Correlation between desiccation stress response and epigenetic modifications of genes in Drosophila melanogaster: An example of environment-epigenome interaction.

Animals from different phyla including arthropods tolerate water stress to different extent. This tolerance is accompanied by biochemical changes which in turn are due to transcriptional alteration. The changes in transcription can be an indirect effect on some of the genes, ensuing from the effect of stress on the regulators of transcription including epigenetic regulators. Within this paradigm, we investigated the correlation between stress response and epigenetic modification underlying gene expression modulation during desiccation stress in Canton-S. We report altered resistance of flies in desiccation stress for heterozygote mutants of PcG and TrxG members. Pc/+ mutant shows lower survival, while ash1/+ mutants show higher survival under desiccation stress as compared to Canton-S. We detect expression alteration in stress related genes as well the genes of the Polycomb and trithorax complex in Canton-S subjected to desiccation stress. Concomitant with this, there is an altered enrichment of H3K27me3 and H3K4me3 at the upstream regions of the stress responsive genes. The enrichment of activating mark, H3K4me3, is higher in non-stress condition. H3K27me3, the repressive mark, is more pronounced under stress condition, which in turn, can be correlated with the binding of Pc. Our results show that desiccation stress induces dynamic switching in expression and enrichment of PcG and TrxG in the upstream region of genes, which correlates with histone modifications. We provide evidence that epigenetic modulation could be one of the mechanisms to adapt to the desiccation stress in Drosophila. Thus, our study proposes the interaction of epigenome and environmental factors.