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. Interacts with HSP90-1, HSP90-2, SGT1A and SGT1B. Forms a ternary complex with SGT1A and barley HSP90. The 2 cysteine and histidine-rich (CHORD) domains bind each 2 zinc ions, and the plant-specific 20 amino acid cysteine and histidine-containing motif (CCCH motif), located between the two CHORDs, binds 1 zinc ion. No visible phenotype under normal growth condition. In case of infection, plants loose R gene resistance mediated by RPP4, RPP5, RPS2, RPS4, RPS5 and RPM1.