Resistance of Drosophila to toxins.

Insects, including Drosophila, readily respond to toxins such as phytotoxins, metal ions, and insecticides in their environment by evolving resistance. Although Drosophila are seldom targets for insecticides, nevertheless populations worldwide have evolved resistance to a variety of insecticides, and these resistance alleles persist in high frequency. In many cases, Drosophila use the same genetic and biochemical mechanisms that underlie resistance in pest insects, including single-site changes in target molecules resulting from point mutations and upregulation of degradative enzymes, particularly cytochrome P450 enzymes and glutathione S-transferases. However, several types of resistance found in pest insects, such as gene amplification and knock-down resistance, have not been reported in Drosophila field populations. Excellent Drosophila-plant models are being studied to understand the adaptation to phytotoxins; P450 enzymes are clearly involved in phytotoxin resistance in one of these models. The genetic advantages of D. melanogaster, including availability of the sequenced genome, should allow further study of these genes and identification of new ones, particularly regulatory genes, responsible for resistance.