Guo Jiaying, Miao Xiaoyan, He Pei, Li Muxiao, Wang Sen, Cui Jie, Huang Cuiqin, He Lan, Zhao Junlong
State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, Hubei, China.
Key Laboratory of Preventive Veterinary Medicine in Hubei Province, Wuhan, 430070, Hubei, China.
Parasitol Res. 2019 Jan;118(1):235-243. doi: 10.1007/s00436-018-6158-2. Epub 2018 Nov 24.
Babesia gibsoni (B. gibsoni), an intracellular apicomplexan protozoan, poses great threat to canine health. Currently, little information is available about the B. gibsoni (WH58) endemic to Wuhan, China. Here, the mitochondrial (mt) genome of B. gibsoni (WH58) was amplified by five pairs of primers and sequenced and annotated by alignment with the reported mt genome sequences of Babesia canis (B. canis, KC207822), Babesia orientalis (KF218819), Babesia bovis (AB499088), and Theileria equi (AB499091). The evolutionary relationships were analyzed with the amino acid sequences of cytochrome c oxidase I (cox1) and cytochrome b (cob) genes in apicomplexan parasite species. Additionally, the mt genomes of Babesia, Theileria, and Plasmodium spp. were compared in size, host infection, form, distribution, and direction of the protein-coding genes. The full size of the mt genome of B. gibsoni (WH58) was 5865 bp with a linear form, containing terminal-inverted repeats on both ends, six large subunit ribosomal RNA fragments, and three protein-coding genes: cox1, cob, and cytochrome c oxidase III (cox3). Babesia, Theileria, and Plasmodium spp. had a similar mt genome size of about 6000 bp. The mt genomes of parasites that cause canine babesiosis showed a slightly smaller size than the other species. Moreover, Babesia microti (R1 strain) was about 11,100 bp in size, which was twice larger than that of the other species. The mt form was linear for Babesia and Theileria spp. but circular for Plasmodium falciparum and Plasmodium knowlesi. Additionally, all the species contained the three protein-coding genes of cox1, cox3, and cob except Toxoplasma gondii (RH strain) which only contained the cox1 and cob genes. The phylogenetic analysis indicated that B. gibsoni (WH58) was more identical to B. gibsoni (AB499087), B. canis (KC207822), and Babesia rossi (KC207823) and most divergent from Babesia conradae in Babesia spp. Despite the highest similarity to B. gibsoni (AB499087) reported in Japan, B. gibsoni (WH58) showed notable differences in the sequence of nucleotides and amino acids and the property in virulence to host and in vitro cultivation. This study compared the mt genomes of the two B. gibsoni isolates and other parasites in the phylum Apicomplexa and provided new insights into their differences and evolutionary relationships.
吉氏巴贝斯虫（B. gibsoni）是一种细胞内顶复门原生动物，对犬类健康构成巨大威胁。目前，关于中国武汉特有的吉氏巴贝斯虫（WH58）的信息很少。在此，通过五对引物扩增了吉氏巴贝斯虫（WH58）的线粒体（mt）基因组，并通过与已报道的犬巴贝斯虫（B. canis，KC207822）、东方巴贝斯虫（KF218819）、牛巴贝斯虫（AB499088）和马泰勒虫（AB499091）的mt基因组序列进行比对来进行测序和注释。利用顶复门寄生虫物种中细胞色素c氧化酶I（cox1）和细胞色素b（cob）基因的氨基酸序列分析了进化关系。此外，还比较了巴贝斯虫属、泰勒虫属和疟原虫属物种的mt基因组在大小、宿主感染情况、形态、分布以及蛋白质编码基因的方向。吉氏巴贝斯虫（WH58）的mt基因组全长5865 bp，呈线性形式，两端含有末端反向重复序列、六个大亚基核糖体RNA片段以及三个蛋白质编码基因：cox1、cob和细胞色素c氧化酶III（cox3）。巴贝斯虫属、泰勒虫属和疟原虫属物种的mt基因组大小相似，约为6000 bp。引起犬巴贝斯虫病的寄生虫的mt基因组大小略小于其他物种。此外，微小巴贝斯虫（R1株）大小约为11,100 bp，是其他物种的两倍。巴贝斯虫属和泰勒虫属物种的mt形态为线性，而恶性疟原虫和诺氏疟原虫的mt形态为环状。此外，除了刚地弓形虫（RH株）仅含有cox1和cob基因外，所有物种都含有cox1、cox3和cob这三个蛋白质编码基因。系统发育分析表明，吉氏巴贝斯虫（WH58）与吉氏巴贝斯虫（AB499087）、犬巴贝斯虫（KC207822）和罗氏巴贝斯虫（KC207823）更为相似，与巴贝斯虫属中的康氏巴贝斯虫差异最大。尽管与日本报道的吉氏巴贝斯虫（AB499087）相似度最高，但吉氏巴贝斯虫（WH58）在核苷酸和氨基酸序列以及对宿主的毒力和体外培养特性方面存在显著差异。本研究比较了两种吉氏巴贝斯虫分离株以及顶复门中的其他寄生虫的mt基因组，为它们的差异和进化关系提供了新的见解。
