Book of Abstracts - Geyseco

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P - Posters growth and development as specific phenotypes related to sugar partitioning, carbon allocation and stress resistance were found. This is more linked to the change in the level of the intermediate Trehalose-6-Phosphate (T6P), which is strongly related to sugar status, than to T itself. Arabidopsis has 21 genes putatively involved in T biosynthesis, only one has showed T6P synthase activity and surprisingly 10 of them, known as T6P Phosphatases (TPPA-TPPJ), are active TPPs. Identification of TPP promoter cell-type activity revealed specific expression patterns of these genes in different organs of the plant. By analyzing loss and gain of function mutants we could find that some TPPs are involved in the development of lateral root primordia and their outgrowth. Phenotypes related to the formation of flowers and high/low biomass have been found also. These observations suggest that TPP genes could be tightly controlling T6P levels in particular cells and times of plant growth instead of producing more or less T. Nevertheless sugars, T6P and metabolite measurements are needed to confirm this hypothesis and to understand why T metabolism is so relevant for plant growth. P06-018: BELOWGROUND VOLATILES FROM WHEAT (TRITICUM AESTIVUM L.) AND FROM PLANT GROWTH-PROMOTING BACTERIA OF THE WHEAT RHIZOSPHERE du Jardin, P.* - Delaplace, P. - Ormenõ, E. - d’Ans, S. - Fauconnier, M.L. - Wathelet, J.P. University of Liège - Gembloux Agro-Bio Tech *Corresponding author e-mail: patrick.dujardin@ulg.ac.be The relevance of organic volatile compounds (VOC) released by leaves in plant–to–plant communication and in the interaction with herbivores, pathogens and their natural enemies is well acknowledged, but their roles in the root environment are much less known. In order to contribute to the unravelling of the nature, origins and functions of volatiles emitted by roots, wheat (Triticum aestivum L.) was chosen as a model with the aim to characterize VOC-mediated interactions between roots and rhizospheric bacteria defined as promoters of plant growth („Plant Growth Promoting Bacteria, or PGPRs). Regarding the plant partner, three questions were first raised: what is the profile of extractable volatiles of roots (in the absence of biotic or abiotic stress), how similar/different is this profile with that of leaf volatiles, and do the released volatiles match the extractable VOCs found within the root organs? Regarding the bacterial partners, 19strains from 8 genera (Azospirillum, Azotobacter, Bacillus, Burkholderia, Paenibacillus, Pseudomonas, Raoultella, Serratia) were selected. Their growth parameters were defined in order to standardize the physiological conditions used when analyzing their VOC emissions. Volatiles were analysed by gas chromatography – mass spectrometry (GC-MS) after both extraction from plant tissues and adsorption of the released volatiles on solidphase micro-extraction fibers. The results indicate that wheat roots produce and release a blend of VOCs mainly derived from the enzymatic oxydation of unsaturated fatty acids. Preliminary results on the VOC profiling of the selected rhizobacteria will also be presented. P06-019: RETINOBLASTOMA-RELATED PROTEIN CONTROLS ROOT EPIDERMAL CELL DIFFERENTIA- TION IN ARABIDOPSIS THALIANA. Desvoyes, B. - Gutierrez, C. Centro de Biología Molecular Severo Ochoa, CSIC-UAM The role of the retinoblastoma related protein (RBR) in restricting cells to enter S-phase by modulating the activity of E2F transcription factors is now well established. New roles of RBR in cell differentiation processes are now emerging. To assess the relevance of the RBR pathway in cell fate specification we are using Arabidopsis root epidermal cells as a model. Root epidermal cells are generated at the root apical meristem and differentiate either in hair or hairless cells in a cell-position dependent manner. The genetic network that control root hair cell patterning is well known and relies on the expression of the homeodomain protein GLABRA2 (GL2), an inhibitor of hair cell specification. Ectopic expression of RBR prevents cell proliferation of