The Gagr gene is a domesticated gag retroelement gene in Drosophila melanogaster, whose function is associated with the stress response. The protein products of the Gagr gene and its homologues in different Drosophila species have a highly conserved structure; however, they demonstrate variability in the promoter region of the gene, which is apparently associated with the gradual acquisition of a new function and involvement in new signaling pathways. In this work, we studied the effect of oxidative stress induced by ammonium persulfate on the survival of various species of the genus Drosophila (D. melanogaster, D. mauritiana, D. simulans, D. yakuba, D. teissieri, and D. pseudoobscura), analyzed the correlation between the structure of promoter regions and stress-induced changes in the expression of the Gagr gene and its homologues in different Drosophila species, and compared the stress-induced changes in the expression of oxidative stress markers: the Jak-STAT signaling pathway activator gene upd3, Jak-STAT pathway effector vir-1, and IMD signaling pathway target Rel. It was found that in D. simulans and D. mauritiana sensitivity to ammonium persulfate is significantly increased, which correlates with a reduced level of transcription of vir-1 gene orthologues. The latter is due to a decrease in the number of binding sites for the transcription factor STAT92E, a component of the Jak-STAT signaling pathway, in the vir-1 promoter region. Consistent changes in the expression of the Gagr, upd3, and vir-1 genes are observed in all species of the melanogaster subgroup, except for D. pseudoobscura, which indicates an increase in the role of Gagr in the regulation of stress response pathways during the phylogenesis of the genus Drosophila.