title: Molecular cloning and expression of CYP6B8: a xanthotoxin-inducible cytochrome P450 cDNA from Helicoverpa zea.
abstract: Xanthotoxin, a plant allelochemical, induces alpha-cypermethrin insecticide tolerance in Helicoverpa zea (corn earworm); inhibition of tolerance by piperonyl butoxide implicates cytochrome P450 monooxygenases (P450s) in the detoxification of this insecticide. To characterize the xanthotoxin-inducible P450 that might mediate alpha-cypermethrin tolerance in this species, a cDNA library prepared from xanthotoxin-induced H. zea fifth instar larvae was screened with cDNAs encoding furanocoumarin-metabolizing P450s from Papilio polyxenes (CYP6B1v2) and P. glaucus (CYP6B4v2) as well as a sequence-related P450 from Helicoverpa armigera (CYP6B2). One full-length cDNA isolated in this screening shares 51-99% amino acid identity with the CYP6B subfamily of P450s isolated from Papilio and Helicoverpa species and, thus, has been designated CYP6B8. All of these CYP6B subfamily members share a number of highly conserved domains, including substrate recognition site 1 (SRS 1) that is critical for xanthotoxin metabolism by CYP6B1v2 from Papilio polyxenes and coumarin metabolism by CYP2a5 from Mus musculus. Northern and RT-PCR analyses indicate that CYP6B8 expression is strongly induced by xanthotoxin and phenobarbital and negligibly induced by alpha-cypermethrin.
authors.affiliation: Department of Plant Protection, Nanjing Agricultural University, PR China.
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: M R
authors.initials: MR
authors.lastname: Berenbaum
authors.forename: M A
authors.initials: MA
authors.lastname: Schuler
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology; D007915:Lepidoptera / Q000235:genetics*; D008730:Methoxsalen / Q000494:pharmacology*; D008969:Molecular Sequence Data; D011722:Pyrethrins / Q000494:pharmacology; D017422:Sequence Analysis, DNA
chemical_list: D018076:DNA, Complementary; D007306:Insecticides; D011722:Pyrethrins; C017160:cypermethrin; D003577:Cytochrome P-450 Enzyme System; D008730:Methoxsalen