Amplification The Complete Mitochondrial Genome Of Four Ticks And Analysis Of Genetic Polymorphism Of Dermacentor Silvarum

Tick is a kind of blood sucking arthropod with many hosts and wide distribution and can carry many harmful pathogens to human and animals.Ticks are often classified and identified according to their morphological structure,however,morphological identification has some limitations,especially for the related species of some tick.Among them,the taxonomic research of Dermacentor is weaker,and most of them are limited to morphological description.Using molecular biological methods combined with morphological characteristics can better classify ticks objectively and scientifically.In this study,the mitochondrial genome sequences of four ticks were analyzed.At the same time,the gene polymorphism of Dermacentor silvarum was analyzed based on mitochondrial cox1、nad1、nad4、16S r DNA and ribosomal ITS r DNA.Mitochondrial genome sequence analysis of four ticks.The ticks were collected from Xinjiang uygur autonomous region,Hebei Province,and Guangxi.Primers were designed to amplify mitochondrial sequences,and the obtained sequences were spliced and analyzed by biological software.The phylogeny of four ticks was analyzed based on 13 protein coding genes with other ticks.The results showed that:(1)The length of mitochondrial whole gene of Argas persicus,Amblyomma geoemydae,Amblyomma testudinarium and Dermacentor marginatus were 14,426 bp,14,780 bp,14,760 bp and 14,882 bp.The mitochondrial genomes of four ticks contain 13 protein coding genes,22 t RNAs,2 r RNAs and 1or 2 non coding regions.(2)The results of evolutionary analysis showed that Argas persicus and Argas tick were clustered together,on the same branch as Argas persicus(Kenya strain),and formed sister branches with other Argas ticks.Amblyomma geoemydae and Amblyomma testudinarium gather together with the ticks of the genus ticks,in which Amblyomma geoemydae and Amblyomma javanense are on the same branch and form sister branches with Amblyomma tick.Dermacentor marginatus(Xinjiang strain)is clustered with the ticks of Dermacentor genus,on the same branch as Dermacentor tick,and forms sister branches with Dermacentor nuttalli and Dermacentor silvarum.Genetic polymorphism analysis of Dermacentor silvarum.The sequences of mitochondrial cox1,16 S r DNA,nad1,nad4,ribosomal ITS-1 and ITS-2 were amplified from 9 cities in 4 provinces in northern China(N=6 per site,54).The obtained sequences were spliced,polymorphic and phylogenetic analyzed by biological software.The results showed that:(1)Analysis of four mitochondrial genes and two ribosomal genes in which haplotype diversity was ranked by the number of species: ITS-2>cox1>nad1>nad4>ITS-1>16S r DNA.(2)Molecular ANOVA in this study revealed that variation in cox1 16 S r DNA in Dermacentor silvarum was from within populations,that in nad1 was from between groups,that in nad4 and ITS-1was from within populations,and that in ITS-2 was from between and within populations(3)Evolutionary analysis showed that the marker genes of each part of Dermacentor silvarum clustered into one branch with Dermacentor silvarum,Dermacentor nuttalli and Dermacentor marginatus.Conclusion:(1)In this study,the whole mitochondrial genome sequences of Argas persicus(Chinese strain),Amblyomma geoemydae,Amblyomma testudinarium and Dermacentor marginatus were obtained for the first time,which not only enriched the mitochondrial gene library of ticks,but also provided an important basis for the study of molecular classification and genetic variation analysis of ticks.The results of this analysis showed that four ticks were clustered with the genus of ticks,which was consistent with the results of traditional taxonomic studies.(2)Based on six marker genes of gene polymorphism of Dermacentor silvarum in some provinces in northern China,it is found that the genetic variation sources of them are different,and differentiation within and between populations is different.They are not clustered according to the geographical units and no obvious geographical differentiation structure.Most of the populations follow the principle of neutral evolution,and only some provinces and cities have experienced population expansion.