日本血吸虫尾蚴(中国大陆株)表达序列标签的获取及同源性分析

Acquisition of expressed sequence tags from Schistosoma japonicum cercariae (China's Mainland strain) and its homology analysis

目的 了解日本血吸虫尾蚴ｃＤＮＡ文库中基因的基本情况，为新基因的筛选鉴定提供依据。方法 日本血吸虫尾 蜘ｃＤＡＮ文库中的噬菌体侵入大肠杆菌ＢＭ２５．８后环化成质粒。筛选出已转入质粒的菌株。提取质粒ＤＮＡ，用质粒上 的一段测序引物序列进行一次性测序，得到一个表达序列标签（ＥＳＴ）。通过ＢＬＡＳＴｘ及ＢＬＡＳＴｎ公共数据库经编辑分 析的ＥＳＴ序列进行同源性比较。经过分析编辑后的新ＥＳＴ序列，以编写好的程序和Ｅ－ｍａｉｌ方式递交，以获得ＧｅｎＢａｎｋ 登录号。通过对同源性比较结果的总结，对该文库的基本情况进行分析。结果与结论 在测出的５８个ＥＳＴ中有３个核 苷酸序列与日本血吸虫已知基因高度同源，有２个核苷酸序列与曼氏血吸虫较高度同源，有７个ＥＳＴ的蛋白质序列与 其他物种有较高同源性而核苷酸序列同源性很低，有２７个ＥＳＴ的蛋白质及核苷酸序列同源性都很低。

Objective To understand the general profiles of the genes included in Schistosoma japonicum (S j) cercarriae cDNA library that we have constructed for the purpose of identifying novel genes. Methods The phages in Sj cercariae cDNA library were transformed into plasmids after they had invaded into E.coli BM25.8, and the E.coli clones containing the plasmids were cultured in LB medium supplemented with aminobenzylpenicillin. The isolated colonies were selected for plasmid extraction and the DNAs subsequently extracted from the plasmids underwent sequence analysis with a sequencing primer to obtain the expressed sequence tags (ESTs). After sequence editing of the resulted ESTs, comparison of these sequences with those listed in the GenBank database was performed for homology analysis. The new sequences generated from the analysis were submitted to GenBank and the accession numbers acquired. Results and Conclusion Altogether 58 ESTs were identified, among which 3 possessed highly homologous nucleotide sequences with the known genes of Sj, 2 showed the homology with Schistosoma mansori genes, 7 had the homologous protein sequences, but not the nucleotide sequences, with other species, and another 27 were poorly homologous in terms of both the nucleotide and protein sequences.