Transcriptome responses to defined insecticide selection pressures in the German cockroach

Purpose: Next-generation transcriptome sequencing was done to understand host and eukaryotic microbiome changes in gene expression in association with defined insecticide selection pressures. The specific goal of this research was to understand whole-body physiological responses in German cockroaches and associated microbiota, at the metatranscriptome level, to defined insecticide selection pressures. Methods: We used the insecticide indoxacarb as the selecting insecticide, which is an important bait active ingredient for cockroach control. Six generations of selection with indoxacarb bait produced a strain with substantial (>20x) resistance relative to inbred control lines originating from the same parental stock. Results: Metatranscriptome sequencing revealed 1123 significantly differentially expressed genes in > two of three statistical models (81 upregulated and 1042 downregulated; FDR p<0.001; log2FC of +/- 1). The majority of upreglated genes were from the host cockroach while the majority of downregulated genes were from associated viruses and the eukaryotic microbiome. Conclusions: We show here significant impacts by insecticide selection on not only host stress-respnses like detoxification, but also on clearace of microbial parasites, pathogens, commensals and/or symbionts. Whole-body mRNA expression profiles in cockroaches subjected to six generations of insecticide selection in comparison to identical genetic lines that inbred without selection (three replicates each; 6 replicate samples total).