Involved in plant innate immunity. Is essential for resistance conferred by multiple R genes recognizing different oomycete pathogen isolates like avirulent H.parasitica (downy mildew). Contributes additively with RAR1 to RPP5-dependent resistance. Not required for RPM1, RPS2, RPS4 and RPS5-mediated resistance. Functions as negative regulator of RPS5 accumulation by assisting its degradation. May be involved in heat shock response by associating with HSC70-1 chaperone. Required for the SCF(TIR1)-mediated degradation of Aux/IAA proteins, but maybe not for SCF(TIR1) assembly or binding to its Aux/IAA substrates. Probably required for SCF-mediated ubiquitination, by coupling HSP90 to SCF complex for ubiquitination of HSP90 client proteins. Required for the coronatine/jasmonic acid-mediated signal transduction pathway. Interacts with RAR1 and HSP90-2. Interacts (via SGS domain) with HSC70-1 and HSC70-3. By infection with the oomycete H.parasitica (downy mildew). Delay in flowering time. Plants loose R gene resistance mediated by RPP2, RPP4, RPP5 and RPP7, and show reduced response to auxin, jasmonate and coronatine, and enhanced tolerance to heat shock. Belongs to the SGT1 family.