ARS | Publication request: Differential response of DDT susceptible and resistant Drosophila melanogaster strains to DDT and oxidative stress

Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2010
Publication Date: January 1, 2011
Citation: Sun, L., Schemerhorn, B.J., Muir, W., Pittendrigh, B. 2011. Differential response of DDT susceptible and resistant Drosophila melanogaster strains to DDT and oxidative stress. Insect Molecular Biology. 100(1);7-15.

Interpretive Summary: The costs of resistance in insect populations has long been a topic of discussion in the pesticide resistance community. For some pesticides, the resistance genes may be costly for the insect population and (i) thus would not increase in frequency, or (ii) resistance would revert to low frequency once the pesticide was no longer applied. However, few examples exist detailing the exact nature of “costs for resistance” and the molecular mechanisms by which these costs may occur. The strain of the fruit fly Drosophila most DDT resistant was also the most susceptible to the dietary oxidative stressor H2O2. Our results suggest that, at least in these strains, one putative “cost” to DDT resistance is greater susceptibility to oxidative stress. This is consistent with the concept that increased expression of certain genes is associated with increased susceptibility to oxidative stress, as we measured a significant increase in expression of genes in the resistant strain of Drosophila. This work will benefit not only agricultural production problems, but reaches into the field of medical entomology as well. This information will increase our knowledge of the phenomenon of pesticide resistance and result in more effective use of insecticides and pesticides for insect control worldwide.

Technical Abstract: Metabolic DDT resistance in Drosophila melanogaster is associated with increased cytochrome P450 expression. Increased P450 activity is also associated with increased oxidative stress. In contrast, increased glutathione S transferase (GST) expression has been associated with a greater ability of organisms to deal with oxidative stress. We observed a negative correlation in four Drosophila strains between DDT and oxidative stress resistance. The most DDT resistant strain, Wisconsin, was the most susceptible to H2O2 and the most DDT susceptible strain, Canton-S, was the most resistant to H2O2. The Wisconsin strain under-transcribed 40% of its GSTs as compared to the Canton-S strain (qRT-PCR comparisons at P<0.05). Thus, in the Wisconsin strain, one putative “cost” to P450-based resistance may be susceptibility to oxidative stress.