The cys-loop ligand-gated ion channel gene superfamilies of the Lepidopteran species, Bombyx mori and Chilo suppressalis.

The rice stem borer, Chilo suppressalis (Walker), is a major pest of rice crops. It is commonly managed by pesticides, several of which act on cys-loop ligand-gated ion channels (cysLGICs). In insects, the cysLGIC superfamily consists of receptors that mediate fast excitatory or inhibitory synaptic transmission in the nervous system as well as performing non-neuronal roles. We present here the cysLGIC superfamily of C. suppressalis as well as that of the silk worm, Bombyx mori (Linnaeus), the first complete gene families from Lepidopteran species, which consists of 27 and 24 subunit-encoding genes, respectively. As with other insects, Chilo and Bombyx possess ion channels predicted to be gated by acetylcholine, γ-aminobutyric acid, glutamate and histamine, as well as orthologues of the Drosophila pH-sensitive chloride channel, CG8916 and CG12344. Both C. suppressalis and B. mori lack GRD (GABA and glycine receptor-like subunit of Drosophila), instead possessing extra RDL (resistance to dieldrin) subunits. Quantitative polymerase chain reaction analysis showed that the C. suppressalis cysLGIC subunits can show differential expression levels throughout the insect's life cycle. Our findings reveal the complete cysLGIC gene families of B. mori and C. suppressalis. These findings enhance our understanding of the evolution of the insect cysLGIC superfamily and provide a useful basis for studying their function and action of pesticides.