Expression of Anthocyanin Biosynthetic Genes during Fruit Development in ‘Fengxiang’ Strawberry

Anthocyanins are the main pigments in flowers and fruits. In most cases, anthocyanin accumulation in fruit is highly controlled by the developmental level. In this study, the cDNA fragments of three genes, chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR), and anthocyanidin synthase (ANS), which are involved in the flavonoid pathway, were isolated from total RNA of strawberry ripe fruit by using polymerase chain reaction technique and labeled as probes to determine the expression of anthocyanin biosynthetic genes. Northern analysis showed that a correlation between anthocyanin accumulation and expression of the flavonoid pathway genes during the ripening of strawberry fruits. At the early stages of fruit development, the mRNA levels encoding CHS, DFR, ANS were high probably responsible for the accumulation of condensed tannins, but the levels decreased dramatically when fruits turned white from green. During the stage of pigment accumulation, their mRNA levels increased strongly to be involved anthocyanin biosynthesis. Difference of CHS in mRNA abundance was correlated with differential accumulation of anthocyanins throughout the process of fruit development. Therefore, CHS could be a key structure gene involved in anthocyanin synthesis. Furthermore, the co-ordination of expression of anthocyanin biosynthetic genes implied a common regulatory mechanism controlling the expression of structural genes in the flavonoid pathway.