[Cloning and expression of dfr in Ribes L. during fruit maturation]

Little is known about the molecular mechanism of currant anthocyanin synthesis. We investigated the effect of dfr, a key gene for anthocyanin synthesis in currant, on anthocyanins of different color currant. Black currant (Ribes nigrum L.), red currant (Ribes rubrum L.) and white currant (Ribes albrum L.) were used as test materials to determine the anthocyanin content at different stages of fruit development. Three full-length cDNA sequences of dfr gene were cloned by RACE (Rapid amplification of cDNA ends), and named as Rndfr, Rrdfr and Radfr. Phylogenetic analysis shows that Rndfr, Rrdfr and Radfr had high homology in evolution. The determination of anthocyanin content in different stages of fruit development shows that the content of anthocyanin in black currant and red currant was higher and gradually increased with the ripening of the fruit. While the content of anthocyanin in white currant was extremely low, and almost no anthocyanin was detected. Quantitative RT-PCR analysis shows that the expression level of dfr in black currant was higher than red currant and white currant in each period of fruit development. As the diameter of the fruit increased and the color of the peel deepened, the expression level of dfr in the black currant showed an increasing trend. In the red currant, the expression level gradually increased until the period of 75% fruit color, then the Rrdfr decreased rapidly. In white currant, the overall trend showed a downward trend, and its expression level was the lowest. All the results suggest that dfr gene plays a role in the process of fruit color.