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Jiang J, Huang LX, Chen F, Sheng CW, Huang QT, Han ZJ, Zhao CQ. Novel alternative splicing of GABA receptor RDL exon 9 from Laodelphax striatellus modulates agonist potency. INSECT SCIENCE 2021; 28:757-768. [PMID: 32293803 DOI: 10.1111/1744-7917.12789] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 04/01/2020] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
The resistance to dieldrin gene (RDL) encodes the primary subunit of the insect ionotropic γ-aminobutyric acid (GABA) receptor (GABAR), which is the target of phenylpyrazole and isoxazoline insecticides. The splice variants in exons 3 and 6 of RDL, which have been widely explored in many insects, modulate the agonist potency of the homomeric RDL GABAR and potentially play an important role in the development of insects. In the present study, four splice variants of exon 9 were identified in RDL of the small brown planthopper, Laodelphax striatellus (LsRDL), resulting in LsRDL-9a, LsRDL-9a', LsRDL-9b, and LsRDL-9c. LsRDL-9a has one more amino acid (E, glutamic acid) compared with LsRDL-9a', and LsRDL-9b lacked two amino acids and had seven different amino acids compared with LsRDL-9c. Two-electrode voltage-clamp recording on LsRDLs expressed in Xenopus oocytes showed that alternative splicing of exon 9 has significant impact on LsRDL sensitivity to the agonists GABA and β-alanine, whereas no significant difference was observed in the potencies of the non-competitive antagonists (NCAs) ethiprole and fluralaner on the splice variants. Our results suggest that alternative splicing of RDL exon 9 broadens functional capabilities of the GABAR in L. striatellus by influencing the action of GABA.
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Affiliation(s)
- Jie Jiang
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Li-Xin Huang
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Feng Chen
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Cheng-Wang Sheng
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
- College of Plant Protection, Anhui Agricultural University, Hefei, China
| | - Qiu-Tang Huang
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Zhao-Jun Han
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Chun-Qing Zhao
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
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Suzuki T, Yamato S. Oxazosulfyl, a Novel Sulfyl Insecticide, Binds to and Stabilizes the Voltage-Gated Sodium Channels in the Slow-Inactivated State. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:4048-4055. [PMID: 33793218 DOI: 10.1021/acs.jafc.0c04617] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Oxazosulfyl is the first representative of a novel sulfyl class of insecticides with a potent and cross-spectrum insecticidal activity, albeit with an unclear mechanism of action. As a potential agent of pest control in rice fields, we investigated the action of oxazosulfyl on the nervous system and voltage-gated sodium channels in insects. After the injection of 10 μg of oxazosulfyl, American cockroaches (Periplaneta americana) were quickly paralyzed, which persisted for more than 7 days. Extracellular recordings revealed a depressed spontaneous nerve activity in the cockroaches injected with oxazosulfyl, which specifically affected the voltage-gated sodium channels (in German cockroaches (Blattella germanica) expressed in Xenopus oocytes) in the slow-inactivated state resulting in the inhibition of sodium currents. The potency of oxazosulfyl and other sodium channel blockers to block sodium channels was consistent with their insecticidal activity. Thus, we conclude that the action mode of oxazosulfyl involves the state-dependent blockage of voltage-gated sodium channels.
