Identification and functional analysis of Magnaporthe oryzae effectors

The ascomycete Magnaporthe oryzae causes « blast disease » affecting several cereals in particular rice. During the compatible interaction, the first phase of M. oryzae infection cycle is biotrophic. M. oryzae is suspected to secrete, as bacterial and oomycete pathogens, an arsenal of effector proteins that disrupt the activation and execution of plant defenses. In order to identify M. oryzae effectors, a search for putatively secreted proteins during rice infection was performed from different sequence datasets such as, genome annotation data, transcriptome data of blast fungus-infected rice leaves, and proteomic data of blast proteins released in culture media. A list of 370 candidate effectors expressed during rice infection and possessing a putative signal peptide for secretion was generated. Among them, 58 where shown to be secreted in vitro in proteomic analyses, while the expression of 10 was found to be down-regulated in the M. oryzae bip1 mutant impaired in a b-zip transcription factor essential for the pathogenesis of the blast fungus. First results of the functional analysis of these candidate effectors will be presente