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Proc Biol Sci. 2018 Jan 10;285(1870). pii: 20172599. doi: 10.1098/rspb.2017.2599.

Rapid seasonal evolution in innate immunity of wild Drosophila melanogaster.

Author information

1
Department of Biology, University of Pennsylvania, 433 S. University Ave., Philadelphia, PA 19104, USA bemily@sas.upenn.edu.
2
Department of Entomology, Cornell University, 3125 Comstock Hall, Ithaca, NY 14853, USA.
3
Department of Ecology and Evolution, University of Lausanne, Lausanne 1015, Switzerland.
4
Department of Biology, Stanford University, 371 Serra St, Stanford, CA 94305-5020, USA.
5
Albert-Ludwigs University, Freiburg, Germany.
6
Department of Biology, University of Virginia, 409 McCormic Rd, Charlottesville, VA 22904, USA.
7
Department of Biology, University of Pennsylvania, 433 S. University Ave., Philadelphia, PA 19104, USA.

Abstract

Understanding the rate of evolutionary change and the genetic architecture that facilitates rapid adaptation is a current challenge in evolutionary biology. Comparative studies show that genes with immune function are among the most rapidly evolving genes across a range of taxa. Here, we use immune defence in natural populations of Drosophila melanogaster to understand the rate of evolution in natural populations and the genetics underlying rapid change. We probed the immune system using the natural pathogens Enterococcus faecalis and Providencia rettgeri to measure post-infection survival and bacterial load of wild D. melanogaster populations collected across seasonal time along a latitudinal transect along eastern North America (Massachusetts, Pennsylvania and Virginia). There are pronounced and repeatable changes in the immune response over the approximately 10 generations between spring and autumn collections, with a significant but less distinct difference observed among geographical locations. Genes with known immune function are not enriched among alleles that cycle with seasonal time, but the immune function of a subset of seasonally cycling alleles in immune genes was tested using reconstructed outbred populations. We find that flies containing seasonal alleles in Thioester-containing protein 3 (Tep3) have different functional responses to infection and that epistatic interactions among seasonal Tep3 and Drosomycin-like 6 (Dro6) alleles underlie the immune phenotypes observed in natural populations. This rapid, cyclic response to seasonal environmental pressure broadens our understanding of the complex ecological and genetic interactions determining the evolution of immune defence in natural populations.

KEYWORDS:

Drosomycin-like 6; Drosophila melanogaster; Thioester-containing protein 3; epistasis; innate immunity; rapid adaptation

PMID:
29321302
PMCID:
PMC5784205
DOI:
10.1098/rspb.2017.2599
[Indexed for MEDLINE]
Free PMC Article

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