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Galloylated catechins in tea leaves, primarily epigallocatechin-3-gallate (EGCG) and epicatechin gallate (ECG), possess prominent biological activities. It is well established that EGCG and ECG are abundantly present in tender leaves but are less prevalent in mature leaves. However, the fundamental regulatory mechanisms underlying this distribution remain unknown. In this study, we integrated transcriptome data and catechin component levels in tea leaves from six leaf positions using weighted gene co-expression network analysis. This analysis revealed a positive correlation between variations in CsWRKY12 expression and EGCG and ECG levels. Further investigation using yeast one-hybrid and dual-luciferase assays, as well as electrophoretic mobility shift assay, demonstrated that CsWRKY12 activated the transcription of CsSCPL4 and CsSCPL5, which encode enzymes responsible for galloylated catechins biosynthesis, by directly binding to W-box elements in their promoters. Overexpression of CsWRKY12 in tea leaves promoted the expression of CsSCPL4 and CsSCPL5, leading to an increase in EGCG and ECG content. Moreover, we found that a VQ motif-containing protein, CsVQ4L, interacted with CsWRKY12 and facilitated its transcriptional function by regulating the expression of CsSCPL4 and CsSCPL5. Collectively, our findings suggest that the interaction between CsWRKY12 and CsVQ4L contributes to the accumulation of galloylated catechins in tender leaves of tea plants.
Zhang et al. (Thu,) studied this question.