151
|
Sengul MS, Tu Z. Expression analysis and knockdown of two antennal odorant-binding protein genes in Aedes aegypti. JOURNAL OF INSECT SCIENCE (ONLINE) 2010; 10:171. [PMID: 21062207 PMCID: PMC3016889 DOI: 10.1673/031.010.14131] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Accepted: 10/22/2009] [Indexed: 05/30/2023]
Abstract
The presence and expression of odorant-binding proteins (OBPs) in the olfactory organs suggest that they play an important role in mosquito olfaction. However, no direct evidence has been found for their involvement in the host-seeking behavior of mosquitoes. It is important to establish a method in which a loss-of-function test can be performed to determine the possible role of these genes in olfaction. In this study, a double subgenomic Sindbis virus expression system was used to reduce the expression of two Obp genes in Aedes aegypti L (Diptera: Culicidae), AaegObp1 and AaegObp2. Quantitative real-time PCR analysis showed predominant expression of both genes in the female antennae, the primary olfactory tissue of mosquitoes. Moreover, at 11 days post virus-inoculation, the mRNA levels of AaegObp1 and AaegObp2 were significantly reduced in olfactory tissues of recombinant virus-inoculated female mosquitoes compared to that of controls by approximately 8 and 100-fold, respectively. These data suggest that the double subgenomic Sindbis virus expression system can be efficiently used to knockdown Obp gene expression in olfactory tissues of mosquitoes. We discuss the potential for a systematic analysis of the molecular players involved in mosquito olfaction using this newly developed technique. Such analysis will provide an important step to interfere with the host-seeking behavior of mosquitoes to prevent the transmission of diseases.
Collapse
Affiliation(s)
- Meryem S. Sengul
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA
- Current address: Department of Biology, Bozok University, Yozgat, 66200, Turkey
| | - Zhijian Tu
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA
| |
Collapse
|
152
|
Functional and molecular evolution of olfactory neurons and receptors for aliphatic esters across the Drosophila genus. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2009; 196:97-109. [PMID: 20033746 DOI: 10.1007/s00359-009-0496-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Revised: 12/02/2009] [Accepted: 12/07/2009] [Indexed: 02/01/2023]
Abstract
Insect olfactory receptor (Or) genes are large, rapidly evolving gene families of considerable interest for evolutionary studies. They determine the responses of sensory neurons which mediate critical behaviours and ecological adaptations. We investigated the evolution across the genus Drosophila of a subfamily of Or genes largely responsible for the perception of ecologically relevant aliphatic esters; products of yeast fermentation and fruits. Odour responses were recorded from eight classes of olfactory receptor neurons known to express this Or subfamily in D. melanogaster and from homologous sensilla in seven other species. Despite the fact that these species have diverged over an estimated 40 million years, we find that odour specificity is largely maintained in seven of the eight species. In contrast, we observe extensive changes in most neurons of the outgroup species D. virilis, and in two neurons across the entire genus. Some neurons show small shifts in specificity, whilst some dramatic changes correlate with gene duplication or loss. An olfactory receptor neuron response similarity tree did not match an Or sequence similarity tree, but by aligning Or proteins of likely functional equivalence we identify residues that may be relevant for odour specificity. This will inform future structure-function studies of Drosophila Ors.
Collapse
|
153
|
Harraca V, Ignell R, Löfstedt C, Ryne C. Characterization of the antennal olfactory system of the bed bug (Cimex lectularius). Chem Senses 2009; 35:195-204. [PMID: 20032111 DOI: 10.1093/chemse/bjp096] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The common bed bug Cimex lectularius (Hemiptera; Cimicidae) is a temporary ectoparasite on humans that is currently reinvading the developed countries. Like other haematophagous arthropods, host seeking and orientation in C. lectularius is partially mediated by olfaction. In this study, we reconfirmed the distribution of the 44 olfactory sensilla and identified 3 different sensillum types located at the distal tip of C. lectularius antenna by external morphology mapping. Using a panel of relevant odorants previously reported to be bioactive in various haematophagous arthropods, we correlated the morphological mapping with an electrophysiological characterization of the olfactory receptor neurons housed in each specific sensillum. We found that all 9 grooved peg sensilla responded specifically in a dose-dependent manner to ammonia, whereas (E)-2-hexenal, (E)-2-octenal, dimethyl trisulfide, 6-methyl-5-hepten-2-one, alpha-pinene, indole, and ethyl butyrate evoked dose-dependent responses within the 6 smooth peg sensilla. Based on the pattern of response to the tested compounds, we were able to separate the 6 smooth peg sensilla of the bed bug into 3 distinct functional classes. We compare our results with previous electrophysiological recordings made with these compounds on other haematophagous arthropods.
