Carotenoid accumulation and gene expression in fruit skins of three differently colored persimmon cultivars during fruit growth and ripening

This study investigated the key carotenoids and their biosynthetic regulation mechanisms in persimmon fruit skin. Carotenoid content and expression patterns of nine carotenogenic genes in skins of 'Jinping', 'Huoguan' and 'Heishi' cultivars were analyzed during fruit development. As skin color changed, lutein content decreased and beta,beta-carotenoid (beta-carotene, beta-cryptoxanthin, zeaxanthin), lycopene and alpha-carotene accumulated especially in late development stages. At harvest, the major carotenoids in 'Jinping' and 'Heishi' were beta-carotene, while the red-colored lycopene was predominant in the skin of 'Huoguan'. The minor carotenoids in all three cultivars were free beta-cryptoxanthin, lutein, alpha-carotene and zeaxanthin. Consistently, the lowered expression of LCYe and increased expression of LCYb also indicated a shift in carotenoid biosynthesis from the beta,epsilon-branch to the beta,beta-branch accompanied fruit development. Simultaneously increased expression levels of DkGGPS, DkPSY, DkPDS, DkZDS, DkLCYb and DkBCH resulted in elevated accumulations of carotenoids. Correlation analysis showed increased DkPSY expression positively correlated with increased lutein, alpha-carotene, lycopene and beta-cryptocanthin, and negatively with zeaxanthin. Both DkZDS and DkBCH expressions showed positive correlations with zeaxanthin, alpha-carotene, lycopene and beta-cryptocanthin accumulation, but a negative correlation with lutein. The expression of DkLCYb was positively correlated with beta-carotene levels only. These results indicate that DkPSY, DkZDS, DkLCYb and DkBCH may play significant roles by contributing coordinately to carotenoid biosynthesis during persimmon fruit development.