Changes in carotenoid profiles and in the expression pattern of the genes in carotenoid metabolisms during fruit development and ripening in four watermelon cultivars

Changes in carotenoid profiles during fruit ripening were investigated in four watermelon cultivars: red-fleshed “CN66”, pink-fleshed “CN62”, yellow-fleshed “ZXG381” and white-fleshed “ZXG507”. The expression pattern of twelve genes (GGPS, PSY, PSY-A, PDS, ZDS, CRTISO, LCYB, CHYB, ZEP, NCED1, NCED2 and NCED3) was analysed. In “CN66” and “CN62”, lycopene appeared at 12 DAP and became a main carotenoid increased at the later stages. The transcript levels of carotenogenic genes in “CN66” sharply increased during 18-30 DAP, and concomitantly, fruit accumulated the massive amounts of carotenoids. In “ZXG381”, violaxanthin and lutein contents were positively correlated, respectively, with CHYB and ZEP transcript levels during fruit ripening. The trace amounts of carotenoids in “ZXG507” were accompanied with the low transcript levels of most biosynthetic genes. The results suggest that differential transcriptional regulation of carotenoid metabolic genes is very important in determining the amount and type of specific carotenoids accumulated during fruit development and ripening.