Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2011
Publication Date: 1/16/2011
Citation: Sun, L., Schemerhorn, B.J., Jannash, A., Walters, K., Adamec, K., Muir, W., Pittendrigh, B. 2011. Differential transcription of cytochrome P450s and glutathione S transferases in DDT-susceptible and resistant Drosophila melanogaster strains in response to DDT and oxidative stress. Journal of Pesticide Biochemistry and Physiology. p. 7-15. Interpretive Summary: It has been suggested that resistance to pesticides may pose a fitness cost to insects such that, if the pesticide were no longer applied, the resistance genes that were harmful would go back to a low number within the insect population. Pesticide resistance is often a dominant trait have been associated with increased production of detoxifying type enzymes. Some of these same pathways that help with the processing of the pesticide chemical in the insect body are also important to deal with oxidative stress. There are very few studies that deal with understanding the ecological ‘costs’ associated with resistance, therefore, the purpose of this study was to understand how resistant and susceptible flies respond to environmental challenges.
Technical Abstract: Metabolic DDT resistance in Drosophila melanogaster has previously been associated with constitutive over-transcription of cytochrome P450s. Increased P450 activity has also been associated with increased oxidative stress. In contrast, over-transcription of glutathione S transferases (GSTs) has been associated with resistance to oxidative stress. However, little is known in regards to the impact of xenobiotics on induction of P450s and GSTs and if there exist differences in inducibility between the pesticide susceptible and resistant strains. Thus, we investigated the transcriptional expression of GSTs and P450s in DDT resistant (Wisconsin) and susceptible (Canton-S) Drosophila strains in response to exposure to DDT and the oxidative stressor H2O2. Wisconsin constitutively over-transcribed P450s, constitutively under-transcribed 27% of its total GSTs, and was more susceptible to H2O2 than Canton-S. DDT exposure induced GST expression only in the Wisconsin strain and not in the Canton-S strain. These results suggest that there are potentially more differences between pesticide susceptible and resistant strains than just constitutive expression of P450s; there may also exist, at least in some strains, differences in their patterns of inducibility of P450s and GSTs. Within the context of the Wisconsin strain, these differences may be contributing to the fly lines increased susceptibility to oxidative stress.