PBL27 directly connects between the chitin receptor, CERK1 and MAPK cascade in chitin-triggered immunity
K. YAMAGUCHI (1), K. Yamada (2), T. Shirakawa (2), A. Mine (3), M. Narusaka (4), Y. Narusaka (4), K. Ichimura (5), K. Tsuda (3), F. Tamo (2), N. Shibuya (6), T. Kawasaki (2) (1) Dept. Adv. Biosci. Kindai Univ., Japan; (2) Dept. Adv. Biosci. Kindai Univ., Japan; (3) MPIPZ, Germany; (4) RIBS Okayama, Japan; (5) Faculty of Agriculture, Kagawa Univ, Japan; (6) Dept. Life Sci., Meiji Univ, Japan

Mitogen-activated protein kinase (MAPK) cascades are highly conserved signaling modules downstream of host cell-surface pattern recognition receptors (PRRs) that transduce extracellular stimuli into intracellular responses. However, it is not known how PRRs transmit immune signals to MAPK cascades in plants. Here, we identified a complete signal transduction pathway from CERK1-mediated pathogen recognition to MAPK activation in Arabidopsis. Previously, we found that knockout of the receptor-like cytoplasmic kinase PBL27 suppressed chitin-induced activation of MAPKs. To understand the molecular mechanism of chitin-induced MAPK activation by PBL27, we searched PBL27 interactor using Y2H and found MAPK kinase kinase MAPKKK5, one of 80 Arabidopsis MAPKKKs. PBL27 interacted with both CERK1 and MAPKKK5 at the plasma membrane. The chitin perception induced disassociation between PBL27 and MAPKKK5 in Arabidopsis protoplast. Chitin-induced MAPK activation in the mapkkk5 mutants was clearly reduced compared with WT. Additionally, both pbl27 and mapkkk5 mutants reduced resistance to fungal pathogen, Alternaria brassicicola, and also suppressed chitin-induced immune responses including gene expression and callose deposition. Thus, it is likely that PBL27 is the component that directly activates MAPKKK5 which triggers the activation of MAPK cascade after chitin perception.

Abstract Number: P17-642
Session Type: Poster