Dehydration-Induced Carotenoid Cleavage Dioxygenase 1 Reveals a Novel Route for β-Ionone Formation during Tea ( Camellia sinensis ) Withering

β-Ionone is a carotenoid-derived flavor and fragrance compound with a complex fruity and woody scent, known for its violet aroma. Due to the low odor threshold, β-ionone dramatically affects the aroma and quality of tea. Previous studies have shown that β-ionone increases during tea withering; however, its formation and regulation during the withering process are far from being understood. As dehydration is the most important stress during the withering of the tea leaves, we isolated a dehydration-induced gene belonging to the subfamily of carotenoid cleavage dioxygenases called carotenoid cleavage dioxygenase 1a ( CsCCD1 a ) from Camellia sinensis and expressed it in Escherichia coli . The recombinant protein could generate volatile β-ionone and pseudoionone from carotenoids. CsCCD1 a was induced by dehydration stress, and its expression was related to the β-ionone accumulation during tea withering. Overall, this study elucidated that CsCCD1 a catalyzes the formation of β-ionone in C. sinensis and enhanced the understanding of the β-ionone formation under multiple stresses during the processing of tea.