Effects of arbuscular mycorrhizal fungi on photosynthesis and biosynthesis of ginsenoside in Panax quinquefolius L.

Panax quinquefolius L., a medicinal plant of Araliaceae family, is used in traditional Chinese medicine. Arbuscular mycorrhizal fungi (AMF) has been shown to promote plant growth and the accumulation of secondary metabolites in many plants. Our group has found a significant positive correlation between AMF infection rate and the accumulation of ginsenoside, while the effects and underlying mechanism of AMF on the growth and accumulation of ginsenoside in P. quinquefolius have been poorly studied. In this study, the effects on the biomass, photosynthesis and expressions of genes involved in biosynthesis of ginsenoside: hydroxymethylglutaryl-CoA reductase (HMGR), geranylgeranyl pyrophosphate synthase (GPS), farnesyl diphosphate synthase (FPS), squalene synthase (SS), squalene epoxidase (SE), dammarendiol synthase (DS) and cytochrome P450 enzyme (CYP716A47, CYP716A53v2) in P. quinquefolius during AMF inoculation were investigated. Plant biomass and photosynthesis of P. quinquefolius were stimulated by AMF treatment. Chlorophyll concentration in P. quinquefolius leaves treated by R. intraradices was higher than those in non-inoculated leaves. The concentration of Rb1 and Re was markedly increased by 26.15% and 22.38% (P < 0.05) with R. intraradices respectively. During the R. intraradices treatment, the expressions of HMGR, SE, DS and CYP716A53v2 genes increased significantly (P < 0.05) to more than three times as compared to non-inoculated plants. This study indicates that the plant growth and ginsenoside accumulation in P. quinquefolius were improved with AMF inoculation. These results could provide insights into the mechanisms of biosynthesis of ginsenoside in P. quinquefolius.