Isolation and molecular characterisation of flavonoid 3'-hydroxylase and flavonoid 3', 5'-hydroxylase genes from a traditional Chinese medicinal plant, Epimedium sagittatum.

The epimedii herb, a traditional Chinese medicinal plant, has significant pharmacological effects on human health. The bioactive components in the herb (Epimedium sagittatum (Sieb. et Zucc.) Maxim) are mainly prenylated flavonol glycosides, which are end-products of the flavonoid biosynthetic pathway. This has not been clearly elucidated until recently. The genes encoding flavonoid 3'-hydroxylase (F3'H) and flavonoid 3', 5'-hydroxylase (F3'5'H) involved in the flavonoid biosynthetic pathway, designated as EsF3'H and EsF3'5'H, were isolated from E. sagittatum using a homology-based cloning method and deposited in the GenBank databases (GenBank ID: HM011054 and HM011055), respectively. EsF3'H and EsF3'5'H proteins shared high homology with other plant-specific flavonoid hydroxylases and were clustered into the CYP75B and CYP75A group, respectively. In addition, four conserved cytochrome P450-featured motifs were found in the amino acid sequences of both genes. Transcription levels of both genes were detected in all tissues tested and were high in most of the pigmented tissues. Moreover, the expression levels of both EsF3'H and EsF3'5'H correlated positively with the anthocyanin accumulation pattern in leaves from E. sagittatum. The cloning and molecular characterisation of EsF3'H and EsF3'5'H genes will accelerate progress in the study of the flavonoid biosynthetic pathway to elucidate the molecular mechanisms of the biosynthesis of the bioactive components in E. sagittatum.