Molecular analysis of multiple CYP6B genes from polyphagous Papilio species

Papilio glaucus (eastern tiger swallowtail) and Papilio. canadensis (Canadi an tiger swallowtail) are two closely related species with broad but overla pping hostplant ranges. P. glaucus encounters toxic furanocoumarins occasio nally in its diet in its rutaceous hostplants, whereas P. canadensis rarely if ever encounters these Compounds. Analysis of their furanocoumarin-metab olic profiles indicates that these species induce cytochrome P450 monooxyge nases (P450s) capable of metabolizing linear and angular furanocoumarins to varying degrees in response to dietary supplementation with xanthotoyin (a linear furanocoumarin). In P. glaucus, metabolism is induced to a signific antly higher level than in A canadensis. Cloning of multiple P450 genes fro m each species has revealed that both species contain and express two group s of P450s, designated CYP6B4 and CYP6B17, that are related to the A glaucu s CYP6B4v1 enzyme known to metabolize an array of furanocoumarins. Expressi on patterns of the CYP6B4 and CYP6B17 group transcripts differ in these spe cies in both their basal and furanocoumarin-inducible levels. In P. glaucus , CYP6B4 transcripts, which are not detectable constitutively, are 311-fold induced by xanthotoxin and CYP6B17 transcripts, which are detectable const itutively, are 3-fold induced by xanthotoxin. In P. canadensis, CYP6B4 tran scripts are only 8-fold induced and CYP6B17 transcripts are 13-fold induced . These findings are consistent with the postulated evolutionary history of these two species, according to which P. glaucus maintains its association with rutaceous hostplants and P. canadensis has differentiated to utilize hostplants in other families more extensively (C) 2001 Elsevier Science Ltd . All rights reserved.