Abstract
OsMPK6 is rapidly activated by several elicitor treatments and may function as a key component during pathogen recognition in rice. In osmpk6 knock-out mutant, gene expression of PR10a was constitutively induced and strongly enhanced by elicitor treatment compared with wild type. Compared osmpk6 mutant with the complementation lines, OsMPK3 gene expression was up-regulated and its kinase activity increased in osmpk6 mutant. OsMPK6 may regulate gene expression and kinase activity of OsMPK3. To elucidate the defense signal pathway downstream of MPK, we analyze OsMKK4, the rice ortholog of NtMEK2. Induction of OsMKK4DD, which is constitutive active mutant, activates OsMPK6 and OsMPK3 and induces several PR gene expression and cell death. These data suggest that OsMKK4 may regulate a series of defense responses via OsMPK3 and OsMPK6 activation.
