Abstract
Wolbachia are the most abundant endosymbiotic bacteria found in arthropod species, known to induce a wide variety of phenotypes on their hosts, with strong evidence indicating that some fitness-associated host traits depend on bacterial load. Here we quantify how Wolbachia titer is influenced by the genome of its host, in Drosophila melanogaster, using the Drosophila Genetic Reference Panel (DGRP). We first found a large variation in Wolbachia titers among 90 DGRP lines, using read mapping coverage data to estimate titers in silico. We found high broad-sense heritability for Wolbachia titer variation. To identify the host loci associated with this phenotype, we performed a genome-wide association study using 1,202,368 biallelic SNPs. Finally, we validated our estimation of Wolbachia titers in silico using direct estimation with qPCR. We discuss our results in light of previous studies in D. melanogaster and D. simulans, and we conclude that our research brings further evidence of Wolbachia titer regulation by the host genome, illustrating the complexity of host-endosymbiont relationships.