ISOLATION OF 7 UNIQUE BIOGENIC-AMINE RECEPTOR CLONES FROM THE HONEY-BEE BY LIBRARY SCANNING

The biogenic amine receptor genes constitute an ancient and highly div ergent family within the larger superfamily of G-protein-coupled recep tors. These receptors play a central role in modulating nerve cell act ivity and thus behaviour. Because the honey bee offers numerous advant ages for behavioural studies we endeavoured to isolate as many members of this gene family as possible from the bee, We compared numerous ap proaches to gene isolation and found that PCR amplification from small subfractions of cDNA or genomic DNA libraries enabled us to isolate c lones that are otherwise undetectable, In total we isolated seven biog enic amine receptor clones and identified five additional related sequ ences by low-stringency Southern hybridization. Two clones, AmBAR4 and AmBAR6, are 84% and 72% identical to the Drosophila 5-HT2 and D1b rec eptors, respectively, and probably represent orthologous genes, Phylog enetic analysis indicates that AmBAR5 clusters loosely with a variety of tyramine and octopamine receptors with which it shares < 66% identi ty. The other four clones, AmBAR1, AmBAR2, AmBAR3 and AmBAR7, are weak ly to moderately related (28-45% identical) to Drosophila dopaminergic or mammalian adrenergic receptors and probably represent receptors of these classes whose orthologues have not previously been isolated fro m any insect. The honey bee clones expand the size of the known insect biogenic amine receptor gene family to sixteen members. Therefore the size of the biogenic amine receptor gene family of insects approaches that of vertebrates. This is true despite the reduced behavioural and genetic complexity of the insects relative to vertebrate animals.