Drosophila glutathione S-transferases.

The Drosophila glutathione S-transferases (GSTs; EC2.5.1.18) comprise a host of cytosolic proteins that are encoded by a gene superfamily and a homolog of the human microsomal GST. Biochemical studies of certain recombinant GSTs have linked their enzymatic functions to important substrates such as the pesticide DDT and 4-hydroxynonenal, a reactive lipid metabolite. Moreover, a correspondence has been observed between resistance to insecticide substrates-such as DDT-and elevated enzyme levels in resistant strains. Such significant, recurring connections suggest that these gst genes may feature in a model for the development of insecticide resistance. We have amassed substantial biochemical support for relating the overexpression of a particular gst gene to insecticide resistance but are still short of solid genetic evidence to affirm a causal relationship. With the Drosophila system, we have at our disposal genetic and molecular techniques such as p-element mutagenesis and excision, siRNA technology, and versatile transgenic techniques. We can use these methods to effect loss-of-function and gain-of-function conditions and, in these rendered contexts, study other potentially important functions of the gst gene superfamily. An immediate problem that comes to mind is the possible causal relationship between GST substrate specificity and chemical resistance phenotype(s). In this chapter, we present an analysis of selected strategies and laboratory methods that may be useful in pursuing a variety of interesting problems. We will cover three kinds of approaches-biochemistry, genetics, and genomics-as important instruments in a toolkit for studies of the Drosophila gst superfamily. We make the case that these approaches (biochemistry, genetics, and genomics) have helped us gain important insights and can continue to help the community gain a more complete understanding of the biological functions of GSTs. Such knowledge may be key in addressing questions about the detoxification of pesticides and how oxidative stresses affect life span. We hope that these techniques will prove fruitful in studying a host of other physiologic functions as well.