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Affiliation(s)
- Tatsuya Suzuki
- Health & Crop Sciences Research Laboratory, Sumitomo Chemical Co., Ltd., 2-1 Takatsukasa 4-chome, Takarazuka, Hyogo 665-8555, Japan
| | - Seiji Yamato
- Health & Crop Sciences Research Laboratory, Sumitomo Chemical Co., Ltd., 2-1 Takatsukasa 4-chome, Takarazuka, Hyogo 665-8555, Japan
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Jeschke P. Status and outlook for acaricide and insecticide discovery. PEST MANAGEMENT SCIENCE 2021; 77:64-76. [PMID: 32926594 PMCID: PMC7756306 DOI: 10.1002/ps.6084] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 09/10/2020] [Accepted: 09/14/2020] [Indexed: 05/03/2023]
Abstract
To guarantee sustainability and progress, the agrochemical industry is faced with several major challenges. Currently, loss of active ingredients due to consumer perception, changing grower needs and ever-changing regulatory requirements is far higher than the number being introduced into the market. Therefore, there is a need to develop new products that can provide improved efficacy, selectivity and favorable environmental profiles. Strategies to achieve these goals are the search for acaricides and insecticides with new modes of action, or the discovery of novel molecules with activity on the most attractive target sites having resistance breaking properties against pest species. In this context, the introduction of halogen atoms or asymmetric centers into an active ingredient remains an important tool to modulate their properties, but so too is the pro-pesticide concept. This review gives an overview of agrochemicals launched over the past 8 years, reflects new insights into known mechanisms of action, and describes the status and outlook for acaricide and insecticide discovery.
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Affiliation(s)
- Peter Jeschke
- Bayer AG, Research & Development, Crop SciencePest Control ChemistryMonheim am RheinGermany
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Gao Y, Zhang Y, Wu F, Pei J, Luo X, Ju X, Zhao C, Liu G. Exploring the Interaction Mechanism of Desmethyl-broflanilide in Insect GABA Receptors and Screening Potential Antagonists by In Silico Simulations. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:14768-14780. [PMID: 33274636 DOI: 10.1021/acs.jafc.0c05728] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Broflanilide, a novel insecticide, is classified as a negative allosteric modulator (NAM) of insect γ-aminobutyric acid (GABA) receptors (GABARs) as desmethyl-broflanilide (DMBF) allosterically inhibits the GABA-induced responses. The G277M mutation of the Drosophila melanogaster GABAR subunit has been reported to abolish the inhibitory activity of DMBF. The binding mode of DMBF in insect GABARs needs to be clarified to understand the underlying mechanism of this mutation and to develop novel, efficient NAMs of insect GABARs. Here, we found that a hydrogen bond formed between DMBF and G277 of the D. melanogaster GABAR model might be the key interaction for the antagonism of DMBF by in silico simulations. The volume increase induced by the G277M mutation blocks the entrance of the binding pocket, making it difficult for DMBF to enter the binding pocket and thereby decreasing its activity. The following virtual screening and bioassay results identified a novel NAM candidate of insect GABARs. Overall, we reported a possible binding mode of DMBF in insect GABARs and proposed the insensitivity mechanism of the G277M mutant GABAR to DMBF using molecular simulations. The identified NAM candidates might provide more alternatives or potentials for the design of GABAR-targeting insecticides.
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Affiliation(s)
- Ya Gao
- Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205, P. R. China
| | - Yichi Zhang
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Fengshou Wu
- Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205, P. R. China
| | - Jianfeng Pei
- Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, P. R. China
| | - Xiaogang Luo
- Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205, P. R. China
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, P. R. China
| | - Xiulian Ju
- Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205, P. R. China
| | - Chunqing Zhao
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Genyan Liu
- Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205, P. R. China
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Guest M, Goodchild JA, Bristow JA, Flemming AJ. RDL A301S alone does not confer high levels of resistance to cyclodiene organochlorine or phenyl pyrazole insecticides in Plutella xylostella. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2019; 158:32-39. [PMID: 31378358 DOI: 10.1016/j.pestbp.2019.04.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/01/2019] [Accepted: 04/12/2019] [Indexed: 06/10/2023]
Abstract
Mutations in the GABA-gated chloride channel are associated with resistance to cyclodiene organochlorine and phenyl pyrazole insecticides. The best characterised of these is A301S, which was initially identified in a Dieldrin resistant strain of Drosophila melanogaster. The orthologous mutation has been found in a variety of different crop pests including the diamond back moth Plutella xylostella. However, the contribution of this mutation to resistance in this species remains unclear. We have used the CRISPR/Cas9 system in order to edit Plutella xylostella PxGABARalpha1 to Serine at the 301 orthologous position (282 in PxGABARalpha1) in an insecticide sensitive strain isolated from Vero Beach (VB) USA. In this edited line, no high level of resistance is conferred to Dieldrin, Endosulfan or Fipronil, rather only a subtle shift in sensitivity which could not confer commercially important resistance. We conclude that the high level of commercial resistance to cyclodiene organochlorine and phenyl pyrazole insecticides observed in some field isolates of Plutella xylostella cannot arise from A282S in PxGABARalpha1 alone.
