MHLC, a novel tea germplasm with cyanidin-dominant anthocyanin profiling and low-catechin trait driven by flavonoid...

The tea plant (Camellia sinensis) is a vital economic crop whose quality and health benefits are primarily determined by flavonoid compounds, particularly catechins and anthocyanins. However, the dynamic regulatory mechanisms of governing flavonoid accumulation remain unclear. A novel tea germplasm, MHLC, with a reddish-purple phenotype was identified in this study. Low catechin and high anthocyanin accumulation in MHLC were revealed through integrated targeted metabolomics and multi-seasonal dynamic analyses. Specifically, catechin content below 40 mg/g was observed in MHLC, along with a 3 to 6-fold higher proportion of dihydroxylated catechins and a remarkable 14-fold increase in the cyanidin/delphinidin ratio compared to conventional varieties, indicating a pronounced flux diversion toward the 3'-hydroxylated B-ring pathway during flavonoid biosynthesis. Transcriptome and gene expression analysis identified key genes associated with the metabolic phenotype in MHLC, including F3'5'H and PAL (catechin biosynthesis), ANS and GST (anthocyanin synthesis/transport), along with eight transcription factors regulating catechin metabolism. Further analysis showed that a 14-bp deletion and other variations within the F3'5'H promoter may be strongly correlated with its low expression levels and low trihydroxylated catechin content in MHLC. Concurrently, upregulated expression of GST promoted anthocyanin accumulation, while downregulated F3'5'H expression contributed to an increased cyanidin/delphinidin ratio. Our results preliminarily elucidate the molecular mechanisms underlying MHLC's low catechin content, high anthocyanin accumulation, and reddish-purple phenotype, enhancing our theoretical understanding of flavonoid metabolic partitioning in tea plants and establishing a fundamental basis for breeding tea cultivars with distinctive leaf coloration and desirable quality attributes.