Insights into the effects of dinotefuran on the silk gland of Bombyx mori at the biochemical and transcriptomic levels

Dinotefuran, a third-generation neonicotinoid insecticide, is widely applied in agriculture to control pests. However, the environmental consequences and risks to non-target species are largely unknown. Bombyx mori, an economically important insects, is highly sensitive to toxic compounds such as insecticides and is a good biological and toxicant detector for environmental assessment. In this study, we investigated the toxic effects of dinotefuran on the silk gland of silkworm. The effect of dinotefuran on the middle silk gland was apparently greater than that on the posterior silk gland, causing increased vacuoles in the inner membrane of the middle silk gland. Ultrastructure analysis showed dinotefuran exposure caused increased autophagic vesicles in silk glands. Reactive oxygen species, the activities of UDP glucuronosyl-transferase and carboxylesterase were induced in the middle silk gland. In contrast, malondialdehyde and reactive oxygen species were increased in the posterior silk gland. Global transcriptional patterns revealed the physiological responses induced by dinotefuran such as silk-associated protein, detoxification, autophagy, fatty acid metabolism, carbon metabolism, and other fundamental physiological processes. In addition, dinotefuran exposure significantly affected several genes involved in the mTOR signaling pathway and PI3K-Akt signaling pathway in the middle silk gland, whereas fatty acid metabolism and pyrimidine metabolism were affected in the posterior silk gland. Western blot results showed that the upregulation of BmATG8 and decrease of BmP62 were consistent with the transcriptomic and ultrastructural changes, indicating that dinotefuran exposure induced increased autophagy in the silk gland. Taken together, these findings highlight the toxicity effects of dinotefuran on the silk gland and provide novel insights into the toxicity of third-generation neonicotinoid insecticides.