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Affiliation(s)
- M Guest
- Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK.
| | - J A Goodchild
- Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK
| | - J A Bristow
- Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK
| | - A J Flemming
- Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK
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Sheng CW, Casida JE, Durkin KA, Chen F, Han ZJ, Zhao CQ. Fiprole insecticide resistance of Laodelphax striatellus: electrophysiological and molecular docking characterization of A2'N RDL GABA receptors. PEST MANAGEMENT SCIENCE 2018; 74:2645-2651. [PMID: 29718557 DOI: 10.1002/ps.5059] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 04/20/2018] [Accepted: 04/27/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Phenylpyrazole (fiprole) insecticides, including ethiprole, fipronil and flufiprole with excellent activity on rice planthoppers, are very important in Asia but resistance has developed after decades of use. The molecular mechanism of fipronil- but not ethiprole-resistance has been previously studied in rice planthoppers. In our laboratory, a small brown planthopper Laodelphax striatellus strain with ethiprole-resistance was cultured and the molecular mechanisms of ethiprole resistance and of cross-resistance among fiprole insecticides were investigated. RESULTS Ethiprole-resistant L. striatellus has >5000-fold resistance compared to the susceptible strain, and exhibits around 200-fold cross-resistance with fipronil and flufiprole. RDL genes were isolated from susceptible and ethiprole-resistant L. striatellus and expressed in Xenopus oocytes. Electrophysiological studies showed fiprole insecticides inhibited γ-aminobutyric acid (GABA)-induced current with IC50 = 0.1-1.4 μM to LsRDL-S homomers. In LsRDL-R with A2'N mutation, only 1-13% inhibition was observed on treatment with 10 μM ethiprole, fipronil or flufiprole. Homology models indicate A2'N mutation allows crosslinking hydrogen bonding between Asn sidechains at the 2' position around the channel pore, blocking insecticides from interacting near this position. In contrast, insecticides showed favorable binding near A2' in wild-type L. striatellus. CONCLUSION Cross-resistance is increasing for fiprole insecticides in L. striatellus and management strategies are necessary to minimize resistance. © 2018 Society of Chemical Industry.
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Affiliation(s)
- Cheng-Wang Sheng
- Key Laboratory of Integrated Pest Management in Crops in Eastern China (Ministry of Agriculture of China), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - John E Casida
- Environmental Chemistry and Toxicology Laboratory, Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA
| | - Kathleen A Durkin
- Molecular Graphics and Computation Facility, College of Chemistry, University of California, Berkeley, CA, USA
| | - Feng Chen
- Key Laboratory of Integrated Pest Management in Crops in Eastern China (Ministry of Agriculture of China), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Zhao-Jun Han
- Key Laboratory of Integrated Pest Management in Crops in Eastern China (Ministry of Agriculture of China), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Chun-Qing Zhao
- Key Laboratory of Integrated Pest Management in Crops in Eastern China (Ministry of Agriculture of China), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
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Nakao T. Mechanisms of resistance to insecticides targeting RDL GABA receptors in planthoppers. Neurotoxicology 2017; 60:293-298. [DOI: 10.1016/j.neuro.2016.03.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 03/11/2016] [Accepted: 03/17/2016] [Indexed: 11/17/2022]
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Taylor-Wells J, Jones AK. Variations in the Insect GABA Receptor, RDL, and Their Impact on Receptor Pharmacology. ACS SYMPOSIUM SERIES 2017. [DOI: 10.1021/bk-2017-1265.ch001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Jennina Taylor-Wells
- Faculty of Health and Life Sciences, Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford OX3 8NZ, United Kingdom
| | - Andrew K. Jones
