Diet-induced plasticity of life-history traits and gene expression in outbred Drosophila melanogaster population
Food is a fundamental requirement for organisms to develop, survive and reproduce. However, access to an optimum diet is not always guaranteed, resulting in a mismatch between the diet and the organism's needs. To comprehend the consequences of this mismatch, it becomes crucial to explore how different compositions of an organism's diet impact its overall performance. In this context, we tested the effect of isocaloric diets with different protein to carbohydrate ratios on eight key life history traits in a large (n = ~2,100) outbred Drosophila melanogaster population. We report accelerated pre-adult development and increased reproductive output, without affecting pre-adult viability and body size, in flies fed on low carbohydrate diet. We also observe that high carbohydrate content in diet shortens fly lifespan. In support, we found that increasing carbohydrate content in food led to faster aging by impairing locomotor activity and gut integrity. Additionally, we noted that the composition of the diet had an impact on gene expression patterns with high carbohydrate diets upregulating genes and high protein diets downregulating them. These results collectively provide a comprehensive understanding of how the balance of macronutrients in an organism's diet intricately shapes its traits. Overall design: Whole RNA was isolated from female flies subject to different dietary conditions (P:C 0.25, P:C 0.40, P:C 0.55, P:C 0.70), on the 13th day post egg collection. RNA libraries prepared using  NEBNext Ultra II RNA Library Prep Kit for Illumina, using standard protocol. Sequencing was carried out on Novaseq6000 platform using 150*2 paired end chemistry. All experiments were carried out on three independnt biological replicates. Raw reads were trimmed and aligned to the BDGP6 genome using Hisat2. DeSeq2 was used to identify differentially expressed genes between different groups