Universality and diversity of gene expression patterns in response to cold acclimation in Drosophila albomicans

Cold acclimation, defined as gradual habituation to low temperatures by exposure to moderately cold temperatures for several days, is known to enhance an organism's cold tolerance and facilitate its adaptation to seasonal temperature changes in temperate regions. The present study focuses on the evolution of the cold acclimation response in Drosophila albomicans, which rapidly expanded its distribution from tropical Southeast Asia to the Japanese main islands in the mid-1980s. This research aims to elucidate the genetic mechanisms underlying cold acclimation through gene expression changes. The gene expression changes due to cold acclimation were compared among five strains with different genetic backgrounds to identify the genes involved in these processes. High-throughput mRNA sequencing was employed to identify differentially expressed genes (DEGs) in strains from China, Taiwan and Japan under cold acclimation and control conditions. The results suggest that the actin genes play a critical role in cellular functions at low temperatures. A reduction in the expression of mElo is likely to result in decreased levels of C18 fatty acids, thereby enhancing cellular cold tolerance. Furthermore, this study highlights the universality and diversity of gene expression changes in response to cold acclimation. While many DEGs shared by all five strains were genes involved in metabolic pathways, many strain-specific DEGs were genes involved in gene regulation. This suggests that genes with critical roles in fundamental cellular and physiological processes are subject to evolutionary constraints, whereas those involved in regulatory functions or responding to local environmental conditions undergo rapid evolution to exhibit significant variability. These results provide insight into the genetic mechanisms of environmental adaptation and population expansion in nature.