Impacts of Sub-lethal DDT Exposures on microRNA and Putative Target Transcript Expression in DDT Resistant and Susceptible Strains.

Ten constitutively differentially expressed miRNAs were previously described between DDT-resistant and -susceptible control strains, and among their predicted target genes were those associated with metabolic DDT resistance mechanisms. The present study evaluated the inducibility of miRNA expression and putative downstream regulation of cytochrome P450s in response to DDT exposure in a time-dependent manner in and the susceptible strain. Specifically, RT-qPCR analysis showed that DDT exposures led to the significant down-regulation (repression) of , , , , and levels in . This is contrasted with the lack of significant changes in at most time-points following DDT exposure. The levels of expression among miRNAs exhibited opposite expression patterns compared to their corresponding putative target cytochrome P450s at the same time points after DDT exposure. Collectively, results from this study suggest that , , , , and might have a potential role in the control of DDT detoxification through the post-transcriptional regulation of target cytochrome P450s in . Conversely, the lack of significant changes of these same miRNAs in following DDT-exposure suggests a possible adaptive mutation that removes repressive control mechanisms. These data are important for the understanding impact of adaptive changes in miRNA expression on post-transcriptional regulatory mechanism involved in the evolution of DDT resistance in .