title: Reduction in mRNA and protein expression of a nicotinic acetylcholine receptor α8 subunit is associated with resistance to imidacloprid in the brown planthopper, Nilaparvata lugens.
abstract: Target-site resistance is commonly caused by qualitative changes in insecticide target-receptors and few studies have implicated quantitative changes in insecticide targets in resistance. Here we show that resistance to imidacloprid in a selected strain of Nilaparvata lugens is associated with a reduction in expression levels of the nicotinic acetylcholine receptor (nAChR) subunit Nlα8. Synergism bioassays of the selected strain suggested resistance was conferred, in part, by a target-site mechanism. Sequencing of N. lugens nAChR subunit genes identified no mutations associated with resistance, however, a decrease in mRNA and protein levels of Nlα8 was observed during selection. RNA interference knockdown of Nlα8 decreased the sensitivity of N. lugens to imidacloprid, demonstrating that a decrease in Nlα8 expression is sufficient to confer resistance in vivo. Radioligand binding assays revealed that the affinity of the high-affinity imidacloprid-binding site of native nAChRs was reduced by selection, and reducing the amount of Nlα8 cRNA injected into Xenopus oocytes significantly decreased imidacloprid potency on recombinant receptors. Taken together, these results provide strong evidence that a decrease in Nlα8 levels confers resistance to imidacloprid in N. lugens, and thus provides a rare example of target-site resistance associated with a quantitative rather than qualitative change. In insects, target-site mutations often cause high resistance to insecticides, such as neonicotinoids acting on nicotinic acetylcholine receptors (nAChRs). Here we found that a quantitative change in target-protein level, decrease in mRNA and protein levels of Nlα8, contributed importantly to imidacloprid resistance in Nilaparvata lugens. This finding provides a new target-site mechanism of insecticide resistance.
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors.forename: Yixi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors.forename: Baojun
authors.initials: B
authors.lastname: Yang
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors.forename: Lixin
authors.initials: L
authors.lastname: Huang
authors.affiliation: Department of Biological Chemistry and Crop Protection, Rothamsted Research, Harpenden, Hertfordshire, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Bass
authors.affiliation: Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors.forename: Zewen
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000818:Animals; D018678:Cholinergic Agents / Q000494:pharmacology*; D004351:Drug Resistance / Q000187:drug effects; D004357:Drug Synergism; D005786:Gene Expression Regulation / Q000187:drug effects*; D007093:Imidazoles / Q000494:pharmacology*; D007313:Insecta; D007306:Insecticides / Q000494:pharmacology; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000494:pharmacology*; D034622:RNA Interference / Q000502:physiology; D012330:RNA, Double-Stranded / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D011978:Receptors, Nicotinic / Q000235:genetics* / Q000378:metabolism*; D014316:Tritium / Q000493:pharmacokinetics
chemical_list: D018678:Cholinergic Agents; D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D011978:Receptors, Nicotinic; D014316:Tritium; C082359:imidacloprid
keywords: insecticide resistance; nicotinic acetylcholine receptors; quantity change; target insensitivity