Regulatory Role of SGT1 in Early R Gene-Mediated Plant Defenses

Abstract
Animal SGT1 is a component of Skp1-Cullin–F-box protein (SCF) ubiquitin ligases that target regulatory proteins for degradation. Mutations in one (SGT1b) of two highly homologousArabidopsis SGT1 genes disable early plant defenses conferred by multiple resistance (R) genes. Loss ofSGT1b function in resistance is not compensated for bySGT1a. R genes differ in their requirements forSGT1b and a second resistance signaling gene,RAR1, that was previously implicated as an SGT1 interactor. Moreover, SGT1b and RAR1 contribute additively toRPP5-mediated pathogen recognition. These data imply both operationally distinct and cooperative functions of SGT1 and RAR1 in plant disease resistance.