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Fly (Austin). 2017 Oct 2;11(4):277-283. doi: 10.1080/19336934.2017.1337612. Epub 2017 Jun 6.

Genomic signatures of local adaptation in the Drosophila immune response.

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a Department of Molecular Biology and Genetics , Cornell University , Ithaca , NY.
b Infectious Disease and Microbiome Program , Broad Institute of MIT and Harvard , Cambridge , MA.


As environments and pathogen landscapes shift, host defenses must evolve to remain effective. Due to this selection pressure, among-species comparisons of genetic sequence data often find immune genes to be among the fastest evolving genes across the genome. The full extent and nature of these immune adaptations, however, remain largely unexplored. In a recent study, we analyzed patterns of selection within distinct components of the Drosophila melanogaster immune pathway. While we found evidence of positive selection within some immune processes, immune genes were not universally characterized by signatures of strong selection. On the contrary, we even found that some immune functions show greater than expected constraint. Overall these results highlight 2 major factors that appear to play an outsize role in determining a gene's evolutionary rate: the type of pathogen the gene targets and the gene's position within the immune network. These results join a growing body of literature that highlight the complexity of immune adaptation. Rather than there being uniformly strong selection across all immune genes, a combination of pathogen-specificity and host genetic constraints appear to play key roles in determining each immune gene's individual evolutionary trajectory.


evolution; host-pathogen interactions; innate immunity; local adaptation; population genetics

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