Abstract
MAPK cascades play an important role in defense signaling after recognition of elicitor signals. In rice, several MAPKs are strongly activated by elicitor treatment but the downstream responses are remained elusive. We analyzed the defense responses regulated by an elicitor-responsive MAPKK, OsMKK4. Using conditional gain-of-function transgenic system, we demonstrated that OsMKK4 induces activation of OsMPK3 and OsMPK6, expression of multiple defense-related genes and cell death but not ROS production. Analysis of genes regulated by OsMKK4-OsMPK3/OsMPK6 MAPK cascade revealed that this MAPK cascade tightly regulates phytoalexin and lignin accumulation. Using osmpk6 mutant, we confirmed that OsMPK6 functions for the induction of cell death and phytoalexin accumulation. We are analyzing transcription factors which are regulated by OsMKK4-OsMPK3/OsMPK6 MAPK cascade. We will compare the expression pattern or expression level between in osmpk6 mutant and in the wild type to identify regulators of cell death and phytoalexin accumulation.
