Biological functions of rice immune factors targeted by Xanthomonas oryzae effectors
T. KAWASAKI (1), K. Yamaguchi (2) (1) Kindai University, Japan; (2) Kindai University, Japan

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight of rice. To interfere with host immune responses, Xoo secretes a variety of effectors into host cells. Previously, we reported that XopY and XopP, non-TAL effectors of Xoo, strongly suppress immune responses induced by OsCERK1-mediated perception of pathogen-associated molecular patterns (PAMPs) including bacterial peptidoglycan and fungal chitin (Yamaguchi et al. Cell Host Microbe 2013; Ishikawa et al. Nat Commun 2014). We have identified the receptor-like cytoplasmic kinase OsRLCK185 and the U-box type E3 ubiquitin ligase OsPUB44 as host targets of XopY and XopP, respectively. In response to chitin, OsRLCK185 was phosphorylated by OsCERK1, and then phosphorylated two of rice MAPKKKs, which triggers intracellular MAPK activation in rice. The immune response was suppressed by inhibition of OsCERK1-meditad phosphorylation of OsRLCK185 by XopY. On the other hand, the OsPUB44 enzymatic activity was suppressed by interaction between the U-box domain and XopP. To understand the OsPUB44-mediated immune response, we identified a plant-specific protein (PBI1) with unknown function interacted with the ARM domain of OsPUB44. Perception of chitin reduced the protein level of PBI1, which was inhibited by silencing of OsPUB44. Thus, it is likely that OsPUB44 regulates immunity through degradation of PBI1.

Abstract Number: S2-4
Session Type: Special Session