The PpWRKY22-PpWRKY70 regulatory module enhances resistance to Monilinia fructicola by regulating the gamma-aminobutyric acid shunt in peach fruit

Peach fruit is susceptible to infection of Monilinia fructicola leading to brown rot. Our previous study demonstrated that nitric oxide (NO) enhanced fruit resistance to M. fructicola by mediating the gamma-aminobutyric acid (GABA) shunt. Herein, two genes, PpWRKY22 and PpWRKY70, were identified whose expression was closely associated with the resistance of peach fruit against M. fructicola and induced by NO treatment. Notably, PpWRKY22 and PpWRKY70 activate the transcription of three GABA shunt-related genes (PpSSADH, PpGABA-T and PpGAD4) by directly binding to their promoters. Protein interaction assays revealed that PpWRKY22 interacts with PpWRKY70, and their protein complex enhances the promoter activities of PpSSADH, PpGABA-T and PpGAD4. Additionally, transient overexpression of PpWRKY22 and PpWRKY70 in peach fruit increases resistance to M. fructicola via up-regulating the transcription level of PpSSADH, PpGABA-T and PpGAD4. Overall, this study uncovers a novel model in which the interaction between PpWRKYs proteins actively enhances peach fruit resistance to M. fructicola by promoting the expression of GABA shunt-related genes.