Neonicotinoid binding, toxicity and expression of nicotinic acetylcholine receptor subunits in the aphid Acyrthosiphon pisum

PLoS One. 2014 May 6;9(5):e96669. doi: 10.1371/journal.pone.0096669. eCollection 2014.

Abstract

Neonicotinoid insecticides act on nicotinic acetylcholine receptor and are particularly effective against sucking pests. They are widely used in crops protection to fight against aphids, which cause severe damage. In the present study we evaluated the susceptibility of the pea aphid Acyrthosiphon pisum to the commonly used neonicotinoid insecticides imidacloprid (IMI), thiamethoxam (TMX) and clothianidin (CLT). Binding studies on aphid membrane preparations revealed the existence of high and low-affinity binding sites for [3H]-IMI (Kd of 0.16 ± 0.04 nM and 41.7 ± 5.9 nM) and for the nicotinic antagonist [125I]-α-bungarotoxin (Kd of 0.008 ± 0.002 nM and 1.135 ± 0.213 nM). Competitive binding experiments demonstrated that TMX displayed a higher affinity than IMI for [125I]-α-bungarotoxin binding sites while CLT affinity was similar for both [125I]-α-bungarotoxin and [3H]-IMI binding sites. Interestingly, toxicological studies revealed that at 48 h, IMI (LC50 = 0.038 µg/ml) and TMX (LC50 = 0.034 µg/ml) were more toxic than CLT (LC50 = 0.118 µg/ml). The effect of TMX could be associated to its metabolite CLT as demonstrated by HPLC/MS analysis. In addition, we found that aphid larvae treated either with IMI, TMX or CLT showed a strong variation of nAChR subunit expression. Using semi-quantitative PCR experiments, we detected for all insecticides an increase of Apisumα10 and Apisumβ1 expressions levels, whereas Apisumβ2 expression decreased. Moreover, some other receptor subunits seemed to be differently regulated according to the insecticide used. Finally, we also demonstrated that nAChR subunit expression differed during pea aphid development. Altogether these results highlight species specificity that should be taken into account in pest management strategies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aphids / drug effects*
  • Aphids / growth & development
  • Aphids / metabolism*
  • Binding Sites
  • Bungarotoxins / chemistry
  • Bungarotoxins / metabolism
  • Cell Membrane / metabolism
  • Chromatography, High Pressure Liquid
  • Guanidines / chemistry
  • Guanidines / metabolism
  • Guanidines / toxicity
  • Imidazoles / chemistry
  • Imidazoles / metabolism
  • Imidazoles / toxicity
  • Insecticides / chemistry
  • Insecticides / metabolism*
  • Insecticides / toxicity
  • Larva / drug effects
  • Larva / metabolism
  • Neonicotinoids
  • Nicotinic Antagonists / chemistry
  • Nicotinic Antagonists / metabolism
  • Nitro Compounds / chemistry
  • Nitro Compounds / metabolism
  • Nitro Compounds / toxicity
  • Oxazines / chemistry
  • Oxazines / metabolism
  • Oxazines / toxicity
  • Protein Binding
  • Protein Subunits / chemistry
  • Protein Subunits / metabolism
  • Receptors, Nicotinic / chemistry
  • Receptors, Nicotinic / metabolism*
  • Tandem Mass Spectrometry
  • Thiamethoxam
  • Thiazoles / chemistry
  • Thiazoles / metabolism
  • Thiazoles / toxicity

Substances

  • Bungarotoxins
  • Guanidines
  • Imidazoles
  • Insecticides
  • Neonicotinoids
  • Nicotinic Antagonists
  • Nitro Compounds
  • Oxazines
  • Protein Subunits
  • Receptors, Nicotinic
  • Thiazoles
  • clothianidin
  • imidacloprid
  • Thiamethoxam

Grants and funding

This work was supported by a specific grant from the French Institute for Agricultural Research (INRA), the Department ‘Santé des Plantes et Environnement (SPE)’: USC RCIM/UMR BIO3P. E. Taillebois acknowledges the French ‘Ministère de la Recherche et de l’Enseignement Supérieur’ for financial support in the framework of Ph.D grant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.