Sorbitol Modulates Resistance to by Regulating the Expression of an Resistance Gene in Apple.

In plant-microbe interactions, plant sugars produced by photosynthesis are not only a carbon source for pathogens, but may also act as signals that modulate plant defense responses. Here, we report that decreasing sorbitol synthesis in apple () leaves by antisense suppression of () leads to downregulation of 56 () genes and converts the phenotypic response to from resistant to susceptible. We identified a resistance protein encoded by the apple gene and a small protein encoded by the fungal gene that interact in both a yeast two-hybrid assay and a bimolecular fluorescence complementation assay. Deletion of in enables gain of virulence on the wild-type control plant. Overexpression of in two antisense lines increases resistance, whereas RNAi suppression of in the wild-type control decreases resistance against MdWRKY79 transcriptionally regulates by binding to the promoter of in response to sorbitol, and exogenous sorbitol feeding partially restores resistance of the antisense lines to These findings indicate that sorbitol modulates resistance to via the MdNLR16 protein that interacts with the fungal effector in a classic gene-for-gene manner in apple.