Identification of parthenogenesis inducing Wolbachia proteins in parasitoid wasps

The bacterium Wolbachia is a maternally transmitted, endosymbiotic reproductive manipulator, found in about half of all insect species. In many haplodiploid organisms such as the parasitoid wasps Trichogramma pretiosum and Leptopilina clavipes, Wolbachia infection is the causative agent of the shift to asexuality. Some asexual populations rely on Wolbachia for diploidization of unfertilized eggs to produce females, but the bacterial genes involved in diploidization culminating in asexuality are not known. We compared parthenogenesis-inducing Wolbachia genomes to uncover two candidate genes, hereinafter “parthenogenesis inducing factors” (Pifs), that may be involved in the diploidization of wasp embryos. As both Wolbachia and parasitoids lack tools for genetic manipulation, we use surrogate approaches such as protein expression in Drosophila melanogaster to bypass limited genetic techniques and characterize the function of the Pif proteins. We find that the Pif genes are expressed by wTpre, and their expression varies across host development. When expressed in Saccharomyces cerevisiae, the Pif proteins impact yeast growth and exhibit localization patterns suggesting interaction with genetic material, both indicating mitotic effects. Full characterization of the proteins and host targets will provide further insight into the parthenogenetic mechanisms employed by some Wolbachia strains, as well as the reversion to asexuality more broadly.