Flavan-3-ol Galloylation-Related Functional Gene Cluster and the Functional Diversification of SCPL Paralogs in Camellia sp

The high accumulation of galloylated flavan-3-ols in Camellia sp. is a noteworthy phenomenon. We identified a flavan-3-ol galloylation-related functional gene cluster in tannin-rich plant Camellia sp., which included UGT84A22 and SCPL-AT gene clusters. We investigated the possible correlation between the accumulation of metabolites and the expression of SCPL-ATs and UGT84A22. The results revealed that C. sinensis, C. ptilophylla, and C. oleifera accumulated galloylated cis-flavan-3-ols (EGCG), galloylated trans-flavan-3-ols (GCG), and hydrolyzed tannins, respectively; however, C. nitidissima did not accumulate any galloylated compounds. C. nitidissima exhibited no expression of SCPL-AT or UGT84A22, whereas the other three species of Camellia exhibited various expression patterns. This indicated that the functions of the paralogs of SCPL-AT vary. Enzymatic analysis revealed that SCPL5 was neofunctionalized as a noncatalytic chaperone paralog, a type of chaerone-like protein, associating with flavan-3-ol galloylation; moreover, CsSCPL4 was subfunctionalized in association with the galloylation of cis- and trans-flavan-3-ols. In C. nitidissima, an SCPL4 homolog was noted with mutations in two cysteine residues forming a disulfide bond, which suggested that this homolog was defunctionalized. The findings of this study improve our understanding of the functional diversification of SCPL paralogs in Camellia sp.