Molecular analysis of Culex quinquefasciatus larvae responses to Lysinibacillus sphaericus Bin toxin.

Lysinibacillus sphaericus produces the mosquito larvicidal binary toxin consisting of BinA and BinB, which are both required for toxicity against Culex and Anopheles larvae. The molecular mechanisms behind Bin toxin-induced damage remain unexplored. We used whole-genome microarray-based transcriptome analysis to better understand how Culex larvae respond to Bin toxin treatment at the molecular level. Our analyses of Culex quinquefasciatus larvae transcriptome changes at 6, 12, and 18 h after Bin toxin treatment revealed a wide range of transcript signatures, including genes linked to the cytoskeleton, metabolism, immunity, and cellular stress, with a greater number of down-regulated genes than up-regulated genes. Bin toxin appears to mainly repress the expression of genes involved in metabolism, the mitochondrial electron transport chain, and the protein transporter of the outer/inner mitochondrial membrane. The induced genes encode proteins linked to mitochondrial-mediated apoptosis and cellular detoxification including autophagic processes and lysosomal compartments. This study is, to our knowledge, the first microarray analysis of Bin toxin-induced transcriptional responses in Culex larvae, providing a basis for an in-depth understanding of the molecular nature of Bin toxin-induced damage.