meristematic cells and alters cell fate specification provoking the appearance of ectopic hairs. Likewise, inactivation of RBR by expression of the RBR-binding RepA protein affects root hair patterning. We will present evidence that RBR is implicated in the control of epidermal cell fate in a dual manner: one that is cell cycle-dependent and, another by regulating specifically the expression of cell fate genes. Our study identifies a novel role of RBR in linking cell proliferation control and cell fate determination during root growth. P06-020: LOCAL SUPPLY OF IRON DISTINCTLY DEFI- NES LATERAL ROOT NUMBER AND ELONGATION IN ARABIDOPSIS THALIANA Ricardo F. H. Giehl* - Joni E. Lima - Nicolaus von Wirén University of Hohenheim *Corresponding author e-mail: hetgiehl@yahoo.com.br Morphological adaptations of the root system to a localized nutrient source are seen as an indication for nutrient sensing by plant roots. With regard to the low mobility of iron (Fe) in soils, we investigated changes in the root system architecture of Arabidopsis plants in response a localized supply of Fe. Increasing Fe concentrations in a homogenous or localized supply on separated agar plates enhanced lateral root number in a similar manner. Lateral root length, however, was twofold higher under localized relative to homogenous Fe supply. With further increasing Fe concentrations lateral root length was repressed even though shoot growth was unaffected. Observing early lateral root development by the use of CYCB1::GUS reporter lines indicated that in particular the emergence of lateral root initials was stimulated by local Fe. We then investigated lateral root growth in the Fe uptake-defective mutant irt1 and in the frd3-1 mutant, which is defective in root-to-shoot translocation of Fe. Based on these observations we propose a differential regulation of lateral root initiation and elongation in response to localized Fe supply that is subject to a local regulation by Fe and involves the high-affinity Fe transporter IRT1. P06-021: ANATOMICAL CHARACTERIZATION OF ROOT SYSTEM OF MAIZE MUTANT LRT1 Husáková, E. - Soukup, A. Charles University in Prague, Faculty of Science, Department of Experimental Plant Biology Maize mutant lrt1 (lateral rootless1) is one of few mutants out of Arabidopsis with defect in lateral root formation. Since its description we present the first detailed anatomical-histochemical analyse along the developing main root. Mutant lrt1 was described as incapable of lateral root initiation during early post germination growth. Our data indicate that lrt1 competency to initiate of the lateral root primordium is highly dependent on environmental factors. However, lrt1 primordia didn’t emerge from the main root, their cells are more vacuolized and the cellular organization of primordia is affected coparing to wildtype. Disturbances with oxidized polyphenolic substances were often found in pericycle where initiation normaly takes place. The outer layers of lrt1 cortex were disorganized and continual ring of exodermal layers were also interrupted. The permeability test of root surface detected changes in exodermis function. Strong activity of peroxidase was detected in all tissues of lrt1 root. The highest activity appeared in central cylinder, mainly in pericycle, and in the subepidermal layers of the root. Our results indicate, that phenotypical traits described for the mutant might be related to cell wall modifications and subsequent higher rigidity of cell walls and/or differentiation of cells. P
FESPB 2010 - XVII Congress of the Federation of European Societies of Plant Biology P06-022: THE ROLE OF TTL GENES IN ROOT INITIA- TION AND DEVELOPMENT Šefrnová, Y. 1 - Hilgert, D.A. 1 - Fischer, L. 1 - Dubrovsky, J.G. 2 Vielle-Calzada, J.