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An Introduction to Parasitic Wasps of Drosophila and the Antiparasite Immune Response
Published on: May 7, 2012
Contrasting evolutionary patterns in Drosophila immune receptors
Francis M Jiggins1, Kang-Wook Kim
1Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, Scotland. Francis.Jiggins@ed.ac.uk
Journal of Molecular Evolution
|November 15, 2006
Summary
Two Drosophila thioester-containing protein (TEP) genes involved in parasite binding evolve rapidly under positive selection, particularly in their variable regions. This suggests an evolutionary arms race between hosts and parasites impacting immune molecule function.
Area of Science:
- Evolutionary biology
- Immunology
- Genomics
Background:
- Vertebrate immune molecules interacting with parasites face strong natural selection due to host-parasite coevolutionary dynamics.
- Insect immune systems possess molecules that bind parasite-derived components, warranting investigation into their evolutionary patterns.
Purpose of the Study:
- To investigate evolutionary patterns in Drosophila immune system components that bind parasite-derived molecules.
- To determine if genes encoding thioester-containing proteins (TEPs) and gram-negative binding proteins (GNBPs) in Drosophila show signs of rapid evolution and positive selection.
Main Methods:
- Comparative genomic analysis of Drosophila melanogaster TEP and GNBP genes.
- Identification of positively selected sites within TEP genes, focusing on the variable "bait-like" region.
- Sequencing of immune-induced peptides with homology to GNBPs.
Main Results:
- Two of the three immune-upregulated Drosophila TEP genes (TepI and TepII) exhibit rapid evolution under positive selection.
- The "bait-like" (variable) region of TepI and TepII shows the strongest signature of positive selection, potentially indicating a site of proteolytic activation.
- In contrast, Drosophila GNBP genes and related immune peptides are highly conserved, showing no signs of rapid evolution.
Conclusions:
- The rapid evolution of specific TEP regions suggests they are key targets in the coevolutionary arms race between Drosophila and its parasites.
- Parasites may evolve to evade TEP-mediated immunity by interfering with proteolytic activation, driving selection for mutations in the TEP "bait-like" region.
- Differential evolutionary pressures on TEPs and GNBPs highlight distinct roles and coevolutionary histories within the insect immune system.
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