The CsHSFA‐CsJAZ6 module‐mediated high temperature regulates flavonoid metabolism in Camellia sinensis

Abstract

High temperatures (HTs) seriously affect the yield and quality of tea. Catechins, derived from the flavonoid pathway, are characteristic compounds that contribute to the flavour of tea leaves. In this study, we first showed that the flavonoid content of tea leaves was significantly reduced under HT conditions via metabolic profiles; and then demonstrated that two transcription factors, CsHSFA1b and CsHSFA2 were activated by HT and negatively regulate flavonoid biosynthesis during HT treatment. Jasmonate (JA), a defensive hormone, plays a key role in plant adaption to environmental stress. However, little has been reported on its involvement in HT response in tea. Herein, we demonstrated that CsHSFA1b and CsHSFA2 activate CsJAZ6 expression through directly binding to heat shock elements in its promoter, and thereby repress the JA pathway. Most secondary metabolites are regulated by JA, including catechin in tea. Our study reported that CsJAZ6 directly interacts with CsEGL3 and CsTTG1 and thereby reduces catechin accumulation. From this, we proposed a CsHSFA-CsJAZ6-mediated HT regulation model of catechin biosynthesis. We also determined that negative regulation of the JA pathway by CsHSFAs and its homologues is conserved in Arabidopsis. These findings broaden the applicability of the regulation of JAZ by HSF transcription factors and further suggest the JA pathway as a valuable candidate for HT-resistant breeding and cultivation.

Recent Progress Regarding Jasmonates in Tea Plants: Biosynthesis, Signaling, and Function in Stress Responses

“…CsJAZ6 could represses catechin biosynthesis by directly interacting with CsEGL3 and CsTTG1, and the silencing of CsJAZ6 in tea leaves causes the upregulation of almost all genes involved in flavonoid biosynthesis and a decrease in catechin content. These findings suggest that JA serves as a central regulator mediating the regulatory effect of high temperature on the flavonoid synthesis pathway [76].…”

Jasmonate enhances cold acclimation in jojoba by promoting flavonol synthesis

“…In Arabidopsis , JAZ proteins weakened the transcriptional activity of the MBW complex by interacting with bHLH and MYB TFs, repressing JA-induced anthocyanin accumulation [ 33 , 69 ]. In tea plant, CsJAZ6 interacted with the MBW components CsEGL3 and CsTTG1, and the induction of JA weakened the inhibitory effect of CsJAZ6 on CsEGL3 and CsTTG1, leading to an increase in the biosynthesis of catechins under heat stress [ 70 ]. In our study, we found 13 ScJAZ genes in the jojoba genome, five of which were selected for analysis of their interactions with bHLH TF—ScTT8.…”

Application of Multi-Perspectives in Tea Breeding and the Main Directions

“…Research on tea plants has often focused attention towards the growing period, while foliar nitrogen application during the winter dormancy of tea plants improves the nitrogen content of mature leaves with the quality and yield of spring tea, while fertilizer dosage can be reduced [ 177 ]. The interaction between hormones and metabolites within the tea plants also influenced quality, as the expression of CsJAZ6 in tea plants inhibited the JA pathway, which regulated most secondary metabolites, notably catechins, and the interaction between CsJAZ6 and catechin biosynthesis regulators negatively regulated catechin accumulation [ 178 ]. Apart from endogenous hormones, endogenous hormone signaling factors could also mediate the synthetic pathways of caffeine, EGCG and theanine to respond to temperature and improve the quality of tea leaves [ 179 ].…”