The nicotinic acetylcholine receptor subunit Mdalpha6 from Musca domestica is diversified via post-transcriptional modification.
Recent studies showed that deletion of a nicotinic acetylcholine receptor (nAChR) subunit gene, Dalpha6 in Drosophila melanogaster results in a strain that is resistant to spinosad, indicating that Dalpha6 is important for the toxic action of this insecticide. To determine if spinosad resistance in house flies was due to a mutation(s) of Mdalpha6 (the orthologue of Dalpha6 from house flies), cDNAs were cloned and characterized from an insecticide-susceptible and a spinosad-resistant strain of the house fly, Musca domestica. The cDNAs contain a 1470-bp open reading frame encoding 490 amino acid residues, 415-bp 5' untranslated region (UTR) and a polymorphic 3'-UTR of approximately 371 bp. The predicted mature protein possesses 468 amino acid residues, has the typical features of a nAChR alpha subunit and is 97% identical to Dalpha6. Quantitative real-time PCR analysis revealed that Mdalpha6 was expressed in the head and the thorax at 1300- and 26-fold higher levels, respectively, than in the abdomen. There was no difference in the expression level of Mdalpha6 between spinosad-resistant and susceptible strains. Ten isoforms arising from alternative splicing were characterized, with isoform II being most common. A-to-I RNA editing was examined and found at 12 sites: editing at 11 of these sites resulted in an amino acid substitution. Mdalpha6 is linked to autosome 1 (spinosad resistance was previously shown to be linked to autosome 1). Single nucleotide polymorphisms, alternative splicing, mRNA levels and A-to-I RNA editing were compared between head and thorax and between insecticide-susceptible and spinosad-resistant strains. These comparisons indicate that Mdalpha6 is not responsible for spinosad resistance in house flies.
Gao
J-R
JR
Department of Entomology, Comstock Hall, Cornell University, Ithaca, NY 14853, USA.
Deacutis
J M
JM
Scott
J G
JG
D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004338:Drug Combinations; D014644:Genetic Variation; D006793:Houseflies / Q000235:genetics*; D007305:Insecticide Resistance / Q000235:genetics; D018942:Macrolides / Q000633:toxicity; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide; D020033:Protein Isoforms / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics*; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D011978:Receptors, Nicotinic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
D017931:DNA Primers; D018076:DNA, Complementary; D004338:Drug Combinations; D018942:Macrolides; D020033:Protein Isoforms; D021122:Protein Subunits; D011978:Receptors, Nicotinic; C415329:spinosad