Genetic polymorphisms of mitochondrial cox1 gene of Echinococcus spp. from rodents and livestock in Xinyuan County, Xinjiang and Shiqu County, Sichuan

doi:10.12140/j.issn.1000-7423.2020.01.004

Abstract

Abstract: Objective To understand the genetic polymorphisms of cytochrome c oxidase subunit 1 (cox1) gene in mitochondria of Echinococcus spp. in Xinyuan County, Xinjiang and Shiqu County, Sichuan, and discuss Echinococcus transmission directions and dynamics in China. Methods From 2014 to 2018, rodents were captured in Xinyuan County (Xinjiang) and Shiqu County (Sichuan) to collect liver tissues, meanwhile lesioned tissue samples of livestock were collected. DNA was extracted from the livers and lesioned tissues, and underwent PCR to amplify part of Echinococcus mitochondrial cox1 gene. PCR products were sequenced, and the sequencing results were aligned in NCBI database to identify the Echinococcus species. The sequences were edited by Clustal X2 and MAGE 7 softwares, and diversity and neutrality indices were calculated by DnaSP v5 and Arlequin 3.5. Genetic diversities were compared between the two regions. By using E. shiquicus as an outgroup, cox1 sequence-based Bayesian phylogenetic trees were established with MrBayes 3.2.4 software. The haplotype networks were drawn for cox1 genes of Echinococcus spp. using Network 5.0 to analyze haplotype structure. Results One hundred and twenty-two Microtus arvalis were captured and 5 lesioned tissues of sheep were collected in Xinyuan County (Xinjiang); while in Shiqu County (Sichuan), 144 Lasiopodomys fuscus, 44 M. limnophilus and 135 Ochotona curzoniae were captured and 4 lesioned tissues of yaks were collected. A total of 40 sequences of E. granulosus cox1 genes (26 from Xinyuan, and 14 from Shiqu) were amplified from lesioned tissues of 5 sheeps and 4 yaks. Fifty-nine sequences of E. multilocularis mitochondrial cox1 genes (20 from Xinyuan, and 39 from Shiqu) were amplified in 8 M. arvalis, 14 L. fuscus, 5 M. limnophilus and 2 O. curzoniae. All PCR products had a length of 875 bp. E. granulosus showed a higher degree of genetic differentiation (Fst = 0.088 63) between the 2 regions than E. multilocularis (Fst = 0.000 88). The genetic diversity of E. granulosus was lower in Xinyuan (0.002 58 ± 0.000 46) than in Shiqu (0.005 88 ± 0.000 58), while E. multilocularis had higher genetic diversity in Xinyuan (0.002 28 ± 0.000 46) than in Shiqu (0.001 37 ± 0.000 30). The Bayesian phylogenetic tree showed that in both regions E. granulosus had the G1 genotype, and E. multilocularis was of the Asian type. Sequences alignment revealed 25 haplotypes for E. granulosus cox1 gene (15 in Xinyuan, 9 in Shiqu, and 1 shared by both) and 29 haplotypes for E. multilocularis (13 in Xinyuan, 15 in Shiqu, 1 shared by both). The haplotype networks of E. multilocularis and E. granulosus both showed a star-shaped network with a centrally placed main haplotype. There were 9 sequences of E. granulosus being the main haplotype type in Xinyuan (34.6%, 9/26), while only 1 sequence of that type was found in Shiqu (1/14), indicating a central role of Xinyuan County in the E. granulosus haplotype network. On the contrary, there were 23 sequences of E. multilocularis being the main haplotype type in Shiqu (58.9%, 23/39) and 7 of that type in Xinyuan (35.0%, 7/20), indicating that Shiqu County was more predominant in the E. multilocularis haplotype structure. Conclusion There is no apparent difference in the mitochondrial cox1 genotype of Echinococcus found between Xinyuan and Shiqu County, but there are some differences in the genetic polymorphism detected in the two sites. The genetic differentiation level of E. granulosus is higher than that of E. multilocularis over the same spatial span. These findings provide important referential basis for further study on transmission direction and dynamics of Echinococcus.

Key words: Echinococcus, Xinyuan, Shiqu, Genetic polymorphism

CLC Number:

R383.33

WANG Xu, HOU Yan-yan, WANG Ying, WANG Zheng-huan, XUE Chui-zhao, ZHANG Yin, LIU Bai-xue, HAN Shuai, ZHENG Can-jun, WU Wei-ping. Genetic polymorphisms of mitochondrial cox1 gene of Echinococcus spp. from rodents and livestock in Xinyuan County, Xinjiang and Shiqu County, Sichuan[J]. CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES, 2020, 38(1): 22-29.

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