Sex-specific epigenomic changes after elevated pupal and adult temperature in Ostrinia moths

Epigenetic changes to DNA methylation may occur in response to environmental stressors including heatwaves and warming climates. DNA methylation may also play an important role in regulating gene expression during male and female reproduction in many insect species. However, it is currently unknown how DNA methylation shifts when individuals are reproducing under warmer temperatures. We exposed European corn borer moths (Ostrinia nubilalis) to elevated temperature during the pupal and adult life stages then investigated changes in DNA methylation across the genome using enzymatic methyl-seq (EM-seq). We compared methylation patterns in reproductive males and females exposed to heat (28°C) to those that experienced an ambient temperature (23°C). We found that heat exposure led to a small but significant increase in the percentage of methylated regions throughout the genome in both sexes. Differential methylation following heat exposure localized to unique regions in each sex. DNA methylation patterns were highly sex-specific in two tissue types: heads and abdomens. Our results suggest that DNA methylation responds to a moderate heat exposure in Lepidoptera and provide insight into epigenetic responses to heatwaves, suggesting these responses may be sexually dimorphic particularly when heat stress occurs during metamorphosis and reproduction.