Investigation of ginsenosides in different tissues after elicitor treatment in Panax ginseng

Abstract

Background: The effect of methyl jasmonate (MJ) on ginsenoside production in different organs of ginseng (Panax ginseng Meyer) was evaluated after the whole plant was dipped in an MJ-containing solution. MJ can induce the production of antioxidant defense genes and secondary metabolites in plants. In ginseng, MJ treatment in adventitious root resulted in the increase of dammarenediol synthase expression but a decrease of cycloartenol synthase expression, thereby enhancing ginsenoside biosynthesis. Although a previous study focused on the application of MJ to affect ginsenoside production in adventitious roots, we conducted our research on entire plants by evaluating the effect of exogenous MJ on ginsenoside production with the aim of obtaining new approaches to study ginsenoside biosynthesis response to MJ in vivo.

Methods: Different parts of MJ-treated ginseng plants were analyzed for ginsenoside contents (fine root, root body, epidermis, rhizome, stem, and leaf) by high-performance liquid chromatography.

Results: The total ginsenoside content of the ginseng root significantly increased after 2 d of MJ treatment compared with the control not subjected to MJ. Our results revealed that MJ treatment enhances ginsenoside production not in the epidermis but in the stele of the ginseng root, implying transportation of ginsenosides from the root vasculature to the epidermis. Application of MJ enhanced protopanaxadiol (PPD)-type ginsenosides, whereas chilling treatment induced protopanaxatriol (PPT)-type ginsenosides.

Conclusion: These findings indicate that the production of PPD-type and PPT-type ginsenosides is differently affected by abiotic and biotic stresses in the ginseng plant, and they might play different defense mechanism roles.

Keywords: Panax ginseng; chilling; elicitor; ginsenoside; methyl jasmonate.

Fig. 1

Photographs of different organs of a 3-yr-old ginseng plant used for ginsenoside analysis. Three-yr-old ginseng plants hydroponically cultured in perlite and peat moss were used for methyl jasmonate (MJ) treatment. For ginsenoside analysis, different organs were sampled separately: the (A) leaf, stem, (B) rhizome, and fine root were sampled. The main root was divided again into the epidermis (the outer surface including the cortex) and (C) the root body (the inner part including the xylem and pith) by peeling. (D) A horizontal close-up image of the main root. All bars indicate 1 cm.

Fig. 2

Effects of methyl jasmonate (MJ) on ginsenoside production in different ginseng plant tissues. Three-yr-old ginseng plants cultured hydroponically in perlite and peat moss were treated with 50μM of MJ by dipping the root in a foil-wrapped glass vial for 2 d. Total ginsenoside contents in (A) the leaf, rhizome, and fine root, as well as (B) the epidermis, root body, and stem, shown in Fig. 1, were analyzed. Vertical bars indicate the mean value ± standard deviation from three independent experiments. *p < 0.05 and **p < 0.01 denote significant difference from the control, respectively.

Fig. 3

Individual ginsenoside contents by methyl jasmonate (MJ) elicitation in different ginseng plant tissues. Three-yr-old ginseng plants were treated with 50μM of MJ for 2 d. Individual ginsenoside contents in the leaf, stem, rhizome, epidermis, root body, and fine root were analyzed. Protopanaxadiol (PPD) indicates the sum of ginsenoside Rb1, Rb2, Rc, and Rd, and protopanaxatriol (PPT) indicates the sum of ginsenoside Re, Rg, Rg1, and Rg2. Vertical bars indicate the mean value ± standard deviation from three independent experiments. *p < 0.05 and **p < 0.01 denote significant difference from the control, respectively.

Fig. 4

Effect of chilling on ginsenoside production in different ginseng plant tissues. (A) Photograph of different organs of a 1-yr-old ginseng root used for ginsenoside analysis. For ginsenoside analysis, different tissues were sampled separately; the rhizome and fine root were sampled. (B) After the epidermis was collected by peeling, the main root body was divided again into upper and lower halves. All bars indicate 1 cm. (C) Total ginsenoside contents in rhizome, epidermis, upper root body, lower root body, and fine root, shown in (A) and (B), were analyzed. Vertical bars indicate the mean value ± standard deviation from three independent experiments. *p < 0.05 and **p < 0.01 denote significant difference from the control, respectively.

Fig. 5

Individual ginsenoside contents upon chilling stress treatment in different ginseng plant tissues. One-yr-old ginseng plants were subjected to chilling for 4 wk. Individual ginsenoside contents in rhizome, epidermis, upper root body, lower root body, and fine root, as shown in Fig. 4, were analyzed. Protopanaxadiol (PPD) indicates the sum of ginsenoside Rb1, Rb2, Rc, and Rd, and protopanaxatriol (PPT) indicates the sum of ginsenoside Re, Rg, Rg1, and Rg2. Vertical bars indicate the mean value ± standard deviation from three independent experiments. *p < 0.05 and **p < 0.01 denote significant difference from the control, respectively.

Fig. 6

Summary of ginsenoside biosynthesis in ginseng root by elicitation. Ginsenoside production is stimulated via mevalonate (MVA) pathway genes, which are upregulated by MJ signaling. MJ elicitation enhanced PPD-type ginsenosides, whereas chilling stress increased PPT-type ginsenosides. CAS, cycloartenol synthase; DDS, dammarenediol synthase; FPP, farnesyl diphosphate; FPS, farnesyl diphosphate synthase; HMGR, 3-hydroxy-3-methylglutaryl-CoA reductase; MJ, methyl jasmonate; MVA, mevalonic acid; PPD, protopanaxadiol; PPDS, PPD synthase (cytochrome P450); PPT, protopanaxatriol; PPTS, PPT synthase (cytochrome P450); SE, squalene epoxidase; SS, squalene synthase.