Phosphoenolpyruvate carboxykinase and gluconeogenesis in grape pericarp

Glycolysis from sugars is necessary at all stages of development of grape pericarp, and this raises the question as to why gluconeogenesis from malate occurs. Phosphoenolpyruvate carboxykinase (PEPCK) is required for gluconeogenesis in grape pericarp. In this study we determined the abundance of PEPCK protein and activity in different parts of grape pericarp during its development. Both PEPCK protein and activity were present throughout development, however, in both the skin and the flesh their abundance increased greatly at the start of ripening. This coincided with the onset of the decrease in the malate content of the berry. The location of PEPCK in the pericarp at different stages of development was determined using both immunohistochemistry and dissection. We provide a possible explanation for the occurrence of gluconeogenesis in grape pericarp. In ripening grape PEPCK may function in gluconeogenesis when malate released from the vacuole exceeds the demand to use it in other processes. [Display omitted] •Glycolysis from sugars is necessary at all stages of development.•This raises the question as to why gluconeogenesis from malate occurs.•PEPCK was present in all berry tissues.•It appears that there can be short-term abundant effluxes of malate from the vacuole.•Gluconeogenesis occurs when malate exceeds the demand to use it in other processes.