Life and death of selfish genes: comparative genomics reveals the dynamic evolution of cytoplasmic incompatibility.
Molecular biology and evolution
Oxford University Press
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Martinez, J., Klasson, L., Welch, J., & Jiggins, F. (2020). Life and death of selfish genes: comparative genomics reveals the dynamic evolution of cytoplasmic incompatibility.. Molecular biology and evolution https://doi.org/10.1093/molbev/msaa209
Cytoplasmic incompatibility is a selfish reproductive manipulation induced by the endosymbiont Wolbachia in arthropods. In males the Wolbachia genes cifA and cifB modify sperm, leading to embryonic mortality in crosses with Wolbachia-free females. In Wolbachia-infected females, cifA rescues the cross and allows development to proceed normally. This provides a reproductive advantage to infected females, allowing the maternally-transmitted symbiont to spread rapidly through host populations. We identified homologs of these genes in 52 of 71 new and published Wolbachia genomes sequences. They are strongly associated with cytoplasmic incompatibility. There are up to seven copies of the genes in each genome, and phylogenetic analysis shows that Wolbachia frequently acquires new copies due to pervasive horizontal transfer between strains. In many cases the genes have subsequently acquired loss-of-function mutations to become pseudogenes. As predicted by theory, this tends to occur first in cifB, whose sole function is to modify sperm, and then in cifA. Although cif genes recombine, recombination is largely restricted to closely related homologs. This is predicted under a ‘lock and key’ model of the coevolution of sperm modification and embryonic rescue, where recombination between distantly related pairs of genes would create a self-incompatible strain. Together, these patterns of gene gain, loss and recombination support evolutionary models of cytoplasmic incompatibility.
Wellcome Trust grant number WT094664MA - Wellcome Trust grant number WT202888/Z/16/Z - ERC grant 281668
Wellcome Trust (094664/Z/10/Z)
European Research Council (281668)
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External DOI: https://doi.org/10.1093/molbev/msaa209
This record's URL: https://www.repository.cam.ac.uk/handle/1810/309143
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