Glutathione S-Transferase (GST) Activities and Gene Expression Patterns of Different GST Classes in Musca domestica L. Depending on Sex and Stage of Development.

Insecticide resistance in insects poses a serious problem in population control of arthropod vectors and spreaders of human and animal diseases. Metabolic resistance to insecticides is facilitated by detoxification system enzymes, including glutathione-S-transferases (GSTs) involved in phase II of xenobiotic biotransformation. The aim of this study was to analyze the glutathione-S-transferase activity and the expression level of different class GST genes in Musca domestica. The test subjects were larvae and 3-5-day-old adults of a laboratory susceptible strain (LabTY) and a field deltamethrin-tolerant population (Nik). Based on the LC50 values, the Nik strain showed sensitivity to chlorpyrifos and chlorfenapyr and tolerance to deltamethrin with a remarkable increase in the level of resistance in males compared to females. Expression analysis of eight GST genes revealed that the expression of the GST-E12 gene (Epsilon class) was significantly elevated and the GST-S1 gene (Sigma class) was significantly decreased in the Nik strain across all groups (larvae, females, and males), with the most pronounced difference in females. A pronounced sexual dimorphism was observed: the expression of most GST genes was significantly higher in males than in females in both strains. For the first time, a consistent male-specific overexpression of multiple GST genes has been demonstrated in M. domestica.