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Ahn JE, Amrein H. Opposing chemosensory functions of closely related gustatory receptors. eLife 2023; 12:RP89795. [PMID: 38060294 PMCID: PMC10703443 DOI: 10.7554/elife.89795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2023] Open
Abstract
In the fruit fly Drosophila melanogaster, gustatory sensory neurons express taste receptors that are tuned to distinct groups of chemicals, thereby activating neural ensembles that elicit either feeding or avoidance behavior. Members of a family of ligand -gated receptor channels, the Gustatory receptors (Grs), play a central role in these behaviors. In general, closely related, evolutionarily conserved Gr proteins are co-expressed in the same type of taste neurons, tuned to chemically related compounds, and therefore triggering the same behavioral response. Here, we report that members of the Gr28 subfamily are expressed in largely non-overlapping sets of taste neurons in Drosophila larvae, detect chemicals of different valence, and trigger opposing feeding behaviors. We determined the intrinsic properties of Gr28 neurons by expressing the mammalian Vanilloid Receptor 1 (VR1), which is activated by capsaicin, a chemical to which wild-type Drosophila larvae do not respond. When VR1 is expressed in Gr28a neurons, larvae become attracted to capsaicin, consistent with reports showing that Gr28a itself encodes a receptor for nutritious RNA. In contrast, expression of VR1 in two pairs of Gr28b.c neurons triggers avoidance to capsaicin. Moreover, neuronal inactivation experiments show that the Gr28b.c neurons are necessary for avoidance of several bitter compounds. Lastly, behavioral experiments of Gr28 deficient larvae and live Ca2+ imaging studies of Gr28b.c neurons revealed that denatonium benzoate, a synthetic bitter compound that shares structural similarities with natural bitter chemicals, is a ligand for a receptor complex containing a Gr28b.c or Gr28b.a subunit. Thus, the Gr28 proteins, which have been evolutionarily conserved over 260 million years in insects, represent the first taste receptor subfamily in which specific members mediate behavior with opposite valence.
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Affiliation(s)
- Ji-Eun Ahn
- Department of Cell Biology and Genetics, School of Medicine, Texas A&M UniversityBryanUnited States
| | - Hubert Amrein
- Department of Cell Biology and Genetics, School of Medicine, Texas A&M UniversityBryanUnited States
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2
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Maier GL, Komarov N, Meyenhofer F, Kwon JY, Sprecher SG. Taste sensing and sugar detection mechanisms in Drosophila larval primary taste center. eLife 2021; 10:67844. [PMID: 34859782 PMCID: PMC8709573 DOI: 10.7554/elife.67844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 11/23/2021] [Indexed: 11/25/2022] Open
Abstract
Despite the small number of gustatory sense neurons, Drosophila larvae are able to sense a wide range of chemicals. Although evidence for taste multimodality has been provided in single neurons, an overview of gustatory responses at the periphery is missing and hereby we explore whole-organ calcium imaging of the external taste center. We find that neurons can be activated by different combinations of taste modalities, including opposite hedonic valence and identify distinct temporal dynamics of response. Although sweet sensing has not been fully characterized so far in the external larval gustatory organ, we recorded responses elicited by sugar. Previous findings established that larval sugar sensing relies on the Gr43a pharyngeal receptor, but the question remains if external neurons contribute to this taste. Here, we postulate that external and internal gustation use distinct and complementary mechanisms in sugar sensing and we identify external sucrose sensing neurons.
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Affiliation(s)
- G Larisa Maier
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Nikita Komarov
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Felix Meyenhofer
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Jae Young Kwon
- Department of Biological Sciences, Sungkyunkwan University, Suwon, Republic of Korea
| | - Simon G Sprecher
- Department of Biology, University of Fribourg, Fribourg, Switzerland
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3
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Komarov N, Sprecher SG. The chemosensory system of the Drosophila larva: an overview of current understanding. Fly (Austin) 2021; 16:1-12. [PMID: 34612150 PMCID: PMC8496535 DOI: 10.1080/19336934.2021.1953364] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Animals must sense their surroundings and be able to distinguish between relevant and irrelevant cues. An enticing area of research aims to uncover the mechanisms by which animals respond to chemical signals that constitute critical sensory input. In this review, we describe the principles of a model chemosensory system: the Drosophila larva. While distinct in many ways, larval behaviour is reminiscent of the dogmatic goals of life: to reach a stage of reproductive potential. It takes into account a number of distinct and identifiable parameters to ultimately provoke or modulate appropriate behavioural output. In this light, we describe current knowledge of chemosensory anatomy, genetic components, and the processing logic of chemical cues. We outline recent advancements and summarize the hypothesized neural circuits of sensory systems. Furthermore, we note yet-unanswered questions to create a basis for further investigation of molecular and systemic mechanisms of chemosensation in Drosophila and beyond.
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Affiliation(s)
- Nikita Komarov
- Institute of Cell and Developmental Biology, Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Simon G Sprecher
- Institute of Cell and Developmental Biology, Department of Biology, University of Fribourg, Fribourg, Switzerland
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4
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Olafson PU, Aksoy S, Attardo GM, Buckmeier G, Chen X, Coates CJ, Davis M, Dykema J, Emrich SJ, Friedrich M, Holmes CJ, Ioannidis P, Jansen EN, Jennings EC, Lawson D, Martinson EO, Maslen GL, Meisel RP, Murphy TD, Nayduch D, Nelson DR, Oyen KJ, Raszick TJ, Ribeiro JMC, Robertson HM, Rosendale AJ, Sackton TB, Saelao P, Swiger SL, Sze SH, Tarone AM, Taylor DB, Warren WC, Waterhouse RM, Weirauch MT, Werren JH, Wilson RK, Zdobnov EM, Benoit JB. The genome of the stable fly, Stomoxys calcitrans, reveals potential mechanisms underlying reproduction, host interactions, and novel targets for pest control. BMC Biol 2021; 19:41. [PMID: 33750380 PMCID: PMC7944917 DOI: 10.1186/s12915-021-00975-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 02/03/2021] [Indexed: 01/01/2023] Open
Abstract
Background The stable fly, Stomoxys calcitrans, is a major blood-feeding pest of livestock that has near worldwide distribution, causing an annual cost of over $2 billion for control and product loss in the USA alone. Control of these flies has been limited to increased sanitary management practices and insecticide application for suppressing larval stages. Few genetic and molecular resources are available to help in developing novel methods for controlling stable flies. Results This study examines stable fly biology by utilizing a combination of high-quality genome sequencing and RNA-Seq analyses targeting multiple developmental stages and tissues. In conjunction, 1600 genes were manually curated to characterize genetic features related to stable fly reproduction, vector host interactions, host-microbe dynamics, and putative targets for control. Most notable was characterization of genes associated with reproduction and identification of expanded gene families with functional associations to vision, chemosensation, immunity, and metabolic detoxification pathways. Conclusions The combined sequencing, assembly, and curation of the male stable fly genome followed by RNA-Seq and downstream analyses provide insights necessary to understand the biology of this important pest. These resources and new data will provide the groundwork for expanding the tools available to control stable fly infestations. The close relationship of Stomoxys to other blood-feeding (horn flies and Glossina) and non-blood-feeding flies (house flies, medflies, Drosophila) will facilitate understanding of the evolutionary processes associated with development of blood feeding among the Cyclorrhapha. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-00975-9.
