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

摘要

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 alpha-glucosidase, a binary toxin receptor, in larval midgut microvilli. In this study, long double-stranded RNA (dsRNA) targeting the alpha-glucosidase gene was used to suppress the expression of alpha-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 alpha-glucosidase gene, were delivered to mosquito larva by feeding with dsRNA-chitosan particles. Reverse transcriptase-polymerase chain reaction results demonstrated that the expression of alpha-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 alpha-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 alpha-glucosidase is essential for the toxicity of B. sphaericus binary toxin to Cx. quinquefasciatus.