Book of Abstracts - Geyseco

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02 - PS - Parallell Sessions Lectures The nine-member β-amylase (BAM) gene family in Arabidopsis is a good example of this. β-Amylase is known as a key enzyme involved in starch degradation. In Arabidopsis, starch is accumulated as a primary product of photosynthesis in leaves during the day, serving as a transitory store of carbohydrate for use during the night. β-Amylases liberate maltose molecules from the ends of the glucan chains that comprise starch. Mutations in Arabidopsis that cause a deficiency in chloroplastic β-amylase (BAM1 and BAM3) result in a block in starch breakdown and an accumulation of leaf starch. However, the chloroplast contains another type of β-amylase-like protein which appears to be non-catalytic (e.g. BAM4). Mutational studies show that these proteins are also important in starch breakdown, although the mechanism by which they act is as-yet unclear. Surprisingly, two Arabidopsis β-amylase-like proteins, BAM7 and BAM8, are nuclear localised and share an amino-terminal DNA-binding domain with a family of plant-specific transcriptional regulators involved in plant steroid hormone signalling. Deregulation of BAM7 and BAM8 expression results in altered plant growth and development, to altered brassinosteroid sensitivity, but not to altered starch metabolism. We have identified the DNA motif to which these two proteins bind and obtained in-vivo evidence that they are transcriptional activators. Homologous genes have been identified in other plants including gymnosperms, and angiosperms (both monocot and dicot species), implying that their functional specialisation occurred early in higher plant evolution. Our hypothesis is that the duplication of the genes encoding β-amylases has given rise to metabolic sensors that control metabolism and provide a regulatory link between carbon availability and growth control. PS14: PLANTS & GLOBAL CHANGE Session lead lectures PS14-001 GLOBAL CHANGE AND THE EFFECTS OF SO- LAR UV RADIATION ON TERRESTRIAL ECOSYSTEMS Ballaré, C.* Universidad de Buenos Aires and CONICET *Corresponding author, e-mail: ballare@ifeva.edu.ar UV radiation (280-400 nm) is a minor component of the solar spectrum reaching the ground surface; yet, it has important effects on organisms and biogeochemical cycles. Many research efforts during the past two decades have thoroughly characterized the effects of the UV-B (280-315 nm) component. In this talk, I will summarize the lessons from this previous work, and highlight some of the important knowledge gaps in connection with the effects of climate change. I will address the following points. A) The effects of UV-B radiation on the growth (biomass accumulation) of terrestrial plants are relatively small. B) On the other hand, UV radiation affects plant secondary chemistry and the activities of canopy arthropods and phyllosphere microorganisms. Therefore, trophic interactions in terrestrial ecosystems are likely to be significantly affected by future variations in UV irradiance. C) Changes in UV resulting from climate change (e.g., variations in cloud cover) may have more important consequences on terrestrial ecosystems than those derived from ozone depletion. This is because the resulting variations in UV may affect a greater range of ecosystems, and will not be restricted solely to the UV-B component. D) Several processes that are not particularly sensitive to UV-B can be strongly affected by UV-A radiation (315-400 nm). One example is the physical degradation of plant litter. Recent work suggests that increased photodegradation (in response to reduced cloudiness or reduced canopy cover) may have important direct and indirect effects on carbon sequestration in terrestrial ecosystems. PS14-002 BEYOND 2050: CAN WE EXPECT CO2 SATU- RATION OF LEAVES AND ECOSYSTEMS? Ellsworth, D.* University of Western Sydney *Corresponding author, e-mail: D.Ellsworth@uws.edu.au As atmospheric CO 2 concentration is rising, one important suite of responses of ecosystems to the atmosphere are those involving the carbon cycle, mediated by photosynthesis. However, leaf photosynthesis saturates at [CO 2 ] air of 500-700 ppm, and hence further increases in [CO 2 ] may suggest no additional impact on ecosystem C cycles beyond these concentrations. Others have suggested that ecosystems are already saturated at current atmospheric [CO 2 ] levels, in part due to nutrient limitations and severe water stress. Here, I will consider the question: are further increases in ecosystem CO 2 flux or productivity in native ecosystems possible beyond the photosynthetic CO 2 saturation threshold? And which systems are closest to this threshold? Results from a series of elevated CO 2 experiments, ecosystem CO 2 flux measurements, and from natural phenomena such as the European drought of 2003 are used to provide evidence of plant and ecosystem CO 2 saturation. Whilst the short-term mechanism of photosynthetic response would suggest a large CO 2 stimulation effect under drought, the longer-term response is very different. The findings have relevance to the Mediterranean region as well as to the significant fraction of global ecosystems that are nutrient- and water-limited. PS17: PLANT-MICROBE INTE- RACTIONS Session lead lectures PS17-001 THE TOMATO – FUSARIUM OXYSPORUM PA- THOSYSTEM Rep, M.