PbAP2 accelerates postharvest chlorophyll degradation by directly activating PbNYC1 transcription in ‘Yuluxiang’pear

Yuluxiang’ pear is a premium pear cultivar widely cultivated in China, but postharvest peel chlorosis caused by chlorophyll degradation severely shortens its shelf life and impairs commercial value. This study investigated the dynamic changes in physicochemical quality and peel pigmentation of ‘Yuluxiang’ pear fruit during ambient storage (24 ± 1℃), and elucidated the transcriptional regulatory mechanism underlying chlorophyll degradation via integrated physiological, transcriptomic, and molecular biological approaches. Results showed that fruit firmness, single fruit weight, titratable acid, ascorbic acid, and chlorophyll contents decreased continuously during storage, while total soluble solids and soluble carbohydrates contents exhibited an initial increase followed by a decline. Transcriptome analysis identified significant enrichment of differentially expressed genes in chlorophyll metabolism, plant hormone signal transduction, and secondary metabolite biosynthesis pathways. Functional validation confirmed that the key structural gene PbNYC1 positively regulated chlorophyll degradation, with a pronounced regulatory effect. Yeast one-hybrid, dual-luciferase, and GUS histochemical staining assays demonstrated that the ethylene-responsive AP2/ERF transcription factor PbAP2 directly bound to the PbNYC1 promoter and activated its transcription. Exogenous ethylene treatment upregulated PbAP2 expression and accelerated peel chlorosis, confirming the critical role of the ethylene-induced PbAP2 - PbNYC1 module in postharvest chlorophyll degradation. This study reveals the transcriptional regulatory mechanism of postharvest chlorophyll degradation in ‘Yuluxiang’ pear, and provides a theoretical basis and molecular targets for the development of green-skin retention and shelf-life extension technologies for green-skinned pears.