Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2006
Publication Date: 8/20/2006
Citation: Sun, W., Margum, V., Sun, L., Buczkowski, G., Bennet, G., Schemerhorn, B.J., Muir, W., Pittendrigh, B. 2006. Genome-wide analysis of phenobarbital-inducible genes in Drosophila melanogaster. Insect Molecular Biology. 15(4):455-464. Interpretive Summary: Many insects use metabolic resistance as a mechanism to overcome resistance to insecticides. Phenobarbital is shown to induce expression of detoxification enzymes, like cytochrome P450s. The purpose of this work was to examine genome-wide analysis of the genes that are differentially expressed in response to Phenobarbital treatment. This work found fifteen genes that were either up-regulated or down-regulated. Some of the genes, are shown to be over-transcribed in DDT-resistant Drosophila, hopefully leading towards a better understanding of the basis of metabolic pesticide resistance. Previously it had been suggested that metabolic resistance was due only to the up regulation of cytochrome P450s, thus calling into question previous work on metabolic resistance. Here we show that phenobarbital induces genes associated with detoxification, development, and carbohydrate metabolism. The impact of this research is that it gives us a better understanding of the mechanisms controlling metabolic resistance to insecticides, and ultimately in the prevention of additional animal and crop losses throughout the United States.
Technical Abstract: It has been well documented that phenobarbital (i) induces differential expression of detoxification enzymes, such as cytochrome P450s, in both mammals and insects, and (ii) influences changes in the metabolic rates in a diverse variety of species. In Drosophila melanogaster it has been previously demonstrated that phenobarbital induces increased expression of at least several cytochrome P450 genes. To date, there has been no genome-wide analysis of the genes that are differentially expressed in Drosophila in response to phenobarbital treatment. In the following article we performed an oligoarray analysis of w1118 third instars exposed to 0.1% phenobarbital in their diet for 24 hr. Using a Statistical Analysis of Microarrays (SAM) approach with a q'0.05 we observed 15 genes that were putatively induced for increased expression. When the false discovery rate for the SAM approach was q'0.12, we observed (i) an additional four up-regulated genes (Cyp12d1, DmGstD4, and two genes with unknown function) and (ii) eleven down-regulated genes with unknown function. We verified differential transcription of fourteen of these genes using quantitative real time PCR: Cyp4d14, Cyp6a2, Cyp6a8, Cyp12d1, Cyp6d5, CG2065, DmGSTD6, DmGSTD7, Amy-p/Amy-d, Ugt86Dd, GC5724, juvenile hormone epoxide hydrolase 1 and 2 (Jheh1 and Jheh2), and CG11893. Some of the genes, and classes of genes, induced by phenobarbital have previously been shown to be over-transcribed in metabolically DDT-resistant Drosophila strains. These data represent a step towards understanding (i) the genomic response of Drosophila to phenobarbital treatment and (ii) the basis of metabolic pesticide resistance.