Journal of Tea Science Research, 2024, Vol.14, No.6, 335-343 http://hortherbpublisher.com/index.php/jtsr 337 responsiveness, such as UV-B-induced expression. Functional confirmation has determined CsCHS, CsCHI, CsDFR, and CsANS functions in flavonoid biosynthesis (Wu et al., 2020). Figure 1 Flavonoid biosynthetic pathway and the expression level of DEGs. A: Flavonoid and anthocyanin biosynthetic pathway; B: Heat map of the expression levels of the flavonoid biosynthetic unigenes in the purple leaves and the green leaves (Adopted from Song et al., 2022) 3.3 Downstream modification-related genes: UGTs, LAR, ANR, etc. Downstream modifications diversify flavonoid structures. UDP-glycosyltransferases (UGTs) catalyze glycosylation, affecting solubility and taste. In tea, CsUGT75L12 and CsUGT79B28 are responsible for sequential glucosylation and rhamnosylation, producing bitter flavonoid 7-O-neohesperidoside (Dai et al., 2022). Leucoanthocyanidin reductase (LAR) and anthocyanidin reductase (ANR) are involved in the biosynthesis of catechins and proanthocyanidins, with their expression correlating with flavonoid accumulation in different tissues and cultivars (Wang et al., 2018).
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