Abstract
Nowadays, with the development and advancement of next-generation sequencing technologies, a new path has been provided for transcriptomic studies. In this study, the transcriptome of Dracocephalum kotschyi Boiss., as an endemic and endangered plant which is contained a large amount of valuable secondary metabolites with antioxidant and anticancer properties, was sequenced. Then functional annotation and gene ontology analysis for 165,597 assembled transcripts were performed, most were associated with the metabolic pathways. This might be because there are various active biochemical pathways in this plant. Furthermore, after comprehensive transcript annotation, the putative genes involved in the main metabolic pathways of D. kotschyi were identified. Then, the biosynthetic pathway of its valuable methoxylated flavones was proposed. Finally, the accumulations of important methoxylated-flavone metabolites in three different tissues were quantified by HPLC. The relative expression of the genes involved in the proposed pathway was investigated by qRT-PCR, which indicated high expression levels in the bud tissue. The present results may lead to the design strategies to preserve the genetic diversity of endangered D. kotschyi plants and apply the new methods for engineering its valuable methoxylated-flavones pathway.
Highlights
Nowadays, with the development and advancement of next-generation sequencing technologies, a new path has been provided for transcriptomic studies
No research has been conducted on whole transcriptome studies and specific biosynthetic pathways analysis of this to identify the genes involved in the biosynthetic pathways of valuable metabolites of D. kotschyi
Transcriptome sequencing of D. kotschyi was performed by the Illumina HiSeq technology (HiSeq2500 platform)
Summary
With the development and advancement of next-generation sequencing technologies, a new path has been provided for transcriptomic studies. No research has been conducted on whole transcriptome studies and specific biosynthetic pathways analysis of this to identify the genes involved in the biosynthetic pathways of valuable metabolites (e.g., xanthomicrol, calycopterin, penduletin, and rosmarinic acid) of D. kotschyi. For organisms without a reference genome, de novo assembly is essential to provide a workable solution for transcriptome analysis This method has already been used to study another species of Dracocephalum[11] and Lamiaceae family[12] to identify candidate genes involved in important secondary metabolic pathways. This study aims to elucidate the methoxylated-flavones biosynthesis pathway in D. kotschyi To reach this goal, leaf transcriptome data of D. kotschyi was generated using a paired-end (PE) Illumina sequencing platform, and putative genes involved in phenylpropanoids and terpenoids biosynthesis pathways were identified. The biosynthetic pathway of main methoxylated flavones of D. kotschyi, including xanthomicrol, calycopterin, and penduletin, was proposed via our results and available literatures[13,14,15]
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