Culex quinquefasciatus Resistant to the Binary Toxin from Lysinibacillus sphaericus Displays a Consistent Downregulation of Pantetheinase Transcripts

resistance to the binary (Bin) toxin, the major larvicidal component from , is associated with mutations in the gene, encoding the Bin-toxin receptor. Downregulation of the transcript was found in the transcriptome of larvae resistant to the IAB59 strain, which produces both the Bin toxin and a second binary toxin, Cry48Aa/Cry49Aa. Here, we investigated the transcription profiles of two other mosquito colonies having Bin resistance only. These confirmed the downregulation and identified transcripts encoding the enzyme pantetheinase as the most downregulated mRNAs in both resistant colonies. Further quantification of these transcripts reinforced their strong downregulation in Bin-resistant larvae. Multiple genes were found encoding this enzyme in and a recombinant pantetheinase was then expressed in and 9 cells, with its presence assessed in the midgut brush border membrane of susceptible larvae. The pantetheinase was expressed as a ~70 kDa protein, potentially membrane-bound, which does not seem to be significantly targeted by glycosylation. This is the first pantetheinase characterization in mosquitoes, and its remarkable downregulation might reflect features impacted by co-selection with the Bin-resistant phenotype or potential roles in the Bin-toxin mode of action that deserve to be investigated.