# Experimental evolution-induced transcriptome and phenotype responses of Drosophila melanogaster to novel thermal environments

## TL;DR

This study shows how fruit flies adapt to different temperature environments through changes in gene activity and physical traits over many generations.

## Contribution

The study reveals parallel and thermal regime-specific transcriptomic and phenotypic adaptations in Drosophila melanogaster under experimental evolution.

## Key findings

- Evolved Drosophila populations showed increased heat tolerance, faster development, and longer lifespan.
- Shared and distinct gene pathways related to chromatin, mitochondria, and protein homeostasis were identified in thermal adaptation.
- RNA sequencing revealed 1288 and 1152 differentially expressed genes in high-temperature and fluctuating-temperature populations.

## Abstract

Thermal stress imposes significant challenges on organisms, influencing cellular functions, morphology and survival. This study investigates the transcriptomic and phenotypic adaptations of Drosophila melanogaster populations subjected to constant high-temperature (HT) and fluctuating-temperature (FT) regimes over 80 generations in experimental evolution settings. RNA sequencing identified 1288 and 1152 differentially expressed genes in HT and FT populations, respectively, relative to the baseline population. Multiple gene ontology (GO) terms, including chromatin organization, nucleosome assembly, nucleic acid binding and polytene chromosome band formation, were enriched under both regimes, suggesting shared adaptive pathways. A weighted gene co-expression network analysis (WGCNA) revealed mitochondrial function and protein homeostasis as central to thermal adaptation, with HT populations showing enrichment of DNA repair and FT populations exhibiting enrichment of RNA processing and translation regulation-related terms. Phenotypic assays demonstrated increased heat tolerance, accelerated development and prolonged longevity in evolved populations, highlighting parallel as well as thermal regime-specific adaptive responses. This study emphasizes the complexity of transcriptomic–phenotypic adaptations to thermal stress in new environments.

Summary: Experimental evolution in Drosophila melanogaster under constant and fluctuating thermal regimes reveals parallel and regime-specific transcriptomic and phenotypic adaptations, highlighting polygenic and regulatory changes that shape responses to environmental stress.