Book of Abstracts - Geyseco

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P - Posters vin cycle enzymes (glyceraldehyde-3-phosphate dehydrogenase, GAPDH, and phosphoribulokinase, PRK) are regulated by CP12-mediated complex formation. Free CP12 is an intrinsically disordered protein with limited propensity to fold into an ordered and stable structure, even if contains two internal disulfide bonds under oxidizing conditions typical of darkned chloroplasts. NMR analysis identified a stable α-helix (Pro59-Asp66) at the C-terminal end of free oxidized CP12. CP12 soaking on pre-formed GAPDH crystals and co-crystallization methods were adopted in order to study the structure of CP12 and the interaction between the two proteins. High resolution structure of crystallized binary complexes demonstrated that two CP12 molecules could bind one tetramer of GAPDH in two deep clefts. The C-terminal fragment of CP12 embedded in each cleft includes α-Helix-C (Pro59- Asp66) followed by loop-C (Asn67-Glu72) and a disulfide, plus an extended C-terminal tail (Tail-C; Arg74-Asn78). The last four amino acids of Tail-C are involved in a great number short-distance interactions with GAPDH and occupy the catalytic site of the enzyme. We propose that thanks to its high flexibility, oxidized CP12 could easily reach its partner GAPDH. Initial recognition events could be driven by the α-Helix-C, already present in free oxidized CP12. Subsequently, the flexible Tail-C would slip into the catalytic site of GAPDH to be fixed into an ordered, extended conformation. The rest of CP12 would remain disordered, possibly an essential requisite for the successive interaction with PRK. P08-014: ANALYSIS OF PHOTOSYNTHESIS RELATED GENES UNDER SALINITY IN DIVERSE RICE CULTI- VARS Chander, S. - Saibo, N. - Oliveira, M. M. ITQB, University of New Lisbon The fundamental mechanism of salt tolerance in plants is a complex phenomenon and remains to be completely understood. High salinity alters plant osmotic and ionic homeostasis, thus leading to reduction of net photosynthesis, one of the major factors limiting plant growth and productivity. Two major genes, Rubisco Activase (RCA) and Sedoheptulose-Bisphosphatase (SBPase), which encode key enzymes in the Calvin cycle, play a vital role in photosynthesis and their expression is modulated by salinity. In addition, over-expression in rice showed enhanced photosynthesis performance in transgenic plants under stress conditions. However, little is known about how salinity affects the expression of these genes in diverse rice cultivars showing differences in salt stress tolerance, which could help to understand the molecular mechanisms underlying salinity tolerance in this species. In the present investigation, two-weeks-old rice seedlings, from four different rice cultivars (LC-93-4, FL478, IR29 and Nipponbare), were grown under control conditions and then exposed or not to salt (150mM NaCl) stress. To study the expression pattern of the RCA and SBPase genes under salinity stress, control and treated seedlings were sampled at specific time points after treatment. The expression analysis of these genes is under progress and will be discussed. Additionally, we are sequencing the promoters of these genes in diverse rice cultivars. Altogether, our results will provide insight into the transcriptional regulation of the photosynthetic response under salt stress conditions. Key words: Photosynthesis, rice, salinity stress, RCA, SBP Acknowledgement: We acknowledge Foundation for Science and Technology (FCT) for PDF grant (SFRH/BPD/64193/20099) to Subhash Chander. P08-015: INTERCEPTION AND USE OF PHOTOSYN- THETICALLY ACTIVE RADIATION UNDER MEDITE- RRANEAN CONDITIONS IN WHEATS CARRYING THE DWARFING GENE RHT-B1B Garcia del Moral, L.F. 1 * - Isidro, J. 1 - Royo, C. 2 - Alvaro, F. 2 - Nuñez, V. 1 1 Dpt. Fisiologia Vegetal, Facultad de Ciencias, Univesridad de Granada 2 IRTA, LLeida *Corresponding author, e-mail: lfgm@ugr.es To study the effect of dwarfing genes on canopy architecture and crop-biomass production under Mediterranean conditions, 5 fields experiments were conducted for 5 years in southern Spain. Twenty-four durum wheat cultivars were selected to represent the germplasm grown during the 20th century before and after the introgression of Rht-B1b dwarfing gene developed during the “Green Revolution”. Fractional absorbed radiation (FRa), was determined at anthesis and maturity by measuring the Photosynthetic Active Radiation (PAR) aboveground and at ground level below the canopy by using a 1-m-long linear ceptometer. The extinction coefficient for light transmission (k) was calculated as the value of the slope