Metabolic Engineering of Glycyrrhizin Pathway by Over-Expression of Beta-amyrin 11-Oxidase in Transgenic Roots of Glycyrrhiza glabra

Abstract

Glycyrrhiza glabra is one of the most important and well-known medicinal plants which produces various triterpene saponins such as glycyrrhizin. Beta-amyrin 11-oxidase (CYP88D6) plays a key role in engineering pathway of glycyrrhizin production and converts an intermediated beta-amyrin compound to glycyrrhizin. In this study, pBI121GUS-9:CYP88D6 construct was transferred to G. glabra using Agrobacterium rhizogene ATCC 15834. The quantitation of transgene was measured in putative transgenic hairy roots using qRT-PCR. The amount of glycyrrhizin production was measured by HPLC in transgenic hairy root lines. Gene expression analysis demonstrated that CYP88D6 was over-expressed only in one of transgenic hairy root lines and was reduced in two others. Beta-amyrin 24-hydroxylase (CYP93E6) was significantly expressed in one of the control hairy root lines. The amount of glycyrrhizin metabolite in over-expressed line was more than or similar to that of control hairy root lines. According to the obtained results, it would be recommended that multi-genes of glycyrrhizin biosynthetic pathway be transferred simultaneously to the hairy root in order to increase glycyrrhizin content.