GC-MS Metabolomic Analysis to Reveal the Metabolites and Biological Pathways Involved in the Developmental Stages and Tissue Response of Panax ginseng

Abstract

Ginsenosides, the major compounds present in ginseng, are known to have numerous physiological and pharmacological effects. The physiological processes, enzymes and genes involved in ginsenoside synthesis in P. ginseng have been well characterized. However, relatively little information is known about the dynamic metabolic changes that occur during ginsenoside accumulation in ginseng. To explore this topic, we isolated metabolites from different tissues at different growth stages, and identified and characterized them by using gas chromatography coupled with mass spectrometry (GC-MS). The results showed that a total of 30, 16, 20, 36 and 31 metabolites were identified and involved in different developmental stages in leaf, stem, petiole, lateral root and main root, respectively. To investigate the contribution of tissue to the biosynthesis of ginsenosides, we examined the metabolic changes of leaf, stem, petiole, lateral root and main root during five development stages: 1-, 2-, 3-, 4- and 5-years. The score plots of partial least squares-discriminate analysis (PLS-DA) showed clear discrimination between growth stages and tissue samples. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis in the same tissue at different growth stages indicated profound biochemical changes in several pathways, including carbohydrate metabolism and pentose phosphate metabolism, in addition, the tissues displayed significant variations in amino acid metabolism, sugar metabolism and energy metabolism. These results should facilitate further dissection of the metabolic flux regulation of ginsenoside accumulation in different developmental stages or different tissues of ginseng.

Keywords: GC-MS metabolite profiling; developmental stages; ginsenoside; plant metabolism.

Figure 1

Total ginsenosides analysis of ginseng at five developmental stages and five tissues. Ginseng samples of five developmental stages 1-, 2-, 3-, 4- and 5-year old were collected for ginsenosides analysis by UPLC-MS. The data represent the mean ± standard error of the mean values for six biological replications.

Figure 2

Metabolic analysis of tissues at five developmental stages. Ginseng samples of five developmental stages 1-, 2-, 3-, 4- and 5-year old were collected for metabolite analysis by GC-MS. (A,C,E,G,I) PLS-DA analysis of developing leaf, petiole, stem, lateral root and root from five stages, respectively; (B,D,F,H,J) Fold change of alcohol, amino acid, organic acid, sugar and other metabolites in leaf, petiole, stem, lateral root and root at five developmental stages. The data represent the mean ± standard error of the mean values for six biological replications.

Figure 3

Metabolic alterations in five tissues during developmental. Ginseng samples of five developmental stages 1-, 2-, 3-, 4- and 5-year old were collected for metabolite analysis by GC-MS. (A,C,E,G,I) PLS-DA analysis of 1-, 2-, 3-, 4- and 5-year from leaf, petiole, stem, lateral root and root, respectively; (B,D,F,H,J) Fold change of alcohol, amino acid, organic acid, sugar and other metabolites in 1-, 2-, 3-, 4- and 5-year at five tissues. The data represent the mean ± standard error of the mean values for six biological replications.

Figure 4

The metabolite-to-metabolite networks involved in the primary pathways of ginseng response to development regulation. Green circles, metabolite pathways; Red diamonds, metabolites.