ABSTRACT
Astragalosides are the main active constituents of traditional Chinese medicine Huang-Qi, of which cycloastragenol-type glycosides are the most typical and major bioactive compounds. This kind of compounds exhibit various biological functions including cardiovascular protective, neuroprotective, etc. Owing to the limitations of natural sources and the difficulties encountered in chemical synthesis, re-engineering of biosynthetic machinery will offer an alternative and promising approach to producing astragalosides. However, the biosynthetic pathway for astragalosides remains elusive due to their complex structures and numerous reaction types and steps. Herein, guided by transcriptome and phylogenetic analyses, a cycloartenol synthase and four glycosyltransferases catalyzing the committed steps in the biosynthesis of such bioactive astragalosides were functionally characterized from Astragalus membranaceus. AmCAS1, the first reported cycloartenol synthase from Astragalus genus, is capable of catalyzing the formation of cycloartenol; AmUGT15, AmUGT14, AmUGT13, and AmUGT7 are four glycosyltransferases biochemically characterized to catalyze 3-O-xylosylation, 3-O-glucosylation, 25-O-glucosylation/O-xylosylation and 2'-O-glucosylation of cycloastragenol glycosides, respectively. These findings not only clarified the crucial enzymes for the biosynthesis and the molecular basis for the structural diversity of astragalosides in Astragalus plants, also paved the way for further completely deciphering the biosynthetic pathway and constructing an artificial pathway for their efficient production.
ABSTRACT
Steroidal saponins, which are the characteristic and main active constituents of Polygonatum, exhibit a broad range of pharmacological functions, such as regulating blood sugar, preventing cardiovascular and cerebrovascular diseases and anti-tumor. In this study, we performed RNA sequencing(RNA-Seq) analysis for the flowers, leaves, roots, and rhizomes of Polygonatum cyrtonema using the BGISEQ-500 platform to understand the biosynthesis pathway of steroidal saponins and study their key enzyme genes. The assembly of transcripts for four tissues generated 129 989 unigenes, of which 88 958 were mapped to several public databases for functional annotation, 22 813 unigenes were assigned to 53 subcategories and 64 877 unigenes were annotated to 136 pathways in KEGG database. Furthermore, 502 unigenes involved in the biosynthesis pathway of steroidal saponins were identified, of which 97 unigenes encoding 12 key enzymes. Cycloartenol synthase, the first key enzyme in the pathway of phytosterol biosynthesis, showed conserved catalytic domain and substrate binding domain based on sequence analysis and homology modeling. Differentially expressed genes(DEGs) were identified in rhizomes as compared to other tissues(flowers, leaves or roots).The 2 437 unigenes annotated by KEGG showed rhizome-specific expression, of which 35 unigenes involved in the biosynthesis of steroidal saponins. Our results greatly extend the public transcriptome dataset of Polygonatum and provide valuable information for the identification of candidate genes involved in the biosynthesis of steroidal saponins and other important secondary metabolites.
Subject(s)
Biosynthetic Pathways , Gene Expression Profiling , Polygonatum , Saponins , Sequence Analysis, RNA , TranscriptomeABSTRACT
Objective To obtain the key enzyme gene involved in alkaloids biosynthesis pathway of Fritillaria cirrhosa, cycloartenol synthase (CAS) gene was cloned, and its bioinformatics analysis and gene expression pattern were also performed. Methods The open reading frame (ORF) of F. cirrhosa CAS (FcCAS) was amplified by PCR based on transcriptome sequencing. The bioinformatics analysis of FcCAS cDNA sequences was carried out by some online tools. Meanwhile, using real-time quantitative PCR (qRT-PCR) to analyze the gene expression patterns between wild and regeneration bulbs. Moreover, the content of total alkaloids in wild and regenerated bulbs were also investigated. Results The results showed that CAS had a length of 2 271 bp ORF, which encoding 756 amino acids. The phylogenetic tree analysis showed that FcCAS were highly similar to the corresponding proteins in Asparagus officinalis, Musa acuminate, and Elaeis gunineensis from the NCBI website, and the similarities were more than 80%. The results of qRT-PCR and total alkaloids assay showed that the changing trend of the expression level of FcCAS was consistent with that of the content of total alkaloids, and higher alkaloid accumulation was in regeneration bulbs than wild bulbs. Conclusion The expression of FcCAS gene varied widely in different tissues. These findings suggested that FcCAS was a biological functional protein induced by hormone combination, which laid a theoretical foundation for the improvement of the alkaloid content by using the genetic engineering.
