Molecular characterization and expression pattern of three GABA receptor-like subunits in the small brown planthopper Laodelphax striatellus (Hemiptera: Delphacidae)

- Three GABA-gated ion channel genes (Lslcch3, Lsgrd and Ls8916) were cloned from Laodelphax striatellus.
- LsLCCH3, LsGRD and Ls8916 showed a high level of amino acid sequence identities (71.6-79%, 44.3-81.9% and 60.7-71.9%, respectively) to the corresponding genes from different insect orders.
- The highest mRNA expressions of the three subunits were observed in fifth-instar nymph and adults.
- Transcripts of three GABA receptor-like subunits were predominantly expressed in the heads of 2-d old female adults.

Ionotropic γ-aminobutyric acid (GABA)-gated chloride channel receptors mediate rapid inhibitory neurotransmission in vertebrates and invertebrates. GABA receptors are well known to be the molecular targets of synthetic insecticides or parasiticides. Three GABA receptor-like subunits, LsLCCH3, LsGRD and LS8916, of the small brown planthopper, Laodelphax striatellus (Fallén), a major insect pest of crop systems in East Asia, had been identified and characterized in this study. All three genes were cloned using the reverse transcriptase polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). They shared common structural features with known Cys-loop ligand-gated ion channels (LGICs): the well-conserved dicysteine-loop structures, an extracellular N-terminal domain containing six distinct regions (loops A-F) that form the ligand binding sites and four transmembrane regions (TM1-4). Additionally, temporal and spatial transcriptional profiling analysis indicated that Lslcch3 was significantly higher than the other two genes. All of them were expressed at higher levels in fifth-instar nymph and adults than in eggs and from first- to fourth-instar nymph. They were predominantly expressed in the heads of 2-d old female adults. These findings enhanced our understanding of cys-loop LGIC functional characterization in Hemiptera and provided a useful basis for the development of improved insecticides that targeting this important agricultural pest.

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