Identification and functional characterization of RsGST1, an anthocyanin-related glutathione S-transferase gene in radish

Anthocyanins not only affect the quality of horticultural crops but are also vital for human health. Glutathione transferase family members (GSTs) are enzymes that help to control plant development and stress responses, and are also involved in anthocyanin accumulation. In this study, we targeted a phi (F) class glutathione S-transferase gene RsGST1 (RSG01330.t1) as a crucial gene in the accumulation of anthocyanins in radish. RsGST1 expression was closely associated with anthocyanin content in the skin and flesh of taproot from different color type radish cultivars. Furthermore, RsGST1 was able to restore anthocyanin accumulation in Arabidopsis tt19 mutants, indicating that RsGST1 has a similar function as AtTT19, a gene responsible for the transport of anthocyanins in Arabidopsis. Transient overexpression of RsGST1 together with the key anthocyanin biosynthesis regulator RsMYB1a in radish leaves significantly enhanced anthocyanin biosynthesis compared with in plants that overexpressed RsMYB1a alone. Dual-luciferase and yeast one-hybrid assays revealed that RsMYB1a binds to promotor and activates the expression of RsGST1. Altogether, these results provide molecular evidence indicating that RsGST1 and RsMYB1a coordinate radish anthocyanin accumulation.