ABSTRACT
Mogrosides and steroid saponins are tetracyclic triterpenoids found in. Squalene synthase (SQS) and cycloartenol synthase (CAS) are key enzymes in triterpenoid and steroid biosynthesis. In this study, full-length cDNAs ofandwere cloned by a rapid amplification of cDNA-ends with polymerase chain reaction (RACE-PCR) approach. ThecDNA has a 1254 bp open reading frame (ORF) encoding 417 amino acids, and thecDNA contains a 2298 bp ORF encoding 765 amino acids. Bioinformatic analysis showed that the deduced SgSQS protein has two transmembrane regions in the C-terminal. Bothandhave significantly higher levels in fruits than in other tissues, suggesting that steroids and mogrosides are competitors for the same precursors in fruits. Combinedprediction and subcellular localization, experiments in tobacco indicated that SgSQS was probably in the cytoplasm or on the cytoskeleton, and SgCAS was likely located in the nucleus or cytosol. These results will provide a foundation for further study ofandgene functions in, and may facilitate improvements in mogroside content in fruit by regulating gene expression.
ABSTRACT
Sterol C24-methyltransferase (SMT) plays multiple important roles in plant growth and development. SMT1, which belongs to the family of transferases and transforms cycloartenol into 24-methylene cycloartenol, is involved in the biosynthesis of 24-methyl sterols. Here, we report the cloning and characterization of a cDNA encoding a sterol C24-methyltransferase from().(GenBank access number KU885950) is a 1530 bp cDNA with a 1041 bp open reading frame predicted to encode a 346-amino acid, 38.62 kDa protein. The polypeptide encoded by thecDNA was expressed and purified as a recombinant protein from() and showed SMT activity. The expression ofwas highly up-regulated incell suspension cultures treated with methyl jasmonate (MeJA). Tissue expression pattern analysis showed higher expression in the phellem layer compared to the other four organs (leaf, stem, xylem and phloem), which is about ten times that of the lowest expression in leaf. The results are meaningful for the study of sterol biosynthesis ofand will further lay the foundations for the research in regulating both the content of other main compounds and growth and development of
ABSTRACT
Cycloartenol, a phytosterol compound, also one of the key precusor substances for biosynthesis of numerous sterol compounds, has a variety of pharmacological activities such as anti-inflammatory, anti-tumor, antioxidant, antibiosis and anti-alzheimer's disease. Furthermore, cycloartenol also plays an important role in the process of plant growth and development. This article reviewed the research progress on cycloartenol pharmacological activity in domestic and foreign articles, and summarized the effect of cycloartenol and "cycloartenol pathway" on the plant growth and development, laying foundation for the its further study, development and utilization.
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The constituents of Cimicifuga plants have been extensively investigated, and the principal metabolites are 9,19-cyclolanostane triterpenoid glycosides, which are distributed widely in Cimicifuga plants, but not in other members of the Ranunculaceae family, and are considered to be characteristics of the Cimicifuga genus. This type of triterpenoid glycoside possesses several important biological activities. More than 120 cycloartane triterpene glycosides have been isolated from Cimicifuga simplex Wormsk. The aim of this review article is to summarize all the major findings based on the available scientific literatures on C. simplex, with a focus on the identified 9,19-cyclolanostane triterpenoid glycosides. Biological studies of cycloartane triterpene glycosides from Cimicifuga spp. are also discussed.
Subject(s)
Animals , Humans , Cimicifuga , Chemistry , Phytosterols , Chemistry , Pharmacology , Plant Extracts , Chemistry , Pharmacology , Saponins , Chemistry , Pharmacology , Triterpenes , Chemistry , PharmacologyABSTRACT
We cloned and analyzed the two genes of the 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase (HDR) gene family from Huperzia serrate. The two transcripts coding HDR, named HsHDR1 and HsHDR2, were discovered in the transcriptome dataset of H. serrate and were cloned by reverse transcription-polymerase chain reaction (RT-PCR). The physicochemical properties, protein domains, protein secondary structure, and 3D structure of the putative HsHDR1 and HsHDR2 proteins were analyzed. The full-length cDNA of the HsHDR1 gene contained 1431 bp encoding a putative protein with 476 amino acids, whereas the HsHDR2 gene contained 1428 bp encoding a putative protein of 475 amino acids. These two proteins contained the conserved domain of 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase (PF02401), but without the transmembrane region and signal peptide. The most abundant expression of HsHDR1 and HsHDR2 was detected in H. serrate roots, followed by the stems and leaves. Our results provide a foundation for exploring the function of HsHDR1 and HsHDR2 in terpenoid and sterol biosynthesis in Huperziaceae plants.