of the regression of ln (1-FRa) on Leaf Area Index and Green Area Index at anthesis. Radiation-use efficiency at anthesis and maturity (RUE) was calculated as the ratio between total crop biomass and the sum of the fraction of the daily global radiation absorbed until these stages, respectively. FRa and k did not significantly differ between cultivars carrying Rht-B1b allele or not, while the crop growth rate (CGR), net assimilation rate (NAR) and leaf:grain ratio (G) during the grainfilling period registered higher values in the cultivars carrying the Rht-B1b allele. Whereas RUE before anthesis was greater in cultivars without the Rht-B1b allele, after anthesis it was significantly greater in the cultivars with the Rht-B1b allele, possibly due to their greater sink capacity, suggesting the existence of a photosynthetic feedback mechanism in cultivars with higher sink capacity. The chlorophyll content at anthesis measured on flag leaves in SPAD units appears to be a reliable predictor of k under Mediterranean conditions. P08-016: CHANGES AT THE ENTRANCE OF THE RU- BISCO CENTRAL SOLVENT CHANNEL INDUCE ALTE- RATIONS IN ENZYME STABILITY Esquivel, M.G.1 - Nogueira, S.A. Spreitzer, R J, 2 1 Centro de Botânica Aplicada a Agricultura CBAA, Technical University of Lisbon 2 Department of Biochemistry, University of Nebraska Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is one of the most important photosynthetic enzymes because it is responsible for the fixation of CO2. The holoenzyme is composed of eight large subunits (55 kDa) and eight small subunits (15 kDa). The X-ray crystal structure has revealed that large subunits are arranged as a tetramer of dimers around a central solvent channel, thereby defining a four-fold symmetry axis. Small subunits are arranged as two tetramers at polar positions of the axis. Four isoleucine-58 (I58) residues, one from each of the four small subunits, define the narrowest point of the central solvent channel entrance in Chlamydomonas reinhardtti Rubisco. To examine the role of the central solvent channel, a mutant was created by directed mutagenesis in which I58 was replaced by three tryptophan residues (I58WWW) to close the entrance of the central solvent channel. We have been looking for structural alterations that are detected by changes in thermal inactivation in vitro and degradation of the enzyme in vivo under oxidative stress. The results show that the purified mutant enzyme is inactivated at a lower temperature than the wild type control enzyme. However, Rubisco degradation under oxidative stress induced by hydrogen peroxide is delayed in the mutant cells compared with the control. These results show that the closure of the central solvent channel by the presence of three tryptophans has an influence on the thermostability of the purified enzyme and gives stability against oxidative stress in vivo. P
FESPB 2010 - XVII Congress of the Federation of European Societies of Plant Biology P08-017: THE THYLAKOID FORMATION 1 PLASTID PROTEIN IN PARASITIC DODDER PLANTS Ludmila Slovakova - Viktor Demko - Andrej Pavlovic Department of Plant Physiology, Faculty of Natural Sciences, Comenius University in Bratislava The Thylakod formation 1 (THF1) protein has been identified in various plant species. Based on a sequence similarity and different functions that were attributed to the protein initially, various names of the same protein exist: THF1, Psb29, chloroplast inositol phosphatase-like protein, ToxA-binding protein, SlALC1, etc. It was suggested previously that THF1 protein is involved in thylakoid membrane differentiation, sugar signaling and responses to fungal and bacterial infections. Even though the THF1 is highly conserved in many oxygenic phototrophs, its precise cell and tissue distribution as well as its biochemical functions in photosynthetic and non-photosynthetic plastids have not yet been elucidated. In our experiments, we use parasitic plants belonging to the genus Cuscuta. Our aim is to elucidate possible role of the THF1-mediated signaling in parasitic plant development. Here we show and discuss the THF1 experssion and localization in dodder cells in respect to the seedling development and plastid differentiation. This research was supported by the grant VEGA 1/0040/09
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FESPB 2010 - XVII Congress of the F
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PLENAR SESSION LECTUR
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PARALL SESSION LECTUR
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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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