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

Abstract

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. MdRdl bd 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. K E Y W O R D S alternative splicing, GABA, γ-Aminobutyric acid receptor, housefly, Rdl, spatiotemporal expression Arch. Insect Biochem. Physiol. 2019;101:e21541.wileyonlinelibrary.com/journal/arch

De novo assembly of the transcriptome for Greenbug (Schizaphis graminum Rondani) and analysis on insecticide resistance‐related genes

“…GABA receptor is highly expressed in the neuronal tissues such as brain and ganglia (Kita et al . ), which is in accordance with our result that expression levels of GABA receptor were significantly higher in head and thorax than in abdomen.…”

“…GABA receptor is highly expressed in the neuronal tissues such as brain and ganglia (Kita et al 2019), which is in accordance with our result that expression levels of GABA receptor were significantly higher in head and thorax than in abdomen. Expression pattern of the 12 genes related to insecticide resistance under insecticide stress condition could certify possible involved in detoxification of exogenous compounds to adapt environment.…”

Potential of Competitive Antagonists of Insect Ionotropic γ-Aminobutyric Acid Receptors as Insecticides

“…41−43 In addition, flunitrazepam, which is a representative benzodiazepine allosteric modulator in mammalian GABA A Rs, is a much less effective modulator in the RDL receptors, whereas flunitrazepam was reported to enhance GABAinduced responses in native insect GABARs. 39,40,44 Alternative splicing of rdl at exons 3 and 6 produces four subunit isoforms: RDL ac , RDL ad , RDL bc , and RDL bd 39,45,46 (Figure 3). GABAR agonists and antagonists have different effects on RDL GABARs containing these four splice variants, 47−49 and thus, alternative splicing may increase the physiological and pharmacological diversities of insect RDL GABARs.…”

“…In comparison to mammalian GABAR subunits, the RDL subunit has a longer M3–M4 intracellular loop and the RDL receptor exhibits different pharmacological properties. For instance, insect RDL GABARs are not sensitive to the GABA A R antagonist bicuculline and are activated by both the GABA A R agonist muscimol and the GABA C R agonist 4-aminocrotonic acid. − In addition, flunitrazepam, which is a representative benzodiazepine allosteric modulator in mammalian GABA A Rs, is a much less effective modulator in the RDL receptors, whereas flunitrazepam was reported to enhance GABA-induced responses in native insect GABARs. ,, Alternative splicing of rdl at exons 3 and 6 produces four subunit isoforms: RDL ac , RDL ad , RDL bc , and RDL bd ,, (Figure ). GABAR agonists and antagonists have different effects on RDL GABARs containing these four splice variants, − and thus, alternative splicing may increase the physiological and pharmacological diversities of insect RDL GABARs. ,− RNA editing further diversifies insect GABA receptors. , The RDL receptors expressed in Xenopus oocytes or cell lines should serve as a convenient model to study insect GABARs or as a suitable platform that can be used to screen novel GABAR-targeting insecticides.…”

Functional Characteristics of the Lepidopteran Ionotropic GABA Receptor 8916 Subunit Interacting with the LCCH3 or the RDL Subunit

“…To date, three candidate genes, RDL (resistance to dieldrin), LCCH3 (ligand-gated chloride channel homologue 3), and GRD (GABA and glycine-like receptor of Drosophila ), are considered as iGABA receptor subunits in insects. ,, RDL has been studied in several insect species, such as fruit fly Drosophila melanogaster, small brown planthopper Laodelphax striatellus, and honeybee Apis mellifera. − Due to amino acid sequence homology, it has been suggested that the 8916 gene is a putative GABA receptor subunit that has been identified in many insect species including D. melanogaster, L.…”