An E3 ubiquitin ligase, PUB4, regulates immune signaling through the interaction with Arabidopsis CERK1
Y. DESAKI (1), S. Takahashi (1), H. Koizumi (1), T. Miura (1), K. Yashima (1), Y. Ishibashi (1), K. Kito (1), M. Narusaka (2), Y. Narusaka (2), H. Kaku (1), N. Shibuya (1) (1) Department of Life Sciences, School of Agriculture, Meiji University, Japan; (2) Research Institute for Biological Sciences Okayama, Japan

Chitin is one of the major fungal cell wall components and recognized as a typical MAMP by plants. Chitin perception by Arabidopsis CERK1 activates signal cascade leading to various defense responses. Recently, a receptor-like cytoplasmic kinase, PBL27 was identified as a CERK1 interactor that acts as an important positive regulator in chitin signaling (Shinya T. et al., Plant J., 2014). On the other hand, as the PBL27-regulated responses did not explain all the chitin responses, it was suggested that still unidentified upstream signaling components would be present in this signaling cascade. Thus, we have been searching for such a component in this system and found a novel CERK1 interactor, an E3 ubiquitin ligase (PUB4), by yeast two-hybrid screening. Knockout of PUB4 resulted in the alteration in chitin-induced defense responses. Moreover, flg22-induced responses were partially affected in the mutant. In the infection assay, pub4 mutant showed increased susceptibility to A. brassicicola, whereas it became more resistant to P. syringae. In addition, PUB4 protein was phosphorylated by CERK1 kinase in vitro. These phosphorylation sites were identified by LC-MS/MS and shown to be located in the loop and a-helix region between the U-box domain and ARM repeats. Functional analysis of these phosphorylation sites in the PUB4-mediated signaling is now underway.

Abstract Number: P17-512
Session Type: Poster