Wen Lingling, Yun Xiaoyun, Zheng Xiasheng, Xu Hui, Zhan Ruoting, Chen Weiwen, Xu Yaping, Chen Ye, Zhang Jie
Key Laboratory of Chinese Medicinal Resource from Lingnan, Research Center of Chinese Herbal Resource Science and Engineering, Guangzhou University of Chinese MedicineGuangzhou, China.
Zhongshan Zhongzhi Pharmaceutical Group, Key Laboratory for Technologies and Applications of Ultrafine Granular Powder of Herbal Medicine, State Administration of Traditional Chinese MedicineZhongshan, China.
Front Plant Sci. 2017 Apr 28;8:634. doi: 10.3389/fpls.2017.00634. eCollection 2017.
Native to Southern China, and are frequently used in traditional Chinese medicine. Both of them produce a large variety of ursane-type triterpenoid saponins, which have been demonstrated to have different pharmacological effects. However, little is known about their biosynthesis. In this study, transcriptomic analysis of and comparison with its closely related specie were carried out to identify potential genes involved in triterpenoid saponin biosynthesis. Through RNA sequencing (RNA-seq) and transcriptome assembly of , a total of 68,688 UniGene clusters are obtained, of which 32,184 (46.86%) are successfully annotated by comparison with the sequences in major public databases (NCBI, Swiss-Prot, and KEGG). It includes 128 UniGenes related to triterpenoid backbone biosynthesis, 11 OSCs (oxidosqualene cyclases), 233 CYPs (cytochrome P450), and 269 UGTs (UDP-glycosyltransferases). By homology-based blast and phylogenetic analysis with well-characterized genes involved in triterpenoid saponin biosynthesis, 5 s, 14 s, and 1 are further proposed as the most promising candidate genes. Transcriptomic comparison between two species using blastp and OrthoMCL method reveals high sequence similarity. All s and s as well as most s are classified as orthologous genes, while only 5 s in and 3 s in are species-specific. One of candidates, named as 1, was successfully cloned and expressed in INV1. Analysis of the yeast extract by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) shows 1 is a mixed amyrin synthase, producing α-amyrin and β-amyrin at ratio of 5:1, which is similar to its ortholog 1 from . This study is the first exploration to profile the transcriptome of , the generated data and gene models will facilitate further molecular studies on the physiology and metabolism in this plant. By comparative transcriptomic analysis, a series of candidate genes involved in the biosynthetic pathway of triterpenoid saponins are identified, providing new insight into their biosynthesis at transcriptome level.
它们原产于中国南方，常用于传统中药。二者都能产生多种乌苏烷型三萜皂苷，这些皂苷已被证明具有不同的药理作用。然而，关于它们的生物合成却知之甚少。在本研究中，对其进行了转录组分析，并与其近缘物种进行比较，以鉴定参与三萜皂苷生物合成的潜在基因。通过RNA测序（RNA-seq）和其转录组组装，共获得68,688个单基因簇，其中32,184个（46.86%）通过与主要公共数据库（NCBI、Swiss-Prot和KEGG）中的序列比较成功注释。其中包括128个与三萜骨架生物合成相关的单基因、11个氧化鲨烯环化酶（OSC）、233个细胞色素P450（CYP）和269个尿苷二磷酸糖基转移酶（UGT）。通过与参与三萜皂苷生物合成的已明确特征的基因进行基于同源性的比对和系统发育分析，进一步提出5个基因、14个基因和1个基因作为最有前景的候选基因。使用blastp和OrthoMCL方法对两个物种进行转录组比较，结果显示序列相似性很高。所有的基因和基因以及大多数基因都被归类为直系同源基因，而在中只有5个基因和在中只有3个基因是物种特异性的。其中一个候选基因，命名为1，已在酿酒酵母INV1中成功克隆并表达。通过气相色谱（GC）和气相色谱-质谱联用（GC-MS）对酵母提取物进行分析表明，1是一种混合的齐墩果烷合酶，以5:1的比例产生α-齐墩果烷和β-齐墩果烷，这与其来自的直系同源基因1相似。本研究是对其转录组进行分析的首次探索，所产生的数据和基因模型将有助于对该植物的生理学和代谢进行进一步的分子研究。通过比较转录组分析，鉴定出一系列参与三萜皂苷生物合成途径的候选基因，为其在转录组水平上的生物合成提供了新的见解。
