Abstract
BackgroundBupleurum chinense DC. is a widely used traditional Chinese medicinal plant. Saikosaponins are the major bioactive constituents of B. chinense, but relatively little is known about saikosaponin biosynthesis. In the present study, we performed an integrated analysis of metabolic composition and the expressed genes involved in saikosaponin biosynthetic pathways among four organs (the root, flower, stem, and leaf) of B. chinense to discover the genes related to the saikosaponin biosynthetic pathway.ResultsTranscript and metabolite profiles were generated through high-throughput RNA-sequencing (RNA-seq) data analysis and liquid chromatography tandem mass spectrometry, respectively. Evaluation of saikosaponin contents and transcriptional changes showed 152 strong correlations (P < 0.05) over 3 compounds and 77 unigenes. These unigenes belonged to eight gene families: the acetoacetyl CoA transferase (AACT) (6), HMG-CoA synthase (HMGS) (2), HMG-CoA reductase (HMGR) (2), mevalonate diphosphate decarboxylase (MVD) (1), 1-deoxy-D-xylulose-5-phosphate synthase (DXS) (3), farnesyl diphosphate synthase (FPPS) (11), β-amyrin synthase (β-AS) (13) and cytochrome P450 enzymes (P450s) (39) families.ConclusionsOur results investigated the diversity of the saikosaponin triterpene biosynthetic pathway in the roots, stems, leaves and flowers of B. chinese by integrated transcriptomic and metabolomic analysis, implying that manipulation of P450s genes such as Bc95697 and Bc35434 might improve saikosaponin biosynthesis. This is a good candidate for the genetic improvement of this important medicinal plant.
Highlights
Bupleurum chinense DC. is a widely used traditional Chinese medicinal plant
isopentenyl diphosphate (IPP) and Dimethylallyl diphosphate (DMAPP) synthesize 2,3-oxidosqualene, which is catalyzed by geranyl pyrophosphate synthetase (GPS), farnesyl diphosphate synthase (FPPS), squalene synthetase (SS) and squalene epoxidase (SE). 2,3-Oxidosqualene is cyclized by β-amyrin synthase (β-AS) to produce β-amyrin
To compare the compositions of metabolites involved in saikosaponin synthesis in the four organs, datasets obtained from high-performance liquid chromatography-tandem mass spectrometry (HPLC-High-performance liquid chromatography-tandem mass spectrometry (MS)/MS) in the ESI+ and ESI– modes were subjected to Principal component analysis (PCA)
Summary
Bupleurum chinense DC. is a widely used traditional Chinese medicinal plant. Saikosaponins are the major bioactive constituents of B. chinense, but relatively little is known about saikosaponin biosynthesis. Plants of the genus Bupleurum are major components of Oriental folk medicine in China, Japan and Korea, and have been officially listed in the Chinese and Japanese Pharmacopoeias [1]. These species are used either alone or in combination with other ingredients for treatment of the common cold, inflammatory disorders, hepatitis and fever [2]. Candidate genes responsible for saikosaponin biosynthesis were identified in B. chinense on the basis of the coordinated upregulation of their expression with β-AS in methyl jasmonate-treated adventitious roots, especially P450s and UGTs [7]. The regulatory mechanism for the saikosaponin biosynthesis pathway is still unknown
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