The metabolome as a link in the genotype-phenotype map for peroxide resistance in the fruit fly, Drosophila melanogaster
Abstract Background Genetic association studies that seek to explain the inheritance of complex traits typically fail to explain more than a small fraction of the heritability of the trait under study. Thus we are left with a gap in the map from genotype to phenotype. Several approaches have been used to fill this gap, including those that attempt to map endophenotype such as the transcriptome, proteome or metabolome, that underlie complex traits. Here we used metabolomics to explore the nature of genetic variation for hydrogen peroxide (H2O2) resistance in the sequenced inbred Drosophila Genetic Reference Panel (DGRP). Results We first studied genetic variation for H2O2 resistance in 180 DGRP lines and identify the insulin signaling modulator u-shaped and several regulators of feeding behavior. We then profiled a portion of the aqueous metabolome in subsets of eight ‘high resistance’ lines and eight ‘low resistance’ lines. We used these lines to represent collections of genotypes that were either resistant or sensitive to the stressor, effectively modeling a discrete trait. Across the range of genotypes in both populations, flies exhibited surprising consistency in their metabolomic signature of resistance. Metabolomic profiles were also able to distinguish stress-resistant from stress-sensitive flies with greater accuracy than the genotype of these same lines. Furthermore, we found a metabolic response to H2O2 that was shared among sensitive, but not resistant genotypes. Metabolomic data further implicated at least two pathways, glycogen and folate metabolism, as determinants of sensitivity to H2O2. We also discovered a confounding effect of feeding behavior on assays involving supplemented food. Conclusions This work suggests that the metabolome can be a point of convergence for genetic variation influencing complex traits, and efficiently elucidate the mechanisms underlying this trait variation.