Isolation and characterization of the carotenoid biosynthetic genes LCYB, LCYE and CHXB from strawberry and their relation to carotenoid accumulation

Abstract

Carotenoids are common pigments in yellow, orange and red fruits, and their compositions and contents are important indexes to evaluate the nutritional and commercial values of the fruits. To investigate the transcriptional regulation of carotenoid biosynthesis genes in relation to carotenoid accumulation during strawberry development, three cDNAs (LCYB, LCYE and CHXB) that encode carotenoid biosynthesis downstream enzymes (lycopene β-cyclase, lycopene ɛ-cyclase and β-ring hydroxylase) were isolated in the present study. Carotenoid accumulation and the expression of these genes along with three previously cloned upstream genes, PSY, PDS and ZDS, were analyzed. The data confirmed that the dominant carotenoids that accumulate in strawberries are lutein and β-carotene, and their contents varied with genotypes and decreased during fruit development. The expression analysis of carotenoid biosynthetic genes revealed that the pattern of upstream genes was opposite that of downstream genes. In contrast to the increased expression of PSY, PDS and ZDS, the decreased expression of LCYB, LCYE and CHXB correlated more closely with carotenoid accumulation in strawberries. Moreover, the expression profiles of LCYB and LCYE were consistent with the changes observed in β-carotene and lutein, respectively. These results suggested that the changes in genes expression related to carotenoid contents varied during strawberry development. In particular, LCYB and LCYE appeared to be the key regulatory genes for carotenoid accumulation in strawberries.