A new method for preparation of template DNA for PCR from special plant materials

A simple method for preparation of template DNA suitable for PCR amplification from herbarium sampies and plant tissues rich in byproducts, e.g. polysaccharides, tannins, polyphenolic, and terpenoids compounds, is described. The total DNA from regular extraction procedure is absorbed by a small amount of glass powder and the final precipitation of glass powder is used directly as a template for PCR. Taking six plant taxa, including the herbarium specimens of Lythraceae collected from Namibia in 1957 and the silicon-dried leaf tissue from mangrove plants (Rhizophoraceae and Combretaceae) rich in by-products as exampies, the PCR products, including nrDNA ITS regions and cpDNA rbcL gene, amplified following the regular and new methods respectively are compared. Our method provides a simple, rapid and economic approach to purify and prepare template DNA for PCR from special plant materials.``     

Phylogenetic position of Ephedra rhytidosperma, a species endemic to China： Evidence from chloroplast and ribosomal DNA sequences

The chloroplast genes matK and rbcL, ribosomal gene 18S and ITS regions of nuclear ribosomal DNA from Ephedra rhytidosperma, a species endemic to China, were sequenced and its phylogenetic position was investigated. Independent and combined phylogenetic analyses for the DNA sequences from 16 taxa representing 15 species of the genus Ephedra were performed using the maximum parsimony （MP）, neighbor-joining （N J）, minimum evolution （ME） and maximum likelihood （ML） methods. The results indicate that E. rhytidosperma is closely related to E. equisetina. The divergence time between them is estimated to be 10.85±2.44 Ma based on the results of the relative-rate tests and the evolutionary rate of rbcL gene.     

基因转换的分子机制及其在nrDNA致同进化过程中的应用研究进展

基因转换是指同源序列之间非交互性的信息转换。基因转换现象已在原核生物及真核生物中被广泛发现。基因转换的主要作用是引起序列的转移、致同进化、抗原的变异、抗抗生素的免疫、缺口的修复等。通过对引起基因转换现象的4种分子重组模型(Holli-day模型、Meselson-Radding模型、DSBR模型和SDSA模型)的介绍,探讨基因转换在nrDNA致同进化过程中的应用。     

西鄂尔多斯特有种四合木与同生境下蒺藜科三个种的核rDNA ITS的序列比较研究

为揭示分布于西鄂尔多斯高原的中国特有种四合木对生境的适应性及与其他属的亲缘关系，用PCR直接测序方法，对四合木与同生境蒺藜科(zygophllyaceae)其他3个种的核糖体DNA ITS片段进行了序列分析，结果表明，4种植物在ITS片段长度、GC百分含量和变异位点数上均存在一定差异，ITSl长177-212bp，ITS2长218-237bp；GC含量为57．7％～62％，信息位点比例30．1％，系统发育分析表明，四合木(Tetraena mongolica Maxim)与霸王(Zygo-phyllum xanthoxylum Maxim)在系统位置上较相近，白刺(Nitraria sibirica Pall)与蒺藜(Tribulus terrestris L．)较相近，ITS所揭示的亲缘关系与这些种的形态学和胚胎学特征相似。