Abstract
BackgroundCulex tritaeniorhynchus and Culex pipiens pallens are the major vectors of the Japanese encephalitis virus and Wuchereria bancrofti, the causative agent of filariasis. The knowledge of mitochondrial genomes has been widely useful for the studies on molecular evolution, phylogenetics and population genetics.MethodsIn this study, we sequenced and annotated the mitochondrial (mt) genomes of Cx. tritaeniorhynchus and Cx. p. pallens, and performed a comparative analysis including four known mt genomes of species of the subgenus Culex (Culex). The phylogenetic relationships of Cx. tritaeniorhynchus, Cx. p. pallens and four known Culex mt genome sequences were reconstructed by maximum likelihood based on concatenated protein-coding gene sequences.ResultsCulex tritaeniorhynchus and Cx. p. pallens mt genomes are 14,844 bp and 15,617 bp long, both consists of 13 PCGs, 22 tRNAs, 2 rRNAs and 1 CR (not sequenced for Cx. tritaeniorhynchus). The initiation and termination codons of PCGs are ATN and TAA, respectively, except for COI starting with TCG, and COI and COII terminated with T. tRNAs have the typical clover-leaf secondary structures except for trnS(AGN) that is lacking the DHU stem. 16S rRNA and 12S rRNA secondary structures were drawn for the first time for mosquito mt genomes. The control region of Cx. p. pallens mt genome is 747 bp long and with four tandem repeat structures. Phylogenetic analyses demonstrated that the mt genome of Cx. tritaeniorhynchus was significantly separated from the remaining five mt genomes of Culex spp. Culex p. pipiens, Cx. p. pallens and Cx. p. quinquefasciatus formed a monophyletic clade with Cx. p. quinquefasciatus linked in the middle of the clade, and Cx. p. pallens should have the same taxonomic level as Culex p. pipiens and Cx. p. quinquefasciatus.ConclusionsThe mt genomes of Cx. tritaeniorhynchus and Cx. p. pallens share the same gene composition and order with those of two other Culex species. Culex p. pallens of the Pipiens complex should have the same taxonomic level as Culex p. pipiens and Cx. p. quinquefasciatus investigated. We enriched the Culex mt genome data and provided a reference basis for further Culex mt genome sequencing and analyses.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1694-z) contains supplementary material, which is available to authorized users.
Highlights
Culex tritaeniorhynchus and Culex pipiens pallens are the major vectors of the Japanese encephalitis virus and Wuchereria bancrofti, the causative agent of filariasis
KT851544; control region (CR) lacking) and 15,617 bp long (Fig. 1b, GenBank number KT851543, with CR), respectively. They both consisted of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs) and 1 CR, which is a composition typical for the metazoan taxa [2] and conserved in the known mosquito mt genomes [29, 30]
There were 16 overlapping nucleotide areas between genes/CR with a total length of 46 bp and 74 bp, respectively; these areas ranged between 1–7 bp except for that between 12S rRNA and CR region of Cx. p. pallens, which was 34 bp long (Table 1)
Summary
Culex tritaeniorhynchus and Culex pipiens pallens are the major vectors of the Japanese encephalitis virus and Wuchereria bancrofti, the causative agent of filariasis. The knowledge of mitochondrial genomes has been widely useful for the studies on molecular evolution, phylogenetics and population genetics. Due to the stable structure, coding content conservation, maternal inheritance, rapid evolution rate, no recombination and a high copy number, the mt genome has been widely used in the pattern analysis of molecular evolution, and in the studies on phylogeography, phylogenetics and population genetics [5,6,7,8,9]. The largest genus in the Culicidae, is worldwide distributed [10], and its many species are important vectors of mosquito-borne diseases, including epidemic encephalitis and lymphatic filariasis [11]. Pipiens from different populations (three of these completely identical) and two mt genome sequences for Cx. p. There are four mt genome sequences for C. p. pipiens from different populations (three of these completely identical) and two mt genome sequences for Cx. p. quinquefasciatus with nucleotide differences, reported in the GenBank
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