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

• Published in: Horticulture research Vol. 8; no. 1
• Main Authors: Zhao, Xuecheng, Zeng, Xiangsheng, Lin, Ning, Yu, Shuwei, Fernie, Alisdair R., Zhao, Jian
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-05-2021; Oxford University Press
• Subjects: 631/449/2667; 631/449/2686; Agriculture; Biomedical and Life Sciences; Biosynthesis; Bitter taste; Ecology; Flavonols; Leaves; Life Sciences; Plant Breeding/Biotechnology; Plant Genetics and Genomics; Plant Sciences; Regulatory mechanisms (biology); Repressors; Shading; Tea; Ultraviolet radiation
• ISSN: 2662-6810; 2052-7276
• DOI: 10.1038/s41438-021-00545-8

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.