Abstract
The complete mitochondrial genome of Haemaphysalis hystricis from China is firstly determined in this study. The complete mitogenome is 14,716 bp in length with 13 PCGs, 22 tRNA, 2 rRNA, and 2 noncoding regions. The total base composition was A: 38.37%, T: 38.86%, G: 9.84% and C: 12.94%. Additionally, the ML tree was constructed based on the concatenated sequences of COX1, CYTB, 12S and 16S genes, and indicated that H. hystricis was clustered with H. longicornis.
Ticks are obligate parasitic arachnids with a worldwide distribution. The Ixodida had three families 17 genera 896 species distributing across different regions of the world with 702 described species in Ixodidae, 193 species in Argasidae and only one species in Nuttalliellidae (Bowman and Nuttall Citation2008; Guglielmore et al. Citation2010). To date, 117 species of ticks were subordinate to 10 genera of 2 families based on large number of literatures in China; these ticks had a nationwide distribution (Yang et al. Citation2008; Chen et al. Citation2010). In the past two decades, partial sequences of 12S rRNA, 16S rRNA, COX1, and ITS2 had been used frequently for research on morphology and systematics (Shao and Barker Citation2007; Lu et al. Citation2013; Lv et al. Citation2014). Nowadays, there is only one report of ‘mostly complete’ (more genic regions unsequenced) mitochondrial genomes of Haemaphysalis hystricis, which is linear DNA with 9576 bp in length (Burger et al. Citation2013).
In this study, the samples parasitizing Arctonyx collaris were collected from Qiliping Town (31°46′07″N, 114°66′21″E), Hong’an County, Hubei Province, China. The specimens now are deposited in Wuhan centers for disease control and prevention museum. Furthermore, high-throughput sequenceing method (Guo et al. Citation2017) was employed to determine the complete mitogenome of H. hystricis with further bioinformatic analysis.
The complete mitogenome of H. hytricis (GenBank accession no. MH510034) was 14,716 bp in length, and consisted of 13 typical invertebrate protein coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 2 noncoding regions. Except for four PCGs, two rRNAs and eight tRNA genes, all other genes were encoded on the H-strand. The base composition was analyzed using Staden Package (Bonfield et al. Citation1995). The whole nucleotide composition was 38.4% A, 38.9% T, 12.9% C, and 9.8% G, presenting an obvious A + T bias (77.3%) with a GC skew of −0.14 and AT skew of 0.006. The mitochondrial genome of H. hystricis contained 66 bp of intergenic spacers spread over twelve regions, ranging from 1 to16 bp. The longest spacer sequence was located between the trnK and COX2. While, it had a total of 59 bp overlapping nucleotides scattering within ten locations, with the longest 23 bp overlap located between trnE and ND1.
The 13 PCGs were 10,818 bp in total encoding 3595 amino acid residues, with the AT content of 76.8%. On the one hand, all protein-coding genes were initiated with ATN (ATT, ATG, ATA, and ATC). On the other hand, 10 protein-coding genes (ND2, COX1, COX2, ATP8, ATP6, COX3, ND1, ND5, ND4L, and CYTB) employed the typical termination codon TAA, the remaining PCGs (ND3, ND4, and ND6) utilized one incomplete stop codon(T–). The 12S rRNA and 16S rRNA were 696 and 1212 bp long, respectively. All of 22 tRNA ranged in size from 51 to 68 bp and had canonical cloverleaf secondary structures in common. The non-coding regions included two misc-feature regions, which might be a control region or two control regions, and a few intergenic spacers.
Phylogenetic relationships between H. hystricis and 29 other ticks were estimated by the method of maximum likelihood using MEGA6.0 with 1000 bootstrap replicates (). The first phylogroup contained only the species of the genus Ixodes, while the ticks in the other seven genera formed the second phylogroup. Within the second phylogroup, H. hystricis was clustered into one group with the six species of Haemaphysalis. Furthermore, the species had a closer relationship with H. longicornis(NC_037493) from Shandong province of China, followed by H. concinna, H. formosensis, H. flava, and H. japonica.
Figure 1. Phylogenetic relationships between Haemaphysalis hystricis and 29 other tick species. The ML tree was based on complete sequences of concatenate mitochondrial COX1, CYTB, 12S, and 16S genes available in GenBank. Phylogenetic analysis occupied the general time reversible model with gamma distribution and a proportion of invariable sites (I + G). Numbers (>50%) above or below branches indicated bootstrap values, and Nuttalliella namaqua was used as an outgroup.
Acknowledgements
The authors thank Dr Mang Shi, from the University of Sydney, Sydney, New South Wales, Australia, for the assistance with high-throughput data analysis.
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The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.
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References
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