CYTOCHROME P450-MEDIATED RESISTANCE TO ISOQUINOLINE ALKALOIDS AND SUSCEPTIBILITY TO SYNTHETIC INSECTICIDES IN DROSOPHILA

It is well documented that cytochrome P450 enzymes pray a central role in metabolic resistance to natural plant toxins and synthetic pestici des. Using insecticide-susceptible and -resistant strains of Drosophil a melanogaster and monophagous Sonoran Desert drosophilids, the curren t study looked for a correlation between resistance to toxic cactus al kaloids and resistance to pesticides (DDT and propoxur) or a toxic, no ncactus alkaloid (nicotine). Resistance to cactus alkaloids in cactoph ilic Drosophila was not associated with resistance to DDT or propoxur. Conversely, a DDT-resistant strain of D. melanogaster (Hikone R) was no more tolerant of cactus alkaloids than a susceptible strain (Canton S). Cactus alkaloid-metabolizing Drosophila were, however, less susce ptible to nicotine than a noncactophilic species (D. melanogaster stra in Canton S). These data suggest that resistance to cactus alkaloids i n monophagous desert Drosophila involves the activity of cytochrome P4 50 isoforms with substrate specificities sufficiently narrow to preclu de detectable in vivo activity on compounds other than those that are chemically similar. These results are in contrast to what has generall y been reported for more highly polyphagous insect species. (C) 1996 A cademic Press