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Open Access Research article

The expression of one ankyrin pk2 allele of the WO prophage is correlated with the Wolbachia feminizing effect in isopods

Samuel Pichon12, Didier Bouchon1, Chao Liu3, Lanming Chen3, Roger A Garrett3 and Pierre Grève1*

Author affiliations

1 Ecologie, Evolution, Symbiose, UMR CNRS 6556, Université de Poitiers, Poitiers, 86022, France

2 Zoological Institute, University of Basel, Basel, 4051, Switzerland

3 Department of Biology, University of Copenhagen, Copenhagen, 2200 N, Denmark

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Citation and License

BMC Microbiology 2012, 12:55  doi:10.1186/1471-2180-12-55

Published: 12 April 2012

Abstract

Background

The maternally inherited α-Proteobacteria Wolbachia pipientis is an obligate endosymbiont of nematodes and arthropods, in which they induce a variety of reproductive alterations, including Cytoplasmic Incompatibility (CI) and feminization. The genome of the feminizing wVulC Wolbachia strain harboured by the isopod Armadillidium vulgare has been sequenced and is now at the final assembly step. It contains an unusually high number of ankyrin motif-containing genes, two of which are homologous to the phage-related pk1 and pk2 genes thought to contribute to the CI phenotype in Culex pipiens. These genes encode putative bacterial effectors mediating Wolbachia-host protein-protein interactions via their ankyrin motifs.

Results

To test whether these Wolbachia homologs are potentially involved in altering terrestrial isopod reproduction, we determined the distribution and expression of both pk1 and pk2 genes in the 3 Wolbachia strains that induce CI and in 5 inducing feminization of their isopod hosts. Aside from the genes being highly conserved, we found a substantial copy number variation among strains, and that is linked to prophage diversity. Transcriptional analyses revealed expression of one pk2 allele (pk2b2) only in the feminizing Wolbachia strains of isopods.

Conclusions

These results reveal the need to investigate the functions of Wolbachia ankyrin gene products, in particular those of Pk2, and their host targets with respect to host sex manipulation.