Evolution of CYP6B Genes Associated with Furanocoumarin Metabolism in the Papilio Glaucus Group

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The vast majority of caterpillars feed on a narrow range of plants, often within only a single family. Among the distinguishing characteristics of such specialized feeders are enzymatic detoxification systems, including cytochrome P450 monooxygenases, that are ideally configured for metabolizing the toxins that typify their hostplants. The tiger swallowtail (Papilio glaucus) and its relatives, however, are exceptional among caterpillars in that they can feed on a much broader range of plant families. In doing so they encounter a substantially greater diversity of plant toxins, which differ in their biosynthetic origin and structure. This project is aimed at determining how the biochemistry and molecular biology of the cytochrome P450 monooxygenases of the tiger swallowtail and its generalist relatives differ from the P450 systems in their specialized relatives in the genus Papilio. Most Papilio species are specialized for feeding on plants containing toxins called furanocoumarins, and these species rely on P450s in the CYP6B family for detoxification. Although they rarely encounter them, tiger swallowtails can metabolize these compounds too, albeit at lower rates. In this project, differences in the structure and regulation of the CYP6B genes will be mapped within the genus Papilio (1) in order to understand how generalized habits can arise within specialized lineages and (2) to determine how P450 evolution can contribute to changes in detoxification capabilities.