PpCBF6 is a low-temperature-sensitive transcription factor that binds the PpVIN2 promoter in peach fruit and regulates sucrose metabolism and chilling injury

Abstract

PpVIN2 is the only vacuolar invertase (VIN) gene in peaches that is sensitive to cold. PpVIN2 functions in sucrose decomposition and chilling injury (CI), but it is unknown how low temperatures induce PpVIN2. Here, we confirmed low-temperature activation of PpVIN2 transcription from a PpVIN2 promoter using a transgenic tobacco model. C-repeat binding factor (CBF) is a conserved cold-responsive gene in plants, and PpCBF6 expression increases rapidly when peaches suffer from cold stress. We studied the interaction between PpCBF6 and PpVIN2 both in vivo and in vitro. Using yeast one-hybrid assay and electrophoretic mobility shift assay, we confirmed that PpCBF6 binds to the promoter of PpVIN2, and results from a dual luciferase assay indicate that PpCBF6 inhibits the promoter activity of PpVIN2. In vivo, transient overexpression of PpCBF6 decreases PpVIN2 expression and VIN activity, and increases sucrose levels. In addition, when PpCBF6 is targeted using virus-induced gene silencing (VIGS), PpVIN2 expression and activity increase, accompanied by a decrease in sucrose content. Compared to the control group, exogenous methyl jasmonate (MeJA) treatment caused a higher expression of PpCBF6, and reduced the rapid rise of PpVIN2 expression level. This resulted in the lower VIN activity and higher sucrose content in MeJA-treated peach fruit, thereby reducing the CI. In general, we proved that PpCBF6 retarded the degradation of sucrose by inhibiting the increased expression of PpVIN2, which improves the chilling resistance of peach fruit.