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Affiliation(s)
- Pia U Olafson
- Livestock Arthropod Pests Research Unit, USDA-ARS, Kerrville, TX, USA.
| | - Serap Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, USA
| | - Geoffrey M Attardo
- Department of Entomology and Nematology, University of California - Davis, Davis, CA, USA
| | - Greta Buckmeier
- Livestock Arthropod Pests Research Unit, USDA-ARS, Kerrville, TX, USA
| | - Xiaoting Chen
- The Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Craig J Coates
- Department of Entomology, Texas A & M University, College Station, TX, USA
| | - Megan Davis
- Livestock Arthropod Pests Research Unit, USDA-ARS, Kerrville, TX, USA
| | - Justin Dykema
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
| | - Scott J Emrich
- Department of Electrical Engineering & Computer Science, University of Tennessee, Knoxville, TN, USA
| | - Markus Friedrich
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
| | - Christopher J Holmes
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA
| | - Panagiotis Ioannidis
- Department of Genetic Medicine and Development, University of Geneva Medical School and Swiss Institute of Bioinformatics, 1211, Geneva, Switzerland
| | - Evan N Jansen
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA
| | - Emily C Jennings
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA
| | - Daniel Lawson
- The European Molecular Biology Laboratory, The European Bioinformatics Institute, The Wellcome Genome Campus, Hinxton, CB10 1SD, UK
| | | | - Gareth L Maslen
- The European Molecular Biology Laboratory, The European Bioinformatics Institute, The Wellcome Genome Campus, Hinxton, CB10 1SD, UK
| | - Richard P Meisel
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA
| | - Terence D Murphy
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Dana Nayduch
- Arthropod-borne Animal Diseases Research Unit, USDA-ARS, Manhattan, KS, USA
| | - David R Nelson
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Kennan J Oyen
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA
| | - Tyler J Raszick
- Department of Entomology, Texas A & M University, College Station, TX, USA
| | - José M C Ribeiro
- Section of Vector Biology, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, Rockville, MD, USA
| | - Hugh M Robertson
- Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | | | - Timothy B Sackton
- Informatics Group, Faculty of Arts and Sciences, Harvard University, Cambridge, MA, USA
| | - Perot Saelao
- Livestock Arthropod Pests Research Unit, USDA-ARS, Kerrville, TX, USA
| | - Sonja L Swiger
- Department of Entomology, Texas A&M AgriLife Research and Extension Center, Stephenville, TX, USA
| | - Sing-Hoi Sze
- Department of Computer Science & Engineering, Department of Biochemistry & Biophysics, Texas A & M University, College Station, TX, USA
| | - Aaron M Tarone
- Department of Entomology, Texas A & M University, College Station, TX, USA
| | - David B Taylor
- Agroecosystem Management Research Unit, USDA-ARS, Lincoln, NE, USA
| | - Wesley C Warren
- University of Missouri, Bond Life Sciences Center, Columbia, MO, USA
| | - Robert M Waterhouse
- Department of Ecology and Evolution, University of Lausanne, and Swiss Institute of Bioinformatics, 1015, Lausanne, Switzerland
| | - Matthew T Weirauch
- Center for Autoimmune Genomics and Etiology, Divisions of Biomedical Informatics and Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - John H Werren
- Department of Biology, University of Rochester, Rochester, NY, USA
| | - Richard K Wilson
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA.,College of Medicine, Ohio State University, Columbus, OH, USA
| | - Evgeny M Zdobnov
- Department of Genetic Medicine and Development, University of Geneva Medical School and Swiss Institute of Bioinformatics, 1211, Geneva, Switzerland
| | - Joshua B Benoit
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA.
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5
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Kendroud S, Bohra AA, Kuert PA, Nguyen B, Guillermin O, Sprecher SG, Reichert H, VijayRaghavan K, Hartenstein V. Structure and development of the subesophageal zone of the Drosophila brain. II. Sensory compartments. J Comp Neurol 2018; 526:33-58. [PMID: 28875566 PMCID: PMC5971197 DOI: 10.1002/cne.24316] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 07/15/2017] [Accepted: 08/15/2017] [Indexed: 12/29/2022]
Abstract
The subesophageal zone (SEZ) of the Drosophila brain processes mechanosensory and gustatory sensory input from sensilla located on the head, mouth cavity and trunk. Motor output from the SEZ directly controls the movements involved in feeding behavior. In an accompanying paper (Hartenstein et al., ), we analyzed the systems of fiber tracts and secondary lineages to establish reliable criteria for defining boundaries between the four neuromeres of the SEZ, as well as discrete longitudinal neuropil domains within each SEZ neuromere. Here we use this anatomical framework to systematically map the sensory projections entering the SEZ throughout development. Our findings show continuity between larval and adult sensory neuropils. Gustatory axons from internal and external taste sensilla of the larva and adult form two closely related sensory projections, (a) the anterior central sensory center located deep in the ventromedial neuropil of the tritocerebrum and mandibular neuromere, and (b) the anterior ventral sensory center (AVSC), occupying a superficial layer within the ventromedial tritocerebrum. Additional, presumed mechanosensory terminal axons entering via the labial nerve define the ventromedial sensory center (VMSC) in the maxilla and labium. Mechanosensory afferents of the massive array of chordotonal organs (Johnston's organ) of the adult antenna project into the centrolateral neuropil column of the anterior SEZ, creating the antenno-mechanosensory and motor center (AMMC). Dendritic projections of dye back-filled motor neurons extend throughout a ventral layer of the SEZ, overlapping widely with the AVSC and VMSC. Our findings elucidate fundamental structural aspects of the developing sensory systems in Drosophila.
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Affiliation(s)
- Sarah Kendroud
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Ali Asgar Bohra
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, India
| | | | - Bao Nguyen
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Oriane Guillermin
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Simon G. Sprecher
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | | | | | - Volker Hartenstein
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
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6
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Almeida-Carvalho MJ, Berh D, Braun A, Chen YC, Eichler K, Eschbach C, Fritsch PMJ, Gerber B, Hoyer N, Jiang X, Kleber J, Klämbt C, König C, Louis M, Michels B, Miroschnikow A, Mirth C, Miura D, Niewalda T, Otto N, Paisios E, Pankratz MJ, Petersen M, Ramsperger N, Randel N, Risse B, Saumweber T, Schlegel P, Schleyer M, Soba P, Sprecher SG, Tanimura T, Thum AS, Toshima N, Truman JW, Yarali A, Zlatic M. The Ol1mpiad: concordance of behavioural faculties of stage 1 and stage 3 Drosophila larvae. J Exp Biol 2017; 220:2452-2475. [DOI: 10.1242/jeb.156646] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/03/2017] [Indexed: 12/25/2022]
Abstract
ABSTRACT
Mapping brain function to brain structure is a fundamental task for neuroscience. For such an endeavour, the Drosophila larva is simple enough to be tractable, yet complex enough to be interesting. It features about 10,000 neurons and is capable of various taxes, kineses and Pavlovian conditioning. All its neurons are currently being mapped into a light-microscopical atlas, and Gal4 strains are being generated to experimentally access neurons one at a time. In addition, an electron microscopic reconstruction of its nervous system seems within reach. Notably, this electron microscope-based connectome is being drafted for a stage 1 larva – because stage 1 larvae are much smaller than stage 3 larvae. However, most behaviour analyses have been performed for stage 3 larvae because their larger size makes them easier to handle and observe. It is therefore warranted to either redo the electron microscopic reconstruction for a stage 3 larva or to survey the behavioural faculties of stage 1 larvae. We provide the latter. In a community-based approach we called the Ol1mpiad, we probed stage 1 Drosophila larvae for free locomotion, feeding, responsiveness to substrate vibration, gentle and nociceptive touch, burrowing, olfactory preference and thermotaxis, light avoidance, gustatory choice of various tastants plus odour–taste associative learning, as well as light/dark–electric shock associative learning. Quantitatively, stage 1 larvae show lower scores in most tasks, arguably because of their smaller size and lower speed. Qualitatively, however, stage 1 larvae perform strikingly similar to stage 3 larvae in almost all cases. These results bolster confidence in mapping brain structure and behaviour across developmental stages.
