Functional Analysis Of BrMYB51-1,BrMYB51-2,BrMYB34-2in Chinese Cabbage(Brassica Rapa)

Plants of the family Brassicaceae are one of the oldest growing plants which has a long history. It has been grown all over the world and was used as bio fuel, cooking oil, bio-fumigants, human food and animal feed. The common cruciferous vegetables are the Chinese cabbage(Brassica. rapa ssp. Pekinensis), cabbage (Brassica oleracea var.capitata) and cauliflower(Brassica oleracea var.botrytis). Brassicaceae contains glucosinolates, which have beneficial to human health and can also reduce the risk of certain degenerative diseases.Glucosinolates are a class of plant secondary metabolites which derived from amino acids and contained nitrogen and sulfur. Currently, the biological role of glucosinolates in the plant (e.g, the interaction with the environment, human health) has been studied extensively. There are three types of glucosinolates in crops that named aliphatic glucosinolate, aromatic glucosinolates and indolic glucosinolates, respectively. At present, the biosynthetic pathways and the regulatory pathways of glucosinolates biosynthesis in Arabidopsis have been very clear. However, the synthetic regulation of glucosinolates in Chinese cabbage is not clear. Therefore, in this study, we investigated the role of BrMYB51-1, BrMYB51-2, BrMYB34-2in Chinese cabbage which involved in biosynthesis of indole glucosinolates by transferring to the Brassicaceae model plant Arabidopsis.The amino acid sequence coded by the BrMYB51-1, BrMYB51-2, BrMYB34-2genes showed high homology with Arabidopsis homologous. After transferring BrMYB51-1, BrMYB51-2, BrMYB34-2genes into Arabidopsis, we found that the content of indolic glucosinolates increased significantly. The expression of the indolic glucosinolate biosynthesis genes also increased significantly. The genes ASA1and TSB1which involved in tryptophan synthesis increased, too. The content of aliphatic glucosinolate in each transgenic plants decreased slightly, at the same time, the expression of two genes related to aliphatic glucosinolates synthesis, MAM1and CYP81F2, decreased as well, while CYP83A1increased slightly. These results suggest that BrMYB51-1, BrMYB51-2, BrMYB34-2genes regulate the synthesis of indolic glucosinolates in Arabidopsis by regulating the expression of genes involved in synthesis of indolic glucosinolates and tryptophan. While the increases of the content of indolic glucosinolates accompanied with a slight decrease in the content of aliphatic glucosinolates. In addition, we treated BrMYB34-2transgenic plants with5MT. The results showed that the growth of wild-type plants roots was inhibited by5MT. On the contrary, the growth of the transgenic plants roots was insensitive to5MT. These results indicated that BrMYB34-2gene can indirectly affect the synthesis of auxin.