OsPHR2 modulates phosphate starvation-induced OsMYC2 signalling and resistance to Xanthomonas oryzae pv. oryzae.

Phosphate (Pi) and MYC2-mediated jasmonate (JA) pathway play critical roles in plant growth and development. In particular, crosstalk between JA and Pi starvation signalling has been reported to mediate insect herbivory resistance in dicot plants. However, its roles and mechanism in monocot-bacterial defense systems remain obscure. Here, we report that Pi starvation in rice activates the OsMYC2 signalling and enhances resistance to Xanthomonas oryzae pv. oryzae (Xoo) infection. The direct regulation of OsPHR2 on the OsMYC2 promoter was confirmed by yeast one-hybrid, electrophoretic mobility shift, dual-luciferase and chromatin immunoprecipitation assays. Molecular analyses and infection studies using OsPHR2-Ov1 and phr2 mutants further demonstrated that OsPHR2 enhances antibacterial resistance via transcriptional regulation of OsMYC2 expression, indicating a positive role of OsPHR2-OsMYC2 crosstalk in modulating the OsMYC2 signalling and Xoo infection. Genetic analysis and infection assays using myc2 mutants revealed that Pi starvation-induced OsMYC2 signalling activation and consequent Xoo resistance depends on the regulation of OsMYC2. Together, these results reveal a clear interlink between Pi starvation- and OsMYC2- signalling in monocot plants, and provide new insight into how plants balance growth and defence by integrating nutrient deficiency and phytohormone signalling. We highlighted a molecular link connecting OsMYC2-mediated JA pathway and phosphate starvation signalling in monocot plant. We demonstrated that phosphate starvation promoted OsMYC2 signalling to enhance rice defence to bacterial blight via transcriptional regulation of OsPHR2 on OsMYC2.