A functional 23-bp InDel in CsFGT promoter determines the accumulation potential of quercetin tri-glycoside in various varieties of Camellia sinensis

Differential accumulation of quercetin 3-O-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosy-(1 → 6)-β-D-glucopyranoside (Q-g-r-g) in various varieties of Camellia sinensis is mainly depended on expression of the relevant glycosyltransferase CsFGT, but the insight molecular regulation mechanism is still unclear. In this study, the promoter sequences of CsFGT were achieved from representative cultivars belonging to sinensis and assamica varieties through genomic walking. The upstream transcription factor CsMYB98-like was screened out through Y1H assay and verified through promoter truncation. EMSA revealed the CsMYB98-like specifically bound the cis-element ‘taacaaa’ located in a 23-bp InDel locus of the CsFGT promoter. Y2H, LUC and Pull-Down assays showed CsMYB98-like could interact with CsWRKY20 protein. AsODN treatment confirmed that expression of CsFGT and content of Q-g-r-g were efficiently modulated by CsMYB98-like and CsWRKY20. The 23-bp InDel locus harboring CsMYB98-like binding site in the promoter was verified to determine the CsFGT expression and Q-g-r-g content in tender leaves of different germplasm resources, indicating evolutionary divergence in promoter architecture underlies metabolic differences between various varieties. These findings can be used for quick identification of the Q-g-r-g profiles during germplasm resource selection.