-P 3 - Soukup, A. 1 1 Department of Plant Experimental Biology, Faculty of Science, Charles University in Prague 2 Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México 3 Laboratorio Nacional de Genómica para la Biodiversidad and Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del I Lateral root initiation and growth are crucial determinants of interaction of plant with rhizosphere, controlled via complex network of regulatory elements (Péret et al., 2009; Fukaki & Tasaka, 2009). TTL3 gene (AT2G42580, Tetratricopetide-repeat Thioredoxin-Like 3) was identified during the forward screening of a collection of gene-trap lines aimed to identify new genes involved in lateral root initiation and subsequent development. In Arabidopsis TTL genes comprise family of four members. TTL proteins contain repeating TRP motif, which is considered to be a protein-protein interaction domain shared among numerous proteins (Schapire et al., 2006) in combination with thioredoxin fold. TTL1 was described as a novel protein taking part in salinity and abscisic acid response (Rosado et al., 2006). TTL3 (VIT) was previously identified as an interaction partner of BRL2/VH1 brassinosteroid receptor and appears to play a role in brassiosteroid and auxin signaling (Ceserani et al., 2009). Transcriptional fusions of Arabidopsis TTL promotors and GUS gene were constructed and their expression pattern is described under various conditions. The phenotypic effects of TTL mutations in selected publically available mutants are described with special emphasis on lateral root initiation and growth. Ceserani,T., Trofka,A., Gandotra,N., and Nelson,T. (2009). Plant J 57, 1000. Fukaki,H. and Tasaka,M. (2009). Plant Mol Biol 69, 437-449. Péret,B., De Rybel,B., Casimiro,I., Benkova,E., Swarup,R., Laplaze,L., Beeckman,T., and Bennett,M.J. (2009). Trends Plant Sci 14, 399-408. Rosado,A., Schapire,A.L., Bressan,R.A., Harfouche,A.L., Hasegawa,P.M., Valpuesta,V., and Botella,M.A. (2006). Plant Physiol. 142, 1113-1126. Schapire,A.L., Valpuesta,V., and Botella,M.A. (2006). Plant Signal Behav 1, 229-230. an expanded expression domain of PHB now encompassing not only the central, but also the peripheral stele. This mutant develops metaxylem in the place of protoxylem. In contrast, multiple mutants in HD-ZIP III genes form protoxylem in the place of metaxylem. Hence, the HD-ZIP III transcription factors act together to determine the xylem cell type. We show that their activity domain is determined by the movement of miR165/6 from the endodermal cell layer. Therefore, we describe a bi-directional signaling pathway where stele-produced SHORT-ROOT protein moves out to the endodermis to activate miR165/6, which then acts non-cell autonomously to restrict HD-ZIP III transcripts from the stele perifery, ultimately leading to proper xylem patterning in the stele. P06-023: MOBILE MIRNA165/6 TARGET HD-ZIP III IN THE ROOT STELE PERIFERY FOR PROPER XYLEM PATTERNING Carlsbecker, Annelie 1 - Lee, Ji-Young 2 - Roberts, Christina J. 1 - Dettmer, J. 3 - Lehesranta, S. 3 - Zhou, Jing 2 - Lindgren, O. 4 - Moreno-Risueno, M.A. 5 - Vaten, A. 3 - Thitamadee, S. 3 - Campilho, A. 3 - Sebastian, J. 2 - Bowman, J.L. 6 - Helariutta, Ykä 3 - Benfey, P. 5 1 Dept. of Physiological Botany, EBC, Uppsala University 2 Boyce Thompson Institute for Plant Research and Graduate Field of Plant Biology, Cornell University 3 Institute of Biotechnology/Department of Biosciences, University of Helsinki 4 Institute of Technology, University of Tartu, Estonia 5 Biology Department and IGSP Center for Systems Biology, Duke University 6 School of Biological Sciences, Monash University A fundamental aspect of developmental biology is information exchange between cells resulting in proper cell identity. In Arabidopsis, the root xylem pattern is very consistent: radially, xylem forms in an axis with protoxylem at either end and metaxylem in the center. How is this pattern determined? We have identified a mutant, phb-7d, harboring a mutation in the microRNA165/6 (miR165/6) target site of the class III homeodomain leucine zipper (HD-ZIP III) gene PHABULOSA (PHB), which leads to
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FESPB 2010 - XVII Congress of the F
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POST 04 POSTERS • Environmental S
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Author Index Aarts, M.G. S18-002 Ab
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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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Book of Abstracts - Geyseco

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