CsWRKY53 and CsWRKY40 synergistically regulate L-theanine hydrolysis by abscisic acid signaling pathway during tea withering.

Abstract

L-Theanine hydrolysis in tea leaves not only reduces tea product quality but also decreases their health benefits. Postharvest dehydration-induced abscisic acid (ABA) contributes to the L-theanine hydrolysis, but the specific mechanism is unexplored. Based on transcriptome analysis and gene silencing experiments, CsNCED3a was shown to be a key gene for ABA synthesis in harvested tea leaves, and CsABF7 up-regulated the expression of CsWRKY40, a transcription factor (TF) that directly regulates a L-theanine hydrolysis gene, resulting in the loss of L-theanine. CsWRKY53 and CsWRKY40 activated CsNCED3a expression. The CsWRKY53-CsWRKY40 complex exhibited a stronger regulatory effect than individual TFs. These findings reveal an ABA-mediated regulatory pathway for L-theanine hydrolysis, and highlight the pivotal role of ABA in postharvest metabolism of critical flavor-contributing metabolites in tea leaves.