Expression Activity of the ras85D Gene in Phylogenetically Distant Drosophila Species

The conserved ras85D gene, belonging to the RAS family, plays a pivotal role in regulating signaling cascades that control cell cycle phases, proliferation activity, and cell differentiation. The functional activity of ras85D suggests conserved regulation of its expression. However, among Drosophila species with varying degrees of evolutionary relatedness, ras85D is characterized by unexpectedly high variability in its promoter region and the upstream intergenic sequence, which typically includes cis-regulatory elements. Variability in the gene’s regulatory region, despite the presence of several conserved fragments within the 5'UTR, raises questions about the similarity of relative expression activity of this gene in species with divergent regulatory sequences. In this study, a comparative analysis of ras85D gene expression was conducted in evolutionarily distant Drosophila species at various developmental stages and in different tissues. Publicly available transcriptomic data for D. melanogaster, D. pseudoobscura, and D. virilis were analyzed. Additionally, the most contrasting changes in ras85D expression activity were examined using real-time PCR and digital PCR methods in D. melanogaster and D. virilis. The results confirmed the similarity of general expression patterns of ras85D at different developmental stages and in actively proliferating tissues across the studied species. Significant differences in the absolute expression activity levels of ras85D between species were also demonstrated.