Activation mechanism of the wheat CC_G10-NLR immune receptor

Plants rely on nucleotide-binding, leucine-rich repeat (NLR) receptors to recognize effector proteins, activating immune responses. In recent years, researchers have elucidated the structures of various plant NLR resistosomes. However, the activation mechanism of the evolutionarily ancient and widely distributed CC_G10-NLR phylogenetic clade has remained elusive. To investigate this scientific question, the research group led by Zhiyong Liu from Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, in collaboration with multiple research groups, identified the wheat spontaneous immunity gene wheat autoimmunity 3 (WAI3), which encodes a CC_G10-NLR protein. Cryo-electron microscopy (cryo-EM) analysis reveals that that activated WAI3 assembles into a distinctive octameric resistosome, which triggers sustained calcium influx. The homologous CC_G10-NLR protein RPS2 in Arabidopsis was also shown to form an octamer and induce calcium influx, indicating that this mechanism is conserved in both monocot and dicot plants. Furthermore, the WAI3 resistosome exhibits a unique conformation of the coiled-coil (CC) domain, which may be associated with the absence of the EDVID (Glu-Asp-Val-Ile-Asp) motif in the CC domain of CC_G10-NLRs. This study reveals a novel mechanism of resistosome assembly and immune signal transduction in plant CC_G10-NLR proteins, broadening the understanding of the diversity and plasticity of plant immune receptors.