Three Camellia sinensis glutathione S-transferases are involved in the storage of anthocyanins, flavonols, and proanthocyanidins

Abstract

Main conclusion: Biochemical, transgenic, and genetic complementation data demonstrate that three glutathione S-transferases are involved in the storage of anthocyanins, flavonols, and proanthocyanins in plant cells. Abstract: Flavonoids are compounds in tea (Camellia sinensis) that confer the characteristic astringent taste of tea beverages; these compounds have numerous benefits for human health. In plant cells, flavonoids are synthesized in different locations within the cytoplasm and are then transported and finally stored in vacuoles. To date, the mechanism involved in the intracellular transport of flavonoids in tea has not been well elucidated. In this study, we report the functional characterization of three cDNAs encoding glutathione S-transferases (CsGSTs) of C. sinensis, namely, CsGSTa, CsGSTb, and CsGSTc. The expression profiles of CsGSTa and CsGSTb were positively correlated with the accumulation of flavonols, anthocyanins and proanthocyanins in tea tissues and cultivars. These three recombinant CsGSTs showed a high affinity for flavonols (kaempferol-3-O-glucoside and quercetin-3-O-glucoside) and anthocyanin (cyanidin-3-O-glucoside) in vitro but had no or weak affinity for epicatechin. In vivo, CsGSTa, CsGSTb and CsGSTc fully or partially restored the storage of anthocyanins and proanthocyanidins in transgenic tt19 mutants. Metabolic profiling revealed that the contents of anthocyanins, flavonols, and proanthocyanidins were increased in the transgenic petals of Nicotiana tabacum. Taken together, all data showed that CsGSTa, CsGSTb, and CsGSTc are associated with the storage of anthocyanins, flavonols, and proanthocyanins in C. sinensis cells.