The identification of a MYB transcription factor controlling anthocyanin biosynthesis regulation in Chrysanthemum flowers

Metabolism of anthocyanin in Chrysanthemum (Chrysanthemum mortfolium Ramat.) is catalyzed by several biosynthetic enzymes, however, the underlying transcriptional regulatory mechanisms remain unknown. In the present research, four MYB transcription factors, CmMYB3-6, were isolated from 'Amadea' Chrysanthemum, by RNA-seq and RACE. Among the four CmMYBs, CmMYB3 and CmMYB6 were expressed concurrently with the expression of biosynthetic genes and accumulation of anthocyanin during flower development. In order to study the transcription regulatory role of CmMYB3 and CmMYB6 in anthocyanin biosynthesis, the promoter region of CmDFR was isolated. Dual luciferase assay showed that CmMYB6 significantly activated the CmDFR promoter more than 8-fold. Furthermore, the combination of CmMYB6 and MrbHLH1 (from Myrica rubra involved in anthocyanin biosynthesis) resulted in approximately 34-fold induction of the CmDFR promoter. Using a transient over-expression system in Nicotiana tabacum leaves, CmMYB6 and MrbHLH1 co-expression lead to transient anthocyanin accumulation. Thus, CmMYB6 is proposed as a novel transcription factor in Chrysanthemum anthocyanin biosynthesis. (C) 2015 Elsevier B.V. All rights reserved.