植物DNA条形码技术

DNA条形码技术是利用标准的、具有足够变异的、易扩增且相对较短的DNA片段在物种内的特异性和种间的多样性而创建的一种新的生物身份识别系统, 从而实现对物种的快速自动鉴定。尽管这一技术在理论上和具体应用上仍存在很多争论, 但DNA条形码概念自2003年由加拿大分类学家Paul Hebert首次提出后就在世界范围内受到了广泛关注。在植物类群中条形码的研究和应用尚处于探索阶段, 稍落后于对动物类群的研究, 这主要表现在: (1) DNA条形码的选择及其评价仍没有统一的标准; (2) 对类群较全面的形态分类学修订和植物DNA条形码研究的结合十分缺乏; (3) 以往研究在取样上尺度较大, 而对具体类群的研究较少, 一个科或一个属只用有限的种类作为代表, 同一种内的取样个体数量也不足, 这样虽然表面上看来利用选定的DNA条形码可以较容易地把代表物种区分开, 但实际上目前建议的植物DNA条形码(例如由生命条形码咨询委员会植物工作组最近提出的rbcL和matK)由于其分子进化速率较慢, 在种级水平上, 特别是对于那些经历了适应辐射或快速进化的属来说, 分辨率较低。而DNA条形码的应用主要集中在属内物种水平的鉴别, 因此只有针对具体类群进行探索研究, 发现进化速率较快、分辨率高且通用性好的条形码, 才可能为建立完整的条形码数据库起到积极有效的作用。

DNA Barcoding Plant Life

DNA barcoding is a new biological tool for accurate, rapid and automated species identification by use of short, standardized genes or DNA regions that can be amplified easily by PCR. Although DNA barcoding involves controversial theoretical and practical aspects, it has received considerable attention since Paul Hebert proposed the concept in 2003. The research into and application of DNA barcoding in plants is still in its early exploration stage and is inferior to that in animals. Three underlying problems for plant DNA barcoding still persist. First, no consistent criteria exist for the selection and assessment of barcodes. Second, research into DNA barcoding based on thorough morphological taxonomic revision is necessary but is lacking. Third, previous studies in plants were mainly carried out on a large scale, with only a few species within one genus and single or few individuals from the same species sampled, which resulted in a superficially high rate of discrimination and low credibility of the reference database. Until now, rbcL and matK are undoubtedly the most useful barcodes and provide a universal framework for land plants at and above generic levels. However, they do not provide enough informative sites to identify all the species within some genera, in particular those with recent rapid radiation. Thus other markers with faster evolutionary rate than these 2 genes are needed, although the plant working group of the Consortium for the Barcode of Life has recommended the 2-locus combination of rbcL and matK as the barcode for plants.