ITS2二级结构系统发育信息在茄属药用植物DNA条形码鉴定中的应用价值

Application of phylogenetic information of ITS2 secondary structure in DNA barcoding of Solanum medicinal plant

ITS2是中药鉴定的核心DNA条形码之一,基于ITS2的中药鉴定方法已被纳入《中国药典》,但分辨力不足仍是制约其推广应用的主要因素,因此需要进一步挖掘其有助于中药鉴定的遗传信息。在细胞内,ITS2以二级结构形式发挥功能,这种结构所蕴含的丰富遗传信息是核酸序列所无法体现的。该研究以茄属Solanum 26个物种的40个样本为研究对象来探究ITS2二级结构在茄属药用植物鉴定中的价值。作者利用Pic XAA-R,MASTR和Loc ARNA软件来比对二级结构,利用RNAstat软件将二级结构信息转为系统发育信息,最后利用最大简约法进行建树分析。研究结果表明将ITS2二级结构转化为系统发育信息后信息位点增加了88.57%,物种关系树上50%,75%,90%以上支持率的支系分别增加了19.05%,66.67%,66.67%,从而很好地解决了茄属几种药用植物的鉴定问题。鉴于以上结果,作者建议将ITS2二级结构信息作为系统发育信息的有益补充加入到目前DNA条形码分析中。

Internal transcript spacer 2（ ITS2） is one of the broadly used standard core barcodes and also the only nuclear barcode in identification of Chinese traditional medicine. Although the DNA barcode method based on ITS2 is popular and has been used in Chinese Pharmacopoeia,its low discriminatory efficiency is still a problem to its extensive application. Therefore,further study is still necessary to explore its phylogenetic information for medicinal plants identification. In cells,ITS2 activity is based on its secondary structure. The secondary structures are particularly useful in phylogenetic analysis because they include information not found in the primary sequence. In this study ITS2 secondary structure of 40 samples from 26 species were predicted and used to explore their utility in addressing the identification problems of Chinese traditional medicine in Solanum. The secondary structures were predicted and aligned,and their consensus models were generated using the three different software of Loc ARNA,MASTR and Pic XAA-R.RNAstat software was used to transform the secondary structures into 28 symbol code data for maximum parsimony（ MP） analysis. The results showed that the phylogenetic information increased 88. 57 % after ITS2 secondary structure information has been added,and then the support values above 50 %,75 % and 90 % in the tree increased 19. 05 %,66. 67 % and 66. 67 %,respectively,indicating that the identification of Solanum medical plants has been well resolved. Thus,our analysis suggests that ITS2 secondary structure information should be incorporated into the current DNA barcoding analysis as a beneficial supplement of phylogenetic information.