Alkaline phosphatases are involved in the response of A edes aegypti larvae to intoxication with B acillus thuringiensis subsp. israelensis C ry toxins

Summary B acillus thuringiensis subsp. israelensis ( B ti) is a natural pathogen of dipterans widely used as a biological insecticide for mosquito control. To characterize the response of mosquitoes to intoxication with B ti, the transcriptome profile of B ti‐exposed susceptible A edes aegypti larvae was analysed using I llumina RNA ‐seq. Gene expression of 11 alkaline phosphatases ( ALPs ) was further investigated by real time quantitative polymerase chain reaction and ALP activity was measured in the susceptible strain and in four strains resistant to a single B ti C ry toxin or to B ti. These strains were unexposed or exposed to their toxin of selection. Although all resistant strains constitutively exhibited a higher level of transcription of ALP genes than the susceptible strain, they showed a lower total ALP activity. The intoxication with different individual C ry toxins triggered a global pattern of ALP gene under‐transcription in all the one‐toxin‐resistant strains but involving different specific sets of ALPs in each resistant phenotype. Most of the ALPs involved are not known C ry‐binding proteins. RNA interference experiment demonstrated that reducing ALP expression conferred increased the survival of larvae exposed to Cry4Aa , confirming the involvement of ALP in Cry4Aa toxicity.