Characterization of Transcriptional Expression and Regulation of Carotenoid Cleavage Dioxygenase 4b in Grapes.

Norisoprenoids are important aromatic volatiles contributing to the pleasant floral/fruity odor in grapes and wine. They are produced from carotenoids through the cleavage of carotenoid cleavage dioxygenases (CCDs). However, the underlying mechanisms regulating expression remain poorly understood. In this study, we showed that expression was positively correlated with the accumulation of β-damascenone, β-ionone, 6-methyl-5-hepten-2-one, geranylacetone, dihydroedulan I, and total norisoprenoids in developing grapes in two vintages from two regions. was found to be principally expressed in flowers, mature leaves, and berries. Abscisic acid strongly induced the expression of this gene. Additionally, the present study preliminarily indicated that the activity of the promoter was dropped under 37°C treatment and also responded to the illumination change. was expressed in parallel with in developing grape berries. The latter is a MADS family transcription factor and nucleus-localized protein that was captured by yeast one-hybrid. A dual-luciferase reporter assay in tobacco leaves revealed that VvMADS4 downregulated the activity of the promoter. overexpression in grape calli and Rehd. leaves repressed the expression. In summary, this work demonstrates that expression is positively correlated with the accumulation of norisoprenoids, and VvMADS4 is a potential negative regulator of . Our results provide a new perspective for understanding the regulation of expression and norisoprenoid accumulation in grapes.