Host defense mechanisms induce genome instability in an opportunistic fungal pathogen

The ability to generate genetic variation facilitates rapid adaptation in stressful environments. The opportunistic fungal pathogen Candida albicans frequently undergoes large-scale genomic changes, including aneuploidy and loss-of heterozygosity (LOH), following exposure to physiological stressors and host environments. However, the specific host factors that induce C. albicans genome instability remains largely unknown. Here, we leveraged genetically-tractable nematode hosts to specifically investigate the innate immune components driving host-associated C. albicans genome instability, which include host production of antimicrobial peptides (AMPs) and reactive oxygen species (ROS). C. albicans associated with wildtype, immunocompetent hosts carried multiple large-scale genomic changes including LOH, whole chromosome, and segmental aneuploidies. In contrast, C. albicans associated with immunocompromised hosts deficient in AMPs or ROS production had reduced LOH frequencies and fewer, if any, additional genomic changes. We also found that C. albicans cap1 Δ/Δ strains deficient in ROS detoxification, were more susceptible to host-produced ROS genome instability compared to wildtype C. albicans . Further, genomic perturbations resulting from host-produced ROS are mitigated by the addition of antioxidants. Taken together, this work suggests that host-produced ROS and AMPs induces genotypic plasticity in C. albicans which may facilitate rapid adaptation and lead to phenotypic changes. ### Competing Interest Statement The authors have declared no competing interest.