title: Chemotaxis behavior mediated by single larval olfactory neurons in Drosophila.
abstract: BACKGROUND
  Odorant receptors (ORs) are thought to act in a combinatorial fashion, in which odor identity is encoded by the activation of a subset of ORs and the olfactory sensory neurons (OSNs) that express them. The extent to which a single OR contributes to chemotaxis behavior is not known. We investigated this question in Drosophila larvae, which represent a powerful genetic system to analyze the contribution of individual OSNs to odor coding.
  
  
  RESULTS
  We identify 25 larval OR genes expressed in 21 OSNs and generate genetic tools that allow us to engineer larvae missing a single OSN or having only a single or a pair of functional OSNs. Ablation of single OSNs disrupts chemotaxis behavior to a small subset of the odors tested. Larvae with only a single functional OSN are able to chemotax robustly, demonstrating that chemotaxis is possible in the absence of the remaining elements of the combinatorial code. We provide behavioral evidence that an OSN not sufficient to support chemotaxis behavior alone can act in a combinatorial fashion to enhance chemotaxis along with a second OSN.
  
  
  CONCLUSIONS
  We conclude that there is extensive functional redundancy in the olfactory system, such that a given OSN is necessary and sufficient for the perception of only a subset of odors. This study is the first behavioral demonstration that formation of olfactory percepts involves the combinatorial integration of information transmitted by multiple ORs.
authors.affiliation: Laboratory of Neurogenetics and Behavior, The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA.
authors.forename: Elane
authors.initials: E
authors.lastname: Fishilevich
authors.forename: Ana I
authors.initials: AI
authors.lastname: Domingos
authors.forename: Kenta
authors.initials: K
authors.lastname: Asahina
authors.forename: Félix
authors.initials: F
authors.lastname: Naef
authors.forename: Leslie B
authors.initials: LB
authors.lastname: Vosshall
authors.forename: Matthieu
authors.initials: M
authors.lastname: Louis
mesh_terms: D000818:Animals; D002633:Chemotaxis / Q000502:physiology*; D004330:Drosophila / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000378:metabolism; D017403:In Situ Hybridization; D007814:Larva / Q000502:physiology / Q000648:ultrastructure; D008854:Microscopy, Electron; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D018035:Receptors, Odorant / Q000235:genetics; D012044:Regression Analysis; D019076:Transgenes / Q000235:genetics
chemical_list: D018035:Receptors, Odorant; D049452:Green Fluorescent Proteins