虾肝肠胞虫感染病理特征、18S rRNA基因序列及系统进化树分析

为调查浙江省部分地区虾肝肠胞虫(Enterocytozoon hepatopenaei, EHP)暴发来源及与其他宿主来源的微孢子虫进化关系, 本研究利用形态学特征和分子鉴定, 尝试对引起浙江多地凡纳对虾生长缓慢综合征的病原进行探究. 同时基于18S rRNA基因序列分析该病原与其他地区及其他宿主来源微孢子虫的进化关系. 结果显示, 所采病虾均为EHP阳性, 采样地区EHP 18S rRNA基因具有高度同源性, 为98.5%~100%. 对国内外EHP基因序列进行同源性分析, 其同源性为86.2%~100%, 所采EHP与印度EHP聚为一个分支. EHP 18S rRNA基因序列与其他水生生物微孢子虫18S rRNA均处于不同分支, 表明18S rRNA可作为EHP的主要鉴别序列. 将本研究所采EHP与NCBI中同源性较高的比氏肠胞虫和金头鲷微孢子虫比较分析, 结果表明微孢子虫基因序列同源性与宿主进化发育程度有关, 宿主之间进化距离越近, 则微孢子虫基因序列同源性相聚越近.

Pathological characteristics of Enterocytozoon hepatopenaei, 18S rRNA gene sequence and phylogenetic analysis

Outbreaks of slow growth syndrome of Penaeus vannamei have occurred in some areas of Zhejiang Province. In the present study, pathological characteristics and molecular identification were determined to examine the pathogen causing slow growth syndrome of Penaeus vanamei in shrimp farms. The relationship was also investigated between this pathogen and the microsporidia from other regions and other host sources based on 18S rRNA gene sequence. The results show that all the shrimps with the disease were EHP positive, and the EHP 18S rRNA gene in the sampling area was high homology (98.5%-100%). The homology analysis of EHP gene sequences at home and abroad was 86.2%-100%. The collected EHP and Indian EHP were clustered into one branch. The sequence of EHP 18S rRNA gene was in different branches from that of other aquatic organisms, indicating that 18S rRNA could be used as the main identification sequence of EHP. The comparative analysis of EHP with Enterocytozoon bieneusi and Enterospora nucleophile showed that the gene sequence homology of microsporidium was related to the degree of host evolution and development. The closer the evolutionary distance between hosts, the closer the gene sequence homology of microsporidium.