Abstract
BackgroundAtractylodes chinensis (DC.) Koidz is a well-known medicinal plant containing the major bioactive compound, atractylodin, a sesquiterpenoid. High-performance liquid chromatography (HPLC) analysis demonstrated that atractylodin was most abundant in 3-year old A. chinensis rhizome, compared with those from 1- and 2-year old rhizomes, however, the molecular mechanisms underlying accumulation of atractylodin in rhizomes are poorly understood.ResultsIn this study, we characterized the transcriptomes from rhizomes of 1-, 2- and 3-year old (Y1, Y2 and Y3, respectively) A. chinensis, to identify differentially expressed genes (DEGs). We identified 240, 169 and 131 unigenes encoding the enzyme genes in the mevalonate (MVA), methylerythritol phosphate (MEP), sesquiterpenoid and triterpenoid biosynthetic pathways, respectively. To confirm the reliability of the RNA sequencing analysis, eleven key gene encoding factors involved in the sesquiterpenoid and triterpenoid biosynthetic pathway, as well as in pigment, amino acid, hormone and transcription factor functions, were selected for quantitative real time PCR (qRT-PCR) analysis. The results demonstrated similar expression patterns to those determined by RNA sequencing, with a Pearson’s correlation coefficient of 0.9 between qRT-PCR and RNA-seq data. Differential gene expression analysis of rhizomes from different ages revealed 52 genes related to sesquiterpenoid and triterpenoid biosynthesis. Among these, seven DEGs were identified in Y1 vs Y2, Y1 vs Y3 and Y2 vs Y3, of which five encoded four key enzymes, squalene/phytoene synthase (SS), squalene-hopene cyclase (SHC), squalene epoxidase (SE) and dammarenediol II synthase (DS). These four enzymes directly related to squalene biosynthesis and subsequent catalytic action. To validate the result of these seven DEGs, qRT-PCR was performed and indicated most of them displayed lower relative expression in 3-year old rhizome, similar to transcriptomic analysis.ConclusionThe enzymes SS, SHC, SE and DS down-regulated expression in 3-year old rhizome. This data corresponded to the higher content of sesquiterpenoid in 3-year old rhizome, and confirmed by qRT-PCR. The results of comparative transcriptome analysis and identified key enzyme genes laid a solid foundation for investigation of production sesquiterpenoid in A. chinensis.
Highlights
Atractylodes chinensis (DC.) Koidz is a well-known medicinal plant containing the major bioactive compound, atractylodin, a sesquiterpenoid
The atrctylodin content in 1, 2‐ and 3‐year old A. chinensis rhizomes As atrctylodin is the main and index bioactive constituent in A. chinensis, its levels in rhizome from 1, 2- and 3-year old A. chinensis plants were measured by High-performance liquid chromatography (HPLC) analysis, with atrctylodine contents (%) recorded as 0.2252, 0.2378 and 0.2939, respectively (Table 1, Table 1 Atractylodin content (%) in rhizomes of 1, 2- and 3-year old A. chinensis
The atractylodin content of 1-year old rhizome was considered as control
Summary
Atractylodes chinensis (DC.) Koidz is a well-known medicinal plant containing the major bioactive compound, atractylodin, a sesquiterpenoid. High-performance liquid chromatography (HPLC) analysis demonstrated that atractylodin was most abundant in 3-year old A. chinensis rhizome, compared with those from 1- and 2-year old rhizomes, the molecular mechanisms underlying accumulation of atractylodin in rhizomes are poorly understood. A. lancea is currently on the verge of extinction, A. chinensis is the main source of the rhizome atractylodes that widely distributed in most areas of Northern China. The main bioactive compounds in A. chinensis rhizome are used to treat digestive disorders, rheumatic diseases and night blindness [6]. The sesquiterpenoid components of A. chinensis rhizome have important pharmacological activities, the molecular mechanisms underlying accumulation of bioactive sesquiterpenoids are poorly understood. Sesquiterpenoids are generally synthesized via MVA and MEP biosynthetic pathways
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