An E3 Ligase Affects the NLR Receptor Stability and Immunity to Powdery Mildew. Issue 4 (25th October 2016)

• Record Type: Journal Article
• Authors: Wang, Tao; Chang, Cheng; Gu, Cheng; Tang, Sanyuan; Xie, Qi; Shen, Qian-Hua
• Is Part Of: Plant physiology. Volume 172:Issue 4(2016)
• Page Start: 2504
• Page End: 2515
• Publication Date: 2016-10-25
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.16.01520
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : The barley MIR1 E3 ubiquitin ligase interacts with MLA immune receptors to promote their ubiquitination and proteasomal degradation, thus regulating receptor stability and immunity. Abstract: Following the detection of pathogen cognate effectors, plant Nod-like receptors (NLRs) trigger isolate-specific immunity that is generally associated with cell death. The regulation of NLR stability is important to ensure effective immunity. In barley ( Hordeum vulgare ), the allelic Mildew locus A (MLA) receptors mediate isolate-specific disease resistance against powdery mildew fungus ( Blumeria graminis f. sp. hordei ). Currently, how MLA stability is controlled remains unknown. Here, we identified an MLA-interacting RING-type E3 ligase, MIR1, that interacts with several MLAs. We showed that the carboxyl-terminal TPR domain of MIR1 mediates the interaction with the coiled-coil domain-containing region of functional MLAs, such as MLA1, MLA6, and MLA10, but not with that of the nonfunctional MLA18-1. MIR1 can ubiquitinate the amino-terminal region of MLAs in vitro and promotes the proteasomal degradation of MLAs in vitro and in planta. Both proteasome inhibitor treatment and virus-induced gene silencing-mediated MIR1 silencing significantly increased MLA abundance in barley transgenic lines. Furthermore, overexpression of MIR1 specifically compromised MLA-mediated disease resistance in barley, while coexpression of MIR1 and MLA10 attenuated MLA10-induced cell death signaling in Nicotiana benthamiana . Together, our data reveal a mechanism for the control of the stability of MLA immune receptors and for the attenuation of MLA-triggered defense signaling by a RING-type E3 ligase via the ubiquitin proteasome system.