The cys-loop ligand-gated ion channel gene superfamily of the Colorado potato beetle, Leptinotarsa decemlineata.

backgroundThe insect cys-loop ligand-gated ion channel (cysLGIC) superfamily includes nicotinic acetylcholine receptors (nAChRs), γ-aminobutyric acid (GABA) receptors, glutamate- or histamine-gated chloride channels (GluCls and HisCls), pH-sensitive chloride channels (pHCls) and several other functionally uncharacterized receptors. Several of these receptors are target sites of neonicotinoids and other insecticides. Characterizing sequences of cysLGIC genes can facilitate the study of functional expression of subunits allowing insecticide/receptor interaction research, provide candidate targets for RNAi interventions, and can promote molecular resistance monitoring tools development. The Colorado potato beetle (CPB) is an agricultural pest that threatens the production of solanaceous crops. Although this insect shows frequent evolution of insecticide resistance, its cysLGIC superfamily is not well characterized.

resultsTwenty-two candidate CPB cysLGIC subunit genes were identified, and the functional regions of their protein sequences were annotated. CPB possesses twenty-two candidate cysLGIC subunit genes such as nAChR α4, nAChR α6, Rdl, and GluCl subunits, with similar sequence, structure, and alternative exon use as that of other insects. RNA A-to-I editing was observed of nAChR α6. Two copies of the pHCl subunit gene were identified, the first duplication of this gene observed in insects.

conclusionThe number of cysLGIC superfamily genes is similar to that of other insect species. Alternative splicing and RNA editing conserved in insect species were also identified in expected subunits, potentially contributing to structural and functional diversity of the receptor. Evidence of naturally truncated nAChR α4 and duplicated pHCl was observed, which invites future validation.