Molecular Ecology of Pyrethroid Knockdown Resistance in Culex pipiens pallens Mosquitoes

Abstract

Pyrethroid insecticides have been extensively used in China and worldwide for public health pest control. Accurate resistance monitoring is essential to guide the rational use of insecticides and resistance management. Here we examined the nucleotide diversity of the para-sodium channel gene, which confers knockdown resistance (kdr) in Culex pipiens pallens mosquitoes in China. The sequence analysis of the para-sodium channel gene identified L1014F and L1014S mutations. We developed and validated allele-specific PCR and the real-time TaqMan methods for resistance diagnosis. The real-time TaqMan method is more superior to the allele-specific PCR method as evidenced by higher amplification rate and better sensitivity and specificity. Significant positive correlation between kdr allele frequency and bioassay-based resistance phenotype demonstrates that the frequency of L1014F and L1014S mutations in the kdr gene can be used as a molecular marker for deltamethrin resistance monitoring in natural Cx. pipiens pallens populations in the East China region. The laboratory selection experiment found that L1014F mutation frequency, but not L1014S mutation, responded to deltamethrin selection, suggesting that the L1014F mutation is the key mutation conferring resistance to deltamethrin. High L1014F mutation frequency detected in six populations of Cx. pipens pallens suggests high prevalence of pyrethroid resistance in Eastern China, calling for further surveys to map the resistance in China and for investigating alternative mosquito control strategies.

Differential resistance of insect sodium channels with kdr mutations to deltamethrin, permethrin and DDT

“…This increase in the rate of fast inactivation may contribute to closed state inactivation and subsequently reduced toxicity of pyrethroid compounds (Vais et al, 2001), thus the channel offers levels of resistance through reducing preferential pyrethroid target state availability. Additionally, the L1014S resistant mutation may offer advantages in the field by reducing potential fitness costs on insects that would be associated with the L1014F/H mutations being 'less excitable channels' (Chen et al, 2010).…”

“…With the scaling-up of malaria control efforts using indoor residual spraying with DDT and pyrethroids, and the use of pyrethroid treated bed nets, the continued selection of resistance may compromise control programmes (Czeher et al, 2008;Protopopoff et al, 2008). L1014S has also been identified in C. pipiens (Martinez-Torres et al, 1999), a vector of West Nile Virus, most recently in the USA (Zhou et al, 2009) and China (Chen et al, 2010). The L1014H substitution confirmed in field resistant strains of the agricultural pest H. virescens (Park and Taylor, 1997) and in common houseflies (Liu and Pridgeon, 2002;Rinkevich et al, 2006) constitutes a third 'natural' resistant allele at the L1014 locus.…”

Venom allergen 5is Associated With Deltamethrin Resistance inCulex pipiens pallens(Diptera: Culicidae)

“…The DR strains (DR1, DR2, and DR3) were selected from early fourth-instar larvae of the DS strain exposed to deltamethrin for >30 generations. Before selection, the 50% larval lethal concentration (LC 50 ) to deltamethrin was determined by larval bioassay (Chen et al 2010) and used as the screening concentration. All laboratory populations were maintained at 28 C, 70-80% humidity, and a photoperiod of 16:8 (L:D) h. The two field populations of Cx.…”

Cloning and overexpression of transferrin gene from cypermethrin-resistant Culex pipiens pallens

“…Here, we report the characterization of one cypermethrin resistance associated gene of C. pipiens pallens. The writer reported insecticide-resistant ribosomal protein L39 gene of C. pipiens pallens , while other researchers in the same laboratory identified several genes differentially expressed in cypermethrin-resistant strain of the mosquito previously (Chen et al 2010;Gong et al 2005a,b;He et al 2009;Hu et al 2007;Shen et al 2002;Tian et al 2001;Xu et al 2008;Yang et al 2008;Zhang et al 2011;Zhu et al 1998Zhu et al , 2000Sun et al 2006). Some of the candidate genes encode for enzymes such as chymotrypsin (Gong et al 2005a), trypsin (Shen et al 2002), and CYP450 (Gong et al 2005b), which are likely involved in more direct functions, e.g., oxidation of cypermethrin, others are likely more upstream factors, such as ribosomal protein L22 (He et al 2009), ribosomal protein S4 , and ribosomal protein S29 .…”