The polygalacturonase-inhibiting protein PpPGIP1, positively regulates vacuolar invertase activity via a protein-protein interaction with PpVIN2 in peach fruit

Abstract

The vacuolar invertase (VIN) gene PpVIN2 is induced at chilling temperatures, and plays an important role in sucrose metabolism in peach fruit during cold storage. Using a dual membrane yeast two-hybrid system, we found 22 proteins interacted with PpVIN2. Of these, PpPGIP1 (polygalacturonase-inhibiting protein) is a leucine-rich repeat glycoprotein and sensitives to chilling temperature (5 °C), based on the expression level of which increased significantly accompanied with the chilling injury. Colocalization of PpPGIP1 and PpVIN2 was demonstrated by confocal microscopy and their interaction between was demonstrated by bimolecular fluorescence complementation (BiFC). Transient overexpression of PpPGIP1 in peach fruit increased VIN activity significantly. Transient virus-induced gene silencing of PpPGIP1 decreased VIN activity significantly, which led to decreases sucrose decomposition. PpPGIP1 recombinant protein was successfully expressed by constructing pMAL-c6T-PpPGIP1, and PpPGIP1 increased the VIN activity in vitro. Taken together, PpPGIP1 positively regulates VIN activity via an interaction with PpVIN2; this interaction results in accelerated sucrose decomposition in peaches under chilling temperature. These findings provide a new perspective for understanding the new function of PpPGIP1 related with the rapid decomposition of sucrose and the occurrence of chilling injury in peach fruit during cold storage.