Moon-Gi Jang

Ginsenoside profiles and related gene expression during foliation in Panax ginseng Meyer

Panax ginseng is one of the most important medicinal plants in Asia. Triterpene saponins, known as ginsenosides, are the major pharmacological compounds in P. ginseng. The present study was conducted to evaluate the changes in ginsenoside composition according to the foliation stage of P. ginseng cultured in a hydroponic system. Among the three tested growth stages (closed, intermediate, and opened), the highest amount of total ginsenoside in the main and fine roots was in the intermediate stage. In the leaves, the highest amount of total ginsenoside was in the opened stage. The total ginsenoside content of the ginseng leaf was markedly increased in the transition from the closed to intermediate stage, and increased more slowly from the intermediate to opened leaf stage, suggesting active biosynthesis of ginsenosides in the leaf. Conversely, the total ginsenoside content of the main and fine roots decreased from the intermediate to opened leaf stage. This suggests movement of ginsenosides during foliation from the root to the leaf, or vice versa. The difference in the composition of ginsenosides between the leaf and root in each stage of foliation suggests that the ginsenoside profile is affected by foliation stage, and this profile differs in each organ of the plant. These results suggest that protopanaxadiol- and protopanaxatriol (PPT)-type ginsenosides are produced according to growth stage to meet different needs in the growth and defense of ginseng. The higher content of PPT-type ginsenosides in leaves could be related to the positive correlation between light and PPT-type ginsenosides.

Functional Analysis of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Encoding Genes in Triterpene Saponin-Producing Ginseng

Coenzyme A reductases contribute to the production of triterpene saponin in ginseng. Ginsenosides are glycosylated triterpenes that are considered to be important pharmaceutically active components of the ginseng (Panax ginseng ‘Meyer’) plant, which is known as an adaptogenic herb. However, the regulatory mechanism underlying the biosynthesis of triterpene saponin through the mevalonate pathway in ginseng remains unclear. In this study, we characterized the role of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) concerning ginsenoside biosynthesis. Through analysis of full-length complementary DNA, two forms of ginseng HMGR (PgHMGR1 and PgHMGR2) were identified as showing high sequence identity. The steady-state mRNA expression patterns of PgHMGR1 and PgHMGR2 are relatively low in seed, leaf, stem, and flower, but stronger in the petiole of seedling and root. The transcripts of PgHMGR1 were relatively constant in 3- and 6-year-old ginseng roots. However, PgHMGR2 was increased five times in the 6-year-old ginseng roots compared with the 3-year-old ginseng roots, which indicates that HMGRs have constant and specific roles in the accumulation of ginsenosides in roots. Competitive inhibition of HMGR by mevinolin caused a significant reduction of total ginsenoside in ginseng adventitious roots. Moreover, continuous dark exposure for 2 to 3 d increased the total ginsenosides content in 3-year-old ginseng after the dark-induced activity of PgHMGR1. These results suggest that PgHMGR1 is associated with the dark-dependent promotion of ginsenoside biosynthesis. We also observed that the PgHMGR1 can complement Arabidopsis (Arabidopsis thaliana) hmgr1-1 and that the overexpression of PgHMGR1 enhanced the production of sterols and triterpenes in Arabidopsis and ginseng. Overall, this finding suggests that ginseng HMGRs play a regulatory role in triterpene ginsenoside biosynthesis.

Transcript expression profiling for adventitious roots of Panax ginseng Meyer

Panax ginseng Meyer is one of the major medicinal plants in oriental countries belonging to the Araliaceae family which are the primary source for ginsenosides. However, very few genes were characterized for ginsenoside pathway, due to the limited genome information. Through this study, we obtained a comprehensive transcriptome from adventitious roots, which were treated with methyl jasmonic acids for different time points (control, 2h, 6h, 12h, and 24h) and sequenced by RNA 454 pyrosequencing technology. Reference transcriptome 39,304,529 (0.04GB) was obtained from 5,724,987,880 bases (5.7GB) of 22 libraries by de novo assembly and 35,266 (58.5%) transcripts were annotated with biological schemas (GO and KEGG). The digital gene expression patterns were obtained from in vitro grown adventitious root sequences which mapped to reference, from that, 3813 (6.3%) unique transcripts were involved in ≥2 fold up and downregulations. Finally, candidates for ginsenoside pathway genes were predicted from observed expression patterns. Among them, 30 transcription factors, 20 cytochromes, and 11 glycosyl transferases were predicted as ginsenoside candidates. These data can remarkably expand the existing transcriptome resources of Panax, especially to predict existence of gene networks in P. ginseng. The entity of the data provides a valuable platform to reveal more on secondary metabolism and abiotic stresses from P. ginseng in vitro grown adventitious roots.

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

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.

Molecular characterization of two glutathione peroxidase genes of Panax ginseng and their expression analysis against environmental stresses

Glutathione peroxidases (GPXs) are a group of enzymes that protect cells against oxidative damage generated by reactive oxygen species (ROS). GPX catalyzes the reduction of hydrogen peroxide (H2O2) or organic hydroperoxides to water or alcohols by reduced glutathione. The presence of GPXs in plants has been reported by several groups, but the roles of individual members of this family in a single plant species have not been studied. Two GPX cDNAs were isolated and characterized from the embryogenic callus of Panax ginseng. The two cDNAs had an open reading frame (ORF) of 723 and 681bp with a deduced amino acid sequence of 240 and 226 residues, respectively. The calculated molecular mass of the matured proteins are approximately 26.4kDa or 25.7kDa with a predicated isoelectric point of 9.16 or 6.11, respectively. The two PgGPXs were elevated strongly by salt stress and chilling stress in a ginseng seedling. In addition, the two PgGPXs showed different responses against biotic stress. The positive responses of PgGPX to the environmental stimuli suggested that ginseng GPX may help to protect against environmental stresses.

