Cloning and expression analysis of three critical triterpenoid pathway genes in Osmanthus fragrans

Background: Osmanthus fragrans is an important ornamental tree and has been widely planted in China because of its pleasant aroma, which is mainly due to terpenes. The monoterpenoid and sesquiterpenoid metabolic pathways of sweet osmanthus have been well studied. However, these studies were mainly focused on volatile small molecule compounds. The molecular regulation mechanism of synthesis of large molecule compounds (triterpenoids) remains unclear. Squalene synthase (SQS), squalene epoxidase (SQE), and beta-amyrin synthase (BETA-AS) are three critical enzymes of the triterpenoid biosynthesis pathway. Results: In this study, the full-length cDNA and gDNA sequences of OfSQS, OfSQE, and OfBETA-AS were isolated from sweet osmanthus. Phylogenetic analysis suggested that OfSQS and OfSQE had the closest relationship with Sesamum indicum, and OfBETA-AS sequence shared the highest similarity of 99% with that of Olea europaea. The qRT-PCR analysis revealed that the three genes were highly expressed in flowers, especially OfSQE and OfBETA-AS, which were predominantly expressed in the flowers of both "Boye" and "Rixiang" cultivars, suggesting that they might play important roles in the accumulation of triterpenoids in flowers of O. fragrans. Furthermore, the expression of OfBETA-AS in the two cultivars was significantly different during all the five flowering stages; this suggested that OfBETA-AS may be the critical gene for the differences in the accumulation of triterpenoids. Conclusion: The evidence indicates that OfBETA-AS could be the key gene in the triterpenoid synthesis pathway, and it could also be used as a critical gene resource in the synthesis of essential oils by using bioengineered bacteria.

Enhancing ergosterol production in Pichia pastoris GS115 by overexpressing squalene synthase gene from Glycyrrhiza uralensis / 中国天然药物

The present study was designed to determine the effects of copy number variations (CNVs) of squalene synthase 1(SQS1) gene on the mevalonate (MVA) pathway. SQS1 gene from G. uralensis (GuSQS1) was cloned and over-expressed in Pichia pastoris GS115. Six recombinant P. pastoris strains containing different copy number of GuSQS1 were constructed. HPLC was used to assay the level of ergosterol in all transgenic P. pastoris strains containing GuSQS1. HPLC analysis showed that the contents of ergosterol in all of the transgenic P. pastoris containing GuSQS1 were higher than that in the negative control. And with the increase of copy number of GuSQS1, the content of ergosterol showed an increasing-decreasing-increasing pattern. The contents of ergosterol in 10-copy-GuSQS1 P. pastoris and 47-copy-GuSQS1 P. pastoris were significantly higher than that in the rest recombinant P. pastoris strains. In conclusion, the CNVs of GuSQS1 influence the content of secondary metabolites in the MVA pathway. The present study provides a basis for over-expressing GuSQS1 and increasing the content of glycyrrhizin in G. uralensis cultivars.

Cloning and prokaryotic expression analysis of squalene synthase 2 (SQS2) from Salvia miltiorrhiza f. alba / 中国中药杂志

According to the designed specific primers of gene fragment based on the Salvia miltiorrhiza transcriptome data, a full-length cDNA sequence of SQS2 from S. miltiorrhiza f. alba was cloned by the method of reverse transcription polymerase chain reaction (RT-PCR). The SmSQS2 cDNA sequence was obtained, this sequence is named SmSQS2 and its GenBank registration number is KM244731. The full length of SmSQS2 cDNA was 1245 bp, encoding 414 amino acids including 5'UTR 115 bp and 3'UTR 237 bp. Sequence alignment and phylogenetic analysis demonstrated that SmSQS2 had relative close relationship to the SQS2 of S. miltiorrhiza. The induction of E. coli [pET28-SQS2] in different temperature, induction time, IPTG concentrations and density of inducing host bacterium (A600) were performed, Shaking the culture at 30 degrees C until the A600 is approximately 0.6 and add IPTG to final concentration of 0.2 mmol x L(-1), and then the optimal expression of SmSQS2 recombinant protein were accumulated after the induction time of 20 h. The research provided important base for the study of sterol and terpene biosynthesis of SQS2 in S. miltiorrhiza f. alba.