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Affiliation(s)
| | - Dimitri Berh
- Institute of Neurobiology and Behavioural Biology, University of Münster, 48149 Münster, Germany
- Department of Mathematics and Computer Science, University of Münster, 48149 Münster, Germany
| | - Andreas Braun
- EMBL/CRG Systems Biology Unit, Centre for Genomic Regulation, 08003 Barcelona, Spain
- Universitat Pompeu Fabra, 08002 Barcelona, Spain
| | - Yi-chun Chen
- Leibniz Institute for Neurobiology (Genetics), 39118 Magdeburg, Germany
| | - Katharina Eichler
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Claire Eschbach
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | | | - Bertram Gerber
- Leibniz Institute for Neurobiology (Genetics), 39118 Magdeburg, Germany
- Institute of Biology, Otto von Guericke University Magdeburg, 39118 Magdeburg, Germany
- Center for Behavioral Brain Sciences, Otto von Guericke University Magdeburg, 39106 Magdeburg, Germany
| | - Nina Hoyer
- Center for Molecular Neurobiology, University of Hamburg, 20251 Hamburg, Germany
| | - Xiaoyi Jiang
- Department of Mathematics and Computer Science, University of Münster, 48149 Münster, Germany
| | - Jörg Kleber
- Leibniz Institute for Neurobiology (Genetics), 39118 Magdeburg, Germany
| | - Christian Klämbt
- Institute of Neurobiology and Behavioural Biology, University of Münster, 48149 Münster, Germany
| | - Christian König
- Leibniz Institute for Neurobiology (Molecular Systems Biology), 39118 Magdeburg, Germany
- Institute of Pharmacology and Toxicology, Otto von Guericke University Magdeburg, 39118 Magdeburg, Germany
| | - Matthieu Louis
- EMBL/CRG Systems Biology Unit, Centre for Genomic Regulation, 08003 Barcelona, Spain
- Universitat Pompeu Fabra, 08002 Barcelona, Spain
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93117, USA
| | - Birgit Michels
- Leibniz Institute for Neurobiology (Genetics), 39118 Magdeburg, Germany
| | | | - Christen Mirth
- Gulbenkian Institute of Science, 2780-156 Oeiras, Portugal
- School of Biological Sciences, Monash University, Melbourne, VIC 3800, Australia
| | - Daisuke Miura
- Department of Biology, Kyushu University, 819-0395 Fukuoka, Japan
| | - Thomas Niewalda
- Leibniz Institute for Neurobiology (Genetics), 39118 Magdeburg, Germany
| | - Nils Otto
- Institute of Neurobiology and Behavioural Biology, University of Münster, 48149 Münster, Germany
| | - Emmanouil Paisios
- Leibniz Institute for Neurobiology (Genetics), 39118 Magdeburg, Germany
| | | | - Meike Petersen
- Center for Molecular Neurobiology, University of Hamburg, 20251 Hamburg, Germany
| | - Noel Ramsperger
- Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Nadine Randel
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Benjamin Risse
- Institute of Neurobiology and Behavioural Biology, University of Münster, 48149 Münster, Germany
- Department of Mathematics and Computer Science, University of Münster, 48149 Münster, Germany
| | - Timo Saumweber
- Leibniz Institute for Neurobiology (Genetics), 39118 Magdeburg, Germany
| | | | - Michael Schleyer
- Leibniz Institute for Neurobiology (Genetics), 39118 Magdeburg, Germany
| | - Peter Soba
- Center for Molecular Neurobiology, University of Hamburg, 20251 Hamburg, Germany
| | - Simon G. Sprecher
- Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Teiichi Tanimura
- Department of Biology, Kyushu University, 819-0395 Fukuoka, Japan
| | - Andreas S. Thum
- Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Naoko Toshima
- Leibniz Institute for Neurobiology (Genetics), 39118 Magdeburg, Germany
- Department of Biology, Kyushu University, 819-0395 Fukuoka, Japan
| | - Jim W. Truman
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
- Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA
| | - Ayse Yarali
- Center for Behavioral Brain Sciences, Otto von Guericke University Magdeburg, 39106 Magdeburg, Germany
- Leibniz Institute for Neurobiology (Molecular Systems Biology), 39118 Magdeburg, Germany
| | - Marta Zlatic
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
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7
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Michels B, Saumweber T, Biernacki R, Thum J, Glasgow RDV, Schleyer M, Chen YC, Eschbach C, Stocker RF, Toshima N, Tanimura T, Louis M, Arias-Gil G, Marescotti M, Benfenati F, Gerber B. Pavlovian Conditioning of Larval Drosophila: An Illustrated, Multilingual, Hands-On Manual for Odor-Taste Associative Learning in Maggots. Front Behav Neurosci 2017; 11:45. [PMID: 28469564 PMCID: PMC5395560 DOI: 10.3389/fnbeh.2017.00045] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 02/27/2017] [Indexed: 01/25/2023] Open
Abstract
Larval Drosophila offer a study case for behavioral neurogenetics that is simple enough to be experimentally tractable, yet complex enough to be worth the effort. We provide a detailed, hands-on manual for Pavlovian odor-reward learning in these animals. Given the versatility of Drosophila for genetic analyses, combined with the evolutionarily shared genetic heritage with humans, the paradigm has utility not only in behavioral neurogenetics and experimental psychology, but for translational biomedicine as well. Together with the upcoming total synaptic connectome of the Drosophila nervous system and the possibilities of single-cell-specific transgene expression, it offers enticing opportunities for research. Indeed, the paradigm has already been adopted by a number of labs and is robust enough to be used for teaching in classroom settings. This has given rise to a demand for a detailed, hands-on manual directed at newcomers and/or at laboratory novices, and this is what we here provide. The paradigm and the present manual have a unique set of features: The present manual can thus foster science education at an earlier age and enable research by a broader community than has been the case to date.
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Affiliation(s)
- Birgit Michels
- Department of Genetics, Leibniz Institute for NeurobiologyMagdeburg, Germany
| | - Timo Saumweber
- Department of Genetics, Leibniz Institute for NeurobiologyMagdeburg, Germany
| | - Roland Biernacki
- Department Neurobiology and Genetics, Julius Maximilians UniversityWürzburg, Germany
| | - Jeanette Thum
- Department Neurobiology and Genetics, Julius Maximilians UniversityWürzburg, Germany
| | - Rupert D V Glasgow
- Department of Genetics, Leibniz Institute for NeurobiologyMagdeburg, Germany
| | - Michael Schleyer
- Department of Genetics, Leibniz Institute for NeurobiologyMagdeburg, Germany
| | - Yi-Chun Chen
- Department of Genetics, Leibniz Institute for NeurobiologyMagdeburg, Germany
| | | | | | - Naoko Toshima
- Department of Genetics, Leibniz Institute for NeurobiologyMagdeburg, Germany
| | | | - Matthieu Louis
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa BarbaraSanta Barbara, CA, USA
| | - Gonzalo Arias-Gil
- Department Systems Physiology, Leibniz Institute for Neurobiology MagdeburgMagdeburg, Germany
| | | | - Fabio Benfenati
- Italian Institute of Technology, Center for Synaptic Neuroscience and TechnologyGenova, Italy
| | - Bertram Gerber
- Department of Genetics, Leibniz Institute for NeurobiologyMagdeburg, Germany.,Institute of Biology, Otto von Guericke UniversityMagdeburg, Germany.,Center for Behavioral Brain SciencesMagdeburg, Germany
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8
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Rohwedder A, Wenz NL, Stehle B, Huser A, Yamagata N, Zlatic M, Truman JW, Tanimoto H, Saumweber T, Gerber B, Thum AS. Four Individually Identified Paired Dopamine Neurons Signal Reward in Larval Drosophila. Curr Biol 2016; 26:661-9. [PMID: 26877086 DOI: 10.1016/j.cub.2016.01.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 12/03/2015] [Accepted: 01/04/2016] [Indexed: 12/01/2022]
Abstract
Dopaminergic neurons serve multiple functions, including reinforcement processing during associative learning [1-12]. It is thus warranted to understand which dopaminergic neurons mediate which function. We study larval Drosophila, in which only approximately 120 of a total of 10,000 neurons are dopaminergic, as judged by the expression of tyrosine hydroxylase (TH), the rate-limiting enzyme of dopamine biosynthesis [5, 13]. Dopaminergic neurons mediating reinforcement in insect olfactory learning target the mushroom bodies, a higher-order "cortical" brain region [1-5, 11, 12, 14, 15]. We discover four previously undescribed paired neurons, the primary protocerebral anterior medial (pPAM) neurons. These neurons are TH positive and subdivide the medial lobe of the mushroom body into four distinct subunits. These pPAM neurons are acutely necessary for odor-sugar reward learning and require intact TH function in this process. However, they are dispensable for aversive learning and innate behavior toward the odors and sugars employed. Optogenetical activation of pPAM neurons is sufficient as a reward. Thus, the pPAM neurons convey a likely dopaminergic reward signal. In contrast, DL1 cluster neurons convey a corresponding punishment signal [5], suggesting a cellular division of labor to convey dopaminergic reward and punishment signals. On the level of individually identified neurons, this uncovers an organizational principle shared with adult Drosophila and mammals [1-4, 7, 9, 10] (but see [6]). The numerical simplicity and connectomic tractability of the larval nervous system [16-19] now offers a prospect for studying circuit principles of dopamine function at unprecedented resolution.
