TY - JOUR
T1 - A substrate-specific cytochrome P450 monooxygenase, CYP6AB11, from the polyphagous navel orangeworm (Amyelois transitella)
AU - Niu, Guodong
AU - Rupasinghe, Sanjeewa G.
AU - Zangerl, Arthur R.
AU - Siegel, Joel P.
AU - Schuler, Mary A.
AU - Berenbaum, May R.
N1 - Funding Information:
We thank Zhimou Wen for advice and assistance in the baculovirus expression and metabolism assays and Terry Harrison for pointing us toward hostplant records for the navel orangeworm and its relatives. This project was funded by a grant from the Almond Board of California ( ABC-C6480 ).
PY - 2011/4
Y1 - 2011/4
N2 - 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.
AB - 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.
KW - Amyelois transitella
KW - Cytochrome P450 monooxygenase
KW - Imperatorin
KW - Insect-plant interactions
KW - Piperonyl butoxide
UR - http://www.scopus.com/inward/record.url?scp=79952193511&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79952193511&partnerID=8YFLogxK
U2 - 10.1016/j.ibmb.2010.12.009
DO - 10.1016/j.ibmb.2010.12.009
M3 - Article
C2 - 21220011
AN - SCOPUS:79952193511
SN - 0965-1748
VL - 41
SP - 244
EP - 253
JO - Insect Biochemistry and Molecular Biology
JF - Insect Biochemistry and Molecular Biology
IS - 4
ER -