Required specifically for plant innate immunity. Is essential for resistance conferred by multiple R genes recognizing different bacterial and oomycete pathogen isolates like avirulent P.syringae or H.parasitica (downy mildew). Contributes additively with SGT1B to RPP5-dependent resistance. Functions as positive regulator of RPS5 accumulation by assisting its stabilization. May function as co-chaperone of HSP90-2 to positively regulate the steady-state accumulation of RPM1 and protect it from SGT1-mediated degradation. Acts as negative regulator of pathogen-associated molecular pattern (PAMP)-triggered immunity.