title: CYP9Q-mediated detoxification of acaricides in the honey bee (Apis mellifera).
abstract: Although Apis mellifera, the western honey bee, has long encountered pesticides when foraging in agricultural fields, for two decades it has encountered pesticides in-hive in the form of acaricides to control Varroa destructor, a devastating parasitic mite. The pyrethroid tau-fluvalinate and the organophosphate coumaphos have been used for Varroa control, with little knowledge of honey bee detoxification mechanisms. Cytochrome P450-mediated detoxification contributes to pyrethroid tolerance in many insects, but specific P450s responsible for pesticide detoxification in honey bees (indeed, in any hymenopteran pollinator) have not been defined. We expressed and assayed CYP3 clan midgut P450s and demonstrated that CYP9Q1, CYP9Q2, and CYP9Q3 metabolize tau-fluvalinate to a form suitable for further cleavage by the carboxylesterases that also contribute to tau-fluvalinate tolerance. These in vitro assays indicated that all of the three CYP9Q enzymes also detoxify coumaphos. Molecular models demonstrate that coumaphos and tau-fluvalinate fit into the same catalytic pocket, providing a possible explanation for the synergism observed between these two compounds. Induction of CYP9Q2 and CYP9Q3 transcripts by honey extracts suggested that diet-derived phytochemicals may be natural substrates and heterologous expression of CYP9Q3 confirmed activity against quercetin, a flavonoid ubiquitous in honey. Up-regulation by honey constituents suggests that diet may influence the ability of honey bees to detoxify pesticides. Quantitative RT-PCR assays demonstrated that tau-fluvalinate enhances CYP9Q3 transcripts, whereas the pyrethroid bifenthrin enhances CYP9Q1 and CYP9Q2 transcripts and represses CYP9Q3 transcripts. The independent regulation of these P450s can be useful for monitoring and differentiating between pesticide exposures in-hive and in agricultural fields.
authors.affiliation: Department of Entomology, University of Illinois, Urbana, IL 61801, USA.
authors.forename: Wenfu
authors.initials: W
authors.lastname: Mao
authors.forename: Mary A
authors.initials: MA
authors.lastname: Schuler
authors.forename: May R
authors.initials: MR
authors.lastname: Berenbaum
mesh_terms: D056810:Acaricides / Q000493:pharmacokinetics* / Q000633:toxicity; D000595:Amino Acid Sequence; D000818:Animals; D001516:Bees / Q000201:enzymology* / Q000469:parasitology; D003372:Coumaphos / Q000493:pharmacokinetics; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006790:Host-Parasite Interactions; D008658:Inactivation, Metabolic; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007306:Insecticides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011722:Pyrethrins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D057077:Varroidae / Q000187:drug effects / Q000502:physiology
chemical_list: D056810:Acaricides; D019476:Insect Proteins; D007306:Insecticides; D007527:Isoenzymes; D009570:Nitriles; D011722:Pyrethrins; C034227:fluvalinate; C099952:bifenthrin; D003577:Cytochrome P-450 Enzyme System; D003372:Coumaphos