Peach fruit ripening: Proteomic comparative analyses of two cultivars with different flesh texture phenotypes at two ripening stages

Firmness is an important textural attribute of peach fruit that directly influences its shelf life and consumer acceptance. To investigate the underlying mechanism that determines the texture of peach flesh, we conducted a proteome study on the fruits of two cultivars: hard melting flesh Xiahui 8 and stony hard Xiacui. Then we compared these at the unripe and ripe stages using the isobaric tags for relative and absolute quantification (iTRAQ) technique. In total, 190 proteins with more than 1.5-fold (P < 0.05) abundance changes were observed, including 57 proteins in Xiacui and 171 proteins in Xiahui 8. The differentially expressed proteins in Xiahui 8 were mainly in classes of proteins involved in cellular activities such as sugar metabolism, membrane structure, and cell-cycle control. Our findings imply that the enzymes polygalacturonase (PG), pectate lyase (PL), calmodulin (CaM), calcineurin B-like protein (CBL), peptidyl-prolyl isomerase (PPIase), and 9-cis-epoxycarotenoid dioxygenase (NCED) play functional roles in controlling fruit development and maintaining textural integrity and fruit quality during ripening. The results shed new light on proteomic differences and protein interactions during the metabolism of ethylene, amino acids, sugars, and carbohydrates; the general defense response in cultivars with varied texture phenotypes; and the underlying mechanisms of-peach fruit ripening. They also provide a knowledge base needed for postharvest quality control and breeding strategies for cultivar improvement.