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 D. melanogaster 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.

Sexual Dimorphism in Metabolic Responses to Western Diet in Drosophila melanogaster

“…Previous studies observed a positive correlation between dIlp5 gene expression and the body size in females. This correlates with our observation of the reduced dIlp5 expression and the reduced body weight of females on the diets [ 45 ]. In contrast, dIlp3 expression, which had a female-biased expression under normal conditions, increased significantly in males on fat and western diets.…”

Dietary restriction reveals sex-specific expression of the mTOR pathway genes in Japanese quails

“…In fruit flies, the effects of dietary restriction on lifespan and mortality rates also differ between sexes, with females showing a peak in lifespan at higher food concentrations and a more pronounced response to restriction 29 . Another experiment in the same species revealed that dietary restriction-mediated sex differences in fitness are associated with sex-specific effects on the expression of genes mediating the mTOR pathway 21 , 22 . The proposed explanation for these differences is rooted in sexual variations in nutrient requirements and energy allocation.…”

Effects of hunger on neuronal histone modifications slow aging in Drosophila

“…S1A) ( 2 , 3 ). We focused our investigation on female flies because of their heightened life span and neuronal responses to protein availability ( 23 , 24 ). We chose two diets, hereafter termed “low BCAA” (8 mM BCAAs/5.6% w/v total amino acid) and “high BCAA” (44 mM BCAAs/7.2% w/v total amino acid), to investigate in detail.…”