Exogenous melatonin enhancing the accumulation of flavonoids and carotenoids in wolfberry fruit at cold storage

The deterioration of fruit quality during refrigeration is a typical symptom of the storage and transportation of Lycium barbarum L. (wolfberry) fruit after harvest. This study aimed to explore the impact of melatonin (MT) treatment on the fruit quality of wolfberry stored at 4°C, using combined transcriptomics and metabolomics analyses. In this study, about 15% of the flavonoid metabolites differed significantly after MT treatment in yellow-fleshed wolfberry, especially for flavanols, flavanones, and flavonols. MT treatment enhanced esterified carotenoid content in red-fleshed wolfberry postharvest. Comparative transcriptomic analysis revealed that MT-induced upregulation of LbaF3’H, LbaHQT and LbaCHS1 might contribute to the increased flavonoids in yellow-flesh wolfberry, and that MT-induced upregulation of LbaPSY, LbaCRTISO and LbaCYCB are responsible for the increased carotenoids in red-flesh wolfberry. Coexpression network analysis showed that several transcription factors such as LbaGATA are involved in MT-mediated regulation of flavonoids and carotenoids. Dual luciferase assay evidenced that LbaGATA and LbaRKD5 depress the expression of LbaPSY. Overall, this study underscores MT's role in maintaining wolfberry postharvest quality during storage, providing a solid foundation of food application.