Spatiotemporally different expression of alternatively spliced GABA receptor subunit transcripts in the housefly Musca domestica

Insect γ-aminobutyric acid (GABA) receptors are important as major inhibitory neurotransmitter receptors and targets for insecticides. The housefly GABA receptor subunit gene MdRdl is alternatively spliced at exons 3 (a or b) and 6 (c or d) to yield the variants of ac, ad, bc, and bd combinations. In the present study, the expression of the MdRdl transcript in the body parts and in the developmental stages of the housefly Musca domestica was examined by quantitative polymerase chain reaction using specific primers that amplify the combinations of alternative exons. The results indicated that the transcripts of MdRdl, including four combinations, were highly expressed in the adult stage. MdRdlbd was the most abundant in the adult head. The expression pattern did not change in the adult stage over 7 days after eclosion. The expression level of the MdRdl bd transcript in the female head was similar to that of the male head. In contrast, MdRdl bc was the predominant transcript in the pupal head and the adult leg. Because the homomeric Rdl bc GABA receptor has a high affinity for GABA, our results provide grounds for designing agonist or competitive-antagonist insecticides that target the orthosteric site of the GABA receptor containing this Rdl variant.