Cuticle Modifications and Over-Expression of the Chitin-Synthase Gene in Diflubenzuron-Resistant Phenotype

Abstract

Insecticide resistance is a major threat challenging the control of harmful insect species. The study of resistant phenotypes is, therefore, pivotal to understand molecular mechanisms underpinning insecticide resistance and plan effective control and resistance management strategies. Here, we further analysed the diflubenzuron (DFB)-resistant phenotype due to the point-mutation I1043M in the chitin-synthase 1 gene (chs1) in the mosquito Culex pipiens. By comparing susceptible and resistant strains of Cx. pipiens through DFB bioassays, molecular analyses and scanning electron microscopy, we showed that the I1043M-resistant mosquitoes have: (i) a striking level of DFB resistance (i.e., resistance ratio: 9006); (ii) a constitutive 11-fold over-expression of the chs1 gene; iii) enhanced cuticle thickness and cuticular chitin content. Culex pipiens is one of the most important vector species in Europe and the rapid spread of DFB resistance can threaten its control. Our results, by adding new data about the DFB-resistant phenotype, provide important information for the control and management of insecticide resistance.

Integrated de novo transcriptome of Culex pipiens mosquito larvae as a resource for genetic control strategies

“…12,05524495) to establish the DFB susceptible and resistant colonies, respectively. In each site, at least five breeding sites were sampled to have a representative sample of the population 30 . The susceptible colony was homozygous for the wild-type allele I1043, while the resistant colony was homozygous for the resistant allele I1043M 30 .…”

“…In each site, at least five breeding sites were sampled to have a representative sample of the population 30 . The susceptible colony was homozygous for the wild-type allele I1043, while the resistant colony was homozygous for the resistant allele I1043M 30 . Mosquitoes from 5 th generation of both colonies were used for the current study.…”

“…A deep analysis of the homozygous I1043M-resistant strain of Cx. pipiens established from field populations also revealed that resistant mosquitoes had an increased cuticle thickness and constitutively up-regulate the chs1 gene 30 .…”