Proteomic analysis reveals dynamic regulation of fruit ripening in response to exogenous ethylene in kiwifruit cultivars

Understanding the fruit ripening mechanism is critical for fruit quality improvement. Although postharvest ethylene application is known to enhance the onset of fruit ripening, the exact mechanisms remain unclear. In this study, a gel-based proteomic analysis was performed to investigate the changes in protein profiles during the ripening of exogenous-ethylene-treated kiwifruit (Actinidia deliciosa) cultivars ‘Hayward’ and ‘Garmrok’. Based on comparative two-dimensional gel electrophoresis, most of the proteins were aggregated in exogenous-ethylene-treated kiwifruit compared to the untreated kiwifruit. Consequently, 90 and 106 proteins were differentially expressed in ‘Hayward’ and ‘Garmrok’ kiwifruit, respectively. Among the successfully identified proteins by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry, the 50% in ‘Hayward’ kiwifruit and 60% in ‘Garmrok’ kiwifruit were associated with ripening. Also, 18% and 10% of proteins were associated with defense response in ‘Hayward’ and ‘Garmrok’ kiwifruit, respectively. The other major proteins were related to protein biosynthesis and photosynthesis/Calvin cycle during kiwifruit ripening. We used bioinformatics analysis to determine the interactions between identified proteins, and this proteomic approach provided insights into biological pathways and molecular functions in postharvest ripening of exogenous-ethylene-treated kiwifruit.