Environmental stressor-induced functional and expression dynamics of glutathione S-transferase genes in bees

As key pollinators, bees are increasingly threatened by environmental stressors such as heavy metals, pesticides, and temperature fluctuations, which can cause oxidative stress and disrupt cellular homeostasis. Glutathione S-transferases (GSTs) play crucial roles in antioxidant defense and detoxification, yet systematic studies on bee GST families remain limited. Here, we conducted a genome-wide analysis of cytosolic GST genes in 13 bee species, identifying 146 genes in total. Delta and Sigma were the dominant subclasses, with Apis mellifera containing only one Delta gene, while Megachile rotundata and Osmia bicornis lacked Theta genes. Synteny analysis revealed high conservation of GST genes across species. Focusing on A. mellifera, all nine cytosolic GST proteins exhibited enzymatic activity toward CDNB. Except AmGSTZ1, most GSTs showed significant antioxidant responses to hydrogen peroxide, cadmium ions, and temperature stress. Notably, AmGSTS3 showed a time-dependent increase under imidacloprid exposure, while AmGSTU1, AmGSTS1, AmGSTO1, AmGSTO2, and AmGSTT1 peaked after 12 h of fipronil treatment. These results highlight the functional diversity of GST genes in stress responses. This study provides new molecular insights into the adaptive roles of GSTs in bees and offers a valuable basis for conservation and risk assessment.