Enhancing the accumulation of beta-amyrin in Saccharomyces cerevisiae by co-expression of Glycyrrhiza uralensis squalene synthase 1 and beta-amyrin synthase genes / 药学学报

Glycyrrhiza uralensis Fisch. ex DC is widely used in traditional Chinese medicine (TCM). Among its various active components, glycyrrhizic acid is believed to be the marker component. Squalene synthase (SQS) and beta-amyrin synthase (beta-AS) are key enzymes in the biosynthetic pathway of glycyrrhizic acid in G uralensis. To reveal the effects of co-expression of SQS1 and beta-AS genes on this pathway, 7 yeast expression vectors harboring different SQS1 variants and beta-AS were constructed and expressed in Saccharomyces cerevisiae as fusion proteins. TLC and GC-MS results showed that co-expression of SQS1 and beta-AS enhanced the accumulation of beta-amyrin. The effects of SQS12 were more obvious than the other two SQS1 variants. This study is significant for further investigations concerned with exploring the biosynthesis of glycyrrhizic acid in vitro and strengthening the efficacy of G. uralensis by means of increasing the content of glycyrrhizic acid.

Molecular cloning of squalene synthase gene form Paris polyphylla and its expression in Escherichia coli / 中国中药杂志

<p><b>OBJECTIVE</b>To clone the cDNA sequence of squalene synthase gene from Paris polyphylla, and characterize the biological features of the obtained SQS.</p><p><b>METHOD</b>Using homology cloning and RACE technique, a full-length cDNA sequence of PpSQS gene was isolated from P. polyphylla. The obtained sequence was analyzed by bioinformatics softwares. A plasmid [named pET-30b (+)-PpSQS] was constructed for prokaryotic expression the recombinant PpSQS.</p><p><b>RESULT</b>The full-length cDNA of PpSQS gene is 1 498 bp, which contains a 1 212 bp ORF. Sequence analysis indicated that PpSQS encoded 403 amino acids residues with a calculated molecular weight (MW) of 46.36 kDa and an isoelectric point (pI) of 6.83. SDS-PAGE results showed that the recombinant PpSQS was expressed in Escherichia coli BL21 (DE3) by inducing with 1 mmol x L(-1) IPTG.</p><p><b>CONCLUSION</b>The full-length cDNA sequence of PpSQS gene was obtained from P. polyphylla, and its molecular features were consisted with classic SQS in plant. The recombinant PpSQS was successfully expressed in E. coli.</p>

The construction of over-expression vector for Panax notoginseng SS gene and its transformation / 药学学报

PNS (Panax notoginseng saponins) is the main medical bioactive component in Panax notoginseng. The medical value of PNS cannot be extended because of its low production. With the deep study of saponins biosynthetic pathway, the control of PNS biosynthesis through metabolic engineering has gradually become possible. In this study, the Squalene synthase (SS) over-expression vector was established. By the way of agrobacterium-mediated method, the vector was transfered and integrated into the Panax notoginseng genome. The result of the PCR detection and the saponin content detection shows that over-expression SS is able to produce high level of Panax notoginseng saponins, and confirms the regulatory function of SS in the biosynthesis of ginsenosides in Panax notoginseng. It provides a theoretical basis and technical basis for the construction of PNS homologous or heterologous efficient expression system in the future.

Cloning and analysis of squalene synthase (HsSQS1) gene in Huperzia serrata / 药学学报

Squalene synthase (SQS) is a key enzyme in plant terpenoid biosynthetic pathway. This study focused on cloning and analysis of Huperzia serrata SQS (HsSQS1) gene. After searching the transcriptome dataset of H serrata, one unique sequence encoding SQS was discovered. The primers were designed according to the transcript sequence of HsSQS1 from the H. serrata transcriptome dataset. The open reading frame of HsSQS1 was cloned using RT-PCR strategy. The bioinformatic analysis of this gene and its corresponding protein were performed. The cDNA (named as HsSQS1) contains a 1263 bp open reading frame and encodes a predicted protein of 420 amino acids. The GenBank accession number for this gene is JQ004938. HsSQS1 contains two transmembrane regions, without signal peptide. The conserved domain of squalene synthase was presented in HsSQS1. HsSQS1 was more abundant in H. serrata root than in leaf and stem. This study cloned and analyzed squalene synthase gene from H. serrata for the first time. The result will provide a foundation for exploring the mechanism ofterpenoid biosynthesis in H. serrata plants.

Researches on influence of squalene synthase gene polymorphism on catalytic efficiency of its encode enzyme in Glycyrrhiza uralensis / 中国中药杂志

