Genome expansion of an obligate parthenogenesis-associated Wolbachia poses an exception to the symbiont reduction model

A. A. Kampfraath*, L. Klasson, S. Y. Anvar, R. H.A.M. Vossen, D. Roelofs, K. Kraaijeveld, J. Ellers

*Corresponding author for this work

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    Background: Theory predicts that dependency within host-endosymbiont interactions results in endosymbiont genome size reduction. Unexpectedly, the largest Wolbachia genome was found in the obligate, parthenogenesis-associated wFol. In this study, we investigate possible processes underlying this genome expansion by comparing a re-annotated wFol genome to other Wolbachia genomes. In addition, we also search for candidate genes related to parthenogenesis induction (PI). Results: Within wFol, we found five phage WO regions representing 25.4% of the complete genome, few pseudogenized genes, and an expansion of DNA-repair genes in comparison to other Wolbachia. These signs of genome conservation were mirrored in the wFol host, the springtail F. candida, which also had an expanded DNA-repair gene family and many horizontally transferred genes. Across all Wolbachia genomes, there was a strong correlation between gene numbers of Wolbachia strains and their hosts. In order to identify genes with a potential link to PI, we assembled the genome of an additional PI strain, wLcla. Comparisons between four PI Wolbachia, including wFol and wLcla, and fourteen non-PI Wolbachia yielded a small set of potential candidate genes for further investigation. Conclusions: The strong similarities in genome content of wFol and its host, as well as the correlation between host and Wolbachia gene numbers suggest that there may be some form of convergent evolution between endosymbiont and host genomes. If such convergent evolution would be strong enough to overcome the evolutionary forces causing genome reduction, it would enable expanded genomes within long-term obligate endosymbionts.

    Original languageEnglish
    Article number106
    Pages (from-to)1-14
    Number of pages14
    JournalBMC Genomics
    Publication statusPublished - 6 Feb 2019


    This work is supported by the Netherlands Organisation for Scientific Research, VICI grant 865.12.003. DR received additional funding from NWO-TTW grant number 15494. These funding bodies had no role in the design of the study and collection, analysis, and interpretation of data or in writing this manuscript.

    FundersFunder number
    Nederlandse Organisatie voor Wetenschappelijk Onderzoek865.12.003


      • Folsomia candida
      • Leptopilina clavipes
      • wFol
      • wLcla
      • Parthenogenesis induction


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