More attention is being paid to the enantioselective toxicity of chiral pesticides. However, limited investigations have been done to assess the ecological risks of chiral pesticides to soil community. Fenvalerate (FV), an extensively used synthetic pyrethroid, is a typical chiral pesticide. The most insecticidally active enantiomer of FV, esfenvalerate (ESFV), also has been marketed and widely used. In this study, the toxicological sensitivity and bioaccumulation of FV and ESFV in earthworms were assessed. The results showed that FV was less toxic than ESFV, but more accumulated in earthworms. ESFV was at least 4 times more toxic to earthworms than FV according to the filter paper contact toxicity test and the artificial soil test. Enantiospecific induction in oxidative stress was observed in earthworms exposed to FV and ESFV. The bioaccumulation of FV and ESFV in earthworm tissues was also enantioselective, preferentially accumulating FV. The uptake of ESFV by earthworms was lower than that of FV, so that the biota to soil accumulation factor (BSAF) value of ESFV was lower than that of FV. Our findings suggest that the enantioselective toxicity and bioaccumulation of chiral pesticides should be considered for evaluating ecological risks of these compounds to non-target organisms.
The beet armyworm, Spodoptera exigua, threatens agriculture due to its rapid evolution of insecticide resistance. CYP9A9a and CYP9A9b are close paralogous P450s, and mutant CYP9A9a (V40L/Q160H/T208A) was previously linked to cyhalothrin resistance but unvalidated in vitro. Here, we studied esfenvalerate resistance mediated by mutant CYP9A9a in the field-derived strain FX21 (960-fold resistance to esfenvalerate) using in vitro and genetic approaches. Both CYP9A9a (1500-fold) and CYP9A9b (670-fold) are overexpressed in the larval midgut. Kinetic analyses showed that CYP9A9a has a similar substrate affinity but a 2.3-fold higher catalytic turnover, yielding 1.9-fold greater metabolic efficiency than CYP9A9b. CRISPR knockout of CYP9A9b alone did not alter susceptibility, whereas dual knockout reduced resistance by 294-fold, underscoring CYP9A9a’s essential role. Thus, CYP9A9a is the principal resistance determinant via qualitative mutations and quantitative overexpression, making it a key marker for monitoring pyrethroid resistance in S. exigua. We also address why CYP9A9b exhibits in vitro activity but does not confer resistance in vivo.
危险品化学品经营许可证（带存储）