Natural Genetic Variation in Drosophila melanogaster Reveals Genes Associated with Coxiella burnetii Infection

The gram-negative bacterium Coxiella burnetii is the causative agent of Query (Q) fever in humans and coxiellosis in livestock. Association between host genetic background and Coxiella burnetii pathogenesis has been demonstrated both in humans and animals; however, specific genes associated with severity of infection remain unknown. We employed the Drosophila Genetics Reference Panel to perform a genome-wide association study and identify host genetic variants that affect Coxiella burnetii infection outcome. The analysis resulted in 64 genome-wide suggestive (P < 10-5) single nucleotide polymorphisms or gene variants in 25 unique genes. We examined the role of each gene in Coxiella burnetii infection using flies carrying a null mutation or RNAi knockdown of each gene and monitoring survival. Of the 25 candidate genes, 15 validated using at least one method. For many, this is the first report establishing involvement of these genes or their homologs with Coxiella burnetii susceptibility in any system. Among the validated genes, FER and tara play roles in the JAK-STAT, JNK, and decapentaplegic/TGF-{beta} signaling pathways that are associated with the innate immune response to Coxiella burnetii infection. Two other two validated genes, CG42673 and DIP-{varepsilon}, play roles in bacterial infection and synaptic signaling but no previous association with Coxiella burnetii pathogenesis. Furthermore, since the mammalian ortholog of CG13404 (PLGRKT) is an important regulator of macrophage function, CG13404 could play a role in Coxiella burnetii susceptibility through hemocyte regulation. These insights provide a foundation for further investigation of genetics of Coxiella burnetii susceptibility across a wide variety of hosts.