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 homologous Arabidopsis SGT1 genes disable early plant defenses conferred by multiple resistance ( R ) genes. Loss of SGT1b function in resistance is not compensated for by SGT1a . R genes differ in their requirements for SGT1b and a second resistance signaling gene, RAR1 , that was previously implicated as an SGT1 interactor. Moreover, SGT1b and RAR1 contribute additively to RPP5 -mediated pathogen recognition. These data imply both operationally distinct and cooperative functions of SGT1 and RAR1 in plant disease resistance.