MOLECULAR CLONING AND CHARACTERIZATION OF TWO NICOTINIC ACETYLCHOLINE RECEPTOR β SUBUNIT GENES FROM Apis cerana cerana

Nicotinic acetylcholine receptors (nAChRs) mediate fast cholinergic synaptic transmission in the insect nervous system and are important targets for insecticides. In this study, we identified and characterized two novel beta subunit genes (Acc beta 1 and Acc beta 2) from Apis cerana cerana. Homology analysis indicated that Acc beta 1 and Acc beta 2 possess characteristics that are typical of nAChR subunits although Acc beta 2 was distinct from Acc beta 1 and the other nAChR subunits, due to its unusual transmembrane structure and uncommon exon-intron boundary within the genomic region encoding the TM1 transmembrane domain. Analysis of the 5' flanking regions indicated that Acc beta 1 and Acc beta 2 possess different regulatory elements, suggesting that the genes might exhibit various expression and regulatory patterns. RT-PCR analysis demonstrated that Acc beta 2 was expressed at a much higher level than Acc beta 1 in the tissues of adult bees. During development, Acc beta 1 was highly expressed at the pupal stages, whereas Acc beta 2 was abundantly expressed at the larval stages. Furthermore, Acc beta 1 and Acc beta 2 were both induced by exposure to various insecticides and environmental stresses although Acc beta 2 was more responsive than Acc beta 1. These results indicate that Acc beta 1 and Acc beta 2 may have distinct roles in insect growth and development and that they may belong to separate regulatory pathways involved in the response to insecticides and environmental stresses. This report is the first description of the differences between the nAChR beta subunit genes in the Chinese honey bee and establishes an initial foundation for further study. (C) 2011 Wiley Periodicals, Inc.