title: Neonicotinoid insecticides: oxidative stress in planta and metallo-oxidase inhibition.
abstract: Neonicotinoids not only control insect pests but also sometimes independently alter plant growth and response to stress. We find that imidacloprid, thiacloprid, acetamiprid, thiamethoxam, and clothianidin but not nitenpyram and dinotefuran induce foliar lesions and peroxidative damage in soybean ( Glycine max ) seedlings assayed with the 3,3'-diaminobenzidine stain. The chloropyridinyl-carboxylic acid (COOH) but not the -carboxaldehyde (CHO) metabolites induce peroxidative damage but in a different pattern. Surprisingly, the chlorothiazolyl -CHO and -COOH metabolites induce chlorosis but no clear superimposable peroxidative damage or cell death. Four metallo-oxidases known to modulate reactive oxygen species were not sensitive in vitro to the parent neonicotinoid itself but were to several CHO and COOH metabolites and related compounds, with a sensitivity order of CHO > COOH and tyrosinase > xanthine oxidase and aldehyde oxidase > catalase. Although metallo-oxidase inhibition does not correlate overall with lesion formation, it may play an as yet unknown role in plant response to neonicotinoids.
authors.affiliation: Environmental Chemistry and Toxicology Laboratory, Department of Environmental Science, Policy and Management, University of California, Berkeley, California 94720-3112, United States.
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Ford
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Gulevich
authors.forename: Tami L
authors.initials: TL
authors.lastname: Swenson
authors.forename: John E
authors.initials: JE
authors.lastname: Casida
mesh_terms: D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007306:Insecticides / Q000494:pharmacology*; D009574:Nitro Compounds / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects*; D010088:Oxidoreductases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010940:Plant Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013025:Glycine max / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D007306:Insecticides; D009574:Nitro Compounds; D010940:Plant Proteins; D010088:Oxidoreductases