Dipsaci Radix is a commonly used Chinese herbal medicine in China, with triterpenoid saponins as the main active components. β-Amyrin synthase, a member of the oxidosqualene cyclase superfamily, plays a crucial role in the biosynthesis of oleanane-type triterpenoid saponins. Asperosaponin Ⅵ is an oleanane-type triterpenoid saponin. To explore the β-amyrin synthase genes involved in the biosynthesis of asperosaponin Ⅵ in Dipsacus asper, this study screened the candidate genes from the transcriptome data of D. asper. Two β-amyrin synthase genes, Da OSC1 and Da OSC2, were identified by phylogenetic analysis and correlation analysis. The coding sequences of Da OSC1 and Da OSC2 were 2 286 bp and 2 295 bp in length, encoding 761 and 764 amino acids,respectively. Multiple sequence alignments showed that Da OSC1 and Da OSC2 had three conserved motifs( DCTAE, QW, and MWCYCR) unique to the oxidosqualene cyclase family. Real-time quantitative PCR results showed that Da OSC1 and Da OSC2 had the highest expression levels in the roots. Compared with normal growth conditions, the low-temperature treatment significantly upregulated the expression of Da OSC1 and Da OSC2. Agrobacterium-mediated transient expression of Da OSC1 and Da OSC2 in Nicotiana benthamiana resulted in the production of β-amyrin, which suggested that Da OSC1 and Da OSC2 were able to catalyze the synthesis of β-amyrin. This study clarified the catalytic functions of two β-amyrin synthases in D. asper, analyzed their expression patterns in different tissue and at low temperatures. The findings provide a foundation for further studying the biosynthetic pathway and regulatory mechanism of asperosaponin Ⅵ in D. asper.
Intramolecular Transferases/chemistry* ; Phylogeny ; Plant Proteins/chemistry* ; Gene Expression Regulation, Plant ; Dipsacaceae/classification* ; Saponins/metabolism* ; Oleanolic Acid/metabolism*

Triterpenoids are one of the most diverse compounds in plant metabolites, and they have a wide variety of physiological activities and are of important economic value. Oxidosqualene cyclases catalyze the cyclization of 2, 3-oxidosqualene to generate different types of sterols and plant triterpenoids, which is of great significance to the structural diversity of natural products. However, the mechanism of the diversified cyclization of 2, 3-oxidosqualene catalyzed by oxidosqualene cyclases remains unclear. This review summarized the research progress of oxidosqualene cyclases from the aspects of catalytic function, molecular evolutionary relationship between genes and proteins, protein structure, molecular simulation and molecular calculations, which may provide a reference for protein engineering and metabolic engineering of triterpene cyclase.
Intramolecular Transferases/metabolism* ; Metabolic Engineering ; Plants/genetics* ; Squalene/chemistry* ; Triterpenes

Dipsaci Radix is one of the commonly used Chinese medicinal materials in China, with a long history. It has the medicinal activities of nourishing liver and kidney, recovering from broken sinews, and treating bone fracture. Triterpenoid saponins are the main functional ingredients of Dipsacus asper. β-Amyrin synthases(β-AS) as a superfamily of oxidosqualene cyclases(OSCs) can catalyze the construction of the skeleton structure of oleanane-type triterpenoid saponins. There are only a few studies about the β-AS in D. asper, and the catalytic mechanism of this enzyme remains to be explored. To enrich the information of β-AS, according to the transcriptome sequencing results, we cloned DaWβ-AS gene from D. asper into a specific vector for heterologous expression in Escherichia coli. In the meantime, real-time PCR was performed to analyze the relative expression of DaWβ-AS in four different tissues of D. asper. The results of RT-qPCR showed DaWβ-AS had the highest expression level in leaves. Bioinformatics results indicated that DaWβ-AS had a conserved domain of PLN03012 superfamily, belonging to the cl31551 superfamily. There was no transmembrane domain or signal peptide in DaWβ-AS. This study provides a scientific basis for revealing the biological pathways of triterpenoid saponins in D. asper, which will facilitate the biosynthesis of the associated saponins and afford reference for the cultivation and development of high-quality resources of D. asper.
Cloning, Molecular ; Computational Biology ; Dipsacaceae/chemistry* ; Intramolecular Transferases ; Protein Sorting Signals ; Saponins/chemistry* ; Triterpenes/chemistry*

OBJECTIVETo analyze the effect of endophytic fungi on expression amount of key enzyme genes SS (squalene synthase gene), SE (squalene epoxidase gene) and bAS (beta-amyrin synthase gene) in saponin biosynthesis and saponins content in Eleutherococcus senticosus.

