Involvement of cytochrome P450 in host-plant utilization by Sonoran Desert Drosophila.

Abstract

The four Drosophila species endemic to the Sonoran Desert (Drosophila mettleri, Drosophila mojavensis, The four species are not closely related phylogenetically, although all are members ofthe major virilis-repleta radiation of the genus Drosophila. These species appear to have adapted independently to the desert environment (2). The major population center of the nearest relative of each species is found outside the desert or overlaps only slightly with the desert. Each of the endemic species also uses a different cactus species as a host, in a nearly one-to-one relationship, as demonstrated by extensive rearing records and collection of adults from naturally occurring rots (1). In any particular location, each Drosophila species generally utilizes the necrotic tissue of only one cactus species. Due to differences in the geographic distribution of the cacti and one case of behavioral preference, three of the four fly species exhibit a shift in host plants between the Baja Peninsula and the mainland Sonoran Desert. D. nigrospiracula uses saguaro (Carnegiea gigantea) on the mainland and card6n (Pachycereus pringlei) on the peninsula. Saguaro cactus is only found on the mainland, and card6n is primarily restricted to the Baja peninsula. The two cacti are morphologically and chemically very similar and have low concentrations (1% dry weight) of simple isoquinoline alkaloids (e.g., carnegine and gigantine in saguaro) as their primary allelochemicals. The host plants for D. mojavensis are agria (Stenocereus gummosus) and organ pipe (Stenocereus thurberi), which are sympatric on the peninsula. D. mojavensis shows a clear preference for agria and utilizes organ pipe on the mainland, where agria is all but absent. Agria and organ pipe do not contain alkaloids, but both have sterol diols, medium-chain

The Role of Cytochrome P450 Monooxygenases in Plant-Insect Interactions

“…3A) more efficiently than Drosophila species not typically exposed to these alkaloids (e.g. D. melanogasfer) (Frank and Fogleman, 1992). Although the products of these P450-mediated reactions are not yet known, it is now evident that the basal activities of the P450s responsible for alkaloid metabolism are induced in response to the presence of cactus alkaloids in the diet of Drosophila larvae and adults (Frank and Fogleman, 1992;Danielson et al, 1994).…”

“…D. melanogasfer) (Frank and Fogleman, 1992). Although the products of these P450-mediated reactions are not yet known, it is now evident that the basal activities of the P450s responsible for alkaloid metabolism are induced in response to the presence of cactus alkaloids in the diet of Drosophila larvae and adults (Frank and Fogleman, 1992;Danielson et al, 1994). Full-length cDNA clones encoding several isoquinoline alkaloid-inducible P450s have been obtained, but their substrate specificities have not yet been defined (J.C. Fogleman, personal communication).…”

Genetic Changes Accompanying the Evolution of Host Specialization in Drosophila sechellia

“…For example, in several cactophillic Drosophila species cytochrome P450s have been implicated in detoxification of host secondary compounds (Frank and Fogleman 1992;Barker et al 1994;Fogleman et al 1997Fogleman et al , 1998Matzkin et al 2006). Most of these genetic studies, however, concentrated on one or a few traits.…”

Induction by alkaloids and phenobarbital of Family 4 Cytochrome P450s in Drosophila : evidence for involvement in host plant utilization

“…In rot exudate-soaked soils, evaporative water loss produces alkaloid concentrations that are often more than an order of magnitude greater (Fogleman et al 1982;Kircher 1982). On the basis of both in vitro metabolism and in vivo viability assays, P450s have been ®rmly implicated in the resistance of D. mettleri to these toxins (Frank and Fogleman 1992). The current study measured the xenobiotic responsiveness of individual P450 genes from this drosophilid in order to identify isoforms likely to play a role in the metabolism of plant defense compounds and thus in the maintenance of insect-hostplant relationships.…”