A Plant Immune Receptor Adopts a Two-Step Recognition Mechanism to Enhance Viral Effector Perception.
- Author(s): Li, Jia
- Huang, Haining
- Zhu, Min
- Huang, Shen
- Zhang, Wenhua
- Dinesh-Kumar, Savithramma P
- Tao, Xiaorong
- et al.
Published Web Locationhttps://www.ncbi.nlm.nih.gov/pubmed/30639751
Plant intracellular nucleotide-binding leucine-rich repeat (NLR) immune receptors play critical roles in pathogen surveillance. Most plant NLRs characterized so far were found to use single domain/sensor to recognize pathogen effectors. Here we report that Sw-5b NLR immune receptor uses two distinct domains to detect the viral movement protein NSm encoded by tospovirus. In addition to the previously reported LRR domain, we found that the N-terminal Solanaceae domain (SD) of Sw-5b also interacts with NSm and a conserved 21-amino acids region of NSm (NSm21). The specific interaction between Sw-5b SD and NSm is required for releasing the CC inhibition on NB-ARC-LRR region. Our results showed that the binding of NSm affects the nucleotide-binding activity of the NB-ARC-LRR in vitro. However, Sw-5b NB-ARC-LRR is activated only when NSm and NSm21 levels were higher. Strikingly, Sw-5b SD could significantly enhance the ability of NB-ARC-LRR to detect low levels of NSm effector and facilitate its activation to induce defense response. The Sw-5b SD mutant that is disrupted in NSm recognition failed to enhance the ability of NB-ARC-LRR in sensing low levels of NSm and NSm21. Taken together, our results suggest that Sw-5b SD functions as an extra sensor and the NB-ARC-LRR functions as an activator and Sw-5b NLR adopts a two-step recognition mechanism to enhance viral effector perception.
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