Required for plant immunity against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). Induced by infection with avirulent Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) carrying the avirulence gene avrRpt2. Down-regulated by Pst DC3000 virulence factors AvrE and HopM1. No visible phenotype under normal growth conditions, but mutant plant display enhanced susceptibility to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (Pst DC3000).