Li Z Y, Chen J, Lu J, Wang C R, Zhu X Q
College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province, China.
State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, China.
Genet Mol Res. 2015 Sep 25;14(3):11403-9. doi: 10.4238/2015.September.25.8.
The protozoan parasite Toxoplasma gondii has a worldwide distribution; it can cause serious diseases in humans and almost all other warm-blooded animals. Different genotypes of T. gondii result in different lesions in the same host. T. gondii rhoptry protein 8 (TgROP8) is a major factor of T. gondii acute virulence. We examined sequence variation in the TgROP8 gene among T. gondii isolates from different hosts and geographical localities. The TgROP8 gene was amplified from individual isolates and sequenced. A phylogenetic tree was constructed using Bayesian inference, maximum parsimony, and maximum likelihood based on the sequences obtained plus TgME49 from the ToxoDB database. The TgROP8 gene was 1728 bp in length for all the examined T. gondii strains, and their A+T contents were 45.37-45.95%. Sequence analysis detected 140 (0.06-5.56%) variable nucleotide positions resulting in 96 (0-10.78%) amino acid substitutions. Sequence variations in the TgROP8 gene resulted in polymorphic restriction sites for endonucleases BstBI, BsaI, and XhoI, which allowed the differentiation of the three classical genotype strains (types I, II, and III) by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). However, phylogenetic analyses indicated that the TgROP8 gene is not a suitable genetic marker for population studies of T. gondii.
原生动物寄生虫刚地弓形虫在全球范围内均有分布；它可在人类及几乎所有其他温血动物中引发严重疾病。不同基因型的刚地弓形虫会在同一宿主中导致不同病变。刚地弓形虫棒状体蛋白8（TgROP8）是刚地弓形虫急性毒力的主要因素。我们检测了来自不同宿主和地理区域的刚地弓形虫分离株中TgROP8基因的序列变异。从各个分离株中扩增出TgROP8基因并进行测序。基于所获得的序列以及来自ToxoDB数据库的TgME49，使用贝叶斯推断、最大简约法和最大似然法构建了系统发育树。所有检测的刚地弓形虫菌株的TgROP8基因长度均为1728 bp，其A + T含量为45.37 - 45.95%。序列分析检测到140个（0.06 - 5.56%）可变核苷酸位点，导致了96个（0 - 10.78%）氨基酸替换。TgROP8基因的序列变异产生了核酸内切酶BstBI、BsaI和XhoI的多态性限制性位点，这使得通过聚合酶链反应 - 限制性片段长度多态性（PCR - RFLP）能够区分三种经典基因型菌株（I型、II型和III型）。然而系统发育分析表明，TgROP8基因并非用于刚地弓形虫群体研究的合适遗传标记。