* - Houterman, P. - Gawehns, F. - Ma, L. - de Sain, M. - Lukasik, E. - van der Does, C. - Cornelissen, B. - Takken, F. University of Amsterdam *Corresponding author, e-mail: M.Rep@uva.nl The tomato xylem-colonizing fungus Fusarium oxysporum f.sp. lycopersici (Fol) secretes small proteins into xylem sap of its host. Three of these ‘effectors’ trigger effector-mediated immunity: Avr1, Avr2 and Avr3 (or their activities) are recognized by the resistance proteins I, I-2 and I-3, respectively. Interestingly, Avr1 suppresses I-2 and I-3-mediated resistance. Several Fol effectors were shown through gene knock-out to contribute to virulence towards susceptible plants. The genes for the effectors in Fol that we identified reside on a ‘pathogenicity chromosome’. This chromosome can be transferred between genetically isolated strains of the asexual fungus, conferring host-specific pathogenicity to the recipient. We aim to uncover the molecular mechanisms by which effectors of Fol trigger susceptibility (suppression of resistance) and immunity (activation of R proteins), beginning with localization of effectors in plant cells and identification of host proteins with which they interact. PS17-002 PLANT TARGETS OF BACTERIAL TYPE III EFFECTOR PROTEINS Bonas, U.* Department of Plant Genetics, Martin-Luther-University Halle- Wittenberg, Halle (Saale), Germany *Corresponding author, e-mail: bonas@genetik.uni-halle.de We study the interaction between pepper and tomato and the Gram-negative plant pathogenic bacterium Xanthomonas campestris pv. vesicatoria (Xcv), which causes bacterial spot disease on its host plants. Successful interactions of Xcv with the plant depend on a functional type III secretion (T3S) system, a molecular syringe, which injects more than 20 effector proteins (termed Avr or Xop = Xanthomonas outer protein) into the plant cell cytoplasm. Among the Xops we find suppressors of the plant innate immunity, putative enzymes and transcription factors. One of the PS
FESPB 2010 - XVII Congress of the Federation of European Societies of Plant Biology best-studied type III effector proteins in our laboratory is the 122 kDa-protein AvrBs3, which acts as transcription factor and induces phenotypic changes in both susceptible and resistant plants. Xcv strains expressing AvrBs3 induce the hypersensitive reaction (HR) in pepper plants carrying the resistance gene Bs3. The HR is a rapid local programmed cell death that halts bacterial multiplication. In pepper plants lacking the Bs3 gene and other solanaceous plants AvrBs3 induces a hypertrophy of mesophyll cells. AvrBs3 activity depends on a central region of 17.5 tandem 34-aa repeats, its localization to the plant cell nucleus and the presence of an acidic activation domain. One of the direct targets of Avr- Bs3 is UPA20 (UPA, upregulated by AvrBs3) which encodes a transcription factor and is a key regulator of hypertrophy. Recent insights into the mechanism of AvrBs3 action will be discussed. PS18: WATER & MINERALS Session lead lectures PS18-001 PHYSIOLOGICAL AND GENETIC DISSEC- TION OF AQUAPORIN FUNCTIONS IN ROOTS AND LEAVES Maurel, C.* - Postaire, O. - Tournaire-Roux, C - Boursiac, Y. - Sutka, M. - Li, G. - Prado, K. - Santoni, V. - Wudick, M. - Doan- Trung, L. Biochemistry and Plant Molecular Physiology, Integrative Biology Institute for Plants, CNRS/INRA UMR5004, 2 place Viala, F-34060 Montpellier, France Corresponding author: maurel@supagro.inra.fr Uptake of soil water by roots and its delivery from xylem vessels to inner leaf tissues are crucial for maintaining the plant water status. Knock-out mutants for plasma membrane aquaporins (PIPs) were used to dissect the osmotic and hydrostatic modes of water transport in the Arabidopsis root. The variability of root hydraulic architecture and of aquaporin expression in a set of 13 natural accessions of Arabidopsis provided complementary insights into root water uptake and its regulation by salt stress. The latter process involves a Reactive Oxygen Species (ROS)-dependent signalling path that triggers an internalisation of PIPs. The mechanisms and routes of ROS-dependent trafficking of PIPs were dissected in detail using a combination of biochemical and cell biological approaches. Pharmacological and reverse genetic approaches also showed that PIPs contribute to water transport in the inner tissues of leaves and can account for light-dependent changes in their hydraulic conductivity. The contribution of specific PIP isoforms to light-dependent water transport in the veins and/or the mesophyll is being elucidated. PS18-002 PIDENTIFICATION OF ARABIDOPSIS GENES INVOLVED IN NUTRIENT ACQUISITION OR HOMEOS- TASIS Giehl 1 - Takahashi, H. 2 - Von Wiren, N. 3 * 1 Molecular Plant Nutrition, University of Hohenheim 2 RIKEN PLant Science Center Yokohama 3 Leibniz-Instuitute for Plant Genetics & Crop Plant Research *Corresponding author, e-mail: vonwiren@ipk-gatersleben.de Plant growth and propagation depend on the acquisition of mineral nutrients by the root, their root-to-shoot translocation and their re-translocation to sink tissues when plants undergo senescence. For most nutrients, molecular mechanisms involved in their acquisition from soils have been described. However, much less is known about the regulatory pathways underlying the uptake and translocation of nutrients in plants. The possibility to perform large-scale elemental analysis and data mining offer the opportunity to screen large populations of mutant lines in the search for genes affecting a plant’s nutriome. In order to search for transcription factors involved in the regulation of nutrient accumulation in plants, we have screened transposon-tagged lines SELE ABS FOR PRE TION with altered expression of transcription factors for their nutrient profiles. For that purpose, 313 Ds-transposon-tagged lines were grown in nutrient solution and leaves and roots were analyzed for 13 mineral elements by ICP-MS and ICP-OES. For each mineral element approximately 1-4% of the lines showed nutrient concentrations in roots and/or shoots that differed from the wildtype. Among these lines, line no. 117 accumulated significantly more K and P in the shoot. Further phenotypical analysis of this line and of an independent mutant allele as well as expression analysis support a role of the transcription factor 117 in root responses to low P availability.
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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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