Selective sweeps in Cryptocercus woodroach antifungal proteins.

Area of Science:

• Evolutionary biology
• Insect genetics
• Antimicrobial peptides

Background:

• Termicin is an antifungal gene crucial for termite immunity.
• Cryptocercus woodroaches are the closest living relatives to termites.
• Understanding termicin's evolution can shed light on insect-pathogen interactions.

Purpose of the Study:

• To identify and analyze the termicin gene in Cryptocercus woodroaches.
• To investigate the evolutionary history and selection pressures on termicin and related immune genes (GNBP1, GNBP2) in Cryptocercus.
• To compare the evolutionary patterns of these genes in Cryptocercus with their termite orthologues.

Main Methods:

• Gene identification and sequencing of termicin, GNBP1, and GNBP2 in multiple Cryptocercus species.
• Phylogenetic analysis to determine evolutionary relationships.
• Selection analysis using methods like detecting selective sweeps and analyzing synonymous site divergence.

Main Results:

• Termicin was identified in three Cryptocercus species, indicating its ancient origin.
• Evidence of past selective sweeps was found in Cryptocercus termicin and GNBP2 genes.
• A conserved variant of GNBP2 was maintained across Cryptocercus species, despite synonymous site divergence.
• Cryptocercus termicin and GNBP2 show similar selective pressures to their termite counterparts.

Conclusions:

• The antifungal role of termicin predates the termite-cockroach divergence.
• Cryptocercus woodroaches share similar immune gene evolution with termites, likely driven by common exposure to fungal pathogens like Metarhizium.
• This study highlights the deep evolutionary roots of termite-like immunity in cockroaches.