Variation in positive selection in termite GNBPs and Relish

Area of Science:

• Evolutionary biology
• Immunology
• Molecular biology

Background:

• Social insects, like termites, are valuable models for studying innate immune system evolution due to group living and pathogen exposure.
• Comparative analysis across diverse termite species offers insights into immune gene adaptation.

Purpose of the Study:

• To investigate molecular evolution and selection pressures on three immunity genes in 13 Australian termite species (Nasutitermes).
• To compare evolutionary models and identify instances of positive selection (dN/dS > 1) across different lineages and genes.

Main Methods:

• Analysis of nucleotide substitution models at nonsynonymous and synonymous sites for three immunity genes.
• Comparative evolutionary analysis across 13 Nasutitermes species, focusing on gram-negative bacterial-binding proteins and the Relish transcription factor.

Main Results:

• Positive selection varies among lineages and the three studied immunity genes.
• Evidence of positive selection driving the evolution of all three genes in an ancestral lineage of subterranean termites.
• The Relish gene experienced the highest selective pressure, with positively selected sites in critical activation regions.

Conclusions:

• Immunity genes in termites, especially Relish, are under significant selective pressure, indicating adaptation to pathogen challenges.
• Changes in diet and ecology in ancestral termites may have increased pathogen exposure, driving immune system evolution.
• Amino acid substitutions in Relish likely represent a co-evolutionary response to pathogen evasion mechanisms.