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. 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.
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. 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.
Authors: Ana Duarte; Adam Pym; William T Garrood; Bartlomiej J Troczka; Christoph T Zimmer; T G Emyr Davies; Ralf Nauen; Andrias O O'Reilly; Chris Bass Journal: PLoS Genet Date: 2022-06-21 Impact factor: 6.020
Authors: Ralf Nauen; Peter Jeschke; Robert Velten; Michael E Beck; Ulrich Ebbinghaus-Kintscher; Wolfgang Thielert; Katharina Wölfel; Matthias Haas; Klaus Kunz; Georg Raupach Journal: Pest Manag Sci Date: 2014-11-27 Impact factor: 4.845
Authors: Konstantinos Mitsakakis; Sebastian Hin; Pie Müller; Nadja Wipf; Edward Thomsen; Michael Coleman; Roland Zengerle; John Vontas; Konstantinos Mavridis Journal: Int J Environ Res Public Health Date: 2018-02-03 Impact factor: 3.390
Authors: Adam Pym; Kumar Saurabh Singh; Åsa Nordgren; T G Emyr Davies; Christoph T Zimmer; Jan Elias; Russell Slater; Chris Bass Journal: BMC Genomics Date: 2019-12-19 Impact factor: 3.969