Functional Dissection of a Wheat NLR Protein Reveals a Minimal Active Region and Key Regulatory Sites for Immune Signalling
Zhu, Xiaoxu ; Jiang, Shuo ; Zhao, Jinchen ; Peng, Fangfang ; Zhao, Ran ; Li, Xinnuo ; Luo, Yi ; Xiong, Zhihao ; Li, Qi ; Rolland, Filip ; Kang, Zhensheng ; Wang, Xiaojie ; Liu, Yunqi ; Huang, Li ; Wang, Xiaojing
DOI：10.1111/mpp.70238
Abstract
Nucleotide-binding site (NBS) leucine-rich repeat (LRR) receptors (NLRs) are crucial for plant immunity but often come with trade-offs in plant growth. Understanding the mechanisms of their self-regulating activity for controlled immune responses is essential for optimising crop resistance. In this study, we investigated the activity fine-tuning of the wheat NLR protein NLRMoro, derived from the cultivars Moro and AvS + Yr10. Overexpression in Nicotiana benthamiana and wheat demonstrated that NLRMoro, or its N-terminal coiled-coil (CC) domain alone, auto-activated cell death and that plasma membrane-localised NLRMoro-CC conferred stripe rust resistance through induction of hypersensitive response, reactive oxygen species accumulation and Ca2+ influx. Through truncation analysis, we identified the amino acids 62-116 region within the CC domain as the minimal active region, essential and sufficient for its activity. Further investigation revealed that the adjacent central NBS domain suppresses the signalling activity of CC, while the C-terminal LRR domain alleviates this suppression, both exclusively via intramolecular interactions. Critical sites outside the CC domain, including the P-loop, RNBS-A and MHD motifs and the phosphorylation site S198, were found to significantly influence NLRMoro-induced cell death, presenting potential targets for fine-tuning NLR activity. This study advances our understanding of CC-NLR protein regulation and provides a theoretical foundation for optimising NLR activity to balance growth-defence trade-offs in plants.