Association analysis of BSA-Seq, BSR-Seq, and RNA-Seq reveals key genes involved in purple leaf formation in a tea population (Camellia sinensis)

Abstract Purple tea, rich in anthocyanins, has a variety of health benefits and is attracting global interest. However, the regulation mechanism of anthocyanin in purple tea populations has not been extensively studied. In this experiment, RNA-seq, BSA-seq, and BSR-seq were performed using 30 individuals with extreme colors (dark-purple and green) in an F1 population of ‘Zijuan’ and ‘Jinxuan’. The results show that 459 genes were differentially expressed in purple and green leaves, among which genes involved in the anthocyanin synthesis and transport pathway, such as CHS, F3H, ANS, MYB75, GST, MATE, and ABCC, were highly expressed in purple leaves. Moreover, there were multiple SNP/InDel variation sites on chromosomes 2 and 14 of the tea plant, as identified by BSA-seq. The integrated analysis identified two highly expressed genes (CsANS and CsMYB75) with SNP/InDel site variations in the purple tea plants. By silencing leaves, we proved that CsMYB75 could positively regulate anthocyanin accumulation and expression of related structural genes in tea plants. A 181-bp InDel in the CsMYB75 promoter was also found to be co-segregating with leaf color. The results of this study provide a theoretical reference for the molecular mechanism of anthocyanin accumulation in purple tea plants and contribute to the creation of new tea cultivars with high anthocyanin content.