MIC5基因在13株不同基因型的刚地弓形虫中的序列变异（英文）

Sequence variability of MIC5 gene among 13 Toxoplasma gondii isolates belonging to different genotypes

目的检验13株来自不同宿主和地理位置,且归属于不同型的刚地弓形虫的MIC5基因的序列变异情况,评价MIC5能否作为研究种群遗传学的理想标记。方法对13株刚地弓形虫的MIC5基因进行了序列比对,并使用了最大简约法,最大似然法以及贝叶斯法对所检验的虫株进行了系统进化分析。结果所有的虫株其MIC5基因的长度都为1 975bp。序列比对显示有52个核酸变异位点(0-1.3%),其中有38变异位点个在3个内含子上,14个变异位点在4个外显子上。所检基因的A+T含量为:51.70%-51.95%。结论 MIC5基因的序列变异率较低,所以MIC5基因并不是一个研究种群遗传学的理想标记。

Toxoplasma gondii （T. gondii） has the ability to infect almost all warm-blooded animals including humans, cau sing a serious toxoplasmosis. MIC5, a member of the microneme proteins, directly regulates the activity of proteases, which is associated with the proteolytic susceptibility of other microneme protein substrates. In this study, we examined the sequence variability of MIC5 gene among 13 T. gondii isolates belonging to different genotypes, which were collected from different hosts and geographical regions. Also, phylogenetic relationships among the examined T. gondii isolates were reconstructed using maximum parsimony （MP）,maximum likelihood （ML） and Bayesian inference （BI） methods. The MIC5 gene from all the isolates possesses 1 975 bp in length. Sequence comparison revealed 52 variable nucleotide positions （0-1.3%）, including 38 variations in 3 introns, and 14 variations in 4 exons, and their A＋T contents were 51.70%-51.95 %. Phylogenetic analysis showed that MIC5 gene is not an ideal marker for studying population genetics of T. gondii due to its low sequence diversity.