A divergent gene family encoding candidate olfactory receptors of the moth Heliothis virescens

Abstract

The antennae of moths have been an invaluable model for studying the principles of odour perception. In spite of the enormous progress in understanding olfaction on the molecular level, for the moth one of the key elements in olfactory signalling, the odourant receptors, are still elusive. We have assessed a genome database of a heliothine moth (Heliothis virescens, Noctuidae) and employed exon-specific probes to screen an antennal cDNA library of this species. Analysis of isolated cDNA-clones led to the discovery of a divergent gene family encoding putative seven-transmembrane domain proteins. The notion that they may encode candidate olfactory receptors of the moth, was supported by a tissue-specific expression; several of the subtypes were exclusively expressed in antennae. By means of double-labelling in situ hybridization studies it was demonstrated that the receptors are indeed expressed in antennal sensory neurons; moreover, each receptor subtype appears to be expressed in a distinct population of sensory cells. The results strongly suggest that the newly discovered gene family indeed encodes olfactory receptors of moth.

Genes encoding candidate pheromone receptors in a moth ( Heliothis virescens )

“…Data mining of a partial genomic database from H. virescens in combination with cDNA-library screening (12) led to the identification of numerous cDNA clones containing long ORFs. BLAST comparisons of the sequences to entries in the EMBL͞GenBank and SwissProt databases revealed that several of the newly isolated cDNAs appear to be related to some of the candidate olfactory receptors from Heliothis (12), Drosophila (4-8), or Anopheles (9-11), thus suggesting that the isolated cDNA clones encode novel members of the olfactory receptor family.…”

“…To find new genes encoding candidate chemoreceptors, we extended the strategy that was used successfully to detect the first candidate olfactory receptors in H. virescens (12) by using the sequences of Heliothis receptor 1-9 (HR1-HR9) and of newly identified HRs, as well as the sequences of candidate olfactory receptors from Drosophila melanogaster (4)(5)(6)(7)(8) and Anopheles gambiae (9)(10)(11) in BLAST analyses (22,23) of the nonpublic Heliothis genomic database.…”

“…In addition, DIG-labeled partial cDNAs discovered with the genomic fragments were used as screening probe. Screening of the cDNA library was performed as described (12). Filters were hybridized to DIG-labeled probes at 37°C.…”

“…12. Hybridizations of DIG-labeled probes were visualized by the anti-DIG alkaline phosphatase-conjugated antibody in combination with HNPP͞Fast Red f luorescence-detection set (Roche).…”

“…One could imagine some identifying features that might distinguish pheromone receptors among general olfactory receptors. A characteristic trait of insect olfactory receptor types is the extreme diversity of their sequences (9,12,19). Because pheromone detection is probably under different kinds of selective pressure than detection of food odors or host odors, one might speculate whether receptors for pheromones are more conserved than other olfactory receptor types.…”