Knockdown of Carotenoid Cleavage Dioxygenase 4 (CCD4) via Virus-Induced Gene Silencing Confers Yellow Coloration in Peach Fruit: Evaluation of Gene Function Related to Fruit Traits

Transgenic approach is an excellent way for the clarification of gene function, but it is generally difficult to create transgenic plants for most of the fruit trees including peach. Even if transgenic lines are successfully obtained, it will be extremely difficult to evaluate fruit traits due to the long juvenile phase of the plants. To overcome this problem, usage of virus vector is one of the excellent approaches. In this study, we evaluated gene function related to fruit traits in peaches via virus-induced gene silencing (VIGS). Carotenoid cleavage dioxygenase 4 (CCD4) is proposed to be the key factor responsible for carotenoid degradation in white flesh peaches. Then, we knocked down the CCD4 gene in the white flesh peaches (“Akatsuki” and “Manami”) via VIGS system. Resultantly, yellow pigmentation and increased contents of carotenoids including lutein, ß-carotene, ß-cryptoxanthin, zeaxanthin, and violaxanthin were observed in the agroinfiltration portions of the white flesh peaches, which is a direct evidence that CCD4 is a determinant for yellow flesh trait of peach. Our results suggested the possible application of VIGS system for functional studies of the genes related to fruit traits.