PgMYB2, a MeJA-Responsive Transcription Factor, Positively Regulates the Dammarenediol Synthase Gene Expression in Panax Ginseng

The MYB transcription factor family members have been reported to play different roles in plant growth regulation, defense response, and secondary metabolism. However, MYB gene expression has not been reported in Panax ginseng. In this study, we isolated a gene from ginseng adventitious root, PgMYB2, which encodes an R2R3-MYB protein. Subcellular localization revealed that PgMYB2 protein was exclusively detected in the nucleus of Allium cepa epidermis. The highest expression level of PgMYB2 was found in ginseng root and it was significantly induced by plant hormones methyl jasmonate (MeJA). Furthermore, the binding interaction between PgMYB2 protein and the promoter of dammarenediol synthase (DDS) was found in the yeast strain Y1H Gold. Moreover, the electrophoretic mobility shift assay (EMSA) identified the binding site of the interaction and the results of transiently overexpressing PgMYB2 in plants also illustrated that it may positively regulate the expression of PgDDS. Based on the key role of PgDDS gene in ginsenoside synthesis, it is reasonable to believe that this report will be helpful for the future studies on the MYB family in P. ginseng and ultimately improving the ginsenoside production through genetic and metabolic engineering.

Sequencing of Panax notoginseng genome reveals genes involved in disease resistance and ginsenoside biosynthesis

Panax notoginseng is a traditional Chinese herb with high medicinal and economic value. There has been considerable research on the pharmacological activities of ginsenosides contained in Panax spp.; however, very little is known about the ginsenoside biosynthetic pathway. We reported the first de novo genome of 2.36 Gb of sequences from P. notoginseng with 35,451 protein-encoding genes. Compared to other plants, we found notable gene family contraction of disease-resistance genes in P. notoginseng, but notable expansion for several ATP-binding cassette (ABC) transporter subfamilies, such as the Gpdr subfamily, indicating that ABCs might be an additional mechanism for the plant to cope with biotic stress. Combining eight transcriptomes of roots and aerial parts, we identified several key genes, their transcription factor binding sites and all their family members involved in the synthesis pathway of ginsenosides in P. notoginseng, including dammarenediol synthase, CYP716 and UGT71. The complete genome analysis of P. notoginseng, the first in genus Panax, will serve as an important reference sequence for improving breeding and cultivation of this important nutraceutical and medicinal but vulnerable plant species.

Sequence Characteristics of Dammarenediol Synthase in Medicinal Plant Panax notoginseng

Panax notoginseng is a commonly used herb in Traditional Chinese Medicine. It is a traditional herb plant of for manufacturing compound Danshen dripping pills, Yunnanbaiyao, et al. Dammarenediol synthase is one of its important ingredients. Some sequence characteristics, such as theoretical isoelectric point, hydrophobicity, molecular properties, transmembrane region, secondary structure and tertiary structure, of dammarenediol synthase in Panax notoginseng are studied in this paper. All results of the study would be benefit for further study on the medicinal properties of Panax notoginseng.

Progress in Understanding of the Key Enzyme Genes of Ginsenoside Biosynthesis in Panax ginseng

Ginsenosides, the major bioactive ingredients of P. ginseng can improve the anti-disease abilities of human being, and generate significant social and economic benefits. However, along with gradually or rapidly or dramatically increasing demand of the ginsenosides, extensive studies have focused on regulating the ginsenoside biosynthetic pathway on a genetic level. In this article, ginsenoside biosynthesis of key enzyme genes are described, including squalene synthase (SS), squalene epoxidase (SE), oxidosqualene cyclase (OSC), dammarenediol synthase (DS), β-amyrin synthase (β-AS), lanosterol synthase (LAS), cycloartenol synthase (CAS) and P450. Additionally, this review critically analyzes and evaluates the background and theoretical basis of the previous researches, as well as the deficiencies of these researches.

Molecular Cloning, Expression, Purification, and Functional Characterization of Dammarenediol Synthase fromPanax ginseng

The objective of this study is to clone and charecterize the expression of dammarenediol synthase gene and then to determine the relationship between the expression of dammarenediol synthase gene that is involved in the ginsenoside biosynthetic pathway and the ginsenoside content. A cDNA phage library was constructed from a five-year-old ginseng root. The cDNA library was screened for the dammarenediol synthase gene by using its specific primers. It was further cloned and expressed in pET-30a vector. The recombinant plasmid pET-30a-DS was expressed in RosettaE. coli. The recombinant DS protein was purified by affinity chromatography. The production of dammarenediol was detected by liquid chromatography-mass spectrometry (LC-MS). Results showed that dammarenediol synthase gene was cloned from the cDNA library and was expressed in RosettaE. coliand the SDS-PAGE analysis showed the presence of purified DS protein. LS-MS showed the activity of DS protein, as the protein content increases the dammarenediol increases. Our results indicate that the recombinant dammarenediol synthase protein could increase the production of dammarenediol and the expression of DS played a vital role in the biosynthesis of ginsenosides inP. ginseng.