Abstract
Mosquitoes’ increasing resistance to insecticides is becoming a major threat for control efforts worldwide. Multiple P450 genes that are up-regulated in permethrin resistant strains of Culex quinquefasciatus have been linked to the development of resistance. In the current study, we characterized the function of six P450 genes, CYP6P14, CYP6BZ2, CYP9J33, CYP9J34, CYP9J40, and CYP9J45, that are overexpressed in the permethrin resistant Culex mosquitoes and showed their capability in metabolism of permethrin. These six P450 genes can convert 3-phenoxybenzoic alcohol (PBCHO) to a less toxic product, 3-phenoxybenzoic acid (PBCOOH), indicating that these P450s play an important role in permethrin degradation pathways. Although we know multiple P450 genes are over-expressed in permethrin resistant Culex mosquitoes, it remains to be seen whether cytochrome P450-reductase (CPR) gene that are co-overexpressed with P450 genes in permethrin resistant mosquitoes do indeed serve as a resistance mechanism. An in-depth investigation of the expression of CPR gene in resistant mosquitoes was conducted in permethrin resistant mosquitoes. The finding of CPR gene overexpression in permethrin resistant mosquitoes suggested the importance of co-overexpression of multiple P450 genes with their obligatory electron donor CPR in the complex detoxification system, boosting the metabolism of permethrin and hence the development of permethrin resistance in Cx. quinquefasciatus.
Highlights
The mosquito Culex quinquefasciatus Say is a primary vector of lymphatic filariasis, St
Each of the P450s was co-expressed with cytochrome P450-reductase (CPR) by simultaneous infection of Sf9 cells through two recombinant viruses, P450recombinant baculovirus (P450rbv) with multiplicity of infection (MOI) 0.5 and CPRrecombinant baculovirus (CPRrbv) with MOI 0.05, in the suspension culture (Gong et al, 2017)
This study examined the co-expression of six P450 genes that are over-expressed in the permethrin resistant strain HAmCqG8 or MAmCqG6 strain with their co-factor cytochrome P450 reductase CPR in insect cells using a baculovirus expression system
Summary
The mosquito Culex quinquefasciatus Say is a primary vector of lymphatic filariasis, St. The development of insecticide resistance in Culex mosquitoes is rapidly becoming a major problem for mosquito control efforts worldwide (Liu, 2008, 2015; Fofana et al, 2012). There is a growing body of evidence to suggest that P450 genes are involved in the development of resistance to pyrethroid insecticides in mosquitoes (Müller et al, 2008; Komagata et al, 2010; Stevenson et al, 2012; Riveron et al, 2013; Smith et al, 2019; Vontas et al, 2020). A study utilizing TALENs and the CRISPR technique has further demonstrated the role of CYP9M10 in conferring permethrin resistance in Culex mosquitoes (Itokawa et al, 2016). As yet there have been no reports regarding the permethrin metabolism function of other P450 genes that are known to be over-expressed in permethrin resistant Culex mosquitoes
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