Sex-specific Plasticity and the Nutritional Geometry of Insulin-Signaling Gene Expression in Drosophila Melanogaster

Abstract

Background: Sexual-size dimorphism (SSD) is replete among animals, but while the selective pressures that drive the evolution of SSD have been well studied, the developmental mechanisms upon which these pressures act are poorly understood. Ours and others’ research has shown that SSD in Drosophila reflects elevated levels of nutritional plasticity in females versus males, such that SSD increases with dietary intake and body size, a phenomenon called sex-specific plasticity (SSP). Additional data indicate that while body size in both sexes responds to variation in protein level, only female body size is sensitive to variation in carbohydrate level. Here we explore whether these difference in sensitivity at the morphological level are reflected by differences in how the insulin/IGF-signaling (IIS) and TOR-signaling pathways respond to changes in carbohydrates and proteins in females versus males, using a nutritional geometry approach. Results: The IIS-regulated transcripts of 4E-BP and InR most strongly correlated with body size in females and males respectively, but neither responded to carbohydrate level and so could not explain the sex-specific response to body size to dietary carbohydrate. Transcripts regulated by TOR-signaling did, however, respond to dietary carbohydrate in a sex-specific manner. In females, expression of dILP5 positively correlated with body size, while expression of dILP2,3 and 8, was elevated on diets with a low concentration of both carbohydrate and protein. In contrast, we detected lower levels of dILP2 and 5 protein in the brains of females fed on low concentration diets. We could not detect any effect of diet on dILP expression in males.Conclusion: Although females and males show sex-specific transcriptional responses to changes in protein and carbohydrate, the patterns of expression do not support a simple model of the regulation of body-size SSP by either insulin- or TOR-signaling. The data also indicate a complex relationship between carbohydrate and protein level, dILP expression and dILP peptide levels in the brain. In general, diet quality and sex both affect the transcriptional response to changes in diet quantity, and so should be considered in future studies that explore the effect of nutrition on body size.

Encoding of hunger by the neuronal epigenome slows aging in Drosophila

“…S1A) (2,3). We subsequently focused our investigation using female flies because of their known, heightened lifespan and neuronal responses to protein availability, which we also observed (25,26). We chose two diets from the range of those initially tested, hereafter termed "low -BCAA" (8mM BCAAs/5.6% w/v total amino acid) and "high-BCAA" (44mM BCAAs/7.2% w/v total amino acid), to investigate in detail.…”

Nutrigonometry I: using right-angle triangles to quantify nutritional trade-offs in multidimensional performance landscapes

“…These studies generate multiple 3D landscapes that are often compared visually, without rigorous analytical methods to measure nutritional trade-offs. For example, eleven 3D-landscapes of the expression of genes involved in the Insulin/IGF pathway were visually compared to provide insights into how a key endocrine pathway is regulated based on nutrient intake, and how gene expression can underlie expression of lifehistories (Post and Tatar 2016;McDonald et al 2021). Likewise, twelve 3D-landscapes with gut microbial diversity or abundance were visually compared to better understand how nutrient composition can modulate host-microbe interactions (Ng et al 2019).…”