Department of Integrated Pest Management, Aarhus University, Denmark.
Pest Manag Sci. 2010 Nov;66(11):1257-62. doi: 10.1002/ps.2007.
Neonicotinoid action as well as resistance involves interaction with nicotinic acetylcholine receptors (nAChRs). In the housefly, neonicotinoid resistance also involves cytochrome P450, as indicated by bioassay with synergist as well as altered expression. In bioassay, synergism was only partial and indicated possible target-site resistance. The nAChR α2 subunit is important in neonicotinoid toxicity to insects, and gene expression of the Mdα2 subunit was investigated in field populations and laboratory strains of neonicotinoid-resistant and insecticide-susceptible houseflies, Musca domestica L. The genomic sequence covering exon III-VII of Mdα2 was analysed for mutations.
Gene expression profiling of Mdα2 revealed notable differences between neonicotinoid-resistant and insecticide-susceptible houseflies. On average, the neonicotinoid-resistant field population 766b and the imidacloprid selected strain 791imi had 60% lower copy numbers of Mdα2 compared with the susceptible reference strain. Sequencing of exon III-VII of the Mdα2, encoding acetylcholine binding-site regions and three out of four transmembrane domains, did not reveal any mutations explaining the increased neonicotinoid tolerance in the strains examined.
Previous discoveries and the results of this study suggest that the neonicotinoid resistance mechanism in Danish houseflies involves both cytochrome P450 monooxygenase-mediated detoxification and reduced expression of the nAChR subunit α2.
新烟碱类药物的作用和抗药性都涉及与烟碱型乙酰胆碱受体（nAChRs）的相互作用。在家蝇中，新烟碱类药物的抗药性也涉及细胞色素 P450，这一点可以通过增效剂的生物测定以及表达的改变来证明。在生物测定中，增效作用只是部分的，并表明可能存在靶位抗性。nAChRα2 亚基在新烟碱类药物对昆虫的毒性中很重要，因此研究了田间种群和新烟碱类药物抗性和杀虫剂敏感的家蝇（Musca domestica L.）实验室品系中 Mdα2 亚基的基因表达。对包含 Mdα2 外显子 III-VII 的基因组序列进行了突变分析。
Mdα2 的基因表达谱分析显示，新烟碱类药物抗性和杀虫剂敏感的家蝇之间存在显著差异。平均而言，新烟碱类药物抗性田间种群 766b 和吡虫啉选择的菌株 791imi 的 Mdα2 拷贝数比敏感参考菌株低 60%。对编码乙酰胆碱结合位点区域和四个跨膜结构域中的三个的 Mdα2 的外显子 III-VII 进行测序，没有发现任何突变可以解释所研究的菌株中对新烟碱类药物耐受性的增加。
先前的发现和本研究的结果表明，丹麦家蝇中的新烟碱类药物抗药性机制涉及细胞色素 P450 单加氧酶介导的解毒作用和 nAChR 亚基α2 的表达降低。
