title: The α6 nicotinic acetylcholine receptor subunit of Frankliniella occidentalis is not involved in resistance to spinosad.
abstract: Insects evolve resistance which constrains the sustainable use of insecticides. Spinosyns, a class of environmentally-friendly macrolide insecticides, is not an exception. The mode of inheritance and the mechanisms of resistance to spinosad (the most common spinosyn insecticide) in Frankliniella occidentalis (Western flower thrips, WFT) were investigated in this study. Resistance (170,000-fold) was autosomal and completely recessive. Recent studies showed that deletion of the nicotinic acetylcholine receptor α6 subunit gene resulted in strains of Drosophila melanogaster, Plutella xylostella and Bactrocera dorsalis that are resistant to spinosad, indicating that nAChRα6 subunit maybe important for the toxic action of this insecticide. Conversely, a G275E mutation of this subunit in F. occidentalis was recently proposed as the mechanism of resistance to spinosad. We cloned and characterized nAChRα6 from three susceptible and two spinosad resistant strains from China and the USA. The Foα6 cDNA is 1873bp and the open reading frame is 1458bp which encodes 485 amino acid residues with a predicted molecular weight of 53.5-kDa, the 5' and 3' UTRs are 121 and 294bp, respectively. There was no difference in the cDNA sequence between the resistant and susceptible thrips, suggesting the G275E mutation does not confer resistance in these populations. Ten isoforms of Foα6, arising from alternative splicing, were isolated and did not differ between the spinosad-susceptible and resistant strains. Quantitative real time PCR analysis showed Foα6 was highly expressed in the first instar larva, pupa and adult, and the expression levels were 3.67, 2.47, 1.38 times that of the second instar larva. The expression level was not significantly different between the susceptible and resistant strains. These results indicate that Foα6 is not involved in resistance to spinosad in F. occidentalis from China and the USA.
authors.affiliation: Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 12 Zhongguancun Nandajie, Beijing 100081, China. Electronic address: houwenjie0628@126.com.
authors.forename: Wenjie
authors.initials: W
authors.lastname: Hou
authors.affiliation: Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 12 Zhongguancun Nandajie, Beijing 100081, China. Electronic address: wsliuqiulei@sina.com.
authors.forename: Qiulei
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 12 Zhongguancun Nandajie, Beijing 100081, China. Electronic address: liouyun555@126.com.
authors.forename: Lixia
authors.initials: L
authors.lastname: Tian
authors.affiliation: Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 12 Zhongguancun Nandajie, Beijing 100081, China. Electronic address: wuqingjun@caas.cn.
authors.forename: Qingjun
authors.initials: Q
authors.lastname: Wu
authors.affiliation: Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 12 Zhongguancun Nandajie, Beijing 100081, China. Electronic address: zhangyoujun@caas.cn.
authors.forename: Youjun
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 12 Zhongguancun Nandajie, Beijing 100081, China. Electronic address: xiewen@caas.cn.
authors.forename: Wen
authors.initials: W
authors.lastname: Xie
authors.affiliation: Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 12 Zhongguancun Nandajie, Beijing 100081, China. Electronic address: wangshaoli@caas.cn.
authors.forename: Shaoli
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Entomology, Cornell University, Ithaca, NY 14853, USA. Electronic address: kds397@cornell.edu.
authors.forename: Keri San
authors.initials: KS
authors.lastname: Miguel
authors.affiliation: Department of Entomology and Nematology, University of Florida, Quincy, FL 32351, USA. Electronic address: jef@ufl.edu.
authors.forename: Joe
authors.initials: J
authors.lastname: Funderburk
authors.affiliation: Department of Entomology, Cornell University, Ithaca, NY 14853, USA. Electronic address: jgs5@cornell.edu.
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Scott
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004338:Drug Combinations; D005260:Female; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D018942:Macrolides / Q000494:pharmacology*; D008297:Male; D008969:Molecular Sequence Data; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*; D061149:Thysanoptera / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
chemical_list: D004338:Drug Combinations; D019476:Insect Proteins; D007306:Insecticides; D018942:Macrolides; D011978:Receptors, Nicotinic; C104518:nicotinic receptor alpha6; C415329:spinosad
keywords: Inheritance; Mechanism of resistance; Nicotinic acetylcholine receptor; Spinosyns; Western flower thrips