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Affiliation(s)
- Astrid Rohwedder
- Department of Biology, University of Fribourg, 1600 Fribourg, Switzerland; Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Nana L Wenz
- Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Bernhard Stehle
- Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Annina Huser
- Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Nobuhiro Yamagata
- Graduate School of Life Sciences, Tohoku University, Katahira 2-1-1, 980-8577 Sendai, Japan
| | | | | | - Hiromu Tanimoto
- Graduate School of Life Sciences, Tohoku University, Katahira 2-1-1, 980-8577 Sendai, Japan
| | - Timo Saumweber
- Abteilung Genetik von Lernen und Gedächtnis, Leibniz Institut für Neurobiologie (LIN), 39118 Magdeburg, Germany.
| | - Bertram Gerber
- Abteilung Genetik von Lernen und Gedächtnis, Leibniz Institut für Neurobiologie (LIN), 39118 Magdeburg, Germany; Otto von Guericke Universität Magdeburg, Institut für Biologie, Verhaltensgenetik, Universitätsplatz 2, 39106 Magdeburg, Germany; Center for Behavioral Brain Sciences (CBBS), 39106 Magdeburg, Germany.
| | - Andreas S Thum
- Department of Biology, University of Fribourg, 1600 Fribourg, Switzerland; Department of Biology, University of Konstanz, 78464 Konstanz, Germany; Zukunftskolleg, University of Konstanz, 78464 Konstanz, Germany.
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9
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Kim H, Choi MS, Kang K, Kwon JY. Behavioral Analysis of Bitter Taste Perception in Drosophila Larvae. Chem Senses 2015; 41:85-94. [PMID: 26512069 DOI: 10.1093/chemse/bjv061] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Insect larvae, which recognize food sources through chemosensory cues, are a major source of global agricultural loss. Gustation is an important factor that determines feeding behavior, and the gustatory receptors (Grs) act as molecular receptors that recognize diverse chemicals in gustatory receptor neurons (GRNs). The behavior of Drosophila larvae is relatively simpler than the adult fly, and a gustatory receptor-to-neuron map was established in a previous study of the major external larval head sensory organs. Here, we extensively study the bitter taste responses of larvae using 2-choice behavioral assays. First, we tested a panel of 23 candidate bitter compounds to compare the behavioral responses of larvae and adults. We define 9 bitter compounds which elicit aversive behavior in a dose-dependent manner. A functional map of the larval GRNs was constructed with the use of Gr-GAL4 lines that drive expression of UAS-tetanus toxin and UAS-VR1 in specific gustatory neurons to identify bitter tastants-GRN combinations by suppressing and activating discrete subsets of taste neurons, respectively. Our results suggest that many gustatory neurons act cooperatively in larval bitter sensing, and that these neurons have different degrees of responsiveness to different bitter compounds.
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Affiliation(s)
- Haein Kim
- Department of Biological Sciences, Sungkyunkwan University, Suwon 16419, Republic of Korea and
| | - Min Sung Choi
- Department of Biological Sciences, Sungkyunkwan University, Suwon 16419, Republic of Korea and
| | - KyeongJin Kang
- Samsung Biomedical Research Institute, Department of Anatomy and Cell Biology, School of Medicine, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jae Young Kwon
- Department of Biological Sciences, Sungkyunkwan University, Suwon 16419, Republic of Korea and
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10
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Mast JD, De Moraes CM, Alborn HT, Lavis LD, Stern DL. Evolved differences in larval social behavior mediated by novel pheromones. eLife 2014; 3:e04205. [PMID: 25497433 PMCID: PMC4270068 DOI: 10.7554/elife.04205] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 10/26/2014] [Indexed: 11/13/2022] Open
Abstract
Pheromones, chemical signals that convey social information, mediate many insect social behaviors, including navigation and aggregation. Several studies have suggested that behavior during the immature larval stages of Drosophila development is influenced by pheromones, but none of these compounds or the pheromone-receptor neurons that sense them have been identified. Here we report a larval pheromone-signaling pathway. We found that larvae produce two novel long-chain fatty acids that are attractive to other larvae. We identified a single larval chemosensory neuron that detects these molecules. Two members of the pickpocket family of DEG/ENaC channel subunits (ppk23 and ppk29) are required to respond to these pheromones. This pheromone system is evolving quickly, since the larval exudates of D. simulans, the sister species of D. melanogaster, are not attractive to other larvae. Our results define a new pheromone signaling system in Drosophila that shares characteristics with pheromone systems in a wide diversity of insects. DOI:http://dx.doi.org/10.7554/eLife.04205.001 The release of chemical signals called pheromones is a common tactic used by animals in many social situations, such as to attract potential mates or to follow trails left by other members of their colony. Larvae of the fruit fly Drosophila melanogaster—a species commonly studied in the laboratory—gather together when sharing a food source and then cooperate in a way that may increase how efficiently they feed. It has been proposed that pheromones coordinate this behavior, but no larval pheromones had been identified. Mast et al. noticed that Drosophila larvae crawling on a surface tended to occupy areas where other larvae had crawled before. This suggested that larvae had left attractive chemicals on the surface. Mast et al. identified two such substances by analyzing the chemicals left on the surface and then by testing the response of larvae to each compound. Ultimately, Mast et al. found that a single sensory neuron in the larva is responsible for detecting these attractive chemical signals. Furthermore, two genes called pickpocket23 and pickpocket29 control this response. These genes were previously known for their roles in detecting sex pheromones, and they are members of a diverse family of calcium channel subunits that are involved in detecting multiple ‘sensory modalities’ such as touch and taste. When either pickpocket23 or pickpocket29 are inactivated, larvae ignore the social cues left by their neighbors. Mast et al. also looked for an evolutionary role for these pheromones. Larvae of a closely related fly species called Drosophila simulans produce a subtly different blend of compounds to D. melanogaster, and this blend is not attractive to any of the species tested. While Drosophila simulans larvae were not attracted to the cues left by their own species, they were attracted to the pheromones produced by Drosophila melanogaster, indicating that they retain the sensory mechanisms to detect and respond to these pheromones. These results suggest that larvae experience a rapidly evolving, complex, pheromone-rich environment that may help them tailor their behavior to survive. DOI:http://dx.doi.org/10.7554/eLife.04205.002
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Affiliation(s)
- Joshua D Mast
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | | | - Hans T Alborn
- Center for Medical, Agricultural, and Veterinary Entomology, USDA-ARS, Gainesville, United States
| | - Luke D Lavis
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - David L Stern
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
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11
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Abstract
Genetic manipulations of neuronal activity are a cornerstone of studies aimed to identify the functional impact of defined neurons for animal behavior. With its small nervous system, rapid life cycle, and genetic amenability, the fruit fly Drosophila melanogaster provides an attractive model system to study neuronal circuit function. In the past two decades, a large repertoire of elegant genetic tools has been developed to manipulate and study neural circuits in the fruit fly. Current techniques allow genetic ablation, constitutive silencing, or hyperactivation of neuronal activity and also include conditional thermogenetic or optogenetic activation or inhibition. As for all genetic techniques, the choice of the proper transgenic tool is essential for behavioral studies. Potency and impact of effectors may vary in distinct neuron types or distinct types of behavior. We here systematically test genetic effectors for their potency to alter the behavior of Drosophila larvae, using two distinct behavioral paradigms: general locomotor activity and directed, visually guided navigation. Our results show largely similar but not equal effects with different effector lines in both assays. Interestingly, differences in the magnitude of induced behavioral alterations between different effector lines remain largely consistent between the two behavioral assays. The observed potencies of the effector lines in aminergic and cholinergic neurons assessed here may help researchers to choose the best-suited genetic tools to dissect neuronal networks underlying the behavior of larval fruit flies.
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12
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Grewal JS, Nguyen C, Robles R, Cho C, Kir K, Fledderman N, Gacharna G, Wesolowski M, Klinger C, Vallejo P, Menhennett L, Nagaraj A, Ebo C, Peacy G, Davelis E, Kucher D, Giers S, Kreher SA. Complex and non-redundant signals from individual odor receptors that underlie chemotaxis behavior in Drosophila melanogaster larvae. Biol Open 2014; 3:947-57. [PMID: 25238759 PMCID: PMC4197443 DOI: 10.1242/bio.20148573] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The rules by which odor receptors encode odors and allow behavior are still largely unexplored. Although large data sets of electrophysiological responses of receptors to odors have been generated, few hypotheses have been tested with behavioral assays. We use a data set on odor responses of Drosophila larval odor receptors coupled with chemotaxis behavioral assays to examine rules of odor coding. Using mutants of odor receptors, we have found that odor receptors with similar electrophysiological responses to odors across concentrations play non-redundant roles in odor coding at specific odor concentrations. We have also found that high affinity receptors for odors determine behavioral response thresholds, but the rules for determining peak behavioral responses are more complex. While receptor mutants typically show loss of attraction to odors, some receptor mutants result in increased attraction at specific odor concentrations. The odor receptor mutants were rescued using transgenic expression of odor receptors, validating assignment of phenotypes to the alleles. Vapor pressures alone cannot fully explain behavior in our assay. Finally, some odors that did not elicit strong electrophysiological responses are associated with behavioral phenotypes upon examination of odor receptor mutants. This result is consistent with the role of sensory neurons in lateral inhibition via local interneurons in the antennal lobe. Taken together, our results suggest a complexity of odor coding rules even in a simple olfactory sensory system.
