Résumé
Unravelling functions implicated in the infection process of plant pathogenic fungi is an important challenge for crop protection. Availability of the fungal genome sequences, in particular Magnaporthe grisea, combined to recent developments in molecular genetics and transcriptomics/proteomics will increase the discovery of genes involved in pathogenicity or growth. Such genes are identified through the molecular/physiological characterisation of non-pathogenic mutants obtained by insertional mutagenesis or reverse genetics. Fungal transposons such as impala, an autonomous TC1/mariner element from Fusarium oxysporum can inactivate and tag genes involved in pathogenicity or development in a large number of fungi. impala could be engineered for enhancer or activation tagging. Agrobacterium mediated transformation is also a versatile tool for insertion mutagenesis and gene replacement. Alternative methods using RNAi induced gene silencing were developed to inactivate rapidly genes of interest. Mutants are currently characterized for modifications in their expression profiles using an EST-based micro-array. These expression profiles highlight pathways controlled by genes required for pathogenicity or growth and can be compared with those obtained with known inhibitors. Microsatellites (SSR) markers were also developed to facilitate positional cloning. A first set of 20 SSRs were positioned on the integrated M. grisea genetic map (GUY11 x 2539) and shown to be dispersed on all seven of the chromosomes. Additional SSR were identified in M. grisea genomic sequence. They will be useful to map avirulence genes identified in different crosses and to anchor sequence contigs on the genetic map. (Texte intégral)