: pauline.feuillebois@bayercropscience.com The cultivated alfalfa, Medicago sativa, is one of the most valuable legumes in the world. It is a perennial dicot with a tetraploid genome, rich in proteins, minerals and vitamins. Alfalfa is thus widely grown as forage for cattle. Chemical weed control is often necessary at an early stage since weeds in alfalfa fields reduce the yield and the crop quality. To enable better weed control in alfalfa, improving crop and seed production quality, our project aims to generate Acetolactate Synthase Inhibitors (ALSi) tolerant alfalfa using both GMO and non-GMO approaches. An in vitro alfalfa tissue culture has been set up by screening RA3 individuals (Medicago sativa L., cv Regen S, clone RA3) for their embryogenic response. Conditions have been optimized allowing regeneration cycles of fifty days on average. As the Acetolactate Synthase (ALS) enzyme is the target of ALSi herbicides, two ALS genes (MEDSA_ALSa and MEDSA_ALSb) have been identified in Medicago sativa and their sequences have been obtained. In the non-GMO approach, chemical mutagenesis is performed on somatic embryos to obtain putative ALSi tolerant mutants, screened using sulfonylurea herbicides (SUs). For the GMO approach, Agrobacterium tumefaciens - mediated alfalfa leaf disc transformations are carried out using an Arabidopsis thaliana mutated ALS gene conferring ALSi tolerance fused to a transit peptide. Somatic embryos obtained are selected with SUs to evaluate the potential herbicide tolerance. Positive tolerant plants will be tested for SUs tolerance in the greenhouse and fully characterized using molecular biology methods. P11-028: MECHANISTIC FRAMEWORK FOR POLAR PIN AUXIN EFFLUX CARRIER TARGETING IN PLANT CELLS Kleine-Vehn, J.* - Jiri Friml VIB - Gent university *Corresponding author, e-mail: jukle@psb.ugent.be Cell polarity is indispensable for differentiation, proliferation and morphogenesis of unicellular and multicellular organism. Most of our knowledge is derived from animal epithelial cells that organize cell polarity via the formation of tight junctions that separate distinct plasma membrane domains. Polarized plant cells lack tight junctions and the underlying mechanism that ensures cell polarity in plants is largely unknown. PIN proteins are prominent polar cargos that determine the direction and rate of the cellular export of the phytohormone auxin. Here we provide molecular and mechanistic insights into polar PIN targeting. Quantitative life-cell imaging techniques revealed that plant cells facilitate spatially defined exo- and endocytosis by regulated endosomal trafficking and subsequent short range vesicle transport. These endosome-based mechanisms enable superpolar exocytosis to an inner core in the apical plasma membrane domain and the retrieval of non-polar PIN proteins by spatially defined endocytosis via a clathrin-dependent mechanism at the apical-lateral cell junction (adjacent to the polar domain). This interweaving mechanism for PIN polarity maintenance gets further stabilized by a sterol-dependent clustering of PIN proteins in the plasma membrane, largely abolishing their lateral diffusion. Our findings provide the first mechanistic insight of how nonepithelial cells, such as plant cells, maintain polar plasma membrane domains. P11-029: REQUIREMENTS FOR NUCLEAR AND NU- CLEOLAR LOCALIZATION OF ARABIDOPSIS RIBO- SOMAL PROTEIN L23A Bonham-Smith, P.* - Savada, R.P. University of Saskatchewan *Corresponding author, e-mail: peta.bonhams@usask.ca The mechanism underlying the transport of plant r-proteins from the cytoplasm into, and their retention in, the nucleus/nucleolus is not understood. R-protein L23a is one of 81 r-proteins in Arabidopsis. It is present in two isoforms; L23aA that is essential for plant development under normal conditions and L23aB is not. Both isoforms have nine putative Nuclear Localisation Sites. Site Directed Mutagenesis of any one NLS has no effect on nuclear/ nucleolar localization of L23aA. Simultaneous mutation of all nine NLSs has no effect on nuclear localization, however, nucleolar localization is completely disrupted. Combinatorial mutation studies show that, five (10KKAD13, 17KALK20, 86KK87, 121KK122, and 133KK134) NLSs are required for nucleolar localization. We are currently investigating: i) if nuclear localization of L23aA is mediated by the classic importin pathway and ii) what differentiates movement into and retention of L23aA in the nucleolus (rRNA binding) from nuclear localisation. P11-030: THE ROLE OF REVERSIBLE ZEATIN GLU- COSYLATION IN THE HOMEOSTASIS OF CYTOKI- NINS Kiran, N. S.* - Dubova, J. - Brzobohaty, B. - *Corresponding author, e-mail: kiran@mendelu.cz Reversible glucosylation of zeatin-type cytokinins is important for the homeostasis of active cytokinin forms at certain developmental stages. The sub-cellular location of this conversion P
