Sucrose Induced HMGR to Promote Ginsenoside Biosynthesis in the Growth of Wild Cultivated Ginseng (Panax ginseng)

Abstract

Wild cultivated ginseng is considered to be of higher quality than field-cultivated ginseng. Many active constituents of wild cultivated ginseng, including ginsenoside, have significant effects on human health. In the development phase of wild cultivated ginseng, we investigated the regulatory factors and pathways of ginsenoside biosynthesis. To determine glycolysis activity, the soluble sugar content, EL activity, and acetyl-CoA content of ginseng at various growth ages were measured. To examine the potential of ginsenoside biosynthesis, the ginsenoside contents and activities of SS, HMGR, and DXR of ginseng were measured at various growth ages. Ginseng cells were treated with various concentrations of sucrose to further test the effect of sugar on ginsenoside biosynthesis. MVA and MEP are the two primary pathways for ginsenoside biosynthesis. The key enzymes HMGR and DXR were detected when the sugar content was changed. The targets and primary pathways of sucrose regulation of ginsenoside biosynthesis in ginseng cells were investigated using MVA and MEP pathway inhibitors. We observed that the glycolysis of older wild cultivated ginseng was increased over that of younger ginseng, suggesting that older ginseng might provide adequate precursors for downstream ginsenoside biosynthesis. Furthermore, the total ginsenoside content and the activities of critical enzymes were increased by the ages of wild cultivated ginseng. Ginsenoside biosynthesis and glycolysis showed a significant linear relationship (R2 = 0.9562). We also verified that sucrose may stimulate glycolysis and ginsenoside biosynthesis at the cellular level. The MVA and MEP pathways were found to contribute to 58.15% and 39.72% of ginsenoside biosynthesis, respectively. The activity of HMGR, the rate-limiting enzyme of the MVA pathway, was increased with the increase of sucrose concentration in a dose-dependent manner (R2 = 0.9579). In contrast, the activity of DXR, the rate-limiting enzyme of the MEP pathway, was unaffected by sucrose concentration (R2 = 0.5414). Our findings suggest that the MVA pathway might be the main source of ginsenoside biosynthesis in wild cultivated ginseng. Sucrose promoted the MVA pathway over the MEP pathway by activating HMGR, resulting in increased ginsenoside biosynthesis year after year. This research contributes to a better understanding of the active constituents found in wild cultivated ginseng as it matures.