Masters Theses

Josh Jenkins

Date of Award

12-2001

Degree Type

Thesis

Degree Name

Master of Science

Major

Biochemistry and Cellular and Molecular Biology

Major Professor

Ranjan Ganguly

Committee Members

Bruce Mckee, Jae Park, Albrecht von Arnim

Abstract

Insecticide resistance is a major problem in today's agricultural world. Metabolic detoxification of insecticides is a prominent factor that causes resistance in insects. Important players in conferring resistance to insecticides are cytochrome P450s (CYPs). These detoxifying enzymes are expressed at high levels in resistant insects. However, not much is known about the mechanisms responsible for the high level of CYP gene expression in resistant insects. Such knowledge is important and may help develop new strategies to combat resistant insects. This study was initiated to gain an understanding of the mechanisms that are responsible for insect CYP gene regulation using Drosophila as a model system. For this purpose two 2nd chromosome-linked CYP gene clusters, one containing five genes (Cyp6gl, Cyp6g2, Cyp6t3, Cyp9hl, and CypSOlal) and the other containing three genes (Cyp4pl, Cyp4p2, and Cyp4p3), were examined for their expression in DDT-resistant (91-R) and susceptible (91-C) strains. Of these two gene clusters, the first one is located very close to a major resistance locus (2-62.0). The results of Northern blot analysis showed that of these eight genes only Cyp6gl is expressed in adult flies. The level of expression was found to be higher in the 91-R resistant strain than in the 91-C strain. Thus 91-R is an overproducer and 91-C is an underproducer of CYP6G1 mRNA. 91-R is also known to be an overproducer of CYP6A2 and CYP6A8 mRNA. Like Cyp6a2 and Cyp6a8, Cyp6gl also shows a higher level of expression in males than in females. However, unlike Cyp6a2 and Cyp6a8, Cyp6gl does not show much inducibility with barbital. To understand whether Cyp6gl is also regulated like Cyp6a2 and Cyp6a8, Cyp6gl expression was measured in chromosome substitution stocks carrying combinations of X, 2nd, and 3rd chromosomes from the overproducer (91-R) and underproducer (91-C) strains. The results showed that unlike Cyp6a2 and Cyp6a8, overexpression of Cyp6gl is not regulated by factors on the 3rd chromosome. On the contrary, it appears, from the results that factors on the 2nd chromosome may be responsible for overexpression of Cyp6gl in the 91-R strain. These factors may be transregulatory genes which differ between the overproducer, 91-R, and the underproducer, 91-C, strains. Alternatively, the cw-regulatory sequence of the 2nd chromosome-linked Cyp6gl-91R allele may be different from that of the Cyp6gl-91C allele.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS