Unveiling Hidden Risks: Cry1Fa-Induced Oxidative Stress and Gut Microbiota Dysbiosis in <i>Propylea japonica</i>

With the elevated prevalence of recombinant <i>Bacillus thuringiensis</i> crop growth, examining the possible influence of Bt on off-target organisms is crucial. The natural insect predator <i>Propylea japonica</i> is exposed to transgenic crops through preying on aphids and other insect pests, triggering an assessment of the impact of Bt proteins on this helpful insect. We found that oral administration of the Bt protein Cry1Fa exhibited no impact on biological indicators such as developmental age, eclosion rate, and insect weight of <i>P. japonica</i> larvae. There were no differences in the expression levels of relevant detoxification genes and enzymes when lower concentrations (0.25, 0.1 mg/mL) of Cry1Fa were applied to second- and third-instar larvae. However, exposure to a high dose of Cry1Fa toxin (1.0 mg/mL) led to a 20.12% increase in catalase activity after 48 h, while peroxidase activity increased significantly by 80.88% after 24 h and by 57.00% after 48 h. Additionally, exposure to Cry1Fa stress resulted in upregulation of detoxification metabolism genes <i>CYP345B1</i> and <i>microsomal GST</i>. Notably, exposure to Cry1Fa disrupted the microbiota stability of <i>P. japonica</i>. Cry1Fa treatment resulted in a significant increase in the abundance of <i>Rhodococcus</i> and <i>Enterococcus</i>. The result highlights the importance of paying closer attention to microlevel effects when considering the safety of multi-non-target organisms in GM crops.