The Intricate Molecular Landscape of Insect Chemosensation: The Sensory Neuron Membrane Protein Gene Family
SNMPs (Sensory Neuron Membrane Proteins) are members of a gene family characterized by human CD36. This family has diverse functions including transportation of fatty acids and interactions with other proteins in cell:cell recognition. SNMPs are membrane proteins observed to associate with chemosensory sensilla in insects, and are conserved throughout four orders of the Holometabolous lineage (Vogt et al., 2009). Two SNMPs (1 and 2) are identified in Manduca sexta (hawkmoth); both are antennal-specific but are only 40% identical in sequence (Rogers et al., 1997, 2001a, b). In Lepidoptera, the transcripts are enriched in the antenna and express in both neurons and support cells (Forstner et al., 2008). In Drosophila melanogaster, the SNMP-1 orthologue CG7000 has been shown to be essential for the detection of the pheromone cis-vaccenyl acetate (Benton et al., 2007; Jin et al., 2008). The D. melanogaster genome contains at least 13 SNMP/CD36 homologues (Vogt 2009); I have focused on the further characterization of DmSNMP-1 (CG7000) and DmSNMP-2 (CG7422). Our expression analysis suggests DmSNMP-1 and DmSNMP-2 associate with a broad array of chemosensory sensilla, both olfactory and non-olfactory. Neuronal and non-neuronal expression is evident for both genes. Using genomic deletions of SNMPs for phenotypic analysis, we collect behavioral data that reveal male SNMP-1 knock-out (KO) mating deficiencies in multiple contexts. SNMP-2 KO male flies also exhibit mating deficiencies in competition and single animal assays, while responses to food-related chemical cues appear normal for all animals. A double SNMP KO fly exhibits severe behavioral deficits and an atypical wing morphology. Taken together, these results suggest SNMPs individually modulate the transmission of a range of socially relevant cues via smell and taste modalities in insects. In combination, SNMP-1 and SNMP-2 may contribute more broadly to normal development or adult physiology. The exact molecular functions of each SNMP remain elusive. Future work should address these mechanistic questions in the contexts we have examined here.
Life Sciences, Medicine and Health Sciences, Physical Sciences and Mathematics, Behavior, Chemosenses, Drosophila, Gustation, Olfaction, SNMP
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