RESEARCH ARTICLE Temperature Stress Mediates Decanalization and Dominance of Gene Expression in Drosophila melanogaster

The regulatory architecture of gene expression remains an area of active research. Here, we studied how the interplay of genetic and environmental variation affects gene expression by exposing Drosophila melanogaster strains to four different developmental temperatures. At 18°C we observed almost complete canalization with only very few allelic effects on gene expression. In contrast, at the two temperature extremes, 13°C and 29°C a large number of allelic differences in gene expression were detected due to both cis- and trans-regulatory ef-fects. Allelic differences in gene expression were mainly dominant, but for up to 62 % of the genes the dominance swapped between 13 and 29°C. Our results are consistent with stabi-lizing selection causing buffering of allelic expression variation in non-stressful environ-ments. We propose that decanalization of gene expression in stressful environments is not only central to adaptation, but may also contribute to genetic disorders in human populations. Author Summary Gene expression is the most direct link between the genetically encoded information and the phenotype. We analyzed the patterns of gene expression in two different D. melanoga-ster genotypes and their offspring at four different temperatures to determine if gene ex-pression regulation is modulated by temperature. Interestingly, we find that at the intermediate temperature (18°C) alleles from both genotypes have very similar gene ex-pression, suggesting a strong canalization of gene expression despite substantial genetic differences. More extreme temperatures break this canalization and result in many differ-ently expressed genes, caused mainly by trans-acting factors. Most of the expression differ-ences are non-additive, with a swap in dominance between the two extreme temperatures