title: Does a parthenogenesis-inducing Wolbachia induce vestigial cytoplasmic incompatibility?
abstract: Wolbachia is a maternally inherited bacterium that manipulates the reproduction of its host. Recent studies have shown that male-killing strains can induce cytoplasmic incompatibility (CI) when introgressed into a resistant host. Phylogenetic studies suggest that transitions between CI and other Wolbachia phenotypes have also occurred frequently, raising the possibility that latent CI may be widespread among Wolbachia. Here, we investigate whether a parthenogenesis-inducing Wolbachia strain can also induce CI. Parthenogenetic females of the parasitoid wasp Asobara japonica regularly produce a small number of males that may be either infected or not. Uninfected males were further obtained through removal of the Wolbachia using antibiotics and from a naturally uninfected strain. Uninfected females that had mated with infected males produced a slightly, but significantly more male-biased sex ratio than uninfected females that had mated with uninfected males. This effect was strongest in females that mated with males that had a relatively high Wolbachia titer. Quantitative PCR indicated that infected males did not show higher ratios of nuclear versus mitochondrial DNA content. Wolbachia therefore does not cause diploidization of cells in infected males. While these results are consistent with CI, other alternatives such as production of abnormal sperm by infected males cannot be completely ruled out. Overall, the effect was very small (9%), suggesting that if CI is involved it may have degenerated through the accumulation of mutations.
authors.affiliation: Institute of Biology, Leiden University, P.O. Box 9505, 2300 RA, Leiden, The Netherlands. ken@kenkraaijeveld.nl
authors.forename: Ken
authors.initials: K
authors.lastname: Kraaijeveld
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Reumer
authors.forename: Laurence
authors.initials: L
authors.lastname: Mouton
authors.forename: Natacha
authors.initials: N
authors.lastname: Kremer
authors.forename: Fabrice
authors.initials: F
authors.lastname: Vavre
authors.forename: Jacques J M
authors.initials: JJ
authors.lastname: van Alphen
mesh_terms: D000818:Animals; D001947:Breeding; D003593:Cytoplasm / Q000502:physiology*; D005260:Female; D005798:Genes, Bacterial / Q000235:genetics; D008297:Male; D008969:Molecular Sequence Data; D012744:Sex Ratio; D014863:Wasps / Q000382:microbiology*; D020577:Wolbachia / Q000235:genetics / Q000502:physiology*