- Faculty of Health and Life Sciences, Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford OX3 8NZ, United Kingdom
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Nakao T, Banba S. Broflanilide: A meta-diamide insecticide with a novel mode of action. Bioorg Med Chem 2016; 24:372-7. [DOI: 10.1016/j.bmc.2015.08.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 07/31/2015] [Accepted: 08/12/2015] [Indexed: 10/23/2022]
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Feyereisen R, Dermauw W, Van Leeuwen T. Genotype to phenotype, the molecular and physiological dimensions of resistance in arthropods. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2015; 121:61-77. [PMID: 26047113 DOI: 10.1016/j.pestbp.2015.01.004] [Citation(s) in RCA: 189] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 01/06/2015] [Accepted: 01/07/2015] [Indexed: 05/13/2023]
Abstract
The recent accumulation of molecular studies on mutations in insects, ticks and mites conferring resistance to insecticides, acaricides and biopesticides is reviewed. Resistance is traditionally classified by physiological and biochemical criteria, such as target-site insensitivity and metabolic resistance. However, mutations are discrete molecular changes that differ in their intrinsic frequency, effects on gene dosage and fitness consequences. These attributes in turn impact the population genetics of resistance and resistance management strategies, thus calling for a molecular genetic classification. Mutations in structural genes remain the most abundantly described, mostly in genes coding for target proteins. These provide the most compelling examples of parallel mutations in response to selection. Mutations causing upregulation and downregulation of genes, both in cis (in the gene itself) and in trans (in regulatory processes) remain difficult to characterize precisely. Gene duplications and gene disruption are increasingly reported. Gene disruption appears prevalent in the case of multiple, hetero-oligomeric or redundant targets.
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Affiliation(s)
- René Feyereisen
- INRA, Institut Sophia Agrobiotech, Sophia Antipolis, France.
| | - Wannes Dermauw
- Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
| | - Thomas Van Leeuwen
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands.
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Nakao T, Banba S. Minireview: Mode of action of meta-diamide insecticides. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2015; 121:39-46. [PMID: 26047110 DOI: 10.1016/j.pestbp.2014.09.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Revised: 09/24/2014] [Accepted: 09/24/2014] [Indexed: 06/04/2023]
Abstract
Meta-diamides [3-benzamido-N-(4-(perfluoropropan-2-yl)phenyl)benzamides] are a distinct class of RDL GABA receptor noncompetitive antagonists showing high insecticidal activity against Spodoptera litura. The mode of action of the meta-diamides was demonstrated to be distinct from that of conventional noncompetitive antagonists (NCAs) such as fipronil, picrotoxin, lindane, dieldrin, and α-endosulfan. It was suggested that meta-diamides act at or near G336 in the M3 region of the Drosophila RDL GABA receptor. Although the site of action of the meta-diamides appears to overlap with that of macrocyclic lactones including avermectins and milbemycins, differential effects of mutations on the actions of the meta-diamides and the macrocyclic lactones were observed. Molecular modeling studies revealed that the meta-diamides may bind to an inter-subunit pocket near G336 in the Drosophila RDL GABA receptor better when in the closed state, which is distinct from the NCA-binding site, which is in a channel formed by M2s. In contrast, the macrocyclic lactones were suggested to bind to an inter-subunit pocket near G336 in the Drosophila RDL GABA receptor when in the open state. Furthermore, mechanisms underlying the high selectivity of meta-diamides are discussed. This minireview highlights the unique features of novel meta-diamide insecticides and demonstrates why meta-diamides are anticipated to become prominent insecticides that are effective against pests resistant to cyclodienes and fipronil.
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Affiliation(s)
- Toshifumi Nakao
- Agrochemicals Research Center, Mitsui Chemicals Agro, Inc., Mobara, Chiba 297-0017, Japan.
| | - Shinichi Banba
- Agrochemicals Research Center, Mitsui Chemicals Agro, Inc., Mobara, Chiba 297-0017, Japan
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Wei Q, Wu SF, Niu CD, Yu HY, Dong YX, Gao CF. Knockdown of the ionotropic γ-aminobutyric acid receptor (GABAR) RDL gene decreases fipronil susceptibility of the small brown planthopper, Laodelphax striatellus (Hemiptera: Delphacidae). ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2015; 88:249-261. [PMID: 25808850 DOI: 10.1002/arch.21232] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Insect γ-aminobutyric acid receptors (GABARs) are important molecular targets of cyclodiene and phenylpyrazole insecticides. Previously GABARs encoding rdl (resistant to dieldrin) genes responsible for dieldrin and fipronil resistance were identified in various economically important insect pests. In this study, we cloned the open reading frame cDNA sequence of rdl gene from fipronil-susceptible and fipronil-resistant strains of Laodelphax striatellus (Lsrdl). Sequence analysis confirmed the presence of a previously identified resistance-conferring mutation. Different alternative splicing variants of Lsrdl were noted. Injection of dsLsrdl reduced the mRNA abundance of Lsrdl by 27-82%, and greatly decreased fipronil-induced mortality of individuals from both susceptible and resistant strains. These data indicate that Lsrdl encodes a functional RDL subunit that mediates susceptibility to fipronil. Additionally, temporal and spatial expression analysis showed that Lsrdl was expressed at higher levels in eggs, fifth-instar nymphs, and female adults than in third-instar and fourth-instar nymphs. Lsrdl was predominantly expressed in the heads of 2-day-old female adults. All these results provide useful background knowledge for better understanding of fipronil resistance related ionotropic GABA receptor rdl gene expressed variants and potential functional differences in insects.
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Affiliation(s)
- Qi Wei
- State and Local Joint Engineering Research Center of Green Pesticide Invention and Application, Department of Pesticide Sciences, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
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Nakao T, Banba S, Nomura M, Hirase K. Meta-diamide insecticides acting on distinct sites of RDL GABA receptor from those for conventional noncompetitive antagonists. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2013; 43:366-375. [PMID: 23416568 DOI: 10.1016/j.ibmb.2013.02.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 02/01/2013] [Accepted: 02/04/2013] [Indexed: 06/01/2023]
Abstract
The RDL GABA receptor is an attractive target of insecticides. Here we demonstrate that meta-diamides [3-benzamido-N-(4-(perfluoropropan-2-yl)phenyl)benzamides] are a distinct class of RDL GABA receptor antagonists showing high insecticidal activity against Spodoptera litura. We also suggest that the mode of action of the meta-diamides is distinct from that of conventional noncompetitive antagonists (NCAs), such as fipronil, picrotoxin, lindane, dieldrin, and α-endosulfan. Using a membrane potential assay, we examined the effects of the meta-diamide 3-benzamido-N-(2-bromo-4-(perfluoropropan-2-yl)-6-(trifluoromethyl)phenyl)-2-fluorobenzamide (meta-diamide 7) and NCAs on mutant Drosophila RDL GABA receptors expressed in Drosophila Mel-2 cells. NCAs had little or no inhibitory activity against at least one of the three mutant receptors (A2'S, A2'G, and A2'N), which were reported to confer resistance to NCAs. In contrast, meta-diamide 7 inhibited all three A2' mutant receptors, at levels comparable to its activity with the wild-type receptor. Furthermore, the A2'S·T6'V mutation almost abolished the inhibitory effects of all NCAs. However, meta-diamide 7 inhibited the A2'S・T6'S mutant receptor at the same level as its activity with the wild-type receptor. In contrast, a G336M mutation in the third transmembrane domain of the RDL GABA receptor abolished the inhibitory activities of meta-diamide 7, although the G336M mutation had little effect on the inhibitory activities of conventional NCAs. Molecular modeling studies also suggested that the binding site of meta-diamides was different from those of NCAs. Meta-diamide insecticides are expected to be prominent insecticides effective against A2' mutant RDL GABA receptors with a different mode of action.
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Affiliation(s)
- Toshifumi Nakao
- Agrochemicals Research Center, Mitsui Chemicals Agro, Inc., Mobara, Chiba 297-0017, Japan.
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