<p><b>OBJECTIVE</b>To analyse the polymorphism of squalene synthase gene and reveal the influence of squalene synthase (SQS) gene polymorphism on the catalytic efficiency of its encode enzyme in Glycyrrhiza uralensi.</p><p><b>METHOD</b>The total RNA was extracted. PCR was used to amplify the coding sequences of squalene synthase gene, which were sequenced and analysed. The expression vectors containing different SQS gene sequences, including SQS1C, SQS1F, SQS2A, SQS2B, were constructed and transformed into Escherichia coli BL21. The fusion protein was induced to express by IPTG, then was isolated, purified and used to carry out the enzymatic reaction in vitro. GC-MS was used to analyse the production.</p><p><b>RESULT</b>There were three kinds of gene polymorphism existing in SQS1 gene of G. uralensis, including single nucleotide polymorphism (SNPs), insertion/deletion length polymorphism (InDels) and level of amino acid, the proportion of conservative replace of SQS1 was 53.94%, and there were 2 mutational sites in structural domains. The proportion of conservative replace of SQS2 was 60%, and there was 1 mutational site in structural domains. The production squalene could be detected by GC-MS in all the 4 kinds of enzymatic reactions. The capacity of accumulating squalene of SQS1F was higher than other SQS genes.</p><p><b>CONCLUSION</b>The polymorphism of SQS gene was quite abundant in G. uralensis, which maybe the molecular foundation of the formation of high-quality liquorice.</p>

Mechanism of genuineness of liquorice Glycyrrhiza uralensis based on CNVs of HMGR, SQS1 and beta-AS gene / 药学学报

This study is to reveal the correlation between CNVs of HMGR, SQS1, beta-AS gene and genuineness of liquorice. Real-time PCR was used to detect the copy number of HMGR, SQS1, beta-AS gene of liquorice. According to the results, the range of the copy number variation of HMGR gene was between 1 and 3, the copy number of SQS1 gene was 1 or 2, and the copy number of beta-AS gene was only 1. On the basis of the copy number of HMGR, SQS1 and beta-AS gene, there were five groups, type A (2 + 1 + 1), type B (1 + 1 + 1), type C (3 + 2 + 1), type D (2 + 2 + 1) and type E (3 + 1 + 1). There were two types, type A and type B, in Hangjinqi of Inner Mongolia, and the ratio of A to B was 1:1.3. There were also two types, type A and type B, in Chifeng of Inner Mongolia, and the ratio of A to B was 3:1. There were four types, type A, type B, type C and type D, in Yanchi of Ningxia province, and the ratio of A to B was 1:5.1. There were three types, type A, type B and type E, in Minqin of Gansu province, and the ratio of A to B was 2:1. So CNVs mainly existed in the liquorice from Ningxia and Gansu provinces. While the genetic background of liquorice from Hangjinqi of Inner Mongolia was stabilized. The results of the experiment proved that the correlation between CNVs and origins was one of the reasons of genuineness of liquorice.

Effect of endophytic fungi on expression amount of key enzyme genes in saponins biosynthesis and Eleutherococcus senticosus saponins content / 中国中药杂志

<p><b>OBJECTIVE</b>To 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.</p><p><b>METHOD</b>Wound 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.</p><p><b>RESULT</b>When 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).</p><p><b>CONCLUSION</b>Endophytic 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.</p>

Establishment of detection system of CNVs HMGR, SQS1, beta-AS synthase gene of Glycyrrhiza uralensis / 中国中药杂志

<p><b>OBJECTIVE</b>To establish a stabilized and reliable detection system of CNVs of HMGR, SQS1, beta-AS gene of Glycyrrhiza uralensis.</p><p><b>METHOD</b>Real time PCR was used to detect the CNVs of HMGR, SQS1, beta-AS gene of G. uralensis.</p><p><b>RESULT</b>In the quantitative detection experiments of HMGR, SQS1, beta-AS gene of G. uralensis, the change of value of C(t) was 25.82-25.88, 29.01-29. 08, 15.52-15.56, 19.06-19.08 respectively, the alue of SD was 0.033, 0.032, 0.024, 0.011 respectively, and the value of CV was 0.12%, 0.22%, 0.16%, 0.06% respectively.</p><p><b>CONCLUSION</b>The repeatability of detection system of Real time PCR was stabilized and reliable, and the method could be used to detect the CNVs of HMGR, SQS1, beta-AS gene of G. uralensis.</p>

Cloning and sequence analysis of squalene synthase gene and cDNA in Glycyrrhiza uralensis / 中国中药杂志

<p><b>OBJECTIVE</b>To clone and sequence the open reading frame and genomic sequence of squalene synthase (SQS) from Glycyrrhiza uralensis.</p><p><b>METHOD</b>The primers were designed according to cDNA sequence of SQS from G. glabra reported by Hiroaki HAYASHI, SQS cDNA was cloned with total RNA extracted from roots of G. uralensis. Specific fragments were amplified by RT-PCR and then were cloned and sequenced. SQS DNA was cloned with total DNA extracted from roots of G. uralensis. Specific fragments were amplified by PCR and then were cloned and sequenced.</p><p><b>RESULT</b>GuSQS1 (GenBank accession number: GQ266154) was 1 242 bp in length encoding proteins with 412 amino acid. NCBI Blast x search results showed GuSQS1 had the highest amino acid similarity to the corresponding proteins from G. uralensis. The identities of GuSQS1 with the two proteins were 98. 55% and 88. 62%. SQS (GenBank accession number: GQ180932) gene with 4 484 bp containing 13 exons and 12 introns was then amplified by PCR with genomic DNA extracted from roots of G. uralensis.</p><p><b>CONCLUSION</b>These findings of cloning and sequencing the open reading frame and genomic sequence of squalene synthase (SQS) from G. uralensis brought some new clues for the further exploration of SmSQS function in sterol and terpenes biosynthesis.</p>