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Affiliation(s)
- Jeewanjot S Grewal
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Christine Nguyen
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Raquel Robles
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Christina Cho
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Karolina Kir
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Nicole Fledderman
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - George Gacharna
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Michael Wesolowski
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Christie Klinger
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Pedro Vallejo
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Lorien Menhennett
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Abhiram Nagaraj
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Chineze Ebo
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Garrett Peacy
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Eftihia Davelis
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - David Kucher
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Sarah Giers
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
| | - Scott A Kreher
- Department of Biological Sciences, Dominican University, 7900 West Division Street, Parmer Hall 244, River Forest, IL 60305, USA
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13
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König C, Schleyer M, Leibiger J, El-Keredy A, Gerber B. Bitter-sweet processing in larval Drosophila. Chem Senses 2014; 39:489-505. [PMID: 24833133 DOI: 10.1093/chemse/bju016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
"Sweet-" and "bitter-" tasting substances distinctively support attractive and aversive choice behavior, respectively, and therefore are thought to be processed by distinct pathways. Interestingly, electrophysiological recordings in adult Drosophila suggest that bitter and salty tastants, in addition to activating bitter, salt, or bitter/salt sensory neurons, can also inhibit sweet-sensory neurons. However, the behavioral significance of such a potential for combinatorial coding is little understood. Using larval Drosophila as a study case, we find that the preference towards fructose is inhibited when assayed in the background of the bitter tastant quinine. When testing the influence of quinine on the preference to other, equally preferred sweet tastants, we find that these sweet tastants differ in their susceptibility to be inhibited by quinine. Such stimulus specificity argues that the inhibitory effect of quinine is not due to general effects on locomotion or nausea. In turn, not all bitter tastants have the same potency to inhibit sweet preference; notably, their inhibitory potency is not determined by the strength of the avoidance of them. Likewise, equally avoided concentrations of sodium chloride differ in their potency to inhibit sugar preference. Furthermore, Gr33a-Gal4-positive neurons, while being necessary for bitter avoidance, are dispensable for inhibition of the sweet pathway. Thus, interactions across taste modalities are behaviorally significant and, as we discuss, arguably diverse in mechanism. These results suggest that the coding of tastants and the organization of gustatory behavior may be more combinatorial than is generally acknowledged.
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Affiliation(s)
- Christian König
- Department of Genetics, Institute of Biology, University of Leipzig, Talstr. 33, 04103 Leipzig, Germany, Research Group Molecular Systems Biology of Learning, Leibniz Institute for Neurobiology, Brenneckestr. 6, 39118 Magdeburg, Germany
| | - Michael Schleyer
- Department of Genetics, Institute of Biology, University of Leipzig, Talstr. 33, 04103 Leipzig, Germany, Department of Genetics of Learning and Memory, Leibniz Institute for Neurobiology, Brenneckestr. 6, 39118 Magdeburg, Germany
| | - Judith Leibiger
- Department of Genetics, Institute of Biology, University of Leipzig, Talstr. 33, 04103 Leipzig, Germany, Department of Genetics of Learning and Memory, Leibniz Institute for Neurobiology, Brenneckestr. 6, 39118 Magdeburg, Germany
| | - Amira El-Keredy
- Department of Genetics, Faculty of Agriculture, Tanta University, Tanta-Kafr El-Sheikh Road, Seberbay Campus, 31527 Tanta, Egypt
| | - Bertram Gerber
- Department of Genetics of Learning and Memory, Leibniz Institute for Neurobiology, Brenneckestr. 6, 39118 Magdeburg, Germany, Institute of Biology, Otto von Guericke University of Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany and Center for Behavioral Brain Sciences, Universitätsplatz 2, 39106 Magdeburg, Germany
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14
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Abstract
Five canonical tastes, bitter, sweet, umami (amino acid), salty, and sour (acid), are detected by animals as diverse as fruit flies and humans, consistent with a near-universal drive to consume fundamental nutrients and to avoid toxins or other harmful compounds. Surprisingly, despite this strong conservation of basic taste qualities between vertebrates and invertebrates, the receptors and signaling mechanisms that mediate taste in each are highly divergent. The identification over the last two decades of receptors and other molecules that mediate taste has led to stunning advances in our understanding of the basic mechanisms of transduction and coding of information by the gustatory systems of vertebrates and invertebrates. In this Review, we discuss recent advances in taste research, mainly from the fly and mammalian systems, and we highlight principles that are common across species, despite stark differences in receptor types.
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Affiliation(s)
- Emily R Liman
- Section of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA.
| | - Yali V Zhang
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Craig Montell
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA 93106, USA; Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA.
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15
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The extracellular matrix protein artichoke is required for integrity of ciliated mechanosensory and chemosensory organs in Drosophila embryos. Genetics 2014; 196:1091-102. [PMID: 24496014 DOI: 10.1534/genetics.113.156323] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sensory cilia are often encapsulated by an extracellular matrix (ECM). In Caenorhabditis elegans, Drosophila melanogaster, and vertebrates, this ECM is thought to be directly involved in ciliary mechanosensing by coupling external forces to the ciliary membrane. Drosophila mechano- and chemosensory cilia are both associated with an ECM, indicating that the ECM may have additional roles that go beyond mechanosensory cilium function. Here, we identify Artichoke (ATK), an evolutionarily conserved leucine-rich repeat ECM protein that is required for normal morphogenesis and function of ciliated sensilla in Drosophila. atk is transiently expressed in accessory cells in all ciliated sensory organs during their late embryonic development. Antibody stainings show ATK protein in the ECM that surrounds sensory cilia. Loss of ATK protein in atk null mutants leads to cilium deformation and disorientation in chordotonal organs, apparently without uncoupling the cilia from the ECM, and consequently to locomotion defects. Moreover, impaired chemotaxis in atk mutant larvae suggests that, based on ATK protein localization, the ECM is also crucial for the correct assembly of chemosensory receptors. In addition to defining a novel ECM component, our findings show the importance of ECM integrity for the proper morphogenesis of ciliated organs in different sensory modalities.
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16
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Mishra D, Chen YC, Yarali A, Oguz T, Gerber B. Olfactory memories are intensity specific in larval Drosophila. ACTA ACUST UNITED AC 2013; 216:1552-60. [PMID: 23596280 DOI: 10.1242/jeb.082222] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Learning can rely on stimulus quality, stimulus intensity, or a combination of these. Regarding olfaction, the coding of odour quality is often proposed to be combinatorial along the olfactory pathway, and working hypotheses are available concerning short-term associative memory trace formation of odour quality. However, it is less clear how odour intensity is coded, and whether olfactory memory traces include information about the intensity of the learnt odour. Using odour-sugar associative conditioning in larval Drosophila, we first describe the dose-effect curves of learnability across odour intensities for four different odours (n-amyl acetate, 3-octanol, 1-octen-3-ol and benzaldehyde). We then chose odour intensities such that larvae were trained at an intermediate odour intensity, but were tested for retention with either that trained intermediate odour intensity, or with respectively higher or lower intensities. We observed a specificity of retention for the trained intensity for all four odours used. This adds to the appreciation of the richness in 'content' of olfactory short-term memory traces, even in a system as simple as larval Drosophila, and to define the demands on computational models of associative olfactory memory trace formation. We suggest two kinds of circuit architecture that have the potential to accommodate intensity learning, and discuss how they may be implemented in the insect brain.
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Affiliation(s)
- Dushyant Mishra
- Universität Würzburg, Biozentrum, Neurobiologie und Genetik, Würzburg, Germany
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17
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Abstract
In the olfactory system of Drosophila melanogaster, it is relatively straightforward to target in vivo measurements of neural activity to specific processing channels. This, together with the numerical simplicity of the Drosophila olfactory system, has produced rapid gains in our understanding of Drosophila olfaction. This review summarizes the neurophysiology of the first two layers of this system: the peripheral olfactory receptor neurons and their postsynaptic targets in the antennal lobe. We now understand in some detail the cellular and synaptic mechanisms that shape odor representations in these neurons. Together, these mechanisms imply that interesting neural adaptations to environmental statistics have occurred. These mechanisms also place some fundamental constraints on early sensory processing that pose challenges for higher brain regions. These findings suggest some general principles with broad relevance to early sensory processing in other modalities.
