Analysis of Anthocyanin Accumulation and Related Gene Expression During Fig Fruit Development

Fig ( Ficus carica L.) is a deciduous tree of the Moraceae family. There are many fig cultivars with a wide variety of skin and flesh colors. Fig anthocyanin content and composition determine the color, quality, nutritional value, and commercial value of figs, and the related enzymes and genes affecting anthocyanin synthesis determine the anthocyanin content and composition. Two fig cultivars, “Japanese Purple Fruit” and “Masui Dauphine,” were used as experimental materials to research the changes in composition and content of anthocyanins. Anthocyanin accumulation and the key enzymes that affect anthocyanin synthesis were analyzed, and the molecular mechanism of anthocyanin accumulation in fig fruits was clarified. The results showed that both “Masui Dauphine” and “Japanese Purple Fruit” fruits contained three types of anthocyanins. Centaureidin-3,5-diglucoside was only present in the ripe fruit peel. The centaureidin-3-glucoside and centaureidin-3-rutinoside contents tended to increase in the peel and decrease in the pulp. Analysis of key enzyme activities for anthocyanin synthesis showed that PAL, CHI, DFR, and UFGT enzyme activities were higher in the peel than in the flesh of both varieties. PAL and UFGT were the key enzymes in the peel flesh of “Masui Dauphine.” PAL and UFGT were the key enzymes in the pulp of “Masui Dauphine.” The transcript levels of the FcPAL, FcCHS1, FcCHS2, FcCHI, FcF3H, FcDFR, FcANS, FcUFGT, FcMYB113, and FcWD40 genes were higher in the pericarp than the pulp. Analysis of genes related to anthocyanin synthesis showed that the transcript levels of the FcPAL, FcCHS1, FcCHS2, FcCHI, FcF3H, FcDFR, FcANS, FcUFGT, FcMYB113, and FcWD40 genes were higher in the pericarp than the pulp. During the fruit ripening period, FcMYB113 had the highest transcript level in “Japanese Purple Fruit” pericarp, which was consistent with the trend of FcCHS1, FcCHS2, FcF3H, FcDFR, FcANS, and FcUFGT expression. It is suggested that FcMYB113 is a key gene that promotes the synthesis of anthocyanin. The correlation analysis between transcript levels and anthocyanin content showed that FcPAL, FcDFR, FcANS, and FcMYB113 were key genes in the peel, and FcPAL was a key gene in the pulp of “Masui Dauphine.” fcPAL and FcUFGT were key genes in the flesh, and FcANS was the key gene in the peel of “Japanese Purple Fruit.”