广西、湖南、云南三地钉螺Cytb基因序列变异和系统进化研究

目的分析广西钉螺与云南、湖南钉螺Cytb基因的遗传多态性和系统进化关系。方法收集广西靖西、云南洱源和湖南岳阳三地钉螺,提取其基因组DNA,PCR法扩增线粒体Cytb基因并测序。用Clustal W（1.82）软件对所测得的Cytb基因序列进行排序,用MEGA3.1计算其碱基组成、转换及颠换;用Kimura双参数法计算遗传距离,用非加权组平均法（UPGMA）和最大简约法（MP）构建系统发生树,同时结合三地钉螺分布和孳生地等资料进行分析。结果PCR扩增获得Cytb基因大小为580 bp。三地钉螺Cytb基因序列富含碱基A和T,A＋T平均含量为61.2%,表现出较强的碱基组成偏倚。三地钉螺Cytb基因578 bp的同源序列中检测到165个变异位点,约占核苷酸总数的28.5%。其中广西钉螺与湖南钉螺Cytb基因序列的变异位点为17个,约占2.94%;广西钉螺与云南钉螺Cytb基因序列的变异位点为160个,约占27.7%。广西钉螺与湖南、云南钉螺Cytb基因的遗传距离分别为0.031、0.405。采用两种方法构建的系统进化树均显示广西钉螺与湖南钉螺同属一个支系,云南钉螺单独形成另一支系。结论广西钉螺与云南钉螺存在较大基因差异,进化速率较大,保守性较小,遗传距离较大,亲缘关系较远;广西钉螺与湖南钉螺基因差异较小,相对保守,进化速率不太大,遗传距离较小,亲缘关系较近。

Variation and phylogenetic analysis of cytochrome B sequences from Oncomelania hupensis isolated from Guangxi,Yunnan and Hunan

Objective To study the genetic polymorphism and phylogenetic evolution of Oncomelania hupensis isolated from Guangxi, Yunnan and Hunan base on mitochondrial cytochrome b（Cytb） gene. Methods Snails were collected from Jingxi of Guangxi, Yueyang of Hunan and Eryuan of Yunnan. Genomic DNA was extracted from the snails, Cytb gene fragments were amplified by PCR method, purified and sequenced. Sequences of each isolates were analyzed by using Clustal W software and the nucleotide composition, transition and transversion were accounted by using MEGA 3.1 software. The genetic distances were computed with Kimura method and phylogenetic trees were constructed with UPGMA and MP method respectively. Results Cytb gene fragment was about 580 bp with strong nucleotide favoritism. The average contents of A＋T （61.2%） was obviously higher than that of G＋C （38. 8%）. A total of 165 mutation spots （28.5%） were tested in 578 homological nucleotides. The mutation spots between Guangxi and Hunan isolates accounted for 2.94%, which is lower than that of between Guangxi and Yunnan ones （27.7%）. The genetic distances were 0. 031 between Guangxi and Hunan isolates and those between Guangxi and Yunnan was 0. 405. Phylogenetic trees constructed by UPGMA and MP took on the similar topo-structure. Isolates of Guangxi and Hunan were clustered into one group, while the Yunnan isolates as another group. Conclusion The results indicated little gene variation, lower evolution speed between Guangxi and Hunan snails and with closer phylogenic relationships than that of between Guangxi and Yunnan ones.