FESPB 2010 - XVII Congress of the Federation of European Societies of Plant Biology is proposed to affect the levels of the active cytokinin forms at particular locations and times during plant development. Using the zeatin-O-glucoside (ZOG)-specific ß-glucosidase Zm-p60.1, we have been able to disrupt the zeatin metabolic network during early tobacco seedling development and have shown that the vacuole is indeed the storage organelle for ZOG. We investigated the phenotypes of the progeny of crosses with tobacco plants over-expressing the glucosyltransferase ZOG1. During early development of the seedling (14 days after sowing - 9-10 days after germination), the different sub-cellular variants of Zm-p60.1 show divergent responses with respect to hypocotyl elongation on MS medium. Root lengths on medium containing zeatin are also divergent. The molecular and physiological changes underlying the observed phenotypes will be discussed. Supported by grant Nos. LC06034 (Czech Ministry of Education, Youth and Sports) and 204/09/P289 (Czech Science Foundation) P11-031: REBELOTE, ANOTHER LINK BETWEEN RI- BOSOMAL PROCESSING AND ARABIDOPSIS DEVE- LOPMENT de Bossoreille, S.* - Morel, P. - Boltz, V. - Tréhin, C. - Negrutiu, I. ENS Lyon *Corresponding author, e-mail: steve.de.bossoreille.de.ribou@ens-lyon.fr Bridges between nucleic acids sequences and proteins, ribosomes are central components and the “auletes” of living cells. Composed of ribosomal proteins and RNA, they move during their biogenesis from the nucleolus to the cytoplasm, where they translate RNA messengers into proteins. In the past years, some mutants of ribosomal-biogenesis-related proteins have shown the importance of these proteins during cell division and Arabidopsis development. The impact of ribosomal defects on development could be explained by dose effect (which could be important for cell fitness), specificity of ribosomes for some mRNA or multifunctional ribosomal proteins (Mary E. Byrne, 2009). Here I present our work on REBELOTE (RBL), one of the two Arabidopsis homologs of the yeast NOC2 protein, which act during the ribosomal 60S subunit biogenesis. Mutations in REBELOTE gene cause a range of phenotypes, from embryo lethality to growth defects (reduced plant size, altered leaf shape…). To have a better understanding of RBL-controlled processes, we first analyzed the ribosomal function of RBL, and searched for its protein partners. Our results shows that RBL act in two different nucleolar complexes supposed to regulate 60S ribosomal subunit biogenesis. Subsequently, we focused on the effects of rbl mutations on the cell division/elongation processes. Our work shows that defects observed at molecular and cellular levels could explain the slow down of cell divisions and growth delay in rbl mutants. P11-032: NATURAL TOLERANCE AS A BASIS FOR THE DEVELOPMENT OF NEW HERBICIDE TOLERANCE TRAITS IN AGRICULTURE Koehler, J. 1 *- Porré, F. 2 - Schaller, A. 3 1 University of Hohenheim, Stuttgart 2 Bayer CropScience Frankfurt 3 Plant Physiology and Biotechnology *Corresponding author, e-mail: judith.koehler@bayercropscience.com Herbicides are chemicals used in agriculture to control unwanted weeds. Since the late 1940s, many herbicidal agents were discovered and extentsively used. As a consequence of extensive herbicide use, herbicide-resistant weed populations emerged over the past years. Modern agriculture has to face these problems and herbicide-tolerant crops are part of new weed control systems: they consist of a non-selective herbicide and a corresponding herbicide-tolerant crop. The underlying difficulty is the identification of traits leading to tolerance in plants and a better understanding of the mechanisms of tolerance is warranted. It was recently shown the the green alga Chlamydomonas reinhardtii shows natural