CDNA cloning and expression analysis of the nicotinic acetylcholine receptor alpha6 subunit in the oriental fruit fly, Bactrocera dorsalis (diptera: Tephritidae)

Abstract

Nicotinic acetylcholine receptors (nAChR) play major roles in the fast synapse cholinergic transmission in the insect central nervous system, and they are recognized as potential target sites for insecticides. In this study, the full-length cDNA sequence of the nAChR alpha6 subunit (Bdor6) was isolated and characterized from the oriental fruit fly, Bactrocera dorsalis, using the Rapid Amplification of cDNA Ends (RACE) technique. The Bdor6 cDNA was 2020 bp long, containing an open reading frame of 1467 bp, which encodes 488 amino acid residues with a predicated molecular mass of 55.6 kDa. Homology analysis indicated that Bdor6 has typical features of a nAChR subunit. Phylogenetic analysis with other insect nAChR subunits suggested that Bdor6 was most closely related to D6 of Drosophila melanogaster. The developmental changes and tissue-specificity of the relative expression levels of Bdor6 were investigated using quantitative real-time PCR. The highest expression level was observed in the first instar larva and the lowest was in the pupa, and there was a descending expression level during the developmental period from the first instar larva to the pupa. The relative expression levels were 23-, 39-, 6-, 2- and 27-fold higher in the egg, first, second and third instar larvae and adult than in the pupa, respectively. Furthermore, Bdor6 was expressed in the head and thorax at 109- and 15-fold higher levels than in the abdomen. The results provided some important baseline data for further molecular studies in Bactrocera dorsalis. .