The PpPHL7-PpbZIP11 transcription complex suppresses malate accumulation via inhibition of PpMDH13 in peach ( Prunus persica )

Malate accumulation is a key determinant of fruit acidity and flavor in peach; however, its transcriptional regulatory mechanisms remain poorly understood. Here, we demonstrate that PpMDH13 encodes a cytosolic malate dehydrogenase, overexpression of PpMDH13 in tomato fruits and peach fruit enhanced malate accumulation, while silencing of PpMDH13 in peach fruit leads to a decrease in malate concentrations. Two transcription factors, PpPHL7 and PpbZIP11, show a negative correlation with PpMDH13 expression and malate content. Yeast one hybrid and dual-luciferase and electrophoretic mobility shift assays verified that PpPHL7 and PpbZIP11 directly bind to the PpMDH13 promoter and inhibit its activity. Functional studies revealed that overexpression of PpPHL7 or PpbZIP11 significantly reduced malate accumulation, whereas silencing these two transcription factors remarkably increased malate concentration. Furthermore, PpPHL7 and PpbZIP11 physically interact to form a nuclear-localized protein complex that further enhances the repression of PpMDH13 promoter activity. These results uncover a novel transcriptional regulatory module in which the PpPHL7-PpbZIP11 complex inhibits malate accumulation by directly inhibiting PpMDH13 expression. Overall, this study provides new insights into the molecular basis of malate metabolism in peach and suggests potential strategies for the genetic improvement of fruit quality.