Mosaic Nature of theWolbachiaSurface Protein

Abstract

Lateral gene transfer and recombination play important roles in the evolution of many parasitic bacteria. Here we investigate intragenic recombination in Wolbachia bacteria, considered among the most abundant intracellular bacteria on earth. We conduct a detailed analysis of the patterns of variation and recombination within the Wolbachia surface protein, utilizing an extensive set of published and new sequences from five main supergroups of Wolbachia. Analysis of nucleotide and amino acid sequence variations confirms four hypervariable regions (HVRs), separated by regions under strong conservation. Comparison of shared polymorphisms reveals a complex mosaic structure of the gene, characterized by a clear intragenic recombining of segments among several distinct strains, whose major recombination effect is shuffling of a relatively conserved set of amino acid motifs within each of the four HVRs. Exchanges occurred both within and between the arthropod supergroups. Analyses based on phylogenetic methods and a specific recombination detection program (MAXCHI) significantly support this complex partitioning of the gene, indicating a chimeric origin of wsp. Although wsp has been widely used to define macro-and microtaxonomy among Wolbachia strains, these results clearly show that it is not suitable for this purpose. The role of wsp in bacterium-host interactions is currently unknown, but results presented here indicate that exchanges of HVR motifs are favored by natural selection. Identifying host proteins that interact with wsp variants should help reveal how these widespread bacterial parasites affect and evolve in response to the cellular environments of their invertebrate hosts.

Toward a Wolbachia Multilocus Sequence Typing System: Discrimination of Wolbachia Strains Present in Drosophila Species

“…16S rDNA evolves too slowly to be useful in MLST. At the other extreme, the hyper-variable wsp gene likely experiences positive selection [29] and recombination [2,3,30,55], so that its utilization in an MLST scheme may be problematic. These caveats aside, 16S rDNA has been used in MLSTs as a reference point for other housekeeping genes [15] or even as a marker to differentiate strains [62].…”

“…The Wolbachia surface protein (wsp) gene has proved to be the fastest evolving and has been 2 3 extensively used for intragroup phylogenetic studies. However, Wolbachia is prone to high rates of recombination, especially within supergroups, and single gene phylogenetics are unreliable for resolving close relationships [2,3,7,30,55]. Taking a new approach to strain typing, Riegler and colleagues reported a number of polymorphic markers, such as size polymorphisms for IS5 insertion sites or minisatellites and the orientation of a chromosomal inversion, to detect and discriminate among five different Wolbachia variants present in D.…”

Wolbachia Are Present in Southern African Scorpions and Cluster with Supergroup F

“…The Wolbachia surface protein (WSP) is used as an additional marker of strain variability. Although the function of WSP remains unknown, the four hypervariable regions (HVRs) of the protein are subject to extensive recombination and likely are involved in the host-symbiont interaction [3]. A typing system based on the profile of the four HVR peptides of a WSP sequence was recently developed [2].…”

A new case of Wolbachia dependence in the genus Asobara: evidence for parthenogenesis induction in Asobara japonica

“…The phylogenetic tree indicates that wAjap was neither directly associated with the Wolbachia strains of A. tabida nor with the strains of M. uniraptor and N. vitripennis (which are grouped together), highlighting the incongruence between MLST and WSPbased phylogenies, as already shown in Baldo et al 2005. Analysis of the entire proteic WSP sequence of the four species clustered in MLST allowed detection of mutations at sites under positive selection (Jiggins et al, 2002) and different potential recombination events between hypervariable regions (Supplementary file S3).…”