title: A conserved dedicated olfactory circuit for detecting harmful microbes in Drosophila.
abstract: Flies, like all animals, need to find suitable and safe food. Because the principal food source for Drosophila melanogaster is yeast growing on fermenting fruit, flies need to distinguish fruit with safe yeast from yeast covered with toxic microbes. We identify a functionally segregated olfactory circuit in flies that is activated exclusively by geosmin. This microbial odorant constitutes an ecologically relevant stimulus that alerts flies to the presence of harmful microbes. Geosmin activates only a single class of sensory neurons expressing the olfactory receptor Or56a. These neurons target the DA2 glomerulus and connect to projection neurons that respond exclusively to geosmin. Activation of DA2 is sufficient and necessary for aversion, overrides input from other olfactory pathways, and inhibits positive chemotaxis, oviposition, and feeding. The geosmin detection system is a conserved feature in the genus Drosophila that provides flies with a sensitive, specific means of identifying unsuitable feeding and breeding sites.
authors.affiliation: Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany. mstensmyr@ice.mpg.de
authors.forename: Marcus C
authors.initials: MC
authors.lastname: Stensmyr
authors.forename: Hany K M
authors.initials: HK
authors.lastname: Dweck
authors.forename: Abu
authors.initials: A
authors.lastname: Farhan
authors.forename: Irene
authors.initials: I
authors.lastname: Ibba
authors.forename: Antonia
authors.initials: A
authors.lastname: Strutz
authors.forename: Latha
authors.initials: L
authors.lastname: Mukunda
authors.forename: Jeanine
authors.initials: J
authors.lastname: Linz
authors.forename: Veit
authors.initials: V
authors.lastname: Grabe
authors.forename: Kathrin
authors.initials: K
authors.lastname: Steck
authors.forename: Sofia
authors.initials: S
authors.lastname: Lavista-Llanos
authors.forename: Dieter
authors.initials: D
authors.lastname: Wicher
authors.forename: Silke
authors.initials: S
authors.lastname: Sachse
authors.forename: Markus
authors.initials: M
authors.lastname: Knaden
authors.forename: Paul G
authors.initials: PG
authors.lastname: Becher
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Seki
authors.forename: Bill S
authors.initials: BS
authors.lastname: Hansson
mesh_terms: D000818:Animals; D001419:Bacteria / Q000737:chemistry*; D002628:Chemoreceptor Cells / Q000378:metabolism; D004330:Drosophila / Q000502:physiology; D004331:Drosophila melanogaster / Q000502:physiology*; D005247:Feeding Behavior; D005260:Female; D005658:Fungi / Q000737:chemistry*; D008297:Male; D009284:Naphthols / Q000737:chemistry; D009833:Olfactory Pathways; D010058:Oviposition; D018035:Receptors, Odorant / Q000378:metabolism; D011984:Sensory Receptor Cells / Q000502:physiology*
chemical_list: D009284:Naphthols; D018035:Receptors, Odorant; C001278:geosmin