Pathogen effector AvrSr35 triggers Sr35 resistosome assembly via a direct recognition mechanism.

Zhao, Yan-Bo; Liu, Meng-Xi; Chen, Tao-Tao; Ma, Xiaomin; Li, Ze-Kai; Zheng, Zichao; Zheng, Si-Ru; Chen, Lifei et al. · Sci Adv · 2022

basic_science · Level V

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Abstract

Nucleotide-binding, leucine-rich repeat receptors (NLRs) perceive pathogen effectors to trigger plant immunity. The direct recognition mechanism of pathogen effectors by coiled-coil NLRs (CNLs) remains unclear. We demonstrate that the <i>Triticum monococcum</i> CNL Sr35 directly recognizes the pathogen effector AvrSr35 from <i>Puccinia graminis</i> f. sp<i>. tritici</i> and report a cryo-electron microscopy structure of Sr35 resistosome and a crystal structure of AvrSr35. We show that AvrSr35 forms homodimers that are disassociated into monomers upon direct recognition by the leucine-rich repeat domain of Sr35, which induces Sr35 resistosome assembly and the subsequent immune response. The first 20 amino-terminal residues of Sr35 are indispensable for immune signaling but not for plasma membrane association. Our findings reveal the direct recognition and activation mechanism of a plant CNL and provide insights into biochemical function of Sr35 resistosome.