The Multipartite Mitochondrial Genome of Liposcelis bostrychophila: Insights into the Evolution of Mitochondrial Genomes in Bilateral Animals

Dan-Dan Wei,Ming-Long Yuan,Jin-Jun Wang,Stephen C Barker,Renfu Shao,Wei Dou,Arnar Palsson

doi:10.1371/journal.pone.0033973

Dan-Dan Wei, Ming-Long Yuan + Show 5 more

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https://doi.org/10.1371/journal.pone.0033973

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Abstract

Booklice (order Psocoptera) in the genus Liposcelis are major pests to stored grains worldwide and are closely related to parasitic lice (order Phthiraptera). We sequenced the mitochondrial (mt) genome of Liposcelis bostrychophila and found that the typical single mt chromosome of bilateral animals has fragmented into and been replaced by two medium-sized chromosomes in this booklouse; each of these chromosomes has about half of the genes of the typical mt chromosome of bilateral animals. These mt chromosomes are 8,530 bp (mt chromosome I) and 7,933 bp (mt chromosome II) in size. Intriguingly, mt chromosome I is twice as abundant as chromosome II. It appears that the selection pressure for compact mt genomes in bilateral animals favors small mt chromosomes when small mt chromosomes co-exist with the typical large mt chromosomes. Thus, small mt chromosomes may have selective advantages over large mt chromosomes in bilateral animals. Phylogenetic analyses of mt genome sequences of Psocodea (i.e. Psocoptera plus Phthiraptera) indicate that: 1) the order Psocoptera (booklice and barklice) is paraphyletic; and 2) the order Phthiraptera (the parasitic lice) is monophyletic. Within parasitic lice, however, the suborder Ischnocera is paraphyletic; this differs from the traditional view that each suborder of parasitic lice is monophyletic.

Highlights

The mitochondrial genomes of bilateral animals typically consist of a single circular chromosome that is 13 to 20 kb in size and contains 37 genes: 13 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes [1]
Mitochondrial genomes that consist of multiple chromosomes, i.e. multipartite mt genomes, have been found in mesozoa, nematodes, rotifers and parasitic lice [2,3,4,5,6,7]
Mt chromosome I has only half of the genes that are typically found in the mt genome of a bilateral animal (Figure 1).we sought the other mt genes with primers that were anchored in rrnL and nad5 (P5, P6 and P7, P8, Figure 1)

Summary

Introduction

The mitochondrial (mt) genomes of bilateral animals typically consist of a single circular chromosome that is 13 to 20 kb in size and contains 37 genes: 13 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes [1]. Mitochondrial genomes that consist of multiple chromosomes, i.e. multipartite mt genomes, have been found in mesozoa, nematodes, rotifers and parasitic lice [2,3,4,5,6,7]. The number of chromosomes in a multipartite mt genome varies from two in the rotifer, Brachionus plicatilis [5], to 20 in the human body louse, Pediculus humanus [6]. In an extreme case in the human body louse, an mt chromosome contains only a single tRNA gene [6]. Different chromosomes in a multipartite mt genome are in unequal abundance [5]; the relative abundance of an mt chromosome varies at different developmental stages [8]

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