Antisense Suppression of Cycloartenol Synthase Results in Elevated Ginsenoside Levels in Panax ginseng Hairy Roots

In Panax ginseng, both ginsenosides and phytosterols are derived from the precursor 2,3-oxidosqualene. The enzymes cycloartenol synthase (CS) and dammarenediol synthase (DS) are responsible for ginsenoside and phytosterol biosynthesis, respectively. Here, we report on enhanced ginsenoside levels detected in P. ginseng hairy roots, following Agrobacterium rhizogenes transformation, by antisense suppression of the CS gene. Several antisense hairy root transgenic lines were recovered exhibiting markedly reduced levels of the CS transcript and corresponding CS enzymatic activity relative to control. Phytosterol levels in tested antisense transgenic lines were similar to 50% lower than those of control, whereas 2,3-oxidosqualene contents in tested antisense lines were higher than those in control lines during the early period of root growth; however, these levels were comparable in both groups at a later stage of root growth. Ginsenoside levels were comparable in both groups during the early stage of root growth; however, the final total ginsenoside contents in antisense lines were about 50-100% higher than those found in control roots. Interestingly, the DS enzyme activity of antisense-CS lines was higher than that of controls. It is proposed that in P. ginseng, the regulation of CS can control the metabolic flux from 2,3-oxidosqualene to both phytosterol and ginsenoside.