Distinct Bomanins at the Drosophila 55C locus function in resistance and resilience to infections

Host defense against many Gram-positive bacteria and fungal pathogens is mainly provided by the Toll-dependent systemic immune response inDrosophila. While antimicrobial peptides active against these categories of pathogens contribute only modestly to protection, Bomanin peptides are major effectors of the Toll pathway. Remarkably, flies deleted for the55Clocus that contains 10Bomaningenes are as sensitive as Toll pathway mutant flies to these infections. Yet, the exact functions of single Bomanins in resistance or resilience to infections remain poorly characterized. Here, we have extensively studied the role of theseBomaningenes. BomT1 functions in resistance toEnterococcus faecaliswhile playing a role in resilience againstMetarhizium robertsiiinfection, like BomS2. BomT1 and BomT2 prevent the dissemination ofCandida albicansthroughout the host, even though they are not sufficient to confer protection to immunodeficient flies against this pathogen in survival experiments. Furthermore,BomT1andBomBc1mutants are sensitive to anAspergillus fumigatusribotoxin. We conclude that55CBomanins have defined albeit sometimes overlapping roles in the different facets of host defense against infections.