Transcription factor NAC64 regulates abscisic acid metabolism and fruit ripening in apricot fruit ( Prunus armeniaca L.)

Fruit ripening is a complex process involving physiological and biochemical changes that are influenced by multiple factors. NAC transcription factors play roles in regulating plant growth, development, and responses to plant hormones, and have been implicated in playing regulatory roles in the ripening of several fruits. However, the mechanisms whereby NACs regulate ripening and quality formation in the climacteric fruit apricot (Prunus armeniaca L.) remain unclear. In this study, we identified ripening-associated PaNAC64 from apricot fruit by WGCNA and RT-qPCR analysis and showed that it is upregulated during fruit ripening and is highly expressed at fruit maturity. Expression experiments confirmed that PaNAC64 can promote fruit ripening and the development of fruit quality attributes. PaNAC64 is not induced by exogenous ABA but its expression is significantly enhanced by ethylene. Through correlation analysis, we found that PaCYP707A is negatively correlated with PaNAC64. Experiments confirmed that PaNAC64 directly inhibits the transcription of PaCYP707A, thereby suppressing the hydroxylation-mediated inactivation of ABA, leading to the accumulation of endogenous ABA, which in turn promotes ethylene synthesis and fruit ripening. Our study demonstrates the importance of the interactions between transcription factors, ABA and ethylene in the regulation of apricot fruit ripening, quality formation, and post-harvest storage.