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Affiliation(s)
- Rachel I Wilson
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
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18
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Mishra D, Miyamoto T, Rezenom YH, Broussard A, Yavuz A, Slone J, Russell DH, Amrein H. The molecular basis of sugar sensing in Drosophila larvae. Curr Biol 2013; 23:1466-71. [PMID: 23850280 DOI: 10.1016/j.cub.2013.06.028] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2013] [Revised: 04/29/2013] [Accepted: 06/12/2013] [Indexed: 11/15/2022]
Abstract
Evaluation of food chemicals is essential to make appropriate feeding decisions. The molecular genetic analysis of Gustatory receptor (Gr) genes and the characterization of the neural circuits that they engage has led to a broad understanding of taste perception in adult Drosophila [1, 2]. For example, eight relatively highly conserved members of the Gr gene family (Gr5a, Gr61a, and Gr64a-f), referred to as sugar Gr genes, are thought to be involved in sugar taste in adult flies [3-8], while the majority of the remaining Gr genes are likely to encode bitter taste receptors [9-11], albeit some function as pheromone [12-14] and carbon dioxide [15, 16] receptors. In contrast to the adult fly, relatively little is known about the cellular and molecular basis of taste perception in larvae. Here, we identify Gr43a, which was recently shown to function as a hemolymph fructose sensor in adult flies [17], as the major larval sugar receptor. We show that it is expressed in taste neurons, proventricular neurons, as well as sensory neurons of the brain. Larvae lacking Gr43a fail to sense sugars, while larvae mutant for all eight sugar Gr genes exhibit no obvious defect. Finally, we show that brain neurons are necessary and sufficient for sensing all main dietary sugars, which probably involves a postingestive mechanism of converting carbohydrates into fructose.
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Affiliation(s)
- Dushyant Mishra
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Science Center, College Station, TX 77843, USA
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19
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Sen S, Reichert H, VijayRaghavan K. Conserved roles of ems/Emx and otd/Otx genes in olfactory and visual system development in Drosophila and mouse. Open Biol 2013; 3:120177. [PMID: 23635521 PMCID: PMC3866872 DOI: 10.1098/rsob.120177] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The regional specialization of brain function has been well documented in the mouse and fruitfly. The expression of regulatory factors in specific regions of the brain during development suggests that they function to establish or maintain this specialization. Here, we focus on two such factors—the Drosophila cephalic gap genes empty spiracles (ems) and orthodenticle (otd), and their vertebrate homologues Emx1/2 and Otx1/2—and review novel insight into their multiple crucial roles in the formation of complex sensory systems. While the early requirement of these genes in specification of the neuroectoderm has been discussed previously, here we consider more recent studies that elucidate the later functions of these genes in sensory system formation in vertebrates and invertebrates. These new studies show that the ems and Emx genes in both flies and mice are essential for the development of the peripheral and central neurons of their respective olfactory systems. Moreover, they demonstrate that the otd and Otx genes in both flies and mice are essential for the development of the peripheral and central neurons of their respective visual systems. Based on these recent experimental findings, we discuss the possibility that the olfactory and visual systems of flies and mice share a common evolutionary origin, in that the conserved visual and olfactory circuit elements derive from conserved domains of otd/Otx and ems/Emx action in the urbilaterian ancestor.
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Affiliation(s)
- Sonia Sen
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, UAS-GKVK Campus, Bellary Road, Bangalore 560065, India
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20
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Poivet E, Gallot A, Montagné N, Glaser N, Legeai F, Jacquin-Joly E. A comparison of the olfactory gene repertoires of adults and larvae in the noctuid moth Spodoptera littoralis. PLoS One 2013; 8:e60263. [PMID: 23565215 PMCID: PMC3614943 DOI: 10.1371/journal.pone.0060263] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 02/24/2013] [Indexed: 11/18/2022] Open
Abstract
To better understand the olfactory mechanisms in a lepidopteran pest model species, the cotton leafworm Spodoptera littoralis, we have recently established a partial transcriptome from adult antennae. Here, we completed this transcriptome using next generation sequencing technologies, namely 454 and Illumina, on both adult antennae and larval tissues, including caterpillar antennae and maxillary palps. All sequences were assembled in 77,643 contigs. Their analysis greatly enriched the repertoire of chemosensory genes in this species, with a total of 57 candidate odorant-binding and chemosensory proteins, 47 olfactory receptors, 6 gustatory receptors and 17 ionotropic receptors. Using RT-PCR, we conducted the first exhaustive comparison of olfactory gene expression between larvae and adults in a lepidopteran species. All the 127 candidate olfactory genes were profiled for expression in male and female adult antennae and in caterpillar antennae and maxillary palps. We found that caterpillars expressed a smaller set of olfactory genes than adults, with a large overlap between these two developmental stages. Two binding proteins appeared to be larvae-specific and two others were adult-specific. Interestingly, comparison between caterpillar antennae and maxillary palps revealed numerous organ-specific transcripts, suggesting the complementary involvement of these two organs in larval chemosensory detection. Adult males and females shared the same set of olfactory transcripts, except two male-specific candidate pheromone receptors, two male-specific and two female-specific odorant-binding proteins. This study identified transcripts that may be important for sex-specific or developmental stage-specific chemosensory behaviors.
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Affiliation(s)
- Erwan Poivet
- INRA, UMR 1272, Physiologie de l’Insecte, Signalisation et Communication, Versailles, France
| | - Aurore Gallot
- INRA, UMR 1272, Physiologie de l’Insecte, Signalisation et Communication, Versailles, France
- IRISA, Équipe GenScale, Campus Universitaire de Beaulieu, Rennes, France
| | - Nicolas Montagné
- UPMC - Université Paris 6, UMR 1272, Physiologie de l’Insecte, Signalisation et Communication, Paris, France
| | - Nicolas Glaser
- INRA, UMR 1272, Physiologie de l’Insecte, Signalisation et Communication, Versailles, France
| | - Fabrice Legeai
- IRISA, Équipe GenScale, Campus Universitaire de Beaulieu, Rennes, France
| | - Emmanuelle Jacquin-Joly
- INRA, UMR 1272, Physiologie de l’Insecte, Signalisation et Communication, Versailles, France
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Olafson PU. Molecular characterization and immunolocalization of the olfactory co-receptor Orco from two blood-feeding muscid flies, the stable fly (Stomoxys calcitrans, L.) and the horn fly (Haematobia irritans irritans, L.). INSECT MOLECULAR BIOLOGY 2013; 22:131-142. [PMID: 23278866 PMCID: PMC3594380 DOI: 10.1111/imb.12009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Biting flies are economically important blood-feeding pests of medical and veterinary significance. Chemosensory-based biting fly behaviours, such as host/nutrient source localization and ovipositional site selection, are intriguing targets for the development of supplemental control strategies. In an effort to expand our understanding of biting fly chemosensory pathways, transcripts encoding the highly conserved insect odorant co-receptor (Orco) were isolated from two representative biting fly species, the stable fly (Scal\Orco) and the horn fly (Hirr\Orco). Orco forms a complex with an odour-specific odorant receptor to form an odour-gated ion channel. The biting fly transcripts were predicted to encode proteins with 87-94% amino acid similarity to published insect Orco sequences and were detected in various immature stages as well as in adult structures associated with olfaction, i.e. the antennae and maxillary palps, and gustation, i.e. the proboscis. Further, the relevant proteins were immunolocalized to specific antennal sensilla using anti-serum raised against a peptide sequence conserved between the two fly species. Results from the present study provide a basis for functional evaluation of repellent/attractant effects on as yet uncharacterized stable fly and horn fly conventional odorant receptors.
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Affiliation(s)
- P U Olafson
- USDA-ARS, Knipling-Bushland US Livestock Insects Research Laboratory, Kerrville, TX 78028, USA.
