Uncovering the genomic basis of infection through co-genomic sequencing of hosts and parasites.

Understanding the genomic basis of infectious disease is fundamental objective in coevolutionary theory with relevance to healthcare, agriculture, and epidemiology. Models of host-parasite coevolution often assume that infection requires specific combinations of host and parasite genotypes. Coevolving host and parasite loci are therefor expected to show associations that reflects an underlying infection/resistance allele matrix, yet little evidence for such genome-to-genome interactions has been observed among natural populations. We conducted a study to search for this genomic signature across 258 linked host (Daphnia magna) and parasite (Pasteuria ramosa) genomes. Our results show a clear signal of genomic association between multiple epistatically-interacting loci in the host genome, and a family of genes encoding for collagen-like protein in the parasite genome. These findings are supported by laboratory-based infection trials, which show strong correspondence between phenotype and genotype at the identified loci. Our study provides clear genomic evidence of antagonistic coevolution among wild populations.