Transcriptomic and functional genetic evidence for distinct ecophysiological responses across complex life cycle...

Area of Science:

• Developmental biology
• Evolutionary biology
• Genomics

Background:

• Organisms with complex life cycles adapt to variable environments by changing phenotypes.
• Thermal sensitivity varies between life stages in insects, with little genetic correlation, enabling independent evolution.
• The mechanisms driving this genetic decoupling of thermal physiology remain poorly understood.

Purpose of the Study:

• To investigate if fundamental physiological differences between life stages drive the genetic decoupling of thermal physiology.
• To test the hypothesis that distinct gene expression patterns underlie stage-specific thermal adaptation.

Main Methods:

• RNA sequencing (RNAseq) was used to compare transcript expression in Drosophila melanogaster larvae and adults under cold stress (-5°C).
• RNA interference (RNAi) was employed to assess the impact of specific gene knockdowns on larval and adult cold tolerance.
• Tissue-specificity analysis of differentially expressed genes was performed using FlyAtlas 2 data.

Main Results:

• Transcriptomic responses to cold stress were largely unique in both gene identity and temporal dynamics between larvae and adults.
• Stage-specific gene expression differences were not solely attributable to variations in tissue composition.
• Gene knockdowns exhibited predominantly stage-specific and sometimes sex-specific effects on cold tolerance.

Conclusions:

• Thermal physiology is largely stage-specific at the gene expression level in Drosophila melanogaster.
• Natural selection may act on different genetic loci for the independent thermal adaptation of different life stages.
• This stage-specific gene expression provides a mechanism for the independent evolution of thermal tolerance across developmental stages.