NPR3 and NPR4 are receptors for the immune signal salicylic acid in plants

摘要

Salicylic acid (SA) is a plant immune signal produced after pathogen challenge to induce systemic acquired resistance. It is the only major plant hormone for which the receptor has not been firmly identified. Systemic acquired resistance in Arabidopsis requires the transcription cofactor nonexpresser of PR genes 1 (NPR1), the degradation of which acts as a molecular switch. Here we show that the NPR1 paralogues NPR3 and NPR4 are SA receptors that bind SA with different affinities. NPR3 and NPR4 function as adaptors of the Cullin 3 ubiquitin E3 ligase to mediate NPR1 degradation in an SA-regulated manner. Accordingly, the Arabidopsis npr3 npr4 double mutant accumulates higher levels of NPR1, and is insensitive to induction of systemic acquired resistance. Moreover, this mutant is defective in pathogen effector-triggered programmed cell death and immunity. Our study reveals the mechanism of SA perception in determining cell death and survival in response to pathogen challenge.%水杨酸是受体尚未被肯定识别出来的惟一主要rn植物激素。它是响应于病原体的挑战而在植rn物中产生的，诱导系统获得对二次感染的抵抗rn力。这个过程需要转录辅因子NPR1，这说明rnNPR1可能是一个水杨酸受体，但NPR1单独并rn不与该激素结合。在这项研究中，Xinnian Dongrn及其同事识别出NPR1的旁系同源物NPR3和rnNPR4为具有不同结合亲和力的水杨酸受体。rn本文作者们提生INPR3 和 NPR4 响应于不同水rn平的水杨酸来调控NPR1的一个模型。