Main content area

Suppression of α-glucosidase gene by RNA interference can increase resistance of Culex quinquefasciatus to Bacillus sphaericus binary toxin

Woradulayapinij, Warunya, Audtho, Mongkon, Wiwat, Chanpen
Biocontrol science and technology 2015 v.25 no.12 pp. 1453-1466
Bacillus sphaericus, Culex quinquefasciatus, RNA interference, Western blotting, alpha-glucosidase, bacterial toxins, biological control, double-stranded RNA, genes, insect larvae, insecticide resistance, messenger RNA, microvilli, midgut, mortality, particles, protein synthesis, reverse transcriptase polymerase chain reaction, toxicity
Bacillus sphaericus binary toxin displays a specific toxicity towards Culex spp. larvae. Resistance of Culex quinquefasciatus to B. sphaericus is associated with the reduction or absence of 66-kDa α-glucosidase, a binary toxin receptor, in larval midgut microvilli. In this study, long double-stranded RNA (dsRNA) targeting the α-glucosidase gene was used to suppress the expression of α-glucosidase in Cx. quinquefasciatus larvae and the consequences of the suppression was investigated. Three sets of dsRNAs, dsGRi1, dsGRi2, and dsGRi3, which are homologous to distinct regions of α-glucosidase gene, were delivered to mosquito larva by feeding with dsRNA–chitosan particles. Reverse transcriptase-polymerase chain reaction results demonstrated that the expression of α-glucosidase mRNA was reduced by 43% in larvae fed with dsGRi3–chitosan, compared to those fed with dsgfp–chitosan particles. Western blot analysis revealed a 7–17% reduction of α-glucosidase protein expression in larvae fed with dsGRi–chitosan. Mortality rates of larvae that received dsRNAs–chitosan particles were only 45–62% compared to those that received dsgfp–chitosan particles. These results indicate that α-glucosidase is essential for the toxicity of B. sphaericus binary toxin to Cx. quinquefasciatus .