Molecular cloning, genomic structure, and genetic mapping of two Rdl‐orthologous genes of GABA receptors in the diamondback moth, Plutella xylostella

Abstract

The Resistance to dieldrin (Rdl) gene encodes a subunit of the insect gamma-aminobutyric acid (GABA) receptor. Cyclodiene resistance in many insects is associated with replacement of a single amino acid (alanine at position 302) with either a serine or a glycine in the Rdl gene. Two Rdl-orthologous genes of GABA receptors (PxGABARalpha1 and PxGABARalpha2) were cloned and sequenced from a susceptible strain (Roth) of Plutella xylostella. PxGABARalpha1 and PxGABARalpha2 showed 84% and 77% identity with the Rdl gene of Drosophila melanogaster at an amino acid level, respectively. The coding regions of PxGABARalpha1 and PxGABARalpha2 both comprise ten exons, with two alternative RNA-splicing forms in exon 3 of both genes. At the orthologous position of alanine-302 in D. melanogaster Rdl, PxGABARalpha1 has a conserved alanine at position 282. PxGABARalpha2 has a serine instead of an alanine at the equivalent position. With two informative DNA markers, both PxGABARalpha1 and PxGABARalpha2 were mapped onto the Z chromosome of P. xylostella.

Neo-sex chromosomes and adaptive potential in tortricid pests

“…2 and 3), and presumably in all other species of the tortricid subfamilies Olethreutinae and Tortricinae, which comprise almost 700 economically important pests worldwide (30). Whereas Rdl orthologs conferring resistance to cyclodiene insecticides are also Z-linked in other Lepidoptera (31,32), the Ace-1 and ABCC2 associated with insensitivity to organophosphates and carbamates, and resistance to Bacillus thuringiensis toxin Cry1Ab, respectively, are assignable to the autosomal linkage group corresponding to B. mori chromosome 15 in distantly related species (15,(33)(34)(35). By contrast, in most tortricids, the sex-linkage of these two genes is thus a direct consequence of F(Z;15).…”

A comparison of the modes of action of novel meta-diamide insecticides and conventional noncompetitive antagonists on the <i>Spodoptera litura</i> RDL GABA receptor

“…In B. mori, Helicoverpa armigera, and H. virescence, three RDL GABA receptor paralogs with Ala, Ser and Gln at the 2′ position were reported. 24,25) Fur- thermore, H. virescence was reported to have two RDL GABA receptor paralogs with Ala and Ser at the 2′ position. 25) It cannot be ruled out that the primers used in this study could not amplify other paralogs.…”

The biology of insecticidal activity and resistance

“…Differences in the fitness impact of A301S in D. melanogaster and L. cuprina are likely to be due to a difference in RDL between the two species. Another layer of complexity is the reported duplication of Rdl in Lepidoptera, of which Bombyx mori, Heliothis virescens and Helicoverpa armigera appear to have three paralogs, while Plutella xylostella and Myzus persicae have at least two paralogs (Anthony et al, 1998;Yuan et al, 2010). In the case of M. persicae, although the A301S allele is fixed in one paralog, the resistance phenotype is associated with the presence of an A301G substitution, suggesting that these genes have been co-opted into distinct functions in the insects (Anthony et al, 1998).…”