Social isolation upregulates takeout expression in female Drosophila melanogaster to promote sucrose feeding

Abstract

Drosophila melanogaster provides a model system to examine how environmental stress interacts with sex to induce changes in brain function and behavior. Previous research suggests that social isolation induces changes in gene expression that encode a starvation-like brain state and reduce sleep. However, the extent to which social isolation alters behaviors via sex-specific brain changes is unclear. Here, we use Drosophila melanogaster to explore sex differences in chronic social isolation-induced behavioral and transcriptomic changes. We focused on takeout (to), a gene encoding a putative juvenile hormone-binding protein, as a target that is upregulated solely in females following social isolation. Male and female adult flies were exposed to chronic social isolation, and multiple behavioral sex differences were identified through tests of activity, motivation, aggression, and sugar consumption. RNA-seq analysis also identified several candidate genes that were associated with sex differences in isolation-induced behavioral changes. Our findings suggest that social isolation is sufficiently stressful to reveal latent sex differences in behavior, despite having no impact on survival. To expression and sucrose consumption were upregulated exclusively in females following social isolation. Following to knockdown in to-expressing cells, sucrose consumption decreased in socially isolated females but increased in males. However, to knock down, to overexpression, and transformer knock down in neurons did not change sucrose-feeding behavior between control and isolated females. Overall, our results suggest that manipulating to expression influences sucrose-feeding in opposite directions between females and males following social isolation, and that isolation-induced to overexpression in non-neuronal cells in the brain or head may play a role in communicating information about females nutritional status to the brain. Additional roles for to in stress-related behaviors and behavioral sex differences should be explored, as well as whether to participates in signaling pathways that may be functionally conserved in human disorders. Author SummaryChronic stress contributes to detrimental health effects, but our understanding of how stress induces sex differences in brain gene expression and behavior is incomplete. Here, we use a combination of behavioral testing, RNA sequencing, and genetic manipulations in Drosophila melanogaster to explore how social isolation reveals latent sex differences in gene expression and stress-relevant behaviors. We found the most pronounced sex differences in behaviors related to feeding and motivation. RNA profiling revealed isolated female-specific upregulation of over 100 genes, with many of them relating to reproduction and energy metabolism. We manipulated expression of the candidate gene takeout (to) and found that downregulating to in all to-expressing cells decreases sucrose-feeding in isolated females but increases it in isolated males. Our results suggest that within a chronic stress context, sex-specific effectors in the head may regulate gene expression related to feeding and macronutrient choice to ensure that females prioritize survival over reproduction. Learning more about this system in flies could provide insight into functionally analogous pathways in humans that may be dysregulated in female-biased stress-related disorders.