Transposable element polymorphism of Wolbachia in the mosquito Culex pipiens: evidence of genetic diversity, superinfection and recombination

Authors

  • OLIVIER DURON,

    1. Team Genetics of Adaptation, Laboratoire Génétique et Environnement, Institut des Sciences de l’Evolution (UMR CNRS 5554), Université Montpellier II (C.C. 065), F-34095 Montpellier cedex 05, France,
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  • JACQUES LAGNEL,

    1. Institute of Molecular Biology and Biotechnology, FORTH, Vassilika Vouton, Heraklion 71110, PO Box 1527, Crete, Greece,
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  • MICHEL RAYMOND,

    1. Team Genetics of Adaptation, Laboratoire Génétique et Environnement, Institut des Sciences de l’Evolution (UMR CNRS 5554), Université Montpellier II (C.C. 065), F-34095 Montpellier cedex 05, France,
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  • KOSTAS BOURTZIS,

    1. Institute of Molecular Biology and Biotechnology, FORTH, Vassilika Vouton, Heraklion 71110, PO Box 1527, Crete, Greece,
    2. Department of Environmental and Natural Resources Management, University of Ioannina, 2 Seferi St., Agrinio 30100, Greece,
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  • PHILIPPE FORT,

    1. Centre de Recherche en Biochime Macromoléculaire, CNRS-FRE2593, F-34095 Montpellier cedex 05, France
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  • MYLÈNE WEILL

    Corresponding author
    1. Team Genetics of Adaptation, Laboratoire Génétique et Environnement, Institut des Sciences de l’Evolution (UMR CNRS 5554), Université Montpellier II (C.C. 065), F-34095 Montpellier cedex 05, France,
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Dr Mylène Weill, Fax: (33) 4 67 14 36 22; E-mail: weill@isem.univ-montp2.fr

Abstract

Wolbachia is a group of maternally inherited endosymbiotic bacteria that infect and induce cytoplasmic incompatibility (CI) in a wide range of arthropods. In contrast to other species, the mosquito Culex pipiens displays an extremely high number of CI types suggesting differential infection by multiple Wolbachia strains. Attempts so far failed to detect Wolbachia polymorphism that might explain this high level of CI diversity found in C. pipiens populations. Here, we establish that Wolbachia infection is near to or at fixation in worldwide populations of the C. pipiens complex. Wolbachia polymorphism was addressed by sequence analysis of the Tr1 gene, a unique transposable element of the IS5 family, which allowed the identification of five C. pipiens Wolbachia strains, differing either by nucleotide substitution, presence or absence pattern, or insertion site. Sequence analysis also showed that recombination, transposition and superinfection occurred at very low frequencies. Analysis of the geographical distributions of each Wolbachia strain among C. pipiens populations indicated a strong worldwide differentiation independent from mosquito subspecies type, except in the UK. The availability of this polymorphic marker now opens the way to investigate evolution of Wolbachia populations and CI dynamics, in particular in regions where multiple crossing types coexist among C. pipiens populations.

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