Biochemical and Molecular Basis for Comparative Responses to Pesticides

Dauterman, Walter

Abstract

This proposal has two distinct objectives. The first objective is to characterize pesticide resistance in a multi-resistant strain of the tobacco budworm. The second objective is to delineate the substrate specificity of isozymes of glutathione S-transferases isolated from various animal sources. Resistance of the tobacco budworm to pesticides involves several enzyme systems, including monooxygenases, esterases and glutathione S- transferases. Preliminary studies suggest possible involvement of a P- glycoprotein; such proteins are known to be involved in resistance to chemotherapeutic drugs. Further biochemical characterization of resistance will involve studies of enzyme synergists, comparative penetration and metabolism of thiodicarb and further characterization of the high molecular weight protein found in the resistant strain. The possible role of alterations in target site will also be examined using assays for knock-down resistance and acetylcholinesterase inhibition studies. Following the biochemical characterization of resistance, enzymes and/or proteins thought to be most responsible for resistance will be purified, antibodies raised, and cDNA libraries screened in an effort to clone the gene(s) responsible for resistance. Further studies will be performed to investigate gene regulation and inheritance of resistance. Glutathione S-transferases are involved in metabolism of a wide variety of toxic compounds, including pesticides. Various isozymes of glutathione S-transferases will be isolated from various animal sources by means of affinity chromatography and chromatofocusing. Known pesticide substrates of glutathione S-transferases will be assayed against the various isozymes. Attempts will be made to categorize the various isozymes from different animal sources into the alpha, mu, and pi classes and to determine whether the class or subunit is responsible for the type of pesticide conjugated.