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A screen for immunity genes evolving under positive selection in Drosophila
1Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK. francis.jiggins@ed.ac.uk
Journal of Evolutionary Biology
|May 1, 2007
Summary
Immune system genes in Drosophila show rapid adaptive evolution, likely due to coevolution with pathogens. Key genes like serine proteases and serpins are evolving under positive selection, highlighting their role in host-parasite interactions.
Area of Science:
- Evolutionary biology
- Immunology
- Genomics
Background:
- Genes in the immune system exhibit higher evolutionary rates compared to other genomic regions.
- This accelerated evolution is hypothesized to be driven by coevolutionary arms races with pathogens.
Purpose of the Study:
- To identify Drosophila genes undergoing adaptive evolution, specifically focusing on immune-related genes.
- To investigate the role of positive selection in the evolution of immune signaling pathways.
Main Methods:
- Comparative genomics of 140 immune loci between Drosophila erecta and D. yakuba to identify rapidly evolving genes.
- Resequencing of 23 fast-evolving genes in Drosophila melanogaster and D. simulans.
- Application of the McDonald-Kreitman test to detect positive selection.
Main Results:
- Strong evidence of positive selection was found in two serine proteases (persephone and spirit) and a homolog of Anopheles serpin SRPN6.
- Weaker evidence for adaptive evolution was observed in another serine protease and the death domain protein dFADD.
- These findings support the hypothesis that immune molecules are subject to rapid evolutionary pressures.
Conclusions:
- Immune signaling pathway molecules frequently evolve rapidly, suggesting they are key targets in host-parasite coevolution.
- The study provides specific examples of immune genes under positive selection in Drosophila.
- This rapid evolution of immune genes is a significant factor in host defense strategies.
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