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22
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Gerber B, Biernacki R, Thum J. Odor-taste learning assays in Drosophila larvae. Cold Spring Harb Protoc 2013; 2013:2013/3/pdb.prot071639. [PMID: 23457337 DOI: 10.1101/pdb.prot071639] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Drosophila larva is an emerging model for studies in behavioral neurogenetics because of its simplicity in terms of cell number. Despite this simplicity, basic features of neuronal organization and key behavior faculties are shared with adult flies and with mammals. Here, we describe a pavlovian-type learning assay in fruit fly larvae. A group of larvae is sequentially exposed to specific odors in the presence or the absence of sugar, and then tested to determine whether they prefer the odor previously experienced with the reward. The protocol uses a two-group, reciprocal training design: One group of Drosophila larvae is exposed to n-amyl acetate (AM) with a sugar reward (+), then subsequently exposed to 1-octanol (OCT) with no reward (denoted AM+/OCT). The other group receives the reciprocal training (AM/OCT+). The two groups of larvae are then tested for their choices between AM and OCT. Relatively higher preferences for AM after AM+/OCT training than after AM/OCT+ training reflect associative learning and are quantified by the learning index (LI). This method offers a robust, simple, cheap, and reasonably quick test for learning ability (an aversive version is available as well, using either high-concentration salt or quinine as punishment). With the concerted efforts of the Drosophila research community, we anticipate it will allow us to unravel the full circuitry underlying odor-taste learning on a single-cell level.
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23
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Abstract
We studied complete dose-response curves for 53 odorants in the third instar larvae of Drosophila melanogaster. All odorants, except one, elicited an attraction response. Some odorants also elicited a decrease from their peak response at higher concentrations. This concentration-dependent decrease in olfactory response could be due to either desensitization or repulsion, 2 possibilities that we cannot distinguish in our current assay. We observed high variations in factors like slopes, thresholds, and peaks of responses that, in agreement with previous studies, suggest that the responses of different receptors are quite different for the similar change in concentration of various ligands. We also observed that lower attraction thresholds predicted higher peak amplitude. This suggests that if odor responses encompassed wider concentration range than can be covered by the dynamic range of a single receptor, then responses tend to be high in magnitude.
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Affiliation(s)
- Sukant Khurana
- National Center for Biological Sciences, GKVK Campus, Bangalore, Karnataka, India.
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24
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‘Decision Making’ in Larval Drosophila. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/b978-0-12-415823-8.00005-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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25
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El-Keredy A, Schleyer M, König C, Ekim A, Gerber B. Behavioural analyses of quinine processing in choice, feeding and learning of larval Drosophila. PLoS One 2012; 7:e40525. [PMID: 22802964 PMCID: PMC3393658 DOI: 10.1371/journal.pone.0040525] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 06/12/2012] [Indexed: 11/19/2022] Open
Abstract
Gustatory stimuli can support both immediate reflexive behaviour, such as choice and feeding, and can drive internal reinforcement in associative learning. For larval Drosophila, we here provide a first systematic behavioural analysis of these functions with respect to quinine as a study case of a substance which humans report as “tasting bitter”. We describe the dose-effect functions for these different kinds of behaviour and find that a half-maximal effect of quinine to suppress feeding needs substantially higher quinine concentrations (2.0 mM) than is the case for internal reinforcement (0.6 mM). Interestingly, in previous studies (Niewalda et al. 2008, Schipanski et al 2008) we had found the reverse for sodium chloride and fructose/sucrose, such that dose-effect functions for those tastants were shifted towards lower concentrations for feeding as compared to reinforcement, arguing that the differences in dose-effect function between these behaviours do not reflect artefacts of the types of assay used. The current results regarding quinine thus provide a starting point to investigate how the gustatory system is organized on the cellular and/or molecular level to result in different behavioural tuning curves towards a bitter tastant.
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Affiliation(s)
- Amira El-Keredy
- Genetics and Neurobiology, University of Würzburg, Würzburg, Germany
- Genetics, Tanta University, Tanta, Egypt
| | - Michael Schleyer
- Genetics and Neurobiology, University of Würzburg, Würzburg, Germany
- Genetics, University of Leipzig, Leipzig, Germany
| | | | - Aslihan Ekim
- Genetics and Neurobiology, University of Würzburg, Würzburg, Germany
- Molecular Biology and Genetics, Bilkent University, Ankara, Turkey
| | - Bertram Gerber
- Genetics and Neurobiology, University of Würzburg, Würzburg, Germany
- Genetics, University of Leipzig, Leipzig, Germany
- Genetics of Learning and Memory, Leibniz Institute for Neurobiology, Magdeburg, Germany
- Behavioural Genetics, University of Magdeburg, Magdeburg, Germany
- * E-mail:
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26
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Secreted semaphorins from degenerating larval ORN axons direct adult projection neuron dendrite targeting. Neuron 2012; 72:734-47. [PMID: 22153371 DOI: 10.1016/j.neuron.2011.09.026] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2011] [Indexed: 12/21/2022]
Abstract
During assembly of the Drosophila olfactory circuit, projection neuron (PN) dendrites prepattern the developing antennal lobe before the arrival of axons from their presynaptic partners, the adult olfactory receptor neurons (ORNs). We previously found that levels of transmembrane Semaphorin-1a, which acts as a receptor, instruct PN dendrite targeting along the dorsolateral-ventromedial axis. Here we show that two secreted semaphorins, Sema-2a and Sema-2b, provide spatial cues for PN dendrite targeting. Sema-2a and Sema-2b proteins are distributed in gradients opposing the Sema-1a protein gradient, and Sema-1a binds to Sema-2a-expressing cells. In Sema-2a and Sema-2b double mutants, PN dendrites that normally target dorsolaterally in the antennal lobe mistarget ventromedially, phenocopying cell-autonomous Sema-1a removal from these PNs. Cell ablation, cell-specific knockdown, and rescue experiments indicate that secreted semaphorins from degenerating larval ORN axons direct dendrite targeting. Thus, a degenerating brain structure instructs the wiring of a developing circuit through the repulsive action of secreted semaphorins.
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27
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Abstract
We examine the molecular and cellular basis of taste perception in the Drosophila larva through a comprehensive analysis of the expression patterns of all 68 Gustatory receptors (Grs). Gr-GAL4 lines representing each Gr are examined, and 39 show expression in taste organs of the larval head, including the terminal organ (TO), the dorsal organ (DO), and the pharyngeal organs. A receptor-to-neuron map is constructed. The map defines 10 neurons of the TO and DO, and it identifies 28 receptors that map to them. Each of these neurons expresses a unique subset of Gr-GAL4 drivers, except for two neurons that express the same complement. All of these neurons express at least two drivers, and one neuron expresses 17. Many of the receptors map to only one of these cells, but some map to as many as six. Conspicuously absent from the roster of Gr-GAL4 drivers expressed in larvae are those of the sugar receptor subfamily. Coexpression analysis suggests that most larval Grs act in bitter response and that there are distinct bitter-sensing neurons. A comprehensive analysis of central projections confirms that sensory information collected from different regions (e.g., the tip of the head vs the pharynx) is processed in different regions of the suboesophageal ganglion, the primary taste center of the CNS. Together, the results provide an extensive view of the molecular and cellular organization of the larval taste system.
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28
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Abstract
The Drosophila larva possesses just 21 unique and identifiable pairs of olfactory sensory neurons (OSNs), enabling investigation of the contribution of individual OSN classes to the peripheral olfactory code. We combined electrophysiological and computational modeling to explore the nature of the peripheral olfactory code in situ. We recorded firing responses of 19/21 OSNs to a panel of 19 odors. This was achieved by creating larvae expressing just one functioning class of odorant receptor, and hence OSN. Odor response profiles of each OSN class were highly specific and unique. However many OSN-odor pairs yielded variable responses, some of which were statistically indistinguishable from background activity. We used these electrophysiological data, incorporating both responses and spontaneous firing activity, to develop a Bayesian decoding model of olfactory processing. The model was able to accurately predict odor identity from raw OSN responses; prediction accuracy ranged from 12%–77% (mean for all odors 45.2%) but was always significantly above chance (5.6%). However, there was no correlation between prediction accuracy for a given odor and the strength of responses of wild-type larvae to the same odor in a behavioral assay. We also used the model to predict the ability of the code to discriminate between pairs of odors. Some of these predictions were supported in a behavioral discrimination (masking) assay but others were not. We conclude that our model of the peripheral code represents basic features of odor detection and discrimination, yielding insights into the information available to higher processing structures in the brain.
