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. Completion of the Arabidopsis genome-sequencing project has revealed the existence of 20 MAPK, 10 MAPKK and 60 MAPKKK genes in its genome. However, detailed functions of each MAPK cascades are still unknown. We have been focused on MKK3, one of the Arabidopsis MAPKK, and found the novel MKK3-MPK6 cascade by using in vitro activation assay. We also demonstrated that MKK3-MPK6 cascade functions in vivo by using DEX mediated conditional expression transgenic system. DEX-treated MKK3 DD plants did not show HR-like cell death phenotype as those found in DEX-treated MKK4 DD plants. Microarray analysis revealed that MKK3 and MKK4 cascade might regulate different sets of downstream genes. Possible function of MKK3-MPK6 cascade will be discussed.
