Abstract
Citrus fruit abundantly contain various kinds of carotenoids that play important roles in pigmentation of the fruit and dietary functions for human health. Carotenoids are metabolized into the precursor of abscisic acid (ABA) or other compounds by enzymes such as 9-cis-epoxycarotenoid dioxygenase (NCED). Therefore, in this study, we investigated the effects of a new NCED inhibitor, SAR29, on carotenoids contents in the fruit of Satsuma mandarin (Citrus unshiu Marc.). In addition, the effects of combination of SAR29 and ethephon that up-regulated carotenoid biosynthesis were also investigated. The levels of ABA in the flavedo decreased by the treatment of SAR29 (100μM) regardless of ethephon treatment. The levels of xanthophylls such as lutein, all-trans-violaxanthin and β-cryptoxanthin in the flavedo increased with the combined treatment of SAR29 and ethephon (100ppm). Accumulation of total carotenoids in the flavedo was also enhanced (about 140% of the level in control) by the combined treatment. These results suggested that SAR29 treatment inhibited biosynthesis of ABA in the flavedo. Moreover, it was thought that the combined treatment of SAR29 and ethephon was effective in increasing carotenoid contents in the flavedo.
