Conservation of chitin-induced MAPK activation mechanisms between rice and Arabidopsis
K. YAMADA (1), K. Yamaguchi (1), A. Terauchi (1), K. Ishikawa (1), T. Kawasaki (1) (1) Dept. Adv. Biosci. Kindai Univ, Japan

MAPK cascades are critical signaling modules for plant immunity. However, it is not clear how the MAPK cascades are activated downstream of pathogen-associated molecular patterns (PAMPs) receptors. In Arabidopsis, we found that a member of receptor-like cytoplasmic kinase (RLCK) family PBL27 phosphorylates MAPKKK5 to regulate activation of MPK3/6 in chitin signaling. Previously, we identified that OsRLCK185, an orthologue of PBL27, functions as a signaling component downstream of chitin receptor complex OsCERK1/CEBiP and regulates OsMPK3/6 activation in rice. Here, we found that OsRLCK185 interacts with OsMAPKKK11 and OsMAPKKK18, which are the orthologues of MAPKKK5. Silencing of OsMAPKKK11/18 reduced chitin-induced OsMPK3/6 activation, whereas the Osmapkkk11 single mutation did not affect the activation. Additionally, we found that the expression level of OsMAPKKK18 is much higher than that of OsMAPKKK11. These results suggest that OsMAPKKK18 predominantly activates OsMPK3/6 in chitin-signaling pathway. Moreover, yeast two-hybrid assay showed that OsRLCK185 interacted with N-terminal and C-terminal domains of OsMAPKKK18. To elucidate how OsRLCK185 activates OsMAPKKK18, we performed in vitro phosphorylation assay and found that OsRLCK185 directly phosphorylates N-terminal and C-terminal domains of OsMAPKKK18. These results suggest that the signaling modules involving in chitin-induced MAPK activation are conserved between rice and Arabidopsis.

Abstract Number: P18-696
Session Type: Poster