Correlation analyses of ecological factors, ginsenoside contents and expression of associated key enzymes in Panax ginseng leaves

Objective  To clarify the physiological and ecological mechanisms of ginsenoside biosynthesis, and reveal the relationship between ecdogical/genetic factors and quality of medicinal materials.

Method  Cultivated four-year-old Panax ginseng leaves at different growth times were used as materials. The contents of eight ginsenosides (Rg₁、Re、Rf、Rb₁、Rb₂、Rb₃、Rc、Rd) in leaves were detected by HPLC. The expression of seven key enzyme genes (HMGR, FPS, SS, SE, DS, β-AS, CYP716A47) involved in ginsenoside biosynthesis in ginseng leaves were determined by real-time quantitative fluorescent PCR. The effect of ecological factors and the expression of key enzyme genes on the synthesis and accumulation of ginsenosides in P. ginseng leaves were investigated by correlation and grey relational analysis.

Result  The expression of key enzyme genes involved in ginsenoside synthesis was active from July 13th to September 29th, and the expression of different genes synergistically increased or decreased. The contents of ginsenoside Re and Rg₁ in P. ginseng leaves were the highest, reached the maximum of 60.30 and 39.38 mg·g^–1 respectively in the growth period of ginseng root from August 31st to September 13th. Temperature, photosynthetic active radiation (PAR), soil water potential and relative humidity all had significant correlation with ginsenoside contents in P. ginseng leaves (P<0.05).HMGR expression in P. ginseng leaves was negatively correlated with Rb₂ content (P<0.05),SS expression was negatively correlated with Rg₁ or Re content (P<0.05), andβ-AS expression was negatively correlated with Rc content (P<0.05) and Rb₂ content (P<0.01). Grey correlation analysis results showed that the major ecological factors that influenced ginsenoside contents inP. ginseng leaves were temperature, PAR, soil water potential and relative humidity, with their grey correlation values ranging from 0.727 9 to 0.871 1.

Conclusion  Under the regulation and control of ecological factors, the synthesis and accumulation of ginsenosides were influenced by the expression of involved key enzyme genes.