Transcriptomic and metabolomic analyses reveal molecular and metabolic regulation of anthocyanin biosynthesis in three varieties of currant.

Anthocyanins are natural plant metabolites that are beneficial for human health. In order to study the fruit coloring mechanism mediated by anthocyanin biosynthesis in three currant varieties (white currant, red currant and black currant), we used a combination of transcriptomics and metabolomics analyses. Our comprehensive examination revealed that anthocyanins play a pivotal role in regulating the red and purple hues of black currant and red currant fruits. Specifically, Delphinidin-3-O-rutinoside, Pelargonidin-3-O-rutinoside, Cyanidin-3-O-rutinoside, Cyanidin-3,5-O-diglucoside, Cyanidin-3-O-rutinoside-5-O-glucoside and Petunidin-3-O-glucoside emerged as key anthocyanins in black currant, while Cyanidin-3-O-rutinoside (Keracyanin), Cyanidin-3-O-sambubioside[Cyanidin-3-O-(2″-O-xylosyl)glucoside], Cyanidin-3-O-glucoside (Kuromanin) and Cyanidin-3-O-(2″-O-xylosyl)rutinoside were identified as crucial anthocyanins in red currant. Transcriptomic data showed that the upregulation of dihydroflavonol 4-reductase (DFR), anthocyanin synthase (ANS), and UDP-glucose-flavonoid-3-O-glucosyltransferase (UFGT) genes significantly promoted the purple coloration of black currant fruit, while increased expression of Chalcone synthase (CHS) and flavonoid 3'-hydroxylase (F3'H) genes significantly intensified the red hue of red currant fruit. Furthermore, through weighted gene co-expression network analysis (WGCNA), we identified 11 transcription factors, including 3 bHLH, 2 MYB, 3 bZIP and 3 WRKY genes, which may serve as key regulators of anthocyanin biosynthesis. These findings provide a foundational understanding of the color dynamics in different currant varieties fruits throughout their developmental stages.