METHODWound method was used for back meeting the endophytic fungi to E. senticosus. With GAPDH as internal control gene, the expression of key enzyme genes was detected by real time PCR method. E. senticosus saponins content was measured by spectrophotometry method.

RESULTWhen wound method back meeting P116-1a and P116-1b after 30 d, the expression content of SS improved significantly (P < 0.05), however the back meeting of P109-4 and P312-1 didnt change the expression of SS. After that SS expression showed reduction-equality-reduction varying trend. Thirty days after back meeting P312-1, the expression content of SE improved significantly (P < 0.05). Ninty days after back meeting P116-1b and P312-1, the expression content of SE improved significantly to 130%,161%, respectively (P < 0.05). After 120 d, back meeting four endophytic fungi, the expression of SE were significantly higher than the control (P < 0.05). Back meeting four endophytic fungi form 60 d to 120 d, the expression of bAS was significantly higher than the control (P < 0.05). The back meeting four endophytic fungi improved E. senticosus saponins content significantly (P < 0.05).

CONCLUSIONEndophytic fungi P116-1a, P116-1b, P1094 and P312-1 significantly effected the expression of key enzyme genes SS, SE and bAS and then affected E. senticosus saponins content. Among the genes, bAS was key target gene.

Eleutherococcus ; chemistry ; metabolism ; microbiology ; Endophytes ; physiology ; Farnesyl-Diphosphate Farnesyltransferase ; genetics ; Fungi ; physiology ; Gene Expression Regulation, Enzymologic ; Gene Expression Regulation, Plant ; Intramolecular Transferases ; genetics ; Saponins ; analysis ; biosynthesis ; Squalene Monooxygenase ; genetics

OBJECTIVETo clone and sequence the open reading frame of cycloartenol synthase (CAS) from Huperzia carinata.

METHODAfter searching the transcriptome dataset of H. carinata, one unique sequence containing oxide squalene cyclases domain was discovered. The primers were designed according to the cDNA sequence of CAS from the dataset. And then, the open reading frame of CAS was cloned by RT-PCR strategy with the template of mixed RNA extracted from root, stem and leaf of H. carinata. The bioinformatic analysis of this gene and its corresponding protein was performed.

RESULTOne unique sequence of CAS, named as HcCAS1 (GenBank accession number JN790125) , was cloned from H. carinata. The open reading frame of HcCAS1 consists of 2 474 bp, encoding one polypeptide with 757 amino acids.

CONCLUSIONThis study cloned and analyzed CAS from H. carinata for the first time. The result will provide a foundation for exploring the mechanism of sterol biosynthesis in Huperziaceae plants.

Amino Acid Sequence ; Cloning, Molecular ; Computational Biology ; Evolution, Molecular ; Huperzia ; enzymology ; genetics ; Intramolecular Transferases ; chemistry ; genetics ; metabolism ; Models, Molecular ; Molecular Sequence Data ; Phylogeny ; Protein Structure, Secondary

OBJECTIVETo analyze heterologous expression in Saccharomyces cerevisiae of two genotypes: beta-AS (A-T) genotype which is related to high content of glycyrrhizic acid and beta-AS(G-C) genotype which is related to low content of glycyrrhizic acid, and compare two different genotypes on the impact of beta-amyrin production in order to provide a foundation for licorice molecular breeding.

METHODThe 2 289 bp fragment in plasmid pMD-19T encoding beta-amyrin synthase was subcloned into the yeast-Escherichia coli shuttle vector pY26, thus an expression recombinant plasmid PY-beta-AS containing target gene was constructed. The PY-beta-AS was introduced into defective mutant INVSc1 of S. cerevisiae by LiAc method, after induced by IPTG, the content of beta-amyrin was determined by GC-MS.

RESULTGC-MS analysis demonstrates that the an occurring peak corresponding to beta-amyrin standards was detected with the same retention time, which is absent in the cell transform with empty vector. Results showed the peak was beta-amyrin and the percentage of beta-amyrin in two genotypes: beta-AS (A-T) genotype and beta-AS (G-C) genotype were 19.08% and 1.40%, respectively. Thus the beta-amyrin synthase exhibited the activity of catalyzing 2, 3-oxidosqualene to beta-amyrin.

CONCLUSIONThe catalytic efficiency of beta-AS(A-T) genotype is higher than that of beta-AS(G-C) genotype, which can lay the foundation for licorice molecular breeding.

Catalysis ; Cloning, Molecular ; Genotype ; Glycyrrhiza uralensis ; chemistry ; enzymology ; genetics ; Intramolecular Transferases ; chemistry ; genetics ; metabolism ; Plant Proteins ; chemistry ; genetics ; metabolism ; Polymorphism, Genetic ; Recombinant Proteins ; chemistry ; genetics ; metabolism ; Saccharomyces cerevisiae ; genetics