Ginsenoside synthesis of adventitious roots in Panax ginseng is promoted by fungal suspension homogenate of Alternaria panax and regulated by several signaling molecules

The adventitious root (AR) culture is an effective approach for mass and rapid production of Panax ginseng C. A. Mey ginsenosides. During AR culture, methyl jasmonate (MeJA) is widely used to increase ginsenoside content. However, its high price is a burden to producers. To replace MeJA using a cheaper elicitor, the present study prepared the fungal suspension homogenate using the pathogenic fungi (Alternaria panax Whetz.) of field-grown ginseng and the homogenate was used as a fungal elicitor. Ginsenoside accumulation was affected by the concentrations and elicitation times of fungal elicitor. The maximum content (29.6 mg/g dry weight) was determined when 30-day-old bioreactor cultured-ARs were treated with 200 mg/L of the fungal elicitor for 8 days, thereby indicating a desirable elicitation effect. Furthermore, the present study investigated whether nitric oxide (NO), polyamines (PAs), and hydrogen peroxide (H2O2) were involved in regulating ginsenoside synthesis to elucidate the mechanism underlying the fungal elicitor's effect. The fungal elicitor-induced NO, putrescine (Put, a kind of PAs), and H2O2 burst, which peaked at 12 h for NO or Put and at 24 h for H2O2. However, the increased contents of these three molecules were decreased by the inhibitors. Subsequently, the reduction of ginsenoside content was determined. The NO, PAs, and H2O2 probably acted as signaling molecules that are involved in regulation of fungal elicitor-induced ginsenoside synthesis during P. ginseng AR culture.