Expression patterns, mutation detection and RNA interference of Rhopalosiphum padi voltage-gated sodium channel genes

Abstract

The voltage-gated sodium channel (VGSC) is the target of sodium-channel-blocking insecticides. Traditionally, animals were thought to have only one VGSC gene comprising a α-subunit with four homologous domains (DI–DIV). The present study showed that Rhopalosiphum padi, an economically important crop pest, owned a unique heterodimeric VGSC (H1 and H2 subunits) encoded by two genes (Rpvgsc1 and Rpvgsc2), which is unusual in insects and other animals. The open reading frame (ORF) of Rpvgsc1 consisted 1150 amino acids, and the ORF of Rpvgsc2 had 957 amino acids. Rpvgsc1 showed 64.1% amino acid identity to DI–DII of Drosophila melanogaster VGSC and Rpvgsc2 showed 64.0% amino acid identity to DIII–DIV of D. melanogaster VGSC. A M918L mutation previously reported in pyrethroids-resistant strains of other insects was found in the IIS4-S6 region of R. padi field sample. The two R. padi VGSC genes were expressed at all developmental stages and showed similar expression patterns after treatment with beta-cypermethrin. Knockdown of Rpvgsc1 or Rpvgsc2 caused significant reduction in mortality rate of R. padi after exposure to beta-cypermethrin. These findings suggest that the two R. padi VGSC genes are both functional genes.

Characterisation of imidacloprid resistance in the bird cherry‐oat aphid, Rhopalosiphum padi, a serious pest on wheat crops

“…Organophosphates, carbamates and pyrethroids were widely used to control R. padi for a long time in China before neonicotinoid insecticides were applied instead. 57 Previous field selection by other chemicals with ester bonds could possibly explain the increased activity of CarEs in this study, although further investigations are needed to determine the detailed biochemical mechanisms of the resistance. Actually, the resistant strain IM-R in this study showed different levels of cross-resistance to other chemicals, including organophosphates and carbamate.…”

“…The imidacloprid‐resistant strain in this study originated from a field population in China. Organophosphates, carbamates and pyrethroids were widely used to control R. padi for a long time in China before neonicotinoid insecticides were applied instead . Previous field selection by other chemicals with ester bonds could possibly explain the increased activity of CarEs in this study, although further investigations are needed to determine the detailed biochemical mechanisms of the resistance.…”

Molecular characterization and functional expression of voltage‐gated sodium channel variants in Apolygus lucorum (Meyer‐Dür)

“…Recently, a new heterodimeric Na v family was discovered, in the aphid species Acyrthosiphon pisum , Myzus persicae , Rhopalosiphum padiand and Toxoptera citricida , which carried a unique typical ‘DENS’ (DI‐aspartate; DII‐glutamate; DIII‐asparagine; DIV‐serine) ion selectivity filter. Na v channels are thought to have evolved from a family of channels …”

Conservation of the voltage‐sensitive sodium channel protein within the Insecta

“…Only two species had non‐DEKA residues in the inner ring of the selectivity filter: A. pisum (DENS) and D. novaeangliae (18‐residue deletion). The inner ring residues DENS have been described in other species of aphids ( Aphis citricidus , Myzus persicae and Rhopalosiphum padi ), and these studies found increased Ca 2+ permeability and reduced tetrodotoxin sensitivity relative to DEKA (Amey et al, ; Zuo et al, ; Jiang et al, ). In the inactivation loop, the hydrophobic triad (MFM) was identical for most species except T. castaneum (LMM) and O. borbonicus (LFM).…”