title: Modulation of feeding behavior by odorant-binding proteins in Drosophila melanogaster.
abstract: Nutrient intake and avoidance of toxins are essential for survival and controlled by attractive and aversive feeding responses. Drosophila melanogaster presents one of the best characterized systems for studies on chemosensation, which is mediated by multigene families of chemoreceptors, including olfactory receptors, gustatory receptors, and odorant-binding proteins (OBPs). Although the response profiles of gustatory receptors have been well studied, the contribution of OBPs to food intake is largely unknown. As most aversive ("bitter") tastants are hydrophobic, we hypothesized that OBPs may fulfill an essential function in transporting bitter tastants to gustatory receptors to modulate feeding behavior. Here, we used 16 RNAi lines that inhibit expression of individual target Obp genes and show that OBPs modulate sucrose intake in response to a panel of nine bitter compounds. Similar to their function in olfaction, OBPs appear to interact with bitter compounds in a combinatorial and sex-dependent manner. RNAi-mediated reduction in expression of individual Obp genes resulted either in enhanced or reduced intake of sucrose in the presence of bitter compounds, consistent with roles for OBPs in transporting tastants to bitter taste receptors, sequestering them to limit their access to these receptors, or interacting directly with gustatory neurons that respond to sucrose.
authors.affiliation: Department of Biological Sciences and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC 27695, USA. anholt@ncsu.edu.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Swarup
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Morozova
authors.forename: Sruthipriya
authors.initials: S
authors.lastname: Sridhar
authors.forename: Michael
authors.initials: M
authors.lastname: Nokes
authors.forename: Robert R H
authors.initials: RR
authors.lastname: Anholt
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D029721:Drosophila Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D015870:Gene Expression; D017344:Genes, Insect; D008297:Male; D009812:Odorants; D034622:RNA Interference; D018035:Receptors, Odorant / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D012727:Sex Characteristics; D013395:Sucrose / Q000008:administration & dosage; D013649:Taste / Q000502:physiology; D013650:Taste Buds / Q000502:physiology
chemical_list: D029721:Drosophila Proteins; D018035:Receptors, Odorant; C045648:odorant-binding protein; D013395:Sucrose
keywords: RNAi; bitter taste; chemosensation; gustation; insects; proboscis extension reflex