Mitochondrial genomes and comparative analyses of Culex camposi, Culex coronator, Culex usquatus and Culex usquatissimus (Diptera:Culicidae), members of the coronator group.

Bruna Demari-Silva,Sabri S Sanabani,Maria Anice M Sallum,Rodrigo Pessôa,Tatiane M P De Oliveira,Eduardo S Bergo,Peter G Foster

doi:10.1186/s12864-015-1951-0

Abstract

BackgroundThe Coronator Group currently encompasses six morphologically similar species (Culex camposi Dyar, Culex coronator Dyar and Knab, Culex covagarciai Forattini, Culex usquatus Dyar, Culex usquatissimus Dyar, and Culex ousqua Dyar). Culex coronator has been incriminated as a potential vector of West Nile Virus (WNV), Saint Louis Encephalitis Virus (SLEV), and Venezuelan Equine Encephalitis Virus (VEEV). The complete mitochondrial genome of Cx. coronator, Cx. usquatus, Cx.usquatissimus, and Cx. camposi was sequenced, annotated, and analyzed to provide genetic information about these species.ResultsThe mitochondrial genomes of Cx. coronator, Cx. usquatus, Cx.usquatissimus, and Cx. camposi varied from 15,573 base pairs in Cx. usquatus to 15,576 in Cx. coronator. They contained 37 genes (13 protein-encoding genes, 2 rRNA genes, and 22 tRNA genes) and the AT-rich control region. Comparative analyses of the 37 genes demonstrated the mitochondrial genomes to be composed of variable and conserved genes. Despite the small size, the ATP8, ATP6 plus NADH5 protein-encoding genes were polymorphic, whereas tRNAs and rRNAs were conserved. The control region contained some poly-T stretch. The Bayesian phylogenetic tree corroborated that both the Coronator Group and the Culex pipens complex are monophyletic taxa.ConclusionsThe mitochondrial genomes of Cx. coronator, Cx. usquatus, Cx. usquatissimus and Cx. camposi share the same gene composition and arrangement features that match to those reported for most Culicidae species. They are composed of the same 37 genes and the AT-rich control region, which contains poly-T stretches that may be involved in the functional role of the mitochondrial genome. Taken together, results of the dN/dS ratios, the sliding window analyses and the Bayesian phylogenetic analyses suggest that ATP6, ATP8 and NADH5 are promising genes to be employed in phylogenetic studies involving species of the Coronator Group, and probably other species groups of the subgenus Culex. Bayesian topology corroborated the morphological hypothesis of the Coronator Group as monophyletic lineage within the subgenus Culex.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1951-0) contains supplementary material, which is available to authorized users.

Highlights

The Coronator Group currently encompasses six morphologically similar species (Culex camposi Dyar, Culex coronator Dyar and Knab, Culex covagarciai Forattini, Culex usquatus Dyar, Culex usquatissimus Dyar, and Culex ousqua Dyar)
Mitochondrial genome organization and nucleotide composition The mitochondrial genomes of Cx. coronator, Cx. usquatus, Cx. usquatissimus and Cx. camposi contain 37 genes, which have been found in other metazoan and Culicidae species, including 13 protein-encoding genes, 22 tRNAs and 2 rRNA genes,( rrnL and rrnS) and the AT-rich control region [31,32,33,34]
The overall AT-skew was positive in all species (0.0025 for Cx. usquatissimus RO and Cx. usquatissimus AC; 0.0012, 0.003 and 0.0038, in Cx coronator, Cx. camposi and Cx. usquatus, respectively), whereas the GC-skew was −0.15 for all species, showing that adenine and cytosine are in the highest proportion compared to thymine and guanine, respectively, in the majority strand

Summary

Introduction

The Coronator Group currently encompasses six morphologically similar species (Culex camposi Dyar, Culex coronator Dyar and Knab, Culex covagarciai Forattini, Culex usquatus Dyar, Culex usquatissimus Dyar, and Culex ousqua Dyar). The complete mitochondrial genome of Cx. coronator, Cx. usquatus, Cx.usquatissimus, and Cx. camposi was sequenced, annotated, and analyzed to provide genetic information about these species. Culex camposi Dyar, Culex coronator Dyar and Knab, Culex covagarciai Forattini, Culex ousqua Dyar, Culex usquatus Dyar and Culex usquatissimus Dyar are members of the Coronator Group of the subgenus Culex [1]. Species of the Coronator Group are largely distributed and some are sympatric in the Neotropics [2]. Because of the lack of studies, there is no evidence of hybridization among species of the Coronator Group

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