Receptors are affected by selection with each Bacillus thuringiensis israelensis Cry toxin but not with the full Bti mixture in Aedes aegypti. Response to Bti

Bacillus thuringiensis israelensis (Bti) toxins are increasingly used for mosquito control, but little is known aboutthe precise mode of action of each of these toxins, and how they interact to kill mosquito larvae. By using RNAsequencing, we investigated change in gene transcription level and polymorphismvariations associatedwith resistanceto each Bti Cry toxin and to the full Bti toxin mixture in the dengue vector Aedes aegypti. The upregulationof genes related to chitin metabolismin all selected strain suggests a generalist, non-toxin-specific responseto Bti selection in Aedes aegypti. Changes in the transcription level and/or protein sequences of several putativeCry toxin receptors (APNs, ALPs, α-amylases, glucoside hydrolases, ABC transporters) were specific to eachCry toxin. Selective sweeps associated with Cry4Aa resistancewere detected in 2 ALP and 1 APNgenes. The lack ofselection of toxin-specific receptors in the Bti-selected strain supports the hypothesis that Cyt toxin acts as a receptorfor Cry toxins in mosquitoes.