Development of the devices for synthetic biology of triterpene saponins at an early stage: cloning and expression profiling of squalene epoxidase genes in panax notoginseng / 药学学报

Synthetic biology of traditional Chinese medicine (TCM) is a new and developing subject based on the research of secondary metabolite biosynthesis for nature products. The early development of synthetic biology focused on the screening and modification of parts or devices, and establishment of standardized device libraries. Panax notoginseng (Burk.) F.H.Chen is one of the most famous medicinal plants in Panax species. Triterpene saponins have important pharmacological activities in P. notoginseng. Squalene epoxidase (SE) has been considered as a key rate-limiting enzyme in biosynthetic pathways of triterpene saponins and phytosterols. SE acts as one of necessary devices for biosynthesis of triterpene saponins and phytosterols in vitro via synthetic biology approach. Here we cloned two genes encoding squalene epoxidase (PnSE1 and PnSE2) and analyzed the predict amino acid sequences by bioinformatic analysis. Further, we detected the gene expression profiling in different organs and the expression level of SEs in leaves elicited by methyl jasmonate (MeJA) treatment in 4-year-old P notoginseng using real-time quantitative PCR (real-time PCR). The study will provide a foundation for discovery and modification of devices in previous research by TCM synthetic biology. PnSE1 and PnSE2 encoded predicted proteins of 537 and 545 amino acids, respectively. Two amino acid sequences predicted from PnSEs shared strong similarity (79%), but were highly divergent in N-terminal regions (the first 70 amino acids). The genes expression profiling detected by real-time PCR, PnSE1 mRNA abundantly accumulated in all organs, especially in flower. PnSE2 was only weakly expressed and preferentially in flower. MeJA treatment enhanced the accumulation of PnSEI mRNA expression level in leaves, while there is no obvious enhancement of PnSE2 in same condition. Results indicated that the gene expressions of PnSE1 and PnSE2 were differently transcribed in four organs, and two PnSEs differently responded to MeJA stimuli. It was strongly suggested that PnSEs play different roles in secondary metabolite biosynthesis in P. notoginseng. PnSE1 might be involved in triterpenoid biosynthesis and PnSE2 might be involved in phytosterol biosynthesis.

New technologies used for Panax genus research / 中国中药杂志

The authors reviewed the new technologies used for Panax genus research, including molecular identification technologies (especially for DNA barcoding), modern biotechnologies (e. g. the first generation and second generation sequencing technologies), and gene cloning and identification in this paper. These technologies have been successfully applied to species identification, transcriptome analysis, secondary metabolite biosynthetic pathway and the key enzyme function identification, indicating that the application of modern biotechnologies provide guarantee for the molecular identification of Panax genus. The application of modern biotechnologies also reveals the genetic information of transcriptome and functional genomics, and promotes the design of Panax plants genomic map. In summary, the application of the new technologies lay the foundation for clarifying the molecular mechanisms of ginsenoside biosynthesis and enforcing the in vitro synthesis of important natural products and new drugs in future.

Full-length cDNA cloning and bioinformatics analysis of PnUGT1 gene in Panax notoginseng / 药学学报

After searching the transcriptome dataset of Panax notoginseng, one unique sequence Pn02086 encoding UDP-glucosyltransferase (UGT), which may be involved in triterpene saponin biosynthesis, was discovered. The open reading frame of the UGT gene, named as PnUGT1, was cloned by 5'-RACE and RT-PCR method from P. notoginseng. The GenBank accession number for this gene is JX018210. The bioinformatic analysis of this gene and its corresponding protein was performed. The PnUGT1 gene contains a 1488 bp open reading frame and encodes a predicted protein of 495 amino acids. The molecular weight is 55.453 kD and the protein is unstable. In the secondary structure, the percentage of alpha helix, beta turn, random coil were 36.16%, 11.31%, 52.53%, respectively. The PnUGT1 contains 7 conserved domains predicted by InterProScan, including PSPG-box which is a unique consensus sequence of glycosyltransferases involved in plant secondary metabolism. The PnUGT1 was most likely to be located in the cytoplasm, without signal peptide and transmembrane region. Sequence alignment and phylogenetic analysis demonstrated that PnUGT1 had relative close relationship to the triterpene UDP-glucosyltransferase of Medicago truncatula (AAW56092), with the 66% similarity of conserved domain PSPG-box. PnUGT1 was more abundant in P. notoginseng leaf than in flower, stem and root. Therefore, PnUGT1 gene may be involved in notoginsenoside biosynthesis.

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.

Cloning and bioinformatic analysis of PqERF1 gene in Panax quinquefolius / 药学学报

ERF family transcription factor (TF) represented ethylene-responsive protein which harbored a conserved AP2 domain. After searching the plant transcription factor database, a total of 75 unigenes was found which contained AP2 domain from the transcriptome dataset of Panax quinquefolius L. One unique sequence of ERF transcript, named as PqERF1, was cloned with entire open reading frame of 933 base pairs (bp). Protein prediction result indicated that the gene was localized in nucleus and had a conserved AP2 domain. PqERF1 gene could be induced by methyl jasmonate (MeJA) which was consistent to the inducing profile of triterpene ginsenosides. InterproScan prediction indicated that PqERF1 was probably a pathogenesis-related gene. Sequence alignment and phylogenetic analysis demonstrated PqERF1 was with high identity and had relative close relationship to the NtERF4 (Nicotiana tabacum), PhERF12 (Petunia x hybrida) and DcERF1 (Daucus carota) which was related to plant defense, regulation of secondary metabolism and the flower senescence respectively. Therefore, the gene was likely involved in regulation of secondary metabolism, plant defense and physical processes which would provide gene resource for further study on secondary metabolite synthesis and molecular breeding of P. quinquefolius.

Transcriptome characterization for Salvia miltiorrhiza using 454 GS FLX / 药学学报

To investigate the profile of gene expression in Salvia miltiorrhiza and elucidate its functional gene, 454 GS FLX platform and Titanium regent were used to produce a substantial expressed sequence tags (ESTs) dataset from the root of S. miltiorrhiza. A total of 46 722 ESTs with an average read length of 414 bp were generated. 454 ESTs were combined with the S. miltiorrhiza ESTs from GenBank. These ESTs were assembled into 18 235 unigenes. Of these unigenes, 454 sequencing identified 13 980 novel unigenes. 73% of these unigenes (13 308) were annotated using BLAST searches (E-value < or = 1e-5) against the SwissProt, KEGG TAIR, Nr and Nt databases. Twenty-seven unigenes (encoding 15 enzymes) were found to be involved in tanshinones biosynthesis, and 29 unigenes (encoding 11 enzymes) involved in phenolic acids biosynthesis. Seventy putative genes were found to encode cytochromes P450 and 577 putative transcription factor genes. Data presented in this study will constitute an important resource for the scientific community that is interested in the molecular genetics and functional genomics of S. miltiorrhiza.