Molecular mechanisms underlying plasticity in a thermally varying environment

To investigate the molecular basis of fluctuating temperature induced phenotypic plasticity, we ran genome-wide transcriptomic analysis on Drosophila melanogaster subjected to acclimation at constant (19 +/- 0 degree Celcius) and fluctuating (19 +/- 8 degree Celcius) temperatures and contrasted the induction of molecular mechanisms in adult males, adult females, and larvae. We investigated whether fluctuations act by permanently activating the involved mechanisms, or whether fluctuations repeatedly activate and repress mechanisms, during the hot (or heating) and the cold (or cooling) phase of thermal fluctuations. We show that adult flies acclimated to fluctuating temperatures tolerate high temperatures better than the constant temperature acclimated controls. Differential gene expression indicated that responses to thermal variability rely partly on life stage and sex specific mechanisms. Our results show that some of the involved mechanisms were permanently activated, while others tracked the thermal fluctuations. Further, for a number of genes, fluctuating temperature resulted in canalization of gene expression. Molecular mechanisms related to environmental sensing and chromatin reorganization seems to be important components of adaptive responses to thermal variability. Overall design: A total of 80 samples were analysed across different timepoints for males, females and larvae, which includes 4 biological replicates per timepoint and sex/lifestage combination. Half of these samples were subjected to fluctating temperature (treatment) and the other half to constant temperature (control).