Identification of a WRKY transcriptional activator from Camellia sinensis that regulates methylated EGCG biosynthesis

Naturally occurring methylated catechins, especially methylated EGCG in tea leaves, are known to have many health benefits. Although the genes involved in methylated EGCG biosynthesis have been studied extensively, the transcription factors that control methylated EGCG biosynthesis are still poorly understood. In the present study, a WRKY domain-containing protein termed CsWRKY57like was identified, which belongs to group IIc of the WRKY family and contains one conserved WRKY motif. CsWRKY57like was found to localize in the nucleus and function as a transcriptional activator; its expression was positively correlated with methylated EGCG level. In addition, CsWRKY57like activated the transcription of three genes related to methylated EGCG biosynthesis (CCoAOMT, CsLAR, and CsDFR), specifically interacting with their promoters by binding to the cis-acting element (C/T)TGAC(T/C). Further assays revealed that CsWRKY57like physically interacts with CsVQ4 and participates in the metabolic regulation of O-methylated catechin biosynthesis. We conclude that CsWRKY57like may positively impact the biosynthesis of methylated EGCG in the tea plant. These results comprehensively enrich the regulatory network of WRKY TFs associated with methylated EGCG and provide a potential strategy for the breeding of specific tea plant cultivars with high methylated EGCG levels.