The transcription factor CsS40 negatively regulates expression and caffeine biosynthesis in connection to leaf senescence in .

Caffeine is considered as one of the most important bioactive components in the popular plant beverages tea, cacao, and coffee, but as a wide-spread plant secondary metabolite its biosynthetic regulation at transcription level remains largely unclear. Here, we report a novel transcription factor () as a caffeine biosynthesis regulator, which was discovered during screening a yeast expression library constructed from tea leaf cDNAs for activation of tea caffeine synthase () promoter. Besides multiple hits of the non-self-activation CsS40 clones that bound to and activated promoter in yeast-one-hybrid assays, a split-luciferase complementation assay demonstrated that acts as a transcription factor to activate the gene and EMSA assay also demonstrated that CsS40 bound to the gene promoter.