Anthocyanin Accumulation And Molecular Mechanism For Brassinolide-induced In Arabidopsis

In this paper, Wild types Col-0,Ws-2and dwf4-102, bril-4mutants were used to study the mechanism by which the cross-talks between brassinosteroid (BR) and jasmonate (JA) or cytokinin (CTK), sucrose regulate anthocyanin accumulation from the biosynthesis and signal transduction of brassinosteroids in Arabidopsis seedlings. The following is the main results:1. Brassinosteroid regulate JA-induced anthocyanin accumulationIn this study it was shown that the JA-induced anthocyanin accumulation was reduced in the BR mutants or wild type treated with brassinazole, an inhibitor of BR biosynthesis, whereas was promoted by an application of exogenous BR. It was also shown that the’late’anthocyanin biosynthesis genes including DFR, LDOX, and UF3GT, were induced slightly by jasmonate in the BR mutants relative to wild type. Moreover, the expression level of JA-induced MYB transcription factors such as PAP1, PAP2, and bHLH transcription factor GL3, was lower in the BR mutants than that in wild type. These results suggested that BR affects the JA-induced anthocyanin accumulation by regulating the’late’anthocyanin biosynthesis genes and this regulation might be mediated by MYB/bHLH transcription factors.2. Brassinosteroid regulate CTK-induced anthocyanin accumulationIn this study it was shown that the CTK-induced anthocyanin accumulation was reduced in the BR mutants, whereas was induced in wild type by treatment with exogenous BR. It was also shown that the expression of the’late’anthocyanin biosynthesis genes was reduced by cytokinins in the BR mutants, yet was increased in wild type. Furthermore, the expression level of CTK-induced bHLH transcription factors including GL3, EGL3, was lower in the BR mutants than that in wild type. These results indicated that BR affects the CTK-induced anthocyanin accumulation by regulating the ’late’ anthocyanin biosynthesis genes and this regulation might be mediated by bHLH ranscription factors. 3. Brassinosteroid affect sucrose-induced anthocyanin accumulationIn this study it was shown that the sucrose-induced anthocyanin accumulation was reduced in the BR mutants, but was enhanced in wild type by an application of exogenous BR. It was also shown that the’late’ anthocyanin biosynthesis genes including DFR, LDOX, and UF3GT, were induced slightly by sucrose in the BR mutants relative to wild type. Furthermore, the expression level of sucrose-induced MYB transcription factors such as PAP1, PAP2, was lower in the BR-insensitive mutant bril-4than that in wild type. However, the expression level of bHLH transcription factors such as GL3, EGL3, and WD-repeat protein TTG1remain unchange in both the bril-4mutant and wild type. Therefore, these results suggested that BR affects the sucrose-induced anthocyanin accumulation by regulating the’late’ anthocyanin biosynthesis genes and this regulation might be mediated by MYB transcription factors.