Essential regulator of plant defense, which plays a central role in resistance in case of infection by a pathogen. It is a common target for both type III avirulence proteins from P.syringae (AvrB, AvrRpm1 and AvrRpt2) and for the plant Resistance (R) proteins RPM1 and RPS2. In strains carrying the appropriate R gene for avirulence proteins of the pathogen, its association with avirulence proteins triggers a defense system including the hypersensitive response, which limits the spread of disease. In contrast, in plants lacking appropriate R genes, its association with avirulence proteins of the pathogen impairs the defense system and leads to the pathogen multiplication. Interacts with the unrelated avirulence proteins AvrB, AvrRpm1 and AvrRpt2 from P.syringae. Interacts with the N-terminal domain of PRM1. Interacts indirectly with RPS2. Its association with AvrB and AvrRpm1 results in its phosphorylation, which is in turn recognized by the resistance RPM1 protein, leading to the activation of RPM1-dependent disease resistance responses. On the other hand, its association with AvrRpt2 results in its destruction, which activates RPS2-dependent disease resistance responses. Interacts (via C-terminus) with NDR1. Interaction with NDR1 is required for association with RPS2 and RPS2-mediated resistance (PubMed:11955429, PubMed:12581526, PubMed:12581527, PubMed:15746386, PubMed:17012600, PubMed:17397263). Interacts with RIPK (PubMed:21320696). Phosphorylated following the interaction with the Pseudomonas syringae effectors AvrB or AvrRpm1 (PubMed:11955429). Phosphorylated at Thr-21, Ser-160 and Thr-166 by RIPK following interaction with the effectors AvrB or AvrRpm1 (PubMed:21320696). Palmitoylation is required for membrane localization. It is uncertain whether Cys-203, Cys-204 or Cys-205 is palmitoylated. Cleavage after Gly-152 by AvrRpt2 is critical for the release of RIN4 from the membrane and its subsequent proteasome-dependent elimination. Belongs to the RIN4 family.