Picoxystrobin causes mitochondrial dysfunction in earthworms by interfering with complex enzyme activity and binding to the electron carrier cytochrome c protein.

Picoxystrobin (PICO) poses a great threat to earthworms due to its widespread use in agriculture and its stability in soil. Mitochondria may be a sensitive target organ for the toxic effects of PICO on worms. Therefore, evaluating the effect of PICO on mitochondria can further understand the toxic mechanism of PICO to earthworms. Here, we investigated the mechanism of mitochondrial toxicity of PICO to earthworms at environmentally relevant concentrations (62.5, 125 and 250 μg/kg). Transmission electron microscopy observed that PICO disrupted mitochondrial ultrastructure. PICO reduced mitochondrial membrane potential and inhibited the expression of mitochondrial dynamics proteins of 51 kDa (MiD51). PICO interfered with the electron transport chain (ETC) complex activity and the relative transcription of its subunits. In particular, PICO inhibited complex III activity, cytochrome c (Cyt c, an electron carrier protein that transfers electrons from complex III to complex IV) activity, and ATP level. These changes were observed at PICO concentrations as low as 62.5 μg/kg. Molecular docking analysis indicated that PICO can directly bind to Cyt c with a minimum free energy of -7.84 kcal/mol, thus hindering electron transfer in the ETC. This study confirmed that PICO induces mitochondrial dysfunction in earthworms and contributes to effective pesticide management.