Accumulation of β-citraurin and expression of carotenoid cleavage dioxygenase4 gene in citrus fruit during maturation

β-citraurin is a red pigment that is specifically accumulated in flavedos of some citrus cultivars.
The citrus cultivars accumulating β-citraurin are considered more attractive because of their red-orange color. Carotenoid cleavage dioxygenase4 (CitCCD4) is a key gene involved in the biosynthesis of β-citraurin in the flavedo of citrus fruit.
In this study, to elucidate the mechanism of the accumulation of β-citraurin in citrus fruit, the changes in the carotenoid contents and the expression of CitCCD4 were investigated in the flavedos of four citrus cultivars, ‘Hayashi-unshiu’ (Citrus unshiu Marc.), ‘Dobashibeni-unshiu’ (Citrus unshiu Marc.), ‘Clementine Vita’ (Citrus clementina hort. ex Tanaka), and ‘Akemi’ (‘Kiyomi’ tangor × ‘Seminole’ tangelo) during maturation.
The results showed that ‘Dobashibeni-unshiu’, ‘Clementine Vita’, and ‘Akemi’ accumulated high amount of β-citraurin in the flavedos during maturation.
In contrast, β-citraurin was undetectable in the flavedo of ‘Hayashi-unshiu’ throughout the maturation process.
In the flavedos of ‘Dobashibeni-unshiu’, ‘Clementine Vita’, and ‘Akemi’, β-citraurin content increased rapidly from October.
Among the three citrus cultivars, ‘Clementine Vita’ accumulated the highest amount of β-citraurin in the flavedo, followed by ‘Dobashibeni-unshiu’ and ‘Akemi’. The gene expression results showed that the expression of CitCCD4 increased significantly with a peak in November in the flavedo of ‘Dobashibeni-unshiu’, ‘Clementine Vita’, and ‘Akemi’; however, it remained at a low level in the flavedo of ‘Hayashi-unshiu’ during maturation.
In November, the expression level of CitCCD4 in the flavedo of ‘Clementine Vita’ was the highest among the three citrus cultivars, followed by ‘Dobashibeni-unshiu’ and ‘Akemi’. The changes in the expression of CitCCD4 were well consistent with the accumulation of β-citraurin in the flavedos of ‘Dobashibeni-unshiu’, ‘Clementine Vita’, and ‘Akemi’. These results suggested that CitCCD4 was a key gene regulating β-citraurin accumulation in the flavedos of citrus fruit.

V Asia Symposium on Quality Management in Postharvest Systems

M. Kato, K. Iida, G. Ma, L.C. Zhang, M. Yahata, M. Kato

β-citraurin, carotenoid, citrus, gene expression

https://doi.org/10.17660/ActaHortic.2022.1336.9