Abstract
Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction modules in eukaryotes. In plants, MAPK cascades are known to function in various biotic and abiotic stress signaling. We have been focused on MKK3, one of the Arabidopsis MAPKK, to find a novel MKK3-MPK6 cascade, which plays a crucial role in JA signaling. In Arabidopsis, JA signaling functions in both the JA/ET pathway and the JA pathway, and crosstalk occurs these two pathways. By using gain-of-function and loss-of-function mutants of MKK3 and MPK6, we analyzed ET accumulation and gene expression profiles, and found that MKK3-MPK6 negatively regulates the JA pathway. In addition, precise analysis of mkk3/atmyc2 double mutant indicates that AtMYC2 is genetically downstream of MKK3. Moreover, further analysis of 35S::MKK3/ein2 and 35S::MKK3/ein3 plants also revealed that the gene expression by the JA-activated MKK3-MPK6 cascade requires endogenous ET signaling. We would discuss the biological function of MKK3-MPK6 cascade in JA signaling.