Culture of transgenic Glycyrrhiza uralensis hairy root with licorice squalene synthase (SQS) gene / 中国中药杂志

A squalene synthase gene cloned (GuSQS1, accession number in GenBank database: AM182329) from Glycyrrhiza uralensis was transferred into G. uralensis via Agrobacterium rhizogenes A4 for investigating biosynthesis pathway and enhancing synthesis of glycyrrhizic acid (GA). Hypocotyl explants from G. uralensis were infected with A. rhizogenes A4 containing GuSQS1 gene to induce the hairy roots. The hairy root lines established were selected in medium containing 0.8 mg x L(-1) phosphinothricin (PPT) and analyzed by PCR and southern blotting. The transgenic hairy roots were cultured in liquid MS medium. GA contents in transgenic hairy roots were detected by HPLC. Results showed that maximal GA content in transgenic hairy root lines was 3.6 times as high as in wild type hairy roots.

Cloning and characterization of cDNA encoding Psammosilene tunicoides squalene synthase / 药学学报

The total triterpene saponins of Psammosilene tunicoides have significant pharmacologic activity. Psammosilene tunicoides squalene synthase (PSS) is a gateway enzyme to regulate the biosynthesis of total triterpene saponins extracted from the root of Psammosilene tunicoides which is an endangered species. In this paper, cDNA encoding of PSS was cloned by the degenerate primer PCR and rapid-amplification of cDNA ends (RACE). The full-length of cDNA of PSS is 1663 bp, with an open reading frame (ORF) of 1 245 bp, encoding 414 amino acid polypeptide (calculated molecular mass, 47.69 kDa), 5'UTR (untranslated region) and 3'UTR are 260 bp and 158 bp, respectively. The deduced amino acid sequence of PSS has higher homology with the known squalene synthases of several species such as Panax notoginseng (83%), Panax ginseng (82%) and Glycyrrhiza glabra (82%) than that with Schizosacharomyces pombe (35%), Candida albicans (39%) and Homo sapiens (47%). The characterization of PSS was done by a series of methods, such as prokaryotic expression, the activity of enzyme in vitro, capillary gas chromatography (GC) and capillary gas chromatography mass spectrometry (GC-MS). The results showed that the cell-free extract of E. coli transformed with the recombinant plasmid can effectively convert farnesyl diphosphate into squalene in vitro. GenBank accession number is EF585250. Our research provided important base for the study of Psammosilene tunicoides secondary metabolism and metabolic engineering.

Study on differentially expressed gene of the liver of treble fatty metabolism genes mutant mice using cDNA microarray / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To study the gene expression profile of liver of young apoE(-/-)/LDLR(-/-)/Lepr(db/db) treble genes mutant mice and disclose its relationship to hyperlipidemia and the following atherosclerotic lesion.</p><p><b>METHODS</b>The gene expression profile was investigated using cDNA microarray technique; the plasma total cholesterol(TC) and triglyceride(TG) levels were analyzed by COD-PAP and GPO-PAP method. And morphological observations of the aorta were made.</p><p><b>RESULTS</b>Among the 4000 target genes, 92 genes were up-regulated and 105 genes were down-regulated in the treble genes mutants, compared with wild type control. Among the differentially expressed lipid metabolism related genes, cholesterol synthesis gene coding for farnesyl diphosphate farnesyl transferase was down-regulated, while triglyceride metabolism gene e.g. pancreatic lipase related protein 1 gene (Pnliprp1) was up-regulated. Expression profile of carbohydrate, cell skeleton and immune related genes were also altered. On the other hand, in the plasma from the treble genes mutant mice at 5 weeks of age, hyperlipidemia was found to be combined with atheroslerotic lesion. All these biochemical and pathological changes were aggravated following aging.</p><p><b>CONCLUSION</b>The data suggested that the multiple genes mutations, especially those involved in lipid metabolism, were contributing to the alteration of liver gene expression profile that might lead to hyperlipidemia and atherosclerotic lesion in the young apoE(-/-)/LDLR(-/-)/Lepr(db/db) mutants.</p>