1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

353 Poster Chemosensory Molecular Genetics andVNO/PheromonePHEROMONE RECEPTOR MEDIATES BEHAVIOR INDROSOPHILASmith D. 1 , Ha T. 1 1 Pharmacology, University of Texas SouthwesternMedical Center at Dallas, Dallas, TXInsect pheromones elicit stereotypic behaviors critical to survival andreproduction. The only identified volatile pheromone in Drosophila is11-cis vaccenyl acetate (VA), a male-specific lipid that mediatesaggregation behavior. VA is detected by a few dozen olfactory neuronslocated on the antenna in a subset of trichoid sensilla (T1 sensilla) inboth male and female flies. We previously showed that sensitivity toVA requires LUSH, a non-neuronal secreted protein present in thesensillum lymph bathing the trichoid olfactory neuron dendrites. Herewe identify a neuronal receptor that mediates VA sensitivity expressedexclusively by the T1, VA-sensitive neurons. We report two mutantslacking T1 sensilla and demonstrate that expression of the VA receptoris reduced or eliminated in these mutants. Importantly, we show misexpressionof this receptor in olfactory neurons that are normallyinsensitive to VA confers pheromone sensitivity in a LUSH-dependentmanner. These data provide new insight into the molecular componentsand neuronal basis of volatile pheromone perception in Drosophila.355 Poster Chemosensory Molecular Genetics andVNO/PheromoneEVOLUTION OF THE SNMP GENE FAMILY IN THEDIPTERA DROSOPHILA MELANOGASTER, D.PSEUDOOBSCURA, AND ANOPHELES GAMBIAENichols Z. 1 , Vogt R. 1 1 Biological Sciences, University of SouthCarolina, Columbia, SCSNMPs are membrane bound proteins that associate with olfactoryneurons in lepidoptera and are thought to play some central role in odordetection. SNMPs belong to a larger gene family characterized byhuman CD36. In this study, we have iteratively blasted the genomes ofDrosophila melanogaster, D. pseudoobscura, and Anopheles gambiaeto identify SNMP/CD36 homologs, finding 12-18 candidates in eachspecies. As the distance between these species differs by an order ofmagnitude (25-50 million years divergence for the two Drosophilaspecies, 220-250 million years divergence from Drosophila to A.gambiae), we have two comparative time scales with which to examinethe evolution of the SNMP family. A neighbor joining tree constructedfrom aligned amino acid sequences suggests that each of the SNMPhomologs found in D. melanogaster has a likely ortholog in D.pseudoobscura with the exception of D. melanogaster CG12789. SinceCG12789 does have a likely ortholog in the A. gambiae SNMPhomologs, we suggest that the related gene was lost in D.pseudoobscura after the divergence of the two Drosophila species.Fewer of the A. gambiae sequences align as orthologs with candidatesfrom the two Drosophila species, unsurprising considering the relativetime since divergence. To further characterize these relationships, a mapwas constructed of intron locations within the aligned amino acidsequences, and a Dollo parsimony tree made by assigning intronlocations a binary value for characters. Both trees have similar structure,providing additional assurance that the phylogeny is reasonable andsuggesting that parsimony trees constructed based in intron locationsare valid.354 Poster Chemosensory Molecular Genetics andVNO/PheromoneCHARACTERIZATION OF A DROSOPHILA MELANOGASTERCHEMOSENSORY SPECIFIC SNMPFernandez K. 1 , Vogt R. 1 1 Biological Sciences, University of SouthCarolina, Columbia, SCSNMP (Sensory Neuron Membrane Protein; Rogers et al., 1997,2001a,b)) is an antennal specific two transmembrane domain proteinabundantly present in the receptive membrane of olfactory neurons inmoths. SNMP is expressed late in adult development and in adult life,well after morphogenic events have occurred. These temporal andspatial expression patterns suggest SNMP is functionally involved inodor detection, either in odor recognition or clearance. Drosophilamelanogaster contains 13 SNMP homologues; one of these sharessignificant similarity with the moth SNMPs. We have constructed atransgenic fly containing the promoter for this gene; this promoterdrives expression of cd8::GFP, labeling cells ostensibly that express theDrosophila SNMP homologue. Studies of the temporal and spatialpatterns of this protein suggests CG7000 expresses in subsets ofchemosensory (olfactory and gustatory) and mechanosensory neuronsof adults, and chemosensory neurons of larvae. We have also conductedin situ hybridization experiments confirming the validity of thecd8::GFP expression pattern. We have generated double stranded RNAstrains for this gene to knockdown normal expression of CG7000.Behavioral studies will allow us to see whether CG7000 is a suitablecandidate for studying SNMP function as it relates to insect olfaction aswell as studying the roles of diverse SNMP/CD36 homologues in asingle species. Rogers et al. (1997), Journal of Biological Chemistry272, 14792-14804. Rogers et al. (2001a), Cell and Tissue Research 303,433-446. Rogers et al. (2001b), Journal of Neurobiology 49, 47-61.356 Poster Chemosensory Molecular Genetics andVNO/PheromoneDROSOPHILA SUGAR RECEPTORSDahanukar A. 1 , Carlson J. 1 1 MCDB, Yale University, New Haven, CTThe sense of taste provides valuable information about the nutritionalquality of food. Like mammals, the fruit fly Drosophila can taste bothattractive and aversive compounds, which are detected via taste neuronson the legs as well as the mouthparts. Gustatory receptor (Gr) genes,which are expressed in these neurons, are members of a large, divergentgene family. Only one of these Gr proteins has been assigned a ligand—previously we have shown that Gr5a is a receptor for the disaccharidesugar trehalose. Gr5a-positive neurons do respond to various othersugars revealing that additional taste receptors are also expressed inthem. Such co-expression of receptors raises intriguing possibilitiesabout the mechanisms of sugar detection and discrimination. To explorethese questions, we sought to identify taste receptors for other sugars.We reasoned that seven Gr genes that are closely related to Gr5a mightencode receptors for other sugars. Consistent with this idea, we find thatat least two of these receptors are expressed in Gr5a neurons. Usingvarious genetic tools we have generated deletion mutations that result inthe loss of multiple receptor genes of the Gr5a sub-family. Analysis ofmutant flies shows that they have electrophysiological or behavioraldefects in their responses to several sugars, including maltose andsucrose, as compared to control flies. Transgenic experiments areunderway to determine the response profiles of individual receptors.Interestingly, we find that some of these deletions have a dramaticeffect on lifespan as well as starvation resistance of mutant flies.Currently, we are investigating further the link between sugar reception,feeding behavior and longevity.89