Cytochrome P450s Cyp4p1 and Cyp4p2 associated with the DDT tolerance in the Drosophila melanogaster strain 91-R

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

Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2019
Publication Date: 6/12/2019
Citation: Seong, K., Coates, B.S., Pittendrigh, B.R. 2019. Cytochrome P450s Cyp4p1 and Cyp4p2 associated with the DDT tolerance in the Drosophila melanogaster strain 91-R. Pesticide Biochemistry and Physiology. 159(2019):136-143. https://doi.org/10.1016/j.pestbp.2019.06.008.
DOI: https://doi.org/10.1016/j.pestbp.2019.06.008

Interpretive Summary: The development of resistance to chemical insecticides within populations of agricultural pest insects cause difficulties for their control by producers and leads to an increase in damage to agricultural commodities. These factors in turn leads to lower the quantity, quality and profitability of farm outputs. An ARS researcher along with university collaborators used a DDT insecticide resistant strain of a fruit fly species to investigate adaptive genetic mechanisms. This study determined that two cytochrome P450 genes, Cyp4p1 and Cyp4p2, are expressed at a significantly higher level in resistant fruit flies compared to susceptible counterparts, and this difference become greater (is inducible) after resistant flies are exposed to DDT. Furthermore, involvement of Cyp4p1 and Cyp4p2 in DDT resistance was validated using transgenic lines that knocked down transcript levels of these two gene. Specifically, experiments within this study demonstrate that flies become more susceptible to DDT insecticides following transcript knockdown, indicating that the expression and function of Cyp4p1 and Cyp4p2 may be required within DDT resistant insects. Thus, this research demonstrates that the increased level of expression of cytochrome P450 genes, Cyp4p1 and Cyp4p2, within DDT resistance fruit flies may contribute to insecticide resistance, potentially by increasing the capacity of resistant insects to detoxify insecticidal compounds. These data are important to government, university, and industry scientists interested in the sustainability of insecticide use for the control of insect populations in the field and will likely benefit producers through the understanding of how insects adapt to current control technologies and development of appropriate insect resistance management strategies.

Technical Abstract: Cytochrome P450s are a part of gene family that has undergone gene duplication, divergence, and losses in function. In Drosophila melanogaster, a pair of strains of common origin have been selected for DDT resistance (91-R) or maintained as a non-selected population (91-C) for over a half-century. Previous work has shown that the loss of function of both Cyp4p1 and Cyp4p2 in 91-C populations, but not in 91-R populations. In this study, we used a comparative approach to demonstrate that transcription of Cyp4p1 and Cyp4p2 was constitutively up-regulated in 91-R as compared to another the DDT susceptible strain Canton-S, which does not have a loss of function of the genes. Furthermore, expression of Cyp4p1 and Cyp4p2 was significantly induced in 91-R in response to sublethal DDT exposure, but not in DDT treated Canton-S. Subsequently, two GAL4/UAS transgenic strains with integrated heat shock-inducible Cyp4p1- or Cyp4p2-RNAi constructs within naïve genetic backgrounds were developed. Following heat shock induction of Cyp4p1 and Cyp4p2 knockdown, these transgenic lines showed increased DDT mortality compared to their corresponding non-heat shock controls. These results provide a functional link of Cyp4p1 and Cyp4p2 in conferring tolerance to DDT exposure and support the hypothesis that these genes may have been maintained in the 91-R strain, contrasting their loss in 91-C, due to their potential role in the polygenic DDT resistance phenotype.