Function of four mitochondrial genes in fumigation lethal mechanisms of Allyl Isothiocyanate against Sitophilus zeamais adults.

Allyl isothiocyanate (AITC) is a promising alternative to chemical fumigants, and mitochondrial dysfunction has been proposed to play a crucial role in its lethal mechanisms; however, the specific lethal mechanisms of AITC remain unknown. Four mitochondrial electron transport chain genes, nd5, nd6, cox1, and cox5, were selected from adult Sitophilus zeamais and processed with RNA interference experiments. Then, the biochemical and biophysical effects were compared between double-stranded RNA (dsRNA)-mediated insects and wild-type insects after AITC fumigation at the concentration of LC values. The bioactivity of AITC against dsnd6-mediated insects increased, while the bioactivity against dcox1-mediated insects decreased. Compared with the wild-type insects, the increase of reactive oxygen species (ROS) levels by AITC in mitochondria from dsnd6-mediated insects increased by 18.95%, while that of dscox1-mediated insects decreased by 27.45%. The effects of AITC on mRNA expression levels of detoxifying enzymes including CAT (down-regulation effect) and CuZnSOD (overexpression effect) partly recovered in the dsnd5-mediated insects, while a greater effect was observed for dscox1-mediated insects. Molecular docking results indicated that ASN511 at the cox1 subunit was the binding site of AITC by one hydrogen bond, with a bond distance of 2.1 Å. These findings provide insight for further applications of AITC and could provide a novel strategy to investigate lethal mechanisms of insecticides.