Duplicated CHSs (chalcone synthase) genes modulate flavonoid production in tea plants in response to light stress1

In tea plants, the abundant flavonoid compounds are responsible for the health benefits for the human body and define the astringent flavor profile. While the downstream mechanisms of flavonoid biosynthesis have been extensively studied, the role of chalcone synthase (CHS) in this secondary metabolic process within tea plants remains less clear. In our current study, we compared the evolutionary profile of the flavonoid metabolism pathway and discovered that gene duplication of CHS occurred in tea plants. We identified three CsCHS genes, along with a CsCHS-like gene, as potential candidates for further functional investigation. Unlike the CsCHS-like gene, the CsCHS genes effectively restored flavonoid production in Arabidopsis chs-mutants. Additionally, CsCHS transgenic tobacco plants exhibited higher flavonoid compound accumulation compared to their wild-type counterparts. Most notably, our examination of promoter and gene expression levels for the selected CHS genes revealed distinct responses to UV-B stress in tea plants. Our findings suggest that environmental factors such as UV-B exposure could be key drivers behind the gene duplication events in CHS.