Cloning, developmental and tissue-specific expression of γ-aminobutyric acid (GABA) receptor alpha2 subunit gene in Spodoptera exigua (Hübner)

Abstract

The full-length cDNA sequence of γ-aminobutyric acid (GABA) receptor alpha2 subunit gene was cloned from Spodoptera exigua, an economically important pest species in China, through rapid amplification of cDNA ends (RACE) and polymerase chain reaction using primers based on the 5′ and 3′-ends of the mRNA. The gene (named as SeGABARα2) was 1620 bp long, with an open reading frame of 1500 bp encoding a predicted GABA receptor protein of 499 amino acids with a molecular weight of 55 kDa. The predicted GABA receptor protein shared 96.19%, 82.16%, 74.30%, 73.95%, 73.42%, 71.40%, 67.11% and 65.13% identity with other GABA receptors proteins isolated from Heliothis virescens, Plutella xylostella, Aedes aegypti, Laodelphax striatellus, Lucilia cuprina, Musca domestica, Drosophila simulans and Drosophila melanogaster, at amino acid level, respectively. The developmental changes and tissue-specificity of the relative mRNA expression levels of SeGABARα2 gene were investigated in S. exigua. The highest expression level was observed in adult and lowest was in the first instar, there was a stable expression level during the developmental period from the second instar to the adult. Expression levels were 1.41-, 1.57-, 1.45-, 1.80-, 1.82- and 1.93-fold higher in the second instar, third instar, fourth instar, fifth instar, pupa and adult than in the first instar larva, respectively. The relative mRNA expression levels of SeGABARα2 gene were 3.51-fold higher in head and 1.77-fold higher in thorax than in abdomen