CsMYBPA1-CsGSTU18 interaction plays an important role in anthocyanin metabolism regulation in tea plant (Camellia sinensis)

Tea is one of the most widely consumed nonalcoholic beverages worldwide and one of the most important economic crops in the world. Tea varieties rich in anthocyanins have become one of the important breeding targets due to their important health care function. In our previous study, an important gene CsGSTU18 involved in anthocyanin transport was identified. However, the corresponding molecular mechanism is still unclear. Here, we used the promoter sequence of CsGSTU18 as bait in a yeast onehybrid (YIH) screen for promoter-binding proteins. We identified an R2R3-MYB transcription factor, CsMYBPA1, that was coordinately expressed with anthocyanin accumulation. Molecular evidence confirmed that CsMYBPA1 activated CsGSTU18 by binding to MBS cis-element, indicating that CsGSTU18 was a direct target gene of CsMYBPA1. In addition, over-expression of CsMYBPA1 elevated anthocyanin content in transgenic Arabidopsis. Transient silencing of CsMYBPA1 reduced anthocyanin accumulation and decreased the expression level of CsGSTU18 in tea plant leaves, whereas the transient over-expression of CsMYBPA1 showed the opposite change trend. Overall, these findings suggest that CsMYBPA1 directly actives CsGSTU18 to enhance anthocyanin accumulation. This study provides important gene resources and theoretical basis for the anthocyanin metabolism regulation and modification.