The VvSEP3-VvCCD1b transcriptional module regulates carotenoid degradation in grape

Carotenoid-derived compounds, particularly norisoprenoids, significantly contribute to fruit aroma in grape ( Vitis vinifera ). Carotenoid cleavage dioxygenases (CCDs) are key enzymes catalyzing carotenoid degradation in plants. This study systematically identified 13 VvCCD genes in grape and analyzed their expression patterns across various tissues and developmental stages. Results showed that VvCCD1b was significantly up-regulated during fruit ripening, negatively correlating with carotenoid content and positively correlating with norisoprenoid accumulation. Overexpression of VvCCD1b in tobacco leaves and grape berries significantly reduced lutein and β -carotene levels, confirming its role in carotenoid degradation. Further investigation revealed that the MADS-box transcription factor VvSEP3 was highly expressed during late fruit development and positively correlated with VvCCD1b expression. Overexpression of VvSEP3 in tobacco leaves and grape berries similarly decreased carotenoid content and induced CCD1 gene expression. Biochemical assays demonstrated that VvSEP3 localized to the nucleus and directly bound to the VvCCD1b promoter to activate its transcription. These results uncover a novel VvSEP3–VvCCD1b regulatory module that integrates developmental signals with specialized metabolism, providing targets for quality improvement in grape breeding.