三峡库区上、下游血吸虫病流行区钉螺线粒体cox1基因遗传变异研究

目的研究三峡库区上、下游血吸虫病流行区钉螺线粒体DNA细胞色素C氧化酶亚单位t（c毗1）基因的遗传变异。方法采集三峡库区上游四川、云南及下游安徽、湖北4省共7个地、市的钉螺样本，提取基因组DNA，PCR特异性扩增线粒体cox1基因并测序，用ClustalX（1．81）软件进行多序列比对，MEGA（4．0）软件Kimura2-parameter法计算遗传距离，邻接法（NJ）和最大简约法（MP）构建系统发生树。结果上游与下游不同地域株钉螺间cox1基因差异约为16％．下游地区的肋壳与光壳钉螺cox1基因差异约为3．7％，上游不同地域株钉螺碱基差异约为5．4％。遗传距离显示，上游四川与云南地域株的遗传距离为0．022～0．050，下游安徽与湖北地域株的遗传距离为0．014～0．027，而上游与下游各地区螺群间的遗传距离在0．127～0．138之间，明显大于上游或下游各地区螺群内的遗传距离。进化树结果表明，下游湖北的荆州、石首和安徽的芜湖、宁国钉螺形成一支系，上游四川的绵竹、新都钉螺同属一支系。但两种方法构建的进化树在云南大理钉螺的归属上存在差异，MP法提示大理钉螺从上游的分支中独立出来，单独形成一类。结论上游与下游不同地域株钉螺cox1基因遗传差异较显著，下游肋壳和光壳钉螺种群内遗传变异较小，而上游光壳钉螺种群内遗传变异较大。

Study on coxl Gene Diversity of Oncomelania hupensis from Upstream and Downstream of The Three Gorges Reservoir

Objective To analysis the genetic variation of mtDNA coxl of Oncomelania hupensis from upstream and downstream of The Three Gorges reservoir. Methods Snails were collected from 7 different areas distributed in upstream and downstream regions. Genomic DNA was extracted from the snails, and the coxl gene fragments were amplified by PCR, then purified and sequenced. Sequences were edited using ClustalX （1.81） software. The genetic distances of the various regions were calculated by Kimura method and phylogenetic trees were constructed with NJ and MP method of MEGA（4.0） software. Results There is 16% difference in the coxl gene between upstream and downstream population. 3.7% of divergence was observed between smooth- and ribbed-shelled of downstream populations, and there is 5.4% nucleotide variance among the smooth-shelled of upstream populations. In the upstream, the genetic distance between Sichuan isolates and Yunan isolates is 0.022-0.050, while in downstream the genetic distance between Anhui isolates and Wubei district isolates is 0.014-0.027. The genetic distance between upstream and downstream is 0.127-0.138, which is obviously greater than that between populations within upstream or downstream. The phylogentic analysis indicates the downstream snails in Jingzhou and Shishou of Wubei, and those in Wuhu and Ningguo of Anhui are clustered; the upstream snails in Mianzhu and Xindu of Sichuan are clustered. However, the clustering results are different in two different methods for constructing the phylogenetic trees. The result of MP method indicates the upstream snails in Dali is separated from others as an independent group. Conclusion There is a large genetic diversity between upstream and downstream snail populations. A little genetic varialbility was found among smooth- and ribbed-shelled of downstream populations, but there is relatively large difference within smooth-shelled of upstream populations.