Integrated Metabolomics, Transcriptomics, and Functional Validation Suggest Oxidoreductase-Associated Strictinin Accumulation in Assam tea Germplasm
Strictinin, a bioactive hydrolyzable tannin in tea, varies widely among germplasm resources, but the basis of this variation remains unclear. Here, a rapid LC-MS/MS method was established and applied to 157 Assam tea accessions, revealing extensive natural variation in strictinin content. Comparative metabolomics of contrasting accessions 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 co-expression 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 Assam tea germplasm. These findings provide analytical and molecular resources for breeding tea germplasm with elevated strictinin content.