A candidate olfactory receptor subtype highly conserved across different insect orders
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Candidate olfactory receptors of the moth Heliothis virescens were found to be extremely diverse from receptors of the fruitfly Drosophila melanogaster and the mosquito Anopheles gambiae, but there is one exception. The moth receptor type HR2 shares a rather high degree of sequence identity with one olfactory receptor type both from Drosophila (Dor83b) and from Anopheles (AgamGPRor7); moreover, in contrast to all other receptors, this unique receptor type is expressed in numerous antennal neurons. Here we describe the identification of HR2 homologues in two further lepidopteran species, the moths Antheraea pernyi and Bombyx mori, which share 86–88% of their amino acids. In addition, based on RT-PCR experiments HR2 homologues were discovered in antennal cDNA of the honey bee (Apis mellifera; Hymenoptera), the blowfly (Calliphora erythrocephala; Diptera) and the mealworm (Tenebrio molitor; Coleoptera). Comparison of all HR2-related receptors revealed a high degree of sequence conservation across insect orders. In situ hybridization of antennal sections from the bee and the blowfly support the notion that HR2-related receptors are generally expressed in a very large number of antennal cells. This, together with the high degree of conservation suggests that this unique receptor subtype may fulfill a special function in chemosensory neurons of insects.
KeywordsAntennae Chemoreception Insects Olfaction Olfactory receptor
This work was supported by the Bayer CropScience AG Monheim and by grants from the Deutsche Forschungsgemeinschaft as part of the Trilateral German-Israeli-Palestinian Research program. We thank Gesa Dreesman and Thomas Gohl for untiring and excellent technical assistance and Sidonie Conzelmann for expert help with in situ hybridizations. The experiments comply with the Principles of Animal Care of the National Institute of Health and with the German laws for animal protection. Data deposition: the sequences reported in this paper have been deposited in the EMBL date base (accession nos.: AperR2=AJ555486; BmorR2=AJ555487; AmelR2=AJ555537; CeryR2=AJ555538 ; TmolR2=AJ555539).
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