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Updated: Jun 29, 2026
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Published on: October 4, 2024
Wolbachia in the Culex pipiens group mosquitoes: introgression and superinfection
Thomas Walker1, Shewu Song, Steven P Sinkins
1Peter Medawar Building for Pathogen Research and Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
Abstract:
Wolbachia bacteria in mosquitoes induce cytoplasmic incompatibility (CI), where sperm from Wolbachia-infected males can produce inviable progeny. The wPip strain in the Culex pipiens group of mosquitoes produces a complexity of CI crossing types. Several factors are thought to be capable of influencing the expression of CI including Wolbachia strain type and host genotype. In this study, the unidirectional CI that occurs between 2 C. pipiens complex laboratory strains, Col and Mol, was further investigated by nuclear genotype introgression. The unidirectional CI between Col and Mol was not found to be influenced by host genetic background, in contrast to a previous introgression study carried out using bidirectionally incompatible C. pipiens group strains. A line containing both wPip strain variants superinfection was also generated by embryonic cytoplasmic transfer. The same crossing type as the parental Col strain was observed in the superinfected line. Quantitative polymerase chain reaction demonstrated a low density of the injected wPipMol variant in the superinfected line after 18 generations, which was considered likely to be responsible for the crossing patterns observed. The Wolbachia density was also shown to be lower in the parental Mol strain males compared with Col strain males, and no inverse relationship between WO phage and Wolbachia density could be detected.
Insights
Wolbachia bacteria in Culex mosquitoes cause cytoplasmic incompatibility (CI). This study found that host genotype does not influence CI between Col and Mol strains, but low Wolbachia density in superinfected lines affects crossing types.
Area of Science:
- Vector-borne disease research
- Microbial genetics
- Insect reproductive biology
Background:
- Wolbachia bacteria induce cytoplasmic incompatibility (CI) in mosquitoes, impacting reproduction.
- The wPip strain in Culex pipiens exhibits complex CI crossing types.
- Factors like Wolbachia strain and host genotype may influence CI expression.
Purpose of the Study:
- Investigate the influence of nuclear genotype on unidirectional CI between C. pipiens Col and Mol strains.
- Analyze the CI crossing type in a superinfected C. pipiens line with both wPip variants.
- Determine the role of Wolbachia density in observed CI patterns.
Main Methods:
- Nuclear genotype introgression between C. pipiens Col and Mol strains.
- Embryonic cytoplasmic transfer to generate a superinfected line.
- Quantitative polymerase chain reaction (qPCR) to assess Wolbachia density.
Main Results:
- Unidirectional CI between Col and Mol strains was not affected by host genetic background.
- A superinfected line exhibited the same CI crossing type as the parental Col strain.
- Low density of the injected wPipMol variant in the superinfected line correlated with observed crossing patterns.
- Wolbachia density was lower in Mol males than Col males; no inverse WO phage-Wolbachia density relationship was found.
Conclusions:
- Host genetic background does not influence the unidirectional CI between C. pipiens Col and Mol strains.
- Low Wolbachia density in superinfected lines is likely responsible for specific CI crossing patterns.
- Findings contribute to understanding the complex interactions between Wolbachia, host genotype, and reproductive incompatibility in mosquitoes.
