Fig. 8: A proposed model for light- and shading-mediated flavonol biosynthesis in tea plants. | Horticulture Research

Fig. 8: A proposed model for light- and shading-mediated flavonol biosynthesis in tea plants.

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

Fig. 8: A proposed model for light- and shading-mediated flavonol biosynthesis in tea plants.

Under high light conditions, UVR8 activates CsbZIP1, which enhances CsMYB12 transcription and activity. Both CsbZIP1 and CsYMB12 synergistically activate CsFLS and CsUFGT expression and promote bitter-tasting flavonol biosynthesis and accumulation, thereby decreasing the processing suitability of tea plant leaves. Meanwhile, CsPIF3, CsMYB7, and CsMYB4 are expressed at low levels and inactivated. However, under shading conditions, CsbZIP1 is repressed, while CsPIF3, CsMYB7, and CsMYB4 are activated. The repression of CsPIF3 by PhyA and PhyB is relieved, allowing CsPIF3 to interact with and repress CsbZIP1 activity. Shading upregulates the expression of the repressor genes CsMYB7 and CsMYB4. CsMYB7 and CsMYB4 can interact with CsMYB12 and thus interfere with CsMYB12 activation of flavonol synthesis. CsMYB7 and 4 also directly repressed CsFLS expression and, as a consequence, flavonol biosynthesis under shading conditions

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