title: Alternatively spliced sodium channel transcripts expressed in field strains of the diamondback moth.
abstract: The frequencies of the L1014F and T929I mutations, both of which are involved in nerve insensitive resistance to pyrethroids, were examined in field and laboratory strains of the diamondback moth, Plutella xylostella at DNA and RNA levels. Results showed that the resistance allele frequencies at the L1014F and T929I sites in the field strains were respectively, 82.8-100% and 72.9-94.4%. No posttranscriptional regulation of the L1014F mutation was observed. The examined insects were classifiable into four groups according to the expression patterns of mutually exclusive exons 18a and 18b. Most insects in the field strains expressed transcripts containing exon 18b more abundantly than those containing exon 18a, although both transcripts were expressed with similar proportions in all insects of the laboratory strains. Some other insects expressed a chimeric transcript comprising parts of exons 18a and 18b. Deduced amino acid sequences of the chimeric transcript encoded amino substitution from Met to Ile at the site corresponding to the super-kdr mutation (M918T) in Musca domestica. The frequencies of the M918I mutation in the field strains were 5.0-19.4%. Analyses of the genomic organization revealed that the chimeric sequences are encoded in the genome.
authors.affiliation: Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama 710-0046, Japan. sonodas@rib.okayama-u.ac.jp
authors.forename: Shoji
authors.initials: S
authors.lastname: Sonoda
authors.forename: Chikako
authors.initials: C
authors.lastname: Igaki
authors.forename: Hisaaki
authors.initials: H
authors.lastname: Tsumuki
mesh_terms: D017398:Alternative Splicing; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D005091:Exons; D015870:Gene Expression; D005787:Gene Frequency; D049750:Genome, Insect; D007305:Insecticide Resistance / Q000235:genetics; D007306:Insecticides; D007928:Lethal Dose 50; D008969:Molecular Sequence Data; D009036:Moths / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011722:Pyrethrins; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D007306:Insecticides; D011722:Pyrethrins; D015222:Sodium Channels