Building a mutant resource for the study of disease resistance in rice reveals the pivotal role of several genes involved in defence.

In Arabidopsis, gene expression studies and analysis of knock-out (KO) mutants have been instrumental in building an integrated view of disease resistance pathways. Such an integrated view is missing in rice where shared tools, including genes and mutants, must be assembled. This work provides a tool kit consisting of informative genes for the molecular characterization of the interaction of rice with the major fungal pathogen Magnaporthe oryzae. It also provides for a set of eight KO mutants, all in the same genotypic background, in genes involved in key steps of the rice disease resistance pathway. This study demonstrates the involvement of three genes, OsWRKY28, rTGA2.1 and NH1, in the establishment of full basal resistance to rice blast. The transcription factor OsWRKY28 acts as a negative regulator of basal resistance, like the orthologous barley gene. Finally, the up-regulation of the negative regulator OsWRKY28 and the down-regulation of PR gene expression early during M. oryzae infection suggest that the fungus possesses infection mechanisms that enable it to block host defences.