The evolution of antimicrobial peptides in Chiroptera

Area of Science:

• Immunology
• Evolutionary Biology
• Genomics

Background:

• Bats are exceptional models for studying host-pathogen interactions due to their high viral tolerance and immune regulation.
• Antimicrobial peptides (AMPs), crucial for innate immunity, are understudied in bats despite numerous reports of immune gene evolution.
• Defensins and cathelicidins are key AMP families with significant roles in host defense against pathogens.

Purpose of the Study:

• To comprehensively explore the diversity, evolution, and distribution of defensin and cathelicidin gene families in bats.
• To identify lineage-specific gene gains and losses within these AMP families across six bat families.
• To investigate potential drivers, such as diet and microbiome, influencing the evolution of bat AMPs.

Main Methods:

• An exhaustive bioinformatic pipeline combining manual and automated procedures was developed.
• Targeted analysis of major AMP gene families, specifically defensins (alpha and beta) and cathelicidins.
• Comparative genomics across six diverse bat families to assess gene family evolution and distribution.

Main Results:

• Identified 29 AMP families, with alpha-defensins, beta-defensins, and cathelicidins comprising approximately 10% of the total diversity.
• Observed gene duplications in alpha-defensins and three beta-defensin subfamilies; alpha-defensins were notably absent in five species.
• Cathelicidins showed stable gene family size but were absent in specific species like *Anoura caudifer* and pteropodids.

Conclusions:

• Diet and microbiome evolution are proposed as key drivers for the diversification of alpha- and beta-defensin gene families in bats.
• Highlights the necessity of species-specific genomic libraries for accurate annotation in non-model organisms.
• Provides a foundational understanding of AMP evolution in bats, crucial for explaining their unique pathogen resistance.