Cytoplasmic incompatibility (CI) is a conditional sterility induced by the bacterium Wolbachia pipientis that infects reproductive tissues in many arthropods. Although CI provides a potential tool to control insect vectors of arthropod-borne diseases, the molecular basis for CI induction is unknown. We hypothesized that a Wolbachia-encoded, CI-inducing factor would be enriched in sperm recovered from spermathecae of female mosquitoes. Using SDS-PAGE and mass spectrometry, we detected peptides from the 56kDa hypothetical protein, encoded by wPip_0282, associated with sperm transferred to females by Wolbachia infected males. We also detected peptides from the same protein in Wolbachia infected ovaries. Homologs of wPip_0282 and the co-transcribed downstream gene, wPip_0283, occur as multiple divergent copies in genomes of CI-inducing strains of Wolbachia. The operon is located in a genomic context that includes mobile genetic elements. The absence of wPip_0282 and wPip_0283 homologs from genomes of Wolbachia in filarial nematodes, as well as other members of the Rickettsiales, suggests a role as a candidate CI effector.
Bibliographical noteFunding Information:
We thank Todd Markowski and Bruce Witthuhn at the University of Minnesota's Center for Mass Spectrometry and Proteomics for help with mass spectrometry detection and gel staining, Cassie Kurtz and Elissa Carroll for help with mosquito maintenance, and Gerald Baldridge, Rod Felsheim, and Tim Kurtti for helpful discussions. This work was supported by NIH grant AI081322 and by the University of Minnesota Agricultural Experiment Station, St. Paul, MN .
Copyright 2013 Elsevier B.V., All rights reserved.
- Culex pipiens
- Cytoplasmic incompatibility
- Mass spectrometry