Rapid evolution of immune proteins in social insects

Lumi Viljakainen, Jay D Evans, Martin Hasselmann, Olav Rueppell, Salim Tingek, Pekka Pamilo

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    Sammanfattning

    The existence of behavioral traits connected to defense against pathogens manifests the importance of pathogens in the evolution of social insects. However, very little is known about how pathogen pressure has affected the molecular evolution of genes involved in their innate immune system. We have studied the sequence evolution of several immune genes in ants and honeybees. The results show high rates of evolution in both ants and honeybees as measured by the ratio of amino acid changes to silent nucleotide changes, the ratio being clearly higher than in Drosophila immune genes or in nonimmunity genes of bees. This conforms to our expectations based on high pathogen pressure in social insects. The codon-based likelihood method found clear evidence of positive selection only in one ant gene, even though positive selection has earlier been found in both ant and termite immune genes. There is now indication that selection on the amino acid composition of the immune-related genes has been an important part in the fight against pathogens by social insects. However, we cannot distinguish in all the cases whether the high observed d(N)/d(S) ratio results from positive selection within a restricted part of the studied genes or from relaxation of purifying selection associated with effective measures of behaviorally based colony-level defenses.
    Originalspråkengelska
    TidskriftMolecular Biology and Evolution
    Volym26
    Nummer8
    Sidor (från-till)1791-1801
    Antal sidor11
    ISSN0737-4038
    DOI
    StatusPublicerad - 2009
    MoE-publikationstypA1 Tidskriftsartikel-refererad

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