Résumé
WRKYs constitute a large familiy of transcription factors (more than 70 genes in A.thaliana), characterized by the presence of one or two ~60 aa consensus sequences with a WRKYGQK highly-conserved motif and a novel zinc-finger domain that provides DNA-binding properties. WRKY proteins were already shown to be involved in plant response to abiotic and biotic stresses in tobacco, barley, A.thaliana and rice. AtWRKY factors have been extensively studied, whereas in rice, apart from annotation studies, few reports investigated biological function of the 109 OsWRKY genes. The main objective of our project is to investigate OsWRKYs function in resistance to pathogen and environmental constraint and to assess the potential role of few of them in the signalling cross-talk between biotic and abiotic stresses. First of all, we performed an exhaustive transcriptome analysis of the whole OsWRKY family in stress conditions, by a custom 60-mer oligo microarray following inoculation with host and non-host strains of Magnaporthe grisea and osmotic stress treatments. A relevant portion of OsWRKY genes showed high expression levels in all experiments, whereas the remaining revealed to be either tissue-/condition-specific. Interestingly, few genes were found to be regulated upon both biotic and abiotic stimuli, suggesting a key role in both signalling pathway. Phylogenetic analyses revealed the existence of six major groups (1C, 1N, 2A-2B, 2C, 2D-2E and 3) and pointed out the existence of a rice specific WRKY group of 18 genes (3C). Detailed expression analyses by Q-PCR and phenotypic characterization of WRKY mutant lines to assess tissue-specificity and specific patterns of expression of selected WRKY genes is undergoing to functionally validated their role in signal transduction pathways leading to resistance to biotic and abiotic stress conditions in rice.