Figure 7.

Models for Viral Effector Recognition and Activation of Tomato NLR Sw-5b to Mediate Broad-Spectrum Resistance to American Tospoviruses.

(A) Sw-5b-mediated broad-spectrum resistance to American-type tospoviruses. Tomato NLR receptor Sw-5b confers a broad-spectrum resistance to American-type tospoviruses but not Euro-Asian-type tospoviruses through the recognition of a conserved epitope in viral movement protein NSm (NSm²¹).

(B) NSm²¹ recognition and activation of Sw-5b NB-ARC-LRR. i, R927 residue is important for LRR to interact with and to lock NB-ARC in an autoinhibited state. Substitution of R927 with an alanine residue results in autoactivation of Sw-5b NB-ARC-LRR. ii, The nonelicitor NSm^21(C118Y) and NSm^21(T120N) enhance the HR induced by Sw-5b NB-ARC-LRR^R927A. iii, The R927 residue and the four polymorphic sites 3, 4, 5, and 6 on Sw-5b LRR are located next to each other. Recognition of NSm²¹ by four polymorphic sites on the Sw-5b LRR domain modulates the R927 site to weaken the intramolecular interaction between NB-ARC and LRR, thus translating recognition of NSm²¹ peptide into activation of Sw-5b NB-ARC-LRR.