Integrated Metabolomics, Transcriptomics, and Functional Validation Suggest Oxidoreductase-Associated Strictinin Accumulation in Individual Large Tea Trees from Yunnan.

Strictinin, a bioactive hydrolyzable tannin in tea, varies widely among individual tea trees, but the basis of this variation remains unclear. Here, a rapid LC-MS/MS method was established and applied to 157 individual large tea trees from Yunnan, revealing extensive natural variation in strictinin content. Comparative metabolomics of contrasting individuals showed that high ST accumulation was associated with altered partitioning of hydrolyzable tannin intermediates rather than increased gallic acid abundance alone, together with broader shifts in phenylpropanoid-related metabolism. Integration of metabolomics, transcriptomics, and weighted gene coexpression network analysis identified strictinin-associated modules and four oxidoreductase candidates, including CsLAC15, CsCYP81C13, CsCYP75B2, and CsCYP75A1. Transient antisense oligonucleotide silencing reduced strictinin accumulation and, for CsCYP81C13, increased gallic acid abundance. These results support an association between oxidoreductase-related metabolism and differential strictinin accumulation in individual large tea trees. These findings provide analytical and molecular resources for breeding tea varieties with elevated strictinin content.