A comprehensive expression analysis of the WRKY gene superfamily in rice plants during defense response

To understand the transcriptional regulatory mechanism of host genes during the activation of defense responses in rice, we isolated WRKY transcription factors whose expressions were altered upon attack of the fungal pathogen Magnaporthe grisea, the causal agent of the devastating rice blast disease. A systematic expression analysis of OsWRKYs (Oryza sativa L. WRKYs) revealed that among 45 tested genes the expression of 15 genes was increased remarkably in an incompatible interaction between rice and M. grisea. Twelve of the M. grisea-inducible OsWRKY genes were also differentially regulated in rice plants infected with the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). In experiments with defense signaling molecules, the expression of two genes, OsWRKY45 and OsWRKY62, was increased in salicylic acid (SA)-treated leaves and the expression of three genes, OsWRKY10, OsWRKY82, and OsWRKY85 was increased by jasmonic acid (JA) treatment. OsWRKY30 and OsWRKY83 responded to both SA- and JA treatments. The expression profiles suggest that a large number of WRKY DNA-binding proteins are involved in the transcriptional activation of defense-related genes in response to rice pathogens.