Date of Award
Master of Music
Mary Ann Handel, Bruce McKee
Insecticide resistance has been a problem in both agriculture and public healthIn most cases, resistance is mediated by the cytochrome P450 monooxygenases. One or more Cyp genes are generally found to be over-expressed in resistant strains compared to susceptible ones. In Drosophila, three Cyp genes (Cyp6a2, Cyp6a8 and Cyp6g1) are known to show over-expression in the resistant 91-R relative to the susceptible 91-C strain. However, the total number of Cyp genes over-expressed in the 91-R strain is not known. This investigation was initiated to identify new Cyp genes that show a higher expression in 91-R relative to 91-C. The expression of four Cyp6 family genes (Cyp6w1, Cyp6u1, Cyp6a14, and Cyp6a13) on chromosome 2 that lie close to a genetically mapped DDT resistance locus was examined in the resistant 91-R and susceptible 91-C strains. It was found that among all four, only Cyp6w1 showed a significantly higher expression in 91-R relative to 91-C. Similar to Cyp6a2 and Cyp6a8 on chromosome 2, Cyp6w1 was found to be inducible by barbital. It also shows a higher expression in males than in females. To understand how Cyp6wl is regulated, its expression was examined in several chromosome substitution stocks carrying different combinations of the three major chromosomes (X, 2nd, and 3rd) of 91-R and 91-C. It was found that, as for Cyp6a2 and Cyp6a8 genes, the 3rd chromosome negatively influences the expression of Cyp6wl, whereas the X chromosome has little or no effect. It was also found that the second chromosome of 91-C has an inhibitory influence on the expression of Cyp6w1-91C allele, whereas the second chromosome of 91-R has a positive influence on the expression of Cyp6w1-91R allele. The results of this investigation imply that Cyp6w1, Cyp6a2, and Cyp6a8 genes may be regulated by the same negative trans-regulatory gene(s) on the third chromosome. A loss-of-function mutation of this gene(s) may be responsible for their elevated expression in 91-R.
Awwad, Rawan, "Expression of four Cytochrome P450 family six (Cyp6) genes in DDT-resistant and susceptible strains of Drosophila melanogaster. " Master's Thesis, University of Tennessee, 2001.