Response of Drosophila melanogaster to selection for P450-mediated resistance to isoquinoline alkaloids

Several species of columnar cacti in the Sonoran Desert contain isoquinolin e alkaloids that are toxic to all but the resident drosophilids that feed a nd breed in necrotic stems. Cytochrome P450 enzymes are known to be involve d in the metabolic detoxification of these alkaloids by the desert Drosophi la and are consequently responsible for their ability to utilize these subs trates. D. melanogaster is not normally exposed to these xenobiotic compoun ds and cannot live in necrotic cactus tissue. However, a previous study fou nd evidence of a phenobarbital-inducible P450 in adults of this species tha t is capable of metabolizing cactus alkaloids. The current investigation so ught to determine whether D. melanogaster responds to selection for alkaloi d resistance. Significant increases in larval viability and adult longevity as well as shorter larvae-to-adult development times were observed after 1 6 generations of selection on medium containing isoquinoline alkaloids. The selected lines that exhibited a positive response can now be used to assay for changes in gene regulation as a possible mechanism of their response. This information will contribute to the understanding of evolution of P450- mediated resistance in insects. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.