DIFFERENTIAL INDUCTION OF CYTOCHROME-P450 TRANSCRIPTS IN PAPILIO POLYXENES BY LINEAR AND ANGULAR FURANOCOUMARINS

Cytochrome P450 monooxygenases play critical roles in the detoxificati on of linear and angular furanocoumarins present in the host plants of Papilio polyxenes (black swallowtail) larvae. To determine the spectr um of linear and angular furanocoumarins that induce isozymes responsi ble for these detoxifications, the metabolic activities of individual P. polyxenes larvae were monitored in response to individual furanocou marins. Two linear furanocoumarins, xanthotoxin and bergapten, as well as the angular furanocoumarin, angelicin, significantly and selective ly induce metabolism of several furanocoumarins. Another angular furan ocoumarin, sphondin, does not induce furanocoumarin metabolism even th ough it is itself capable of being metabolized in vivo. Northern analy sis of the mRNAs induced in response to each of four naturally occurri ng furanocoumarins indicates that mRNAs related to CYP6B1 are highly i nduced by the two linear furanocoumarins (xanthotoxin, bergapten) and by angelicin, the angular furanocoumarin. RNase protection analysis in dicates that CYP6B1v1-3 transcripts, which we have already cloned, are specifically induced by xanthotoxin and that additional CYP6B1-relate d transcripts are induced in response to angelicin, These data indicat e that a complex array of CYP6B1 transcripts, derived from a minimum o f two loci, is responsible for furanocoumarin metabolism in P. polyxen es. Transcripts derived from these loci appear to be differentially in duced by linear and angular furanocoumarins.