Variation in positive selection in termite GNBPs and Relish

Bulmer, Mark S., and Crozier, Ross H. (2006) Variation in positive selection in termite GNBPs and Relish. Molecular Biology and Evolution, 23 (2). pp. 317-326.

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Social insects are model organisms for investigating molecular evolution in the innate immune system. Their diversity affords comparative analysis among closely related species, and group living is likely to contribute to the pathogen stress imposed on the immune system. We used different models of nucleotide substitution at nonsynonymous (amino acid altering) and synonymous (silent) sites to compare the different levels and type of selection among three immunity genes in 13 Australian termite species (Nasutitermes). The immunity genes include two encoding pathogen recognition proteins (gram-negative bacterial-binding proteins) that duplicated and diverged before or soon after the evolution of the termites and a transcription factor (Relish), which induces the production of antimicrobial peptides. A comparison of evolutionary models that assign four unrestricted classes of dN/dS (the ratio of the nonsynonymous to synonymous substitution rate) to different Nasutitermes lineages revealed that the occurrence of positive selection (dN/dS > 1) varies among lineages and the three genes. Positive selection appears to have driven the evolution of all three genes in an ancestral lineage of three subterranean termites. It had previously been suggested that there was a transition along this ancestral lineage to termite morphology and ecology associated with a diet of decayed wood, a diet that may expose termites to elevated levels of fungal and bacterial pathogens. Relish appears to have experienced the highest levels of selective pressure for change among all three genes. Positively selected sites in the molecule are located in regions that are important for its activation, which suggests that amino acid substitutions at these sites are a counter response to pathogen mechanisms that disrupt the activation of Relish.

Item ID: 4153
Item Type: Article (Research - C1)
ISSN: 1537-1719
Keywords: evolutionary immunology; GNBP; innate immunity; positive selection; Relish; termites
Date Deposited: 03 Nov 2009 05:28
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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