A substrate-specific cytochrome P450 monooxygenase, CYP6AB11, from the polyphagous navel orangeworm (Amyelois transitella)

Guodong Niu, Sanjeewa G. Rupasinghe, Arthur R. Zangerl, Joel P. Siegel, Mary A. Schuler, May R. Berenbaum

Research output: Contribution to journalArticle

Abstract

The navel orangeworm Amyelois transitella (Walker) (Lepidoptera: Pyralidae) is a serious pest of many tree crops in California orchards, including almonds, pistachios, walnuts and figs. To understand the molecular mechanisms underlying detoxification of phytochemicals, insecticides and mycotoxins by this species, full-length CYP6AB11 cDNA was isolated from larval midguts using RACE PCR. Phylogenetic analysis of this insect cytochrome P450 monooxygenase established its evolutionary relationship to a P450 that selectively metabolizes imperatorin (a linear furanocoumarin) and myristicin (a natural methylenedioxyphenyl compound) in another lepidopteran species. Metabolic assays conducted with baculovirus-expressed P450 protein, P450 reductase and cytochrome b5 on 16 compounds, including phytochemicals, mycotoxins, and synthetic pesticides, indicated that CYP6AB11 efficiently metabolizes imperatorin (0.88pmol/min/pmol P450) and slowly metabolizes piperonyl butoxide (0.11pmol/min/pmol P450). LC-MS analysis indicated that the imperatorin metabolite is an epoxide generated by oxidation of the double bond in its extended isoprenyl side chain. Predictive structures for CYP6AB11 suggested that its catalytic site contains a doughnut-like constriction over the heme that excludes aromatic rings on substrates and allows only their extended side chains to access the catalytic site. CYP6AB11 can also metabolize the principal insecticide synergist piperonyl butoxide (PBO), a synthetic methylenedioxyphenyl compound, albeit slowly, which raises the possibility that resistance may evolve in this species after exposure to synergists under field conditions.

Original languageEnglish (US)
Pages (from-to)244-253
Number of pages10
JournalInsect Biochemistry and Molecular Biology
Volume41
Issue number4
DOIs
StatePublished - Apr 1 2011

Keywords

  • Amyelois transitella
  • Cytochrome P450 monooxygenase
  • Imperatorin
  • Insect-plant interactions
  • Piperonyl butoxide

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Insect Science

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