Variation in mitochondrial minichromosome composition between blood-sucking lice of the genus Haematopinus that infest horses and pigs

Simon D Song,Stephen C Barker,Renfu Shao

doi:10.1186/1756-3305-7-144

Simon D Song, Stephen C Barker + Show 1 more

Open Access

https://doi.org/10.1186/1756-3305-7-144

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Abstract

BackgroundThe genus Haematopinus contains 21 species of blood-sucking lice, parasitizing both even-toed ungulates (pigs, cattle, buffalo, antelopes, camels and deer) and odd-toed ungulates (horses, donkeys and zebras). The mitochondrial genomes of the domestic pig louse, Haematopinus suis, and the wild pig louse, Haematopinus apri, have been sequenced recently; both lice have fragmented mitochondrial genomes with 37 genes on nine minichromosomes. To understand whether the composition of mitochondrial minichromosomes and the gene content and gene arrangement of each minichromosome are stable within the genus, we sequenced the mitochondrial genome of the horse louse, Haematopinus asini.MethodsWe used a PCR-based strategy to amplify four mitochondrial minichromosomes in near full-length, and then amplify the entire coding regions of all of the nine mitochondrial minichromosomes of the horse louse. These amplicons were sequenced with an Illumina Hiseq platform.ResultsWe identified all of the 37 mitochondrial genes typical of bilateral animals in the horse louse, Haematopinus asini; these genes are on nine circular minichromosomes. Each minichromosome is 3.5–5.0 kb in size and consists of a coding region and a non-coding region except R-nad4L-rrnS-C minichromosome, which contains two coding regions and two non-coding regions. Six of the nine minichromosomes of the horse louse have their counterparts in the pig lice with the same gene content and gene arrangement. However, the gene content and arrangement of the other three minichromosomes of the horse louse, including R-nad4L-rrnS-C, are different from that of the other three minichromosomes of the pig lice.ConclusionsComparison between the horse louse and the pig lice revealed variation in the composition of mitochondrial minichromosomes within the genus Haematopinus, which can be accounted for by gene translocation events between minichromosomes. The current study indicates that inter-minichromosome recombination plays a major role in generating the variation in the composition of mitochondrial minichromosomes and provides novel insights into the evolution of fragmented mitochondrial genomes in the blood-sucking lice.

Highlights

IntroductionThe genus Haematopinus contains 21 species of blood-sucking lice, parasitizing both even-toed ungulates (pigs, cattle, buffalo, antelopes, camels and deer) and odd-toed ungulates (horses, donkeys and zebras)
The genus Haematopinus contains 21 species of blood-sucking lice, parasitizing both even-toed ungulates and odd-toed ungulates
The sequence-reads are all 90 bp each in length. We assembled these sequencereads into contigs and identified all of the 37 mt genes typical of bilateral animals in H. asini, distributed on nine circular minichromosomes (Figure 2; Figure 1C)

Summary

Introduction

The genus Haematopinus contains 21 species of blood-sucking lice, parasitizing both even-toed ungulates (pigs, cattle, buffalo, antelopes, camels and deer) and odd-toed ungulates (horses, donkeys and zebras). The mitochondrial genomes of the domestic pig louse, Haematopinus suis, and the wild pig louse, Haematopinus apri, have been sequenced recently; both lice have fragmented mitochondrial genomes with 37 genes on nine minichromosomes. The extent of mt genome fragmentation, the number of minichromosomes and the distribution of genes on the minichromosomes vary remarkably between genera of the blood-sucking lice, but are the same for the species within the same genus [14,15,16] Both the human body louse, Pe. humanus, and the human head louse, Pe. capitis, have 20 mt minichromosomes and an identical pattern for the distribution of mt genes on these minichromosomes [14,16]. The human head louse and the human body louse, are very closely related and had their most recent common ancestor (MRCA) ~107,000 years ago [17,18]; so are the domestic pig louse and the wild pig louse, which had their MRCA ~9,000 years ago [19]

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