CsbZIP1-CsMYB12 mediates the production of bitter-tasting flavonols in tea plants (Camellia sinensis) through a coordinated activator–repressor network

Abstract

Under high light conditions or UV radiation, tea plant leaves produce more flavonols, which contribute to the bitter taste of tea; however, neither the flavonol biosynthesis pathways nor the regulation of their production are well understood. Intriguingly, tea leaf flavonols are enhanced by UV-B but reduced by shading treatment. CsFLS, CsUGT78A14, CsMYB12, and CsbZIP1 were upregulated by UV-B radiation and downregulated by shading. CsMYB12 and CsbZIP1 bound to the promoters of CsFLS and CsUGT78A14, respectively, and activated their expression individually. CsbZIP1 positively regulated CsMYB12 and interacted with CsMYB12, which specifically activated flavonol biosynthesis. Meanwhile, CsPIF3 and two MYB repressor genes, CsMYB4 and CsMYB7, displayed expression patterns opposite to that of CsMYB12. CsMYB4 and CsMYB7 bound to CsFLS and CsUGT78A14 and repressed their CsMYB12-activated expression. While CsbZIP1 and CsMYB12 regulated neither CsMYB4 nor CsMYB7, CsMYB12 interacted with CsbZIP1, CsMYB4, and CsMYB7, but CsbZIP1 did not physically interact with CsMYB4 or CsMYB7. Finally, CsPIF3 bound to and activated CsMYB7 under shading to repress flavonol biosynthesis. These combined results suggest that UV activation and shading repression of flavonol biosynthesis in tea leaves are coordinated through a complex network involving CsbZIP1 and CsPIF3 as positive MYB activators and negative MYB repressors, respectively. The study thus provides insight into the regulatory mechanism underlying the production of bitter-tasting flavonols in tea plants.

Screening the Key Region of Sunlight Regulating the Flavonoid Profiles of Young Shoots in Tea Plants (Camellia sinensis L.) Based on a Field Experiment

“…Different tea cultivars and different growing stages of tea plants, such as plant age, cultivation method (pot culture or field culture), and leaf maturity, are non-negligible factors affecting the responses of tea plants to altered light conditions. The accumulation of flavonoids in tea leaves is closely related to leaf maturity [ 39 ].…”

Mechanism Underlying the Shading-Induced Chlorophyll Accumulation in Tea Leaves

“…Considerable practical experience and scientific research have confirmed that shading can increase the overall quality of tea plants, both internally and externally ( Chen et al, 2021 ). Moreover, shading enhances the taste and aroma of tea by affecting the synthesis of free amino acids, flavonoids, and aromatic compounds, while also affecting the appearance of tea by influencing the abundance of chlorophyll and other plant pigments as well as structural components (e.g., lignin; Ku et al, 2010 ; Liu et al, 2017 ; Zeng et al, 2020 ; Chen et al, 2021 ; Teng et al, 2021 ; Zhao et al, 2021 ). During tea plant cultivation, providing plants with sufficient shade can significantly improve tea color quality.…”

Integrative Analysis of Long- and Short-Read Transcriptomes Identify the Regulation of Terpenoids Biosynthesis Under Shading Cultivation in Oenanthe javanica

“…Altered volatile substance content was related to the flavor improvement of water dropwort. Similarly, the high levels of flavonols resulted in the bitter flavor of tea, and the flavonols contents of tea were increased under UV-B and decreased after shading treatments ( Zhao et al, 2021 ).…”