Antagonistic Control of Disease Resistance Protein Stability in the Plant Immune System

TLDR

Plant pathogen recognition depends on polymorphic disease‑resistance (R) proteins whose activity is mediated by RAR1 and SGT1b, with RAR1 controlling pre‑activation R protein accumulation and, together with SGT1 and HSP90, modulating accumulation and signaling competence. Arabidopsis SGT1b has two separable roles: it antagonizes RAR1 to suppress pre‑infection R protein accumulation, and independently regulates programmed cell death during infection.

Abstract

Pathogen recognition by the plant immune system is governed by structurally related, polymorphic products of disease resistance (R) genes. RAR1 and/or SGT1b mediate the function of many R proteins. RAR1 controls preactivation R protein accumulation by an unknown mechanism. We demonstrate that Arabidopsis SGT1b has two distinct, genetically separable functions in the plant immune system: SGT1b antagonizes RAR1 to negatively regulate R protein accumulation before infection, and SGT1b has a RAR1-independent function that regulates programmed cell death during infection. The balanced activities of RAR1 and SGT1, in concert with cytosolic HSP90, modulate preactivation R protein accumulation and signaling competence.