Cloning and Characterization of a cDNA Encoding β-Amyrin Synthase Involved in Glycyrrhizin and Soyasaponin Biosyntheses in Licorice

An oxidosqualene cyclase cDNA, termed GgbAS1, was isolated from cultured cells of licorice (Glycyrrhiza glabra) by heterologous hybridization with cDNA of Arabidopsis thaliana LUP1 lupeol synthase. The yeast transformed with an expression vector containing the open reading frame of GgbAS1 produced β-amyrin, indicating that GgbAS1 encodes β-amyrin synthase involved in the glycyrrhizin and soyasaponin biosyntheses in licorice. Northern blot analysis showed that the level of β-amyrin synthase mRNA was drastically changed in the cultured licorice cells, whereas the mRNA level of cycloartenol synthase was relatively constant.