RESUMO
BACKGROUND: Glutamate-gated chloride channels (GluCl) mediate fast inhibitory neurotransmission in invertebrate nervous systems. Although only one GluCl gene was presented in insects, it showed diverse alternative splicing that was speculated could affect channel function and pharmacology. RESULTS: In this study, we isolated GluCl cDNAs from adults of the small brown planthopper (SBPH) Laodelphax striatellus and showed that six L. striatellus GluCl variants (LsGluCl-AS, LsGluCl-BS, LsGluCl-CS, LsGluCl-AL, LsGluCl-BL, LsGluCl-CL) were present in the SBPH. The expression patterns of six variants differed among developmental stages (egg, first- to fifth-instar nymphs, male and female adults) and among the body parts (head, thorax, abdomen, leg) of the female adult SBPH. All the transcripts were abundant in the head of the adult. When expressed in African clawed frog, Xenopus laevis, oocytes, the two functional variants (LsGluCl-AS, LsGluCl-AL) had similar EC50 and IC50 values for L-glutamate and channel blockers picrotoxinin and fipronil. CONCLUSION: This study represents a comprehensive molecular, expression and pharmacological characterisation of GluCl in the SBPH. These findings should be useful in providing more opportunities to discover novel insect control chemicals. © 2016 Society of Chemical Industry.
Assuntos
Canais de Cloreto/genética , Antagonistas de Receptores de GABA-A/farmacologia , Hemípteros/efeitos dos fármacos , Hemípteros/genética , Proteínas de Insetos/genética , Inseticidas/farmacologia , Processamento Alternativo , Sequência de Aminoácidos , Animais , Sequência de Bases , Canais de Cloreto/química , Canais de Cloreto/metabolismo , Clonagem Molecular , DNA Complementar/genética , DNA Complementar/metabolismo , Feminino , Ácido Glutâmico/metabolismo , Hemípteros/crescimento & desenvolvimento , Hemípteros/metabolismo , Proteínas de Insetos/química , Proteínas de Insetos/metabolismo , Dose Letal Mediana , Masculino , Ninfa/efeitos dos fármacos , Ninfa/genética , Ninfa/crescimento & desenvolvimento , Ninfa/metabolismo , Picrotoxina/análogos & derivados , Picrotoxina/farmacologia , Pirazóis/farmacologia , Alinhamento de Sequência , SesterterpenosRESUMO
Insect γ-aminobutyric acid receptors (GABARs) are important molecular targets of cyclodiene and phenylpyrazole insecticides. Previously GABARs encoding rdl (resistant to dieldrin) genes responsible for dieldrin and fipronil resistance were identified in various economically important insect pests. In this study, we cloned the open reading frame cDNA sequence of rdl gene from fipronil-susceptible and fipronil-resistant strains of Laodelphax striatellus (Lsrdl). Sequence analysis confirmed the presence of a previously identified resistance-conferring mutation. Different alternative splicing variants of Lsrdl were noted. Injection of dsLsrdl reduced the mRNA abundance of Lsrdl by 27-82%, and greatly decreased fipronil-induced mortality of individuals from both susceptible and resistant strains. These data indicate that Lsrdl encodes a functional RDL subunit that mediates susceptibility to fipronil. Additionally, temporal and spatial expression analysis showed that Lsrdl was expressed at higher levels in eggs, fifth-instar nymphs, and female adults than in third-instar and fourth-instar nymphs. Lsrdl was predominantly expressed in the heads of 2-day-old female adults. All these results provide useful background knowledge for better understanding of fipronil resistance related ionotropic GABA receptor rdl gene expressed variants and potential functional differences in insects.
