Phosphorylated RIN4 interacts with a unique set of client proteins in the absence of NLR perception
T. TORUNO (1), D. Lee (1), . Shen (2), D. Mackey (2), G. Coaker (1) (1) University of California, Davis, U.S.A.; (2) The Ohio State University, U.S.A.

The Arabidopsis RPM1-interacting protein4 (RIN4) is targeted by several Pseudomonas syringae effectors and is guarded by two NLR immune receptors, RPM1 and RPS2. AvrB induces RIN4 phosphorylation at Thr-166 by host kinases resulting in activation of RPM1. In a susceptible Arabidopsis genotype (rpm1 rps2 background), RIN4 phosphorylation mimics enhance disease susceptibility to virulent P. syringae. RIN4 phosphorylation mimics exhibit wider stomatal apertures and enhanced pathogen entry. In addition, RIN4 phosphorylation mimics have reduced PAMP-triggered immune responses. These results highlight the importance of effector-induced RIN4 phosphorylation to promote disease susceptibility. RIN4 does not possess homology to proteins of known function. We hypothesize that RIN4 acts as an adapter to facilitate protein complex formation and immune signaling. To understand how RIN4 phosphorylation promotes disease susceptibility in the absence of NLR perception, T7-tagged wild type RIN4 and phosphorylation mimics were subjected to immunoprecipitation in the presence and absence of flagellin perception. RIN4 protein complexes were identified by mass spectrometry across three biological replicates. We have identified multiple statistically significant complex constituents as well as protein associations specific to RIN4 phosphomimics. We are currently investigating individual proteins for their role in plant immunity as part of the RIN4 signaling complex.

Abstract Number: P17-629
Session Type: Poster