川续断β-香树脂醇合酶的基因克隆及生物信息学分析

Cloning and bioinformatics analysis of β-amyrin synthase in Dipsacus asper

续断是我国常用中药材之一,药用历史悠久,具有补肝肾、强筋骨、续折伤等功效。三萜皂苷类化合物是川续断科植物川续断的主要药效成分。β-香树脂醇合酶(β-AS)属于氧化角鲨烯环化酶(OSCs)超家族,在生物合成途径中具有催化齐墩果烷型三萜皂苷骨架形成的功能。目前有关川续断β-香树脂醇合酶的研究较少,其催化机制仍待探究。为进一步挖掘与丰富该类酶的信息,该研究通过对转录组测序结果进行分析,从川续断中克隆得到1个β-香树脂醇合酶基因DaWβ-AS,并构建至大肠杆菌载体中实现蛋白表达;并采用实时荧光定量PCR技术分析其在川续断4个不同组织中的相对表达量,结果显示DaWβ-AS基因在叶中的相对表达量最高。生物信息学分析表明,DaWβ-AS蛋白含有PLN03012保守结构域,属于cl31551超家族,无跨膜区且不含信号肽。通过对川续断β-AS的克隆、表达及生物信息学分析,为川续断三萜皂苷生物途径解析提供了科学依据,有助于推动后期川续断三萜皂苷的定向生物合成,并为高质量川续断资源培育与开发提供相关参考。

Dipsaci Radix is one of the commonly used Chinese medicinal materials in China, with a long history. It has the medicinal activities of nourishing liver and kidney, recovering from broken sinews, and treating bone fracture. Triterpenoid saponins are the main functional ingredients of Dipsacus asper. β-Amyrin synthases(β-AS) as a superfamily of oxidosqualene cyclases(OSCs) can catalyze the construction of the skeleton structure of oleanane-type triterpenoid saponins. There are only a few studies about the β-AS in D. asper, and the catalytic mechanism of this enzyme remains to be explored. To enrich the information of β-AS, according to the transcriptome sequencing results, we cloned DaWβ-AS gene from D. asper into a specific vector for heterologous expression in Escherichia coli. In the meantime, real-time PCR was performed to analyze the relative expression of DaWβ-AS in four different tissues of D. asper. The results of RT-qPCR showed DaWβ-AS had the highest expression level in leaves. Bioinformatics results indicated that DaWβ-AS had a conserved domain of PLN03012 superfamily, belonging to the cl31551 superfamily. There was no transmembrane domain or signal peptide in DaWβ-AS. This study provides a scientific basis for revealing the biological pathways of triterpenoid saponins in D. asper, which will facilitate the biosynthesis of the associated saponins and afford reference for the cultivation and development of high-quality resources of D. asper.