title: Pymetrozine is hydroxylated by CYP6CM1, a cytochrome P450 conferring neonicotinoid resistance in Bemisia tabaci.
abstract: BACKGROUND
  Resistance to neonicotinoid insecticides such as imidacloprid in the cotton whitefly, Bemisia tabaci, is linked to its hydroxylation by constitutively overexpressed CYP6CM1, a cytochrome P450 enzyme. Here, an investigation was conducted to establish whether CYP6CM1 functionally expressed in Sf9 cells also detoxifies pymetrozine, a selective homopteran feeding blocker known to be cross-resistant to neonicotinoids in whiteflies.
  
  
  RESULTS
  Incubation of pymetrozine with functionally expressed Bemisia CYP6CM1 and subsequent LC-MS/MS analysis revealed a rapid formation of two pymetrozine metabolites by hydroxylation of its heterocyclic 1,2,4-triazine ring system. Enzyme kinetics revealed a Km value of 5.9 ± 0.3 µM and a time-dependent depletion of pymetrozine.
  
  
  CONCLUSIONS
  The known cross-resistance between imidacloprid, other neonicotinoid insecticides and pymetrozine in B. tabaci is most likely conferred by the very same detoxification mechanism, i.e. a monooxygenase-based hydroxylation mechanism linked to the overexpression of CYP6CM1. These insecticide chemistries should not be alternated in whitefly resistance management strategies.
authors: Bayer CropScience AG, RD-Research Crop Protection, Monheim, Germany. ralf.nauen@bayer.com
authors: Ralf
authors: R
authors: Nauen
authors: John
authors: J
authors: Vontas
authors: Martin
authors: M
authors: Kaussmann
authors: Katharina
authors: K
authors: Wölfel
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006430:Hemiptera / Q000201:enzymology*; D006900:Hydroxylation; D007305:Insecticide Resistance; D014227:Triazines / Q000378:metabolism*
chemical_list: D014227:Triazines; D003577:Cytochrome P-450 Enzyme System; C480311:pymetrozine