Transgenerational Epigenetic Inheritance following Dietary Stress in Drosophila

Temperature, food resources, and water availability, among other environmental conditions, fluctuate widely. One way living organisms respond to environmental stress is by altering their gene expression. This response is regulated by the epigenome, the set of DNA and histone modifications that directly impact the accessibility of genes to transcriptional machinery. Epigenomic modifications can be heritable, such that stressed organisms influence gene expression in their offspring, potentially increasing their odds of survival if the stressor reappears. In this study, I investigated the heritability of stress-induced phenotypes following dietary restriction over two generations in Drosophila melanogaster. Although body size, as measured by wing length, and dry body mass were unaffected by the treatment, dietary stress significantly delayed adult eclosion and reduced larval stage mobility. Larval mobility was rescued, and developmental speed, measured by eclosion rate, was partially rescued for at least two generations of continued dietary stress. These beneficial changes at the juvenile stage may have been produced at a cost, however, as by the third generation of exposure adults displayed significantly reduced thermal tolerance. These results provide support for the hypothesis that stress-induced epigenetic change is heritable and can provide protection against future stressors. The syndrome of phenotypes impacted are all associated with energy conservation pathways involving AMP-activated protein kinase (AMPK), a protein that alters the epigenome in response to depleted energy stores (ATP), meriting investigation of AMPK as a potential master regulator of stress-induced transgenerational epigenetic inheritance.