Proceedings of the 57th Italian Society of Agricultural Genetics Annual Congress Foggia, Italy – 16/19 September, 2013 ISBN 978-88-904570-3-6

Poster Communication Abstract – 8.10

RNA-SEQ ANALYSIS OF DIFFERENTIAL RESPONSE TO OSMOTIC STRESS IN ITALIAN RICE CULTIVARS

BALDONI E.*, BAGNARESI P.**, LOCATELLI F.*, MATTANA M.*, GENGA A.*

*) Institute of Agricultural Biology and Biotechnology, IBBA-CNR, Via Bassini 15, 20133 Milano (Italy) **) Agricultural Research Council (CRA) - Genomics Research Centre, Via S. Protaso 302, 29017 Fiorenzuola d’Arda, Piacenza (Italy)

Oryza sativa, Italian cultivars, osmotic stress, RNA-seq

Abiotic stresses are the primary cause of crop loss worldwide, reducing average yields for most major crop plants by more than 50%. Rice is particularly susceptible to dehydration, and cultivars may considerably differ in their vegetative response to water deficit. The identification of key genes regulated by water shortage is a major objective for the development of drought-tolerant varieties by molecular breeding. Here, we provide a physiological analysis of the response to osmotic stress in 17 Italian rice cultivars (Oryza sativa L. ssp japonica). Rice plants were grown in hydroponic culture and then subjected to PEG treatment (20% PEG 6000). Based on the measurement of two physiological parameters (leaf Relative Water Content, RWC, and Electrolyte Leakage, EL), the cultivars exhibited differential responses to osmotic stress. After 48h of treatment, Carnaroli, Gigante Vercelli, Loto, Maratelli and Vialone Nano exhibited the lowest RWC values (<15%), whereas Augusto and Eurosis appeared to be the most tolerant genotypes, showing RWC values >80%. Similarly, the first group of cultivars exhibited the highest EL values (>94%), whereas the second group maintained EL values lower than 40%. The other varieties exhibited an intermediate sensitivity. Therefore, the cultivars Eurosis (tolerant) and Loto (sensitive) were selected for transcriptome analysis, to identify differentially regulated genes (DEGs) and pathways. Total RNAs were separately extracted from leaves and roots, after 3h and 24h of osmotic stress treatment, and used for RNA sequencing through Illumina (HiSeq2000) technology. The analysis of transcriptomic data revealed that a 3h osmotic treatment led to a substantial modulation of genes in the roots of the tolerant genotype Eurosis (6007 genes), whereas fewer DEGs were called in the roots of the sensitive cv Loto (3962 genes). At 24h of treatment, a similar number of DEGs was found in Eurosis and Loto (3065 and 3102 genes, respectively). In leaves, the highest number of DEGS was observed in Loto at 3h of stress treatment. The responses of the two genotypes were different, both in roots and leaves, especially at 3h of treatment. In roots, at 3h of treatment 2552 DEGs were common to Eurosis and Loto, whereas 3455 were specific to Eurosis and 1410 to Loto. At 24h, 1789 DEGs were common to the two cultivars, whereas 1276 and 1313 DEGs were specific to Eurosis and Loto, respectively. In leaves, at 3h of treatment 1953 DEGs were common to the two cultivars, whereas 589 were specific to Eurosis and 2860 to Loto. At 24h, 1973 DEGs were common to the two cultivars, whereas 1778 and 1115 were specific to Eurosis and Loto, respectively. GO enrichment analysis of DEGs in the various contrasts is in progress to reveal biological trends differentiating tolerant and sensitive genotypes. This work was supported by Progetto AGER, grant n° 2010-2369 (RISINNOVA - Integrated genetic and genomic approaches for new Italian rice breeding strategies).