Mutations of voltage-gated sodium channel contribute to pyrethroid resistance in Panonychus citri

Overexpression of an Integument Esterase Gene LbEST-inte4 Infers the Malathion Detoxification in Liposcelis bostrychophila (Psocoptera: Liposcelididae)

Liposcelis bostrychophila, commonly known as booklouse, is an important stored-product pest worldwide. Studies have demonstrated that booklices have developed resistance to several insecticides. In this study, an integument esterase gene, LbEST-inte4, with upregulated expression, was characterized in L. bostrychophila. Knockdown of LbEST-inte4 resulted in a substantial increase in the booklice susceptibility to malathion. Overexpression of LbEST-inte4 in Drosophila melanogaster significantly enhanced its malathion tolerance. Molecular modeling and docking analysis suggested potential interactions between LbEST-inte4 and malathion. When overexpressed LbEST-inte4 in Sf9 cells, a notable elevation in esterase activity and malathion tolerance was observed. HPLC analysis indicated that the LbEST-inte4 enzyme could effectively degrade malathion. Taken together, the upregulated LbEST-inte4 appears to contribute to malathion tolerance in L. bostrychophila by facilitating the depletion of malathion. This study elucidates the molecular mechanism underlying malathion detoxification and provides the foundations for the development of effective prevention and control measures against psocids.

Sublethal and transgenerational effects of lufenuron on the biological traits of Panonychus citri (McGregor) (Acari: Tetranychidae)

The citrus red mite, Panonychus citri (McGregor), is a globally important pest that has developed severe resistance to various pesticides. Lufenuron has been widely used in the control of the related pests in citrus orchard ecosystem. In this study, the susceptibilities of egg, larva, deutonymph and female adult of P. citri to lufenuron was determined, and the LC50 values were 161.354 mg/L, 49.595 mg/L, 81.580 mg/L, and 147.006 mg/L, respectively. Life-table analysis indicated that the fecundities were significantly increased by 11.86% and 26.84% after the mites were treated with LC20 concentrations of lufenuron at the egg or deutonymph stages, respectively. After eggs were treated with lufenuron, the immature stage and longevity were also affected, and resulted in a significant increase in r, R0 and λ. After exposure of female adults to LC20 of lufenuron, the fecundity and longevity of F0 generation significantly decreased by 31.99% and 10.94%, respectively. Furthermore, the expression level of EcR and Vg was significantly inhibited upon mites was treated with lufenuron. However, lufenuron exposure has a positive effect on fecundity and R0 in F1 generation, the expression of all reproduction-related genes was significantly up-regulated. In conclusion, there was a stimulating effect on the offspring population. Our results will contribute to the assessment of the resurgence of P. citri in the field after the application of lufenuron and the development of integrated pest control strategies in citrus orchards.

CYP4CL2 Confers Metabolic Resistance to Pyridaben in the Citrus Pest Mite Panonychus citri

The citrus red mite Panonychus citri has developed strong resistance to acaricides. Cytochrome P450 monooxygenases (P450s) can detoxify pesticides and are involved in pesticide resistance in many insects. Here, a pyridaben-resistant P. citri strain showed cross-resistance to cyenopyrafen, bifenazate, fenpyroximate, and tolfenpyrad. Piperonyl butoxide, a P450 inhibitor, significantly increased the toxicity of pyridaben to resistant (Pyr_Rs) and susceptible (Pyr_Control) P. citri strains. P450 activity was significantly higher in Pyr_Rs than in Pyr_Control. Analyses of RNA-Seq data identified a P450 gene (CYP4CL2) that is potentially involved in pyridaben resistance. Consistently, it was up-regulated in two field-derived resistant populations (CQ_WZ and CQ_TN). RNA interference-mediated knockdown of CYP4CL2 significantly decreased the pyridaben resistance in P. citri. Transgenic Drosophila melanogaster expressing CYP4CL2 showed increased pyridaben resistance. Molecular docking analysis showed that pyridaben could bind to several amino acids at substrate recognition sites in CYP4CL2. These findings shed light on P450-mediated pyridaben resistance in pest mites.