MOLECULAR CLONING ANDCHARACTERIZATION OF TWONICOTINIC ACETYLCHOLINERECEPTOR beta SUBUNIT GENESFROM Apis cerana cerana

摘要

Nicotinic acetylcholine receptors (nAChRs) mediate fast cholinergicsynaptic transmission in the insect nervous system and are importanttargets for insecticides. In this study, we identified and characterized twonovel beta subunit genes (Accb1andAcc beta 2) from Apis cerana cerana.Homology analysis indicated that Accb1andAcc beta 2 possess characteristicsthat are typical of nAChR subunits although Acc beta 2 was distinct fromAcc beta 1 and the other nAChR subunits, due to its unusual transmembranestructure and uncommon exon–intron boundary within the genomic regionencoding 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 andregulatory patterns. RT-PCR analysis demonstrated that Accb2wasexpressed at a much higher level than Accb1 in the tissues of adult bees.During development, Accb1 was highly expressed at the pupal stages,whereas Acc beta 2 was abundantly expressed at the larval stages. Furthermore, Accb1 and Accb2 were both induced by exposure to various insecticides and environmental stresses although Acc beta 2 was moreresponsive than Accb1. These results indicate that Acc beta 1andAcc beta 2mayhave distinct roles in insect growth and development and that they maybelong to separate regulatory pathways involved in the response toinsecticides and environmental stresses. This report is the first descriptionof the differences between the nAChR b subunit genes in the Chinese honeybee and establishes an initial foundation for further study.