Department of Veterinary Parasitology, Lala Lajpat Rai University of Veterinary and Animal Sciences, 125004, Hisar, Haryana, India.
Department of Veterinary Medicine, Lala Lajpat Rai University of Veterinary and Animal Sciences, 125004, Hisar, Haryana, India.
BMC Vet Res. 2022 Dec 28;18(1):454. doi: 10.1186/s12917-022-03540-w.
There had been isolated reports of the presence of novel Theileria annulata genotypes based on the 18S rRNA gene sequence data from India, Pakistan and Saudi Arabia; but, these studies were restricted to limited field samples. Additionally, no comparative study has been conducted on all the isolates of this parasite from different countries whose sequences are available in the nucleotide databases. Therefore, we aimed to study the genetic diversity of T. annulata based on all available nearly complete 18S rRNA gene sequences in the GenBank™. Out of a total of 312 gene sequences of T. annulata available in the NCBI database, only 70 nearly complete sequences (> 1527 bp) were used for multiple sequence alignment.
The maximum likelihood tree obtained using TN93 + G + I model manifested two major clades. All the valid host-cell transforming Theileria species clustered in one clade. The T. annulata designated sequences occupying this clade clustered together, excluding two isolates (DQ287944 and EU083799), and represented the true T. annulata sequences (n = 54). DQ287944 and EU083799 exhibited close association with Theileria lestoquardi. In addition, 14 Indian sequences formed a large monophyletic group with published Theileria orientalis sequences. The broad range of sequence identity (95.8-100%) of T. annulata designated sequences indicated the presence of different Theileria spp. A closer analysis revealed the presence of three Theileria spp., namely, T. annulata, T. orientalis, and two isolates (DQ287944 and EU083799) closely related to T. lestoquardi. The true T. annulata sequences manifested 98.8-100% nucleotide identity within them. EU083799 and 14 misidentified Indian T. annulata sequences exhibited the highest similarity with T. lestoquardi (98.6-98.8%) and T. orientalis (98.0-99.9%) in comparison with the other Theileria spp. of domestic and wild ruminants.
In the course of analyzing the genetic diversity of T. annulata, we identified the nearly complete 18S rRNA gene sequences of other Theileria spp. that have not only been misidentified as T. annulata in the GenBank™, but are also published as T. annulata. Moreover, a high level of sequence conservation was noticed in the 18S rRNA gene of true T. annulata and T. orientalis sequences.
已有关于新型环形泰勒虫基因型的零星报道，这些报道基于印度、巴基斯坦和沙特阿拉伯的 18S rRNA 基因序列数据；但是，这些研究仅限于有限的实地样本。此外，尚未对来自不同国家的所有该寄生虫分离株进行比较研究，这些分离株的序列可在核苷酸数据库中获得。因此，我们旨在基于 GenBank™中所有可用的近乎完整的 18S rRNA 基因序列研究环形泰勒虫的遗传多样性。在 NCBI 数据库中总共 312 个环形泰勒虫基因序列中，仅使用 70 个近乎完整的序列（＞1527 bp）进行多序列比对。
使用 TN93 + G + I 模型获得的最大似然树显示出两个主要分支。所有有效的宿主细胞转化泰勒虫物种聚集在一个分支中。环形泰勒虫指定序列占据这个分支聚集在一起，除了两个分离株（DQ287944 和 EU083799），并代表真正的环形泰勒虫序列（n = 54）。DQ287944 和 EU083799 与泰勒虫 lestoquardi 密切相关。此外，14 个印度序列与已发表的东方泰勒虫序列形成一个大的单系群。环形泰勒虫指定序列的广泛序列同一性（95.8-100%）表明存在不同的泰勒虫属。更仔细的分析显示存在三种泰勒虫属，即环形泰勒虫、东方泰勒虫和两个分离株（DQ287944 和 EU083799）与泰勒虫 lestoquardi 密切相关。真正的环形泰勒虫序列在它们内部表现出 98.8-100%的核苷酸同一性。EU083799 和 14 个被错误识别的印度环形泰勒虫序列与泰勒虫 lestoquardi（98.6-98.8%）和东方泰勒虫（98.0-99.9%）表现出最高的相似性，与其他家畜和野生动物的泰勒虫属相比。
在分析环形泰勒虫遗传多样性的过程中，我们鉴定了其他泰勒虫属的近乎完整的 18S rRNA 基因序列，这些序列不仅在 GenBank™中被错误识别为环形泰勒虫，而且也被发表为环形泰勒虫。此外，真正的环形泰勒虫和东方泰勒虫序列的 18S rRNA 基因中观察到高度的序列保守性。
