Impacts of sub-lethal DDT exposures on microRNA and putative target transcript expression in DDT resistant and susceptible Drosophila melanogaster strains

Authors: SEONG, KEON MOOK - Michigan State University; Coates, Brad; PITTENDRIGH, BARRY - Michigan State University

Submitted to: Frontiers in Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2019
Publication Date: 2/5/2019
Citation: Seong, K., Coates, B.S., Pittendrigh, B.R. 2019. Impacts of sub-lethal DDT exposures on microRNA and putative target transcript expression in DDT resistant and susceptible Drosophila melanogaster strains. Frontiers in Genetics. https://doi.org/10.3389/fgene.2019.00045.
DOI: https://doi.org/10.3389/fgene.2019.00045

Interpretive Summary: The evolution of resistance to chemical insecticides among pest arthropods populations can result in the reduced efficacy of control measures and subsequent increases in damage to agricultural commodities. These factors in turn lead to lower producer output and profitability. An ARS researcher along with university collaborators used a strain of fruit fly, a model insect species, to investigate the genomic basis of high resistance to DDT insecticides. The study measured the expression of a class of small RNA molecules, called microRNAs, that regulate gene activity. Comparison between resistant and susceptible fruit flies exposed to DTT and controls found that expression of subset of microRNAs increased (were induced) in response to DDT exposure in susceptible flies, but remained at constantly low levels in resistant flies. Furthermore, these differentially expressed microRNAs were associated with the differences in expression of genes that control the degradation of chemical insecticides. This research demonstrates that microRNAs may be potent modifiers of genes involved in the evolution of insecticide resistance mechanisms via increasing the capacity of resistant flies to detoxify insecticidal compounds. These data are important to university, government and industry scientists interested in the efficacy of insect population control in the field, and will likely benefit producers by understanding how insects react to selection pressures and in ongoing efforts to develop tactics to preserve the efficacy of insect control technologies.

Technical Abstract: Eight constitutively differentially expressed miRNAs were previously described between dichlorodiphenyltrichloroethane (DDT)-resistant 91-R and -susceptible control Drosophila melanogaster 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 91-R and the susceptible Canton-S strain. Specifically, RT-qPCR analysis showed that DDT exposures led to the significant up-regulation (induction) of miR-310-3p, miR-311-3p, miR-312-3p, miR-313-3p, and miR-92a-3p levels in Canton-S. This, which contrasted with the lack of significant changes in 91-R at most time points following DDT exposure. The levels of expression among miRNAs were negatively correlated with that of their corresponding putative target cytochrome P450s at the same time points after DDT exposure. Collectively, results from this study may suggest that miR-310-3p, miR-311-3p, miR-312-3p, miR-313-3p, and miR-92a-3p might have are potential role in the control of DDT detoxification through the post-transcriptional regulation of target cytochrome P450s in Canton-S. Conversely, the lack of induction of these same miRNAs in 91-R 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 91-R.