Differential Expression of Amaranth AtrDODA Gene Family Members in Betalain Synthesis and Functional Analysis of AtrDODA1-1 Promoter

Betalains differ from anthocyanins, and they cannot coexist in the same plant under natural conditions. The L-DOPA 4,5-dioxygenase encoded by theDODAgene is a key step in the pathway of betalain biosynthesis in Caryophyllales plants. Amaranth is an important resource for the study and extraction of betalains. In order to clarify the function ofAtrDODAfamily genes in betalain biosynthesis, we screened out threeAtrDODAfamily gene members associated with betalains based on a genome database and RNA-seq databases ofAmaranthus tricolor. Their characterization and expression pattern were further analyzed. The result of subcellular localization showed that all three AtrDODA members were located in the nucleus. Betacyanin and betaxanthin were promoted by paclobutrazol treatment in the leaves and stems of ‘Suxian No.1’ (red), while they were inhibited by gibberellin and darkness, which were consistent with the gene expression pattern ofAtrDODAs. After heterologous transformation of theAtrDODA1-1promoter into tobacco with GUS staining analysis, the promoter activity ofAtrDODA1-1of ‘Suxian No.1’ (red) amaranth was significantly higher than that of ‘Suxian No.2’ (green) amaranth. Furthermore, we analyzed the promoter activity ofAtrDODA1-1by GUS staining and qRT-PCR after sprayed exogenous MeJA and GA3on theAtrDODA1-1promoter transformed tobacco plants. The results showed thatAtrDODA1-1responded to plant hormones. This study could lay a foundation for revealing the biological functions of the amaranthDODAgene family, and provide new clues for the molecular mechanism of betalain synthesis.