Lucchesi V, Grimaldi L, Mastrantonio V, Porretta D, Di Bella L, Ruspandini T, Di Salvo ML, Vontas J, Bellini R, Negri A, Epis S, Caccia S, Bandi C, Urbanelli S.
Insect pests are a major problem worldwide and their control represents an urgency for human well-being. Insecticides acting as chitin-synthesis inhibitors (CSIs) are one of the major tools used to control these insects, but resistance is evolving in many species against several chemical classes, such as oxazolines and benzoylureas. Genetic studies showed that resistance is associated with point mutations in position 1043 of the chitin-synthase 1 gene (chs1), which change an isoleucine into phenylalanine, leucine or methionine (i.e., I1043F; I1043L; I1043M, respectively). Here, we studied the molecular and phenotypic characteristics of the homozygous I1043M strain in the mosquito Culex pipiens by comparing susceptible and resistant individuals. Our results showed that resistant mosquitoes have a striking level of resistance when exposed to the CSI diflubenzuron. Furthermore, cuticle modifications and the over-expression of the chs1 gene were detected in resistant Cx. pipiens, which are associated and, thus, likely contribute to resistance, as well as to the intensity of the resistant phenotype. Since mutations on the chs1 gene are conserved among different arthropod pest species, our results could be valuable to understand CSI resistance not only in mosquitoes, but also in a wider perspective.