基于ITS2序列的滨海白首乌及其近缘种DNA分子鉴定

目的采用ITS2条形码鉴定滨海白首乌及其近缘种药用植物。方法采集滨海白首乌Cynanchum auriculatum及其近缘种植物样品共54份,分别提取基因组DNA,通过PCR扩增ITS2序列并进行双向测序,测序结果提交至GenBank;从GenBank下载萝藦科植物16种47条序列,并通过ITS2数据库注释出ITS2序列;对提交与下载的101条序列,应用MEGA5.0软件进行序列比对,计算种内和种间距离,采用相似性搜索法、最近距离法进行鉴定分析,并构建neighber-joining(NJ)系统进化树直观反映鉴定结果。结果滨海白首乌ITS2序列长度均为249 bp,是1个单倍型,与萝藦科鹅绒藤属植物距离较近,与萝藦科其他属近缘种之间遗传距离较远,NJ树结果显示滨海白首乌及其近缘种药用植物均可明显区分,表现出良好的单系性,依据ITS2二级结构,也可以直观地将滨海白首乌与萝藦科近缘种区分。结论 ITS2序列作为DNA条形码能稳定、准确鉴别滨海白首乌,为保障安全用药提供了新的技术手段。

Molecular identification of Cynanchum auriculatum and its closely related species based on ITS2 sequence

Objective To identify Cynanchum auriculatum and its closely related species using the ITS2 barcode. Methods A total of 54 samples of C. auriculatum and its related species were collected. Genomic DNAs were extracted from these samples. The ITS2 sequences of these samples were amplified and bidirectional sequenced by PCR. The obtained sequences were submitted to the Gen Bank and the ITS2 sequences of 47 samples belonging to 15 species were downloaded from the GenBank, and ITS2 sequences were annotated by ITS2 database. A total of 101 ITS2 sequences were aligned and the intraspecific and interspecific distances were calculated using the MEGA 5.0. Identification analyses were performed using the similarity search method and nearest distance method, and were presented intuitively by constructing neighbor-joining (NJ) tree. Results The length of all ITS2 sequences of C. auriculatum was 249 bp, which was a haplotype and was close to Cynanchum. There was a significant difference between the interspecific and intraspecific genetic distances of the ITS2 sequences. The NJ tree showed that C. auriculatum obviously differed from its closely related species, which showed high monophyly. According to the secondary structure of ITS2, it was also possible to distinguish between C. auriculatumi and Asclepiadaceae related species. Conclusion As a DNA barcode, ITS2 sequences can stably and accurately distinguish C. auriculatum from its closely related species and also provide a new technique to ensure the clinical safety in utilization of Chinese materia medica.