Pymetrozine is hydroxylated by CYP6CM1 , a cytochrome P450 conferring neonicotinoid resistance in Bemisia tabaci

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 inwhiteflies.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 K m value of 5.9 ± 0.3 µ M and a time‐dependent depletion of pymetrozine.CONCLUSION 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. © 2012 Society of Chemical Industry