Wolbachia variability and host effects on crossing type in Culex mosquitoes


Wolbachia is a common maternally inherited bacterial symbiont able to induce crossing sterilities known as cytoplasmic incompatibility (CI) in insects1,2. Wolbachia-modified sperm are unable to complete fertilization of uninfected ova, but a rescue function allows infected eggs to develop normally. By providing a reproductive advantage to infected females, Wolbachia can rapidly invade uninfected populations3, and this could provide a mechanism for driving transgenes through pest populations4,5. CI can also occur between Wolbachia-infected populations and is usually associated with the presence of different Wolbachia strains1. In the Culex pipiens mosquito group (including the filariasis vector C. quinquefasciatus) a very unusual degree of complexity of Wolbachia-induced crossing-types has been reported, with partial or complete CI that can be unidirectional or bidirectional6,7,8,9,10,11, yet no Wolbachia strain variation was found11. Here we show variation between incompatible Culex strains in two Wolbachia ankyrin repeat-encoding genes associated with a prophage region, one of which is sex-specifically expressed in some strains, and also a direct effect of the host nuclear genome on CI rescue.

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Figure 1: Wolbachia -mediated CI in C. quinquefasciatus.
Figure 2: Wolbachia ANK gene variability.
Figure 3: Effects of host genome introgression on CI.
Figure 4: Results of a model investigating host effects on CI.


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We thank S. O'Neill for Wolbachia genomics input, and S. Song for providing Culex material. This research was supported by grants from the Wellcome Trust, and the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR).

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Correspondence to Steven P. Sinkins.

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Sequences have been deposited with NCBI GenBank under accession numbers DQ000469– DQ000472. Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

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