Abstract
Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction modules in eukaryotes. In Arabidopsis genome, there are 20 genes encoding possible MAPKs, and these MAPKs can be divided into at least four groups (A-D). Group D has 8 members, and forms the largest subgroup. Group D MAPKs contain TDY motifs instead of TEY motifs in their T-loop and larger C-terminal regions relative to other groups. We have focused our work on MPK8, one of the group D MAPK, for further functional analysis. Yeast two-hybrid and Arabidopsis protoplast BiFC analysis revealed that MPK8 interacts with various types of calmodulin. We have shown that calmodulin can activate MPK8 without calcium in vitro. These results suggest a novel activation mechanism of MAPK by calmodulin in plant. We will discuss the activation mechanism of MPK8.
