OsWRKY22, a monocot WRKY gene, plays a role in the resistance response to blast

With the aim of identifying novel regulators of host and non host resistance to fungi in rice we carried out a systematic mutant screen of mutagenized lines. Two mutant wrky22 knock-out lines revealed clear-cut enhanced susceptibility to both virulent and avirulent M. oryzae strains and altered cellular responses to non host Magnaporthe grisea and Blumeria graminis fungi. Additionally, the analysis of pathogen responses of 24 overexpressor OsWRKY22 lines revealed enhanced resistance phenotypes upon infection with virulent M. oryzae strain, confirming that OsWRKY22 is involved in rice resistance to blast. Bioinformatic analyses determined that the OsWRKY22 gene belongs to a well-defined cluster of monocot specific WRKYs. The co-regulatory analysis revealed no significant co-regulation of OsWRKY22 with a representative panel of OsWRKYs, supporting its unique role in a subset of transcriptional responses. In contrast, inquiring a sub-set of biotic stress related Affymetrix data, a large number of resistance and defence-related genes were found to be putatively co-expressed with OsWRKY22. Taken together all gathered experimental evidences place the monocot-specific OsWRKY22 gene at the convergence point of signal transduction circuits in response to both host and non host fungi encountering rice plants.