Identification and Functional Characterization of the DcF3’H Promoter from Dracaena cambodiana

Dragon’s blood is a traditional medicine that is produced mainly from Dracaenas plants and is widely used in the world. The main chemical compounds in dragon’s blood are flavonoids. Flavonoid 3′-hydroxylase (F3’H) is an enzyme that synthesizes 3′-hydroxylated flavonoids. DcF3’H plays a vital role in determining the flavonoid content during the production of dragon′s blood; however, the regulation of DcF3’H expression in Dracaenas plants is poorly understood. In this study, a 759-bp promoter region of DcF3’H was isolated from Dracaena cambodiana. The promoter sequence contained cis-acting elements related to various environmental stresses and hormones responses. Dual-luciferase assays showed that the DcF3’H promoter was up-regulated by 6-benzyl aminopurine (6-BA) and down-regulated by methyl jasmonate (MeJA), and these results were consistent with transcription levels of DcF3’H in stems that were verified by quantitative real-time PCR (qPCR). DcHLH1, a bHLH transcription factor identified in yeast one-hybrid screening, was capable of both binding to the promoter and activating the transcription of DcF3’H by ~10-fold. The results provide new insights into the regulatory mechanisms of DcF3’H in Dracaena cambodiana.