Abstract
SGT1-HSP90 complex is essential for disease resistance in plants triggered by resistance (R) proteins and is also necessary for innate immunity in animals induced by R protein homologues, Nod family proteins. Here, we present the structural and functional characterization of the plant SGT1-HSP90 complex. X-ray crystal structural analysis, NMR-based interaction surface mapping and mutational analyses reveal that (1) the CHORD-II domain of RAR1 and the N-terminal domain of HSP90 interact with opposite sides of the CS domain of SGT1, and (2) SGT1 binds to different surface of HSP90 than those to which other co-chaperones, P23 and AHA1 bind. This analysis allowed us to obtain a compensatory mutant pair between both partners that is able to restore virus resistance in vivo through Rx (Resistance to potato virus X) immune sensor stabilization. These results directly show the critical role of SGT1-HSP90 interaction in innate immunity in plants.
