Differentially expressed microRNAs associated with changes in transcript levels in detoxification pathways and DDT-resistance in the Drosophila melanogaster strain 91-R

Authors: SEONG, KEON MOOK - Michigan State University; Coates, Brad; KIM, DO-HYUP - University Of California; HANSEN, ALLISON - University Of California; PITTENDRIGH, BARRY - Michigan State University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2018
Publication Date: 4/26/2018
Citation: Seong, K., Coates, B.S., Kim, D., Hansen, A.K., Pittendrigh, B.R. 2018. Differentially expressed microRNAs associated with changes in transcript levels in detoxification pathways and DDT-resistance in the Drosophila melanogaster strain 91-R. PLoS One. 13(4):e0196518. https://doi.org/10.1371/journal.pone.0196518.
DOI: https://doi.org/10.1371/journal.pone.0196518

Interpretive Summary: The evolution of resistance to chemical insecticides among pest insect populations can result in reduced levels of efficacy and increased commodity damage suffered by crop and livestock producers, that in turn leads to lower output and profitability. In the current study, an ARS researcher along with university collaborators used a strain of a model insect species (fruit fly) to investigate the genomic basis of high resistance to DDT insecticides. The study used estimated the difference in expression of microRNAs, a class of molecules that affect the posttranscriptional stability and downstream expression of genes within a cell. In doing so, the estimated levels of 10 microRNAs were significantly different between insecticide resistant and susceptible fruit flies. A subset of these microRNAs were computationally predicted to affect key detoxification genes at the posttranscriptional level, predictions which were confirmed by experimental analyses. This research demonstrates that microRNAs may be potent modifiers of gene expression in insects, and changes in microRNA levels can impact genes involved in insecticide resistance mechanisms. These data are important to university, government and industry scientists interested in current difficulties found in controlling insect populations 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: Dichloro-diphenyl-trichloroethane (DDT) resistance among arthropod species is a model for understanding the molecular adaptations in response to insecticide exposures. Previous studies reported that DDT resistance may involve one or multiple detoxification genes, such as cytochrome P450 monooxygenases (P450s), glutathione S-transferases (GSTs), esterases, and ATP binding cassette (ABC) transporters, or changes in the voltage sensitive sodium channel. However, the possible involvement of microRNAs (miRNAs) in the post-transcriptional regulation of genes associated with DDT resistance in the Drosophila melanogaster strain 91-R remains poorly understood. In this study, the majority of the resulting miRNAs discovered in small RNA libraries from 91-R and the susceptible control strain, 91-C, ranged from 16-25 nt, and contained163 precursors and 256 mature forms of previously-known miRNAs along with17 putative novel miRNAs. Quantitative analyses predicted the differentially expression of 10 miRNAs between 91-R and 91-C, and, based on Gene Ontology and pathway analysis, these 10 miRNAs putatively target transcripts encoding proteins involved in detoxification mechanisms. RT-qPCR validated an inverse correlation between levels of differentially-expressed miRNAs and their putatively targeted transcripts implying a role of these miRNAs in the differential regulation of detoxification pathways in 91-R compared to 91-C. This study provides seminal evidence associating the differential expression of miRNAs in response to multigenerational DDT selection in Drosophila, and provides important clues for understanding the possible roles of miRNAs in mediating insecticide resistance traits.