tolerance to some herbicides. Therefore, we are trying to identify the mechanism responsible for this tolerance. In the last decades, this unicellular alga has become a powerful model organism for the study of a number of fundamental topics in molecular biology and many tools are available that will help in the identification of the mechanism. Two species of the genus Callistemon have also been shown to be tolerant to herbicides. The mechanism of tolerance will be identified and compared to the one present in the algae. A better understanding of herbicide tolerance and also the identification of traits are essential for agricultural purposes in modern weed control systems P11-033: THE CONSERVED MEMBRANE PROTEIN BAB REGULATES BASL POLAR LOCALIZATION AND IS REQUIRED FOR ASYMMETRIC CELL DIVISIONS IN ARABIDOPSIS Michniewicz, M.* - Bergmann, D. Stanford University *Corresponding author, e-mail: martap@stanford.edu Asymmetric cell division is fundamental for generation of cellular diversity during animal and plant development. The regulation of this process is mainly achieved by polarization of the cell along its axis and asymmetric segregation of cell fate determinants. The recently identified BASL protein is a novel regulator of asymmetric divisions in Arabidopsis. BASL exhibits a unique subcellular pattern of localization within stomatal-lineage cells: before asymmetric division BASL accumulates in a polarized crescent at the cell periphery and after division re-localizes to the nucleus and a peripheral crescent in self-renewing cells and their sisters. Acquisition and maintenance of such an intricate pattern of protein localization require involvement of complex regulatory systems. Here we will present characterization of the first component we have identified that controls subcellular distribution of BASL, the membrane protein BOCCA A BOCCA (BAB). We demonstrate that in the absence of BAB, BASL loses its polarized plasma membrane localization and appears diffuse within cells. BAB is conserved throughout evolution and is broadly expressed in the plant suggesting that it may be part of a general polarity mechanism. Notably, however, BAB is not required for subcellular localization of other polarized proteins (such as PIN1 and PIN2), suggesting high specificity of BAB activity. P11-034: IDENTIFICATION OF HYPERACTIVE FORMS OF ARABIDOPSIS THALIANA MAP KINASES BERRIRI S (URGV) Berriri S., Pateyron. S, Merlot S., Leung J., Hirt H. and Colcombet J. URGV, France Protein phosphorylations and dephosphorylations are common events occurring during intracellular signalling processes. Among plant kinases, Mitogen-Activated Protein Kinases (MAPKs) are more specifically involved in stress responses. However, despite an abundant literature, the exact roles and direct targets of the 20 Arabidopsis MAPKs are still not completely defined. Although many aspects of the activation mechanism of MAPKs have been unveiled, constitutive active MAPKs are difficult to generate. Classical strategies used to trigger kinase activation by mutation of the phosphorylated residues failed. To bypass this problem, we built a screen based on functional expression in yeast in order to identify mutated MAPK which are active without upstream signal. We therefore aim to identify important residues involved in the activity control and will generate point mutants in other plant MAPKs. At the same time, these active MAPKs will be used to complement a MAPK mutant. Apart from studying the phenotypic consequences, our goal will be the identification of the molecular targets of the kinases using microarray-based transcriptome analysis. Overall, the proposed work should provide direct information on
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Page 206 and 207: Author Index Aarts, M.G. S18-002 Ab
Page 208 and 209: Cattivelli, L. P01-031 Cawly, J. P1
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Gallego, B. P17-037 Gallego, P.P. P
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Kersten, B. P10-017 Keskin, O. P05-
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Miguel, C. S02-001, P01-122 Milhinh
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Ramiro, M. P09-018 Ramon, M P13-002
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Tanimoto, E. P01-045 Tarakanov, I.
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