Grouping and characterization of putative glycosyltransferase genes from Panax ginseng Meyer

Glycosyltransferases are members of the multigene family of plants that can transfer single or multiple activated sugars to a range of plant molecules, resulting in the glycosylation of plant compounds. Although the activities of many glycosyltransferases and their products have been recognized for a long time, only in recent years were some glycosyltransferase genes identified and few have been functionally characterized in detail. Korean ginseng (Panax ginseng Meyer), belonging to Araliaceae, has been well known as a popular mysterious medicinal herb in East Asia for over 2,000 years. A total of 704 glycosyltransferase unique sequences have been found from a ginseng expressed sequence tag (EST) library, and these sequences encode enzymes responsible for the secondary metabolite biosynthesis. Finally, twelve UDP glycosyltransferases (UGTs) were selected as the candidates most likely to be involved in triterpenoid synthesis. In this study, we classified the candidate P. ginseng UGTs (PgUGTs) into proper families and groups, which resulted in eight UGT families and six UGT groups. We also investigated those gene candidates encoding for glycosyltransferases by analysis of gene expression in methyl jasmonate (MeJA)-treated ginseng adventitious roots and different tissues from four-year-old ginseng using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). For organ-specific expression, most of PgUGT transcription levels were higher in leaves and roots compared with flower buds and stems. The transcription of PgUGTs in adventitious roots treated with MeJA increased as compared with the control. PgUGT1 and PgUGT2, which belong to the UGT71 family genes expressed in MeJA-treated adventitious roots, were especially sensitive, showing 33.32 and 38.88-fold expression increases upon 24h post-treatments, respectively.

Cloning and characterization of pathogenesis-related protein 4 gene from Panax ginseng

The family of pathogenesis-related protein 4 (PR4) is a group of proteins with a Barwin domain in C-terminus and generally thought to be involved in plant defense responses. In the present study, PR4 (designated as PgPR4) cDNA was isolated from the leaf of Panax ginseng C.A. Meyer. and characterized. The ORF is 513 bp with a deduced amino acid sequence of 170 residues. A GenBank BlastX search revealed that the deduced amino acid of PgPR4 shares the highest sequence similarity to PR4 of Sambucus nigra (72% identity). Sequence and structural analysis indicated that PgPR4 belongs to class II of PR4 proteins. This is the first report on the isolation of PR4 gene from the P. ginseng genome. The high-level expression of PgPR4 was observed in the root as revealed by quantitative real-time PCR. The temporal expression analysis demonstrated that PgPR4 expression could be up-regulated by pathogen infection, salt, wounding, and hormone stresses. These results suggest that PgPR4 could play a role in the molecular defense response of ginseng to abiotic stress and pathogen attack.

Development of interspecies hybrids to increase ginseng biomass and ginsenoside yield

Key messageInterspecific hybrids betweenPanax ginsengandP. quinquefoliusresults in hybrid vigor and higher ginsenoside contents.AbstractGinseng is one of the most important herbs with valued pharmaceutical effects contributing mainly by the presence of bioactive ginsenosides in the roots. However, ginseng industry is impeded largely by its biological properties, because ginseng plants are slow-growing perennial herbs with lower yield. To increase the ginseng yield and amounts of ginsenosides, we developed an effective ginseng production system using the F1 progenies obtained from the interspecific reciprocal cross between two Panax species: P. ginseng and P. quinquefolius. Although hybrid plants show reduced male fertility, F1 hybrids with the maternal origin either from P. ginseng or P. quinquefolius displayed heterosis; they had larger roots and higher contents of ginsenosides as compared with non-hybrid parental lines. Remarkably, the F1 hybrids with the maternal origin of P. quinquefolius had much higher ginsenoside contents, especially ginsenoside Re and Rb1, than those with the maternal origin of P. ginseng. Additionally, non-targeted metabolomic profiling revealed a clear increase of a large number of primary and secondary metabolites including fatty acids, amino acids and ginsenosides in hybrid plants. To effectively identify the F1 hybrids for the large-scale cultivation, we successfully developed a molecular marker detection system for discriminating F1 reciprocal hybrids. In summary, this work provided a practical system for reciprocal hybrid ginseng production, which would facilitate the ginseng production in the future.

Molecular characterization and expression analysis of pathogenesis related protein 6 from Panax ginseng

Panax ginseng Meyer is one of the important medicinal plants in the world, particularly in Asian countries. Ginseng encounters many stress exposure during its long cultivation period. However, the molecular mechanism of stress resistance is still poorly understood in spite of its importance. In this study, pathogenesis-related protein 6 (PR6), also called proteinase inhibitor (PI), was isolated from ginseng embryogenic callus, named PgPR6. The small size of PR6, containing an open reading frame of 219 bp encoding 72 amino acids, the typical characteristic of PR6 protein, shares the highest sequence similarity to PR6 of Theobroma cacao (69% identity). Sequence and structural analysis indicated that PgPR6 belongs to class Kunitz-type PI family. This is the first report pertaining to the identification of PR6 gene from the P. ginseng genome. The high-level expression of PgPR6 was observed in root as revealed by quantitative real-time PCR. The temporal expression analysis demonstrated that PgPR6 expression was highly up-regulated by signaling molecules, heavy metals, mechanical wounding, chilling, salt, sucrose, and mannitol stress, indicating that PgPR6 may play an important role in the molecular defense response of ginseng to a various range of environmental stresses.