Résumé
WRKY gene family encode for transcription factors characterized by having one or two ~60 as consensus sequence with a WRKYGQK highly conserved motif and a novel zinc-finger domain that provides binding properties to DNA. WRKY proteins, already studied in tobacco, potato, parsley, wild oat, Arabidopsis thaliana and rice, have been shown to be involved in the regulation of several cellular processes such as control of metabolic pathways, drought, heat shock, senescence, development and hormone signalling. However, the most studied role of this gene family appears to be in response to biotic and abiotic stress stimuli. Aim of this work is to perform a whole rice WRKY gene family transcription analysis upon application of biotic and abiotic stress conditions to identify WRKY genes involved in signal transduction pathways. Firstly, we performed transcriptome and phylogenetic analyses of WRKY genes in rice to investigate the existence of "key transcriptional regulators" to biotic and/or abiotic stress. We integrated our WKRY thematic array with microarray results obtained by NIAS (Japan) using a rice genome-wide microarray and the bioinformatic analysis of these data points to the existence of co-regulated WRKY genes. In an effort to test the involvement of WRKY genes of rice in response to pathogens and abiotic stress, we are currently screening several WRKY mutant lines. Fifteen lines containing a T -DNA insertion in WRKY genes were inoculated with host and non-host strains of Magnaporthe grisea (isolates BR29, BR32 and FR13) and no phenotype was detected. A T -DNA insertion event in OsWRKY55 promoter showed a tissue-specific Gus expression in roots, vascular tissues and in the cotyledon of a 10-days old seedling. According to our phylogenetic analysis, this gene belongs to a subgroup of Monocot specific WRKY genes. A more detailed analysis is currently ongoing to characterize the expression pattern of the WRKY55 gene. (Texte intégral)