Differences in temperature-sensitive expression of PcG-regulated genes among natural populations of Drosophila melanogaster.

Environmental temperature can affect chromatin-based gene regulation, in particular in ectotherms such as insects. Genes regulated by the Polycomb group (PcG) vary in their transcriptional output in response to changes in temperature. Expression of PcG-regulated genes typically increases with decreasing temperatures. Here, we examined variations in temperature-sensitive expression of PcG target genes in natural populations from different climates of Drosophila melanogaster, and differences thereof across different fly stages and tissues. Temperature-induced expression plasticity was found to be stage- and sex-specific with differences in the specificity between the examined PcG target genes. Some tissues and stages, however, showed a higher number of PcG target genes with temperature-sensitive expression than others. Overall, we found higher levels of temperature-induced expression plasticity in African tropical flies from the ancestral species range than in flies from temperate Europe. We also observed differences between temperate flies, however, with more reduction of expression plasticity in warm-temperate than in cold-temperate populations. Although in general, temperature-sensitive expression appeared to be detrimental in temperate climates, there were also cases in which plasticity was increased in temperate flies, as well as no changes in expression plasticity between flies from different climates.