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29
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Saumweber T, Husse J, Gerber B. Innate attractiveness and associative learnability of odors can be dissociated in larval Drosophila. Chem Senses 2011; 36:223-35. [PMID: 21227902 PMCID: PMC3038274 DOI: 10.1093/chemse/bjq128] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/22/2010] [Indexed: 12/25/2022] Open
Abstract
We investigate olfactory associative learning in larval Drosophila. A reciprocal training design is used, such that one group of animals receives a reward in the presence of odor X but not in the presence of odor Y (Train: X+ // Y), whereas another group is trained reciprocally (Train: X // Y+). After training, differences in odor preference between these reciprocally trained groups in a choice test (Test: X - Y) reflect associative learning. The current study, after showing which odor pairs can be used for such learning experiments, 1) introduces a one-odor version of such reciprocal paradigm that allows estimating the learnability of single odors. Regarding this reciprocal one-odor paradigm, we show that 2) paired presentations of an odor with a reward increase odor preference above baseline, whereas unpaired presentations of odor and reward decrease odor preference below baseline; this suggests that odors can become predictive either of reward or of reward absence. Furthermore, we show that 3) innate attractiveness and associative learnability can be dissociated. These data deepen our understanding of odor-reward learning in larval Drosophila on the behavioral level, and thus foster its neurogenetic analysis.
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Affiliation(s)
- Timo Saumweber
- Department of Neurobiology and Genetics, Universität Würzburg, Biozentrum Am Hubland, 97074 Würzburg, Germany
- Department of Genetics, Institute for Biology, Universität Leipzig, Talstr. 33, 04103 Leipzig, Germany
| | - Jana Husse
- Department of Neurobiology and Genetics, Universität Würzburg, Biozentrum Am Hubland, 97074 Würzburg, Germany
- Present address: Max Planck Institut für Biophysikalische Chemie, Abteilung Genetik und Verhalten, Am Faßberg 11, 37077 Göttingen, Germany
| | - Bertram Gerber
- Department of Neurobiology and Genetics, Universität Würzburg, Biozentrum Am Hubland, 97074 Würzburg, Germany
- Department of Genetics, Institute for Biology, Universität Leipzig, Talstr. 33, 04103 Leipzig, Germany
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30
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Chen YC, Mishra D, Schmitt L, Schmuker M, Gerber B. A behavioral odor similarity "space" in larval Drosophila. Chem Senses 2011; 36:237-49. [PMID: 21227903 PMCID: PMC3038273 DOI: 10.1093/chemse/bjq123] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
To provide a behavior-based estimate of odor similarity in larval Drosophila, we use 4 recognition-type experiments: 1) We train larvae to associate an odor with food and then test whether they would regard another odor as the same as the trained one. 2) We train larvae to associate an odor with food and test whether they prefer the trained odor against a novel nontrained one. 3) We train larvae differentially to associate one odor with food, but not the other one, and test whether they prefer the rewarded against the nonrewarded odor. 4) In an experiment like (3), we test the larvae after a 30-min break. This yields a combined task-independent estimate of perceived difference between odor pairs. Comparing these perceived differences to published measures of physicochemical difference reveals a weak correlation. A notable exception are 3-octanol and benzaldehyde, which are distinct in published accounts of chemical similarity and in terms of their published sensory representation but nevertheless are consistently regarded as the most similar of the 10 odor pairs employed. It thus appears as if at least some aspects of olfactory perception are “computed” in postreceptor circuits on the basis of sensory signals rather than being immediately given by them.
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Affiliation(s)
- Yi-chun Chen
- Department of Neurobiology and Genetics, Universität Würzburg, Biozentrum Am Hubland, 97074 Würzburg, Germany
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31
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Larkin A, Karak S, Priya R, Das A, Ayyub C, Ito K, Rodrigues V, Ramaswami M. Central synaptic mechanisms underlie short-term olfactory habituation in Drosophila larvae. Learn Mem 2010; 17:645-53. [PMID: 21106688 DOI: 10.1101/lm.1839010] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Naive Drosophila larvae show vigorous chemotaxis toward many odorants including ethyl acetate (EA). Chemotaxis toward EA is substantially reduced after a 5-min pre-exposure to the odorant and recovers with a half-time of ∼20 min. An analogous behavioral decrement can be induced without odorant-receptor activation through channelrhodopsin-based, direct photoexcitation of odorant sensory neurons (OSNs). The neural mechanism of short-term habituation (STH) requires the (1) rutabaga adenylate cyclase; (2) transmitter release from predominantly GABAergic local interneurons (LNs); (3) GABA-A receptor function in projection neurons (PNs) that receive excitatory inputs from OSNs; and (4) NMDA-receptor function in PNs. These features of STH cannot be explained by simple sensory adaptation and, instead, point to plasticity of olfactory synapses in the antennal lobe as the underlying mechanism. Our observations suggest a model in which NMDAR-dependent depression of the OSN-PN synapse and/or NMDAR-dependent facilitation of inhibitory transmission from LNs to PNs contributes substantially to short-term habituation.
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Affiliation(s)
- Aoife Larkin
- School of Genetics and Microbiology, Smurfit Institute of Genetics and Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland
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32
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Sen S, Hartmann B, Reichert H, Rodrigues V. Expression and function of the empty spiracles gene in olfactory sense organ development of Drosophila melanogaster. Development 2010; 137:3687-95. [PMID: 20940227 DOI: 10.1242/dev.052407] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Drosophila, the cephalic gap gene empty spiracles plays key roles in embryonic patterning of the peripheral and central nervous system. During postembryonic development, it is involved in the development of central olfactory circuitry in the antennal lobe of the adult. However, its possible role in the postembryonic development of peripheral olfactory sense organs has not been investigated. Here, we show that empty spiracles acts in a subset of precursors that generate the olfactory sense organs of the adult antenna. All empty spiracles-expressing precursor cells co-express the proneural gene amos and the early patterning gene lozenge. Moreover, the expression of empty spiracles in these precursor cells is dependent on both amos and lozenge. Functional analysis reveals two distinct roles of empty spiracles in the development of olfactory sense organs. Genetic interaction studies in a lozenge-sensitized background uncover a requirement of empty spiracles in the formation of trichoid and basiconic olfactory sensilla. MARCM-based clonal mutant analysis reveals an additional role during axonal targeting of olfactory sensory neurons to glomeruli within the antennal lobe. Our findings on empty spiracles action in olfactory sense organ development complement previous studies that demonstrate its requirement in olfactory interneurons and, taken together with studies on the murine homologs of empty spiracles, suggest that conserved molecular genetic programs might be responsible for the formation of both peripheral and central olfactory circuitry in insects and mammals.
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Affiliation(s)
- Sonia Sen
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India
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33
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Abstract
Little is known about how individual olfactory receptor neurons (ORNs) select, from among many odor receptor genes, which genes to express. Abnormal chemosensory jump 6 (Acj6) is a POU domain transcription factor essential for the specification of ORN identity and odor receptor (Or) gene expression in the Drosophila maxillary palp, one of the two adult olfactory organs. However, the mechanism by which Acj6 functions in this process has not been investigated. Here, we systematically examine the role of Acj6 in the maxillary palp and in a major subset of antennal ORNs. We define an Acj6 binding site by a reiterative in vitro selection process. The site is found upstream of Or genes regulated by Acj6, and Acj6 binds to the site in Or promoters. Mutational analysis shows that the site is essential for Or regulation in vivo. Surprisingly, a novel ORN class in acj6 adults is found to arise from ectopic expression of a larval Or gene, which is repressed in wild type via an Acj6 binding site. Thus, Acj6 acts directly in the process of receptor gene choice; it plays a dual role, positive and negative, in the logic of the process, and acts in partitioning the larval and adult receptor repertoires.
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Abstract
Sensing the chemical environment is critical for all organisms. Diverse animals from insects to mammals utilize highly organized olfactory system to detect, encode, and process chemostimuli that may carry important information critical for health, survival, social interactions and reproduction. Therefore, for animals to properly interpret and react to their environment it is imperative that the olfactory system recognizes chemical stimuli with appropriate selectivity and sensitivity. Because olfactory receptor proteins play such an essential role in the specific recognition of diverse stimuli, understanding how they interact with and transduce their cognate ligands is a high priority. In the nearly two decades since the discovery that the mammalian odorant receptor gene family constitutes the largest group of G protein-coupled receptor (GPCR) genes, much attention has been focused on the roles of GPCRs in vertebrate and invertebrate olfaction. However, is has become clear that the 'family' of olfactory receptors is highly diverse, with roles for enzymes and ligand-gated ion channels as well as GPCRs in the primary detection of olfactory stimuli.
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Affiliation(s)
- Marc Spehr
- Department of Chemosensation, Institute for Biology II, RWTH Aachen University, Aachen, Germany
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