Collapse
Affiliation(s)
- Vincent Harraca
- Division of Chemical Ecology, Department of Ecology, Ecology Building, Lund University, SE-223 62 Lund, Sweden
| | | | | | | |
Collapse
|
154
|
Towards plant-odor-related olfactory neuroethology in Drosophila. CHEMOECOLOGY 2009; 20:51-61. [PMID: 20461131 PMCID: PMC2864897 DOI: 10.1007/s00049-009-0033-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Accepted: 11/25/2009] [Indexed: 02/01/2023]
Abstract
Drosophila melanogaster is today one of the three foremost models in olfactory research, paralleled only by the mouse and the nematode. In the last years, immense progress has been achieved by combining neurogenetic tools with neurophysiology, anatomy, chemistry, and behavioral assays. One of the most important tasks for a fruit fly is to find a substrate for eating and laying eggs. To perform this task the fly is dependent on olfactory cues emitted by suitable substrates as e.g. decaying fruit. In addition, in this area, considerable progress has been made during the last years, and more and more natural and behaviorally active ligands have been identified. The future challenge is to tie the progress in different fields together to give us a better understanding of how a fly really behaves. Not in a test tube, but in nature. Here, we review our present state of knowledge regarding Drosophila plant-odor-related olfactory neuroethology to provide a basis for new progress.
Collapse
|
155
|
Abstract
The olfactory system of Drosophila melanogaster is one of the best characterized chemosensory systems. Identification of proteins contained in the third antennal segment, the main olfactory organ, has previously relied primarily on immunohistochemistry, and although such studies and in situ hybridization studies are informative, they focus generally on one or few gene products at a time, and quantification is difficult. In addition, purification of native proteins from the antenna is challenging because it is small and encased in a hard cuticle. Here, we describe a simple method for the large-scale detection of soluble proteins from the Drosophila antenna by chromatographic separation of tryptic peptides followed by tandem mass spectrometry with femtomole detection sensitivities. Examination of the identities of these proteins indicates that they originate both from the extracellular perilymph and from the cytoplasm of disrupted cells. We identified enzymes involved with intermediary metabolism, proteins associated with regulation of gene expression, nucleic acid metabolism and protein metabolism, proteins associated with microtubular transport, 8 odorant-binding proteins, protective enzymes associated with antibacterial defense and defense against oxidative damage, cuticular proteins, and proteins of unknown function, which represented about one-third of all soluble proteins. The procedure described here opens the way for precise quantification of any target protein in the Drosophila antenna and should be readily applicable to antennae from other insects.
Collapse
Affiliation(s)
- Robert R H Anholt
- Department of Biology, North Carolina State University, Raleigh, NC 27695-7617, USA.
| | | |
Collapse
|
156
|
Abstract
Remarkable advances in our understanding of olfactory perception have been made in recent years, including the discovery of new mechanisms of olfactory signaling and new principles of olfactory processing. Here, we discuss the insight that has been gained into the receptors, cells, and circuits that underlie the sense of smell.
Collapse
Affiliation(s)
| | | | - John R. Carlson
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven 06520, USA
| |
Collapse
|
157
|
Patel M, Rangan AV, Cai D. A large-scale model of the locust antennal lobe. J Comput Neurosci 2009; 27:553-67. [PMID: 19548077 DOI: 10.1007/s10827-009-0169-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Revised: 03/11/2009] [Accepted: 06/02/2009] [Indexed: 11/27/2022]
Abstract
The antennal lobe (AL) is the primary structure within the locust's brain that receives information from olfactory receptor neurons (ORNs) within the antennae. Different odors activate distinct subsets of ORNs, implying that neuronal signals at the level of the antennae encode odors combinatorially. Within the AL, however, different odors produce signals with long-lasting dynamic transients carried by overlapping neural ensembles, suggesting a more complex coding scheme. In this work we use a large-scale point neuron model of the locust AL to investigate this shift in stimulus encoding and potential consequences for odor discrimination. Consistent with experiment, our model produces stimulus-sensitive, dynamically evolving populations of active AL neurons. Our model relies critically on the persistence time-scale associated with ORN input to the AL, sparse connectivity among projection neurons, and a synaptic slow inhibitory mechanism. Collectively, these architectural features can generate network odor representations of considerably higher dimension than would be generated by a direct feed-forward representation of stimulus space.
Collapse
Affiliation(s)
- Mainak Patel
- The Sackler Institute of Graduate Biomedical Sciences, NYU School of Medicine, New York, NY 10016, USA.
| | | | | |
Collapse
|
158
|
Muezzinoglu MK, Huerta R, Abarbanel HDI, Ryan MA, Rabinovich MI. Chemosensor-driven artificial antennal lobe transient dynamics enable fast recognition and working memory. Neural Comput 2009; 21:1018-37. [PMID: 19018701 DOI: 10.1162/neco.2008.05-08-780] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The speed and accuracy of odor recognition in insects can hardly be resolved by the raw descriptors provided by olfactory receptors alone due to their slow time constant and high variability. The animal overcomes these barriers by means of the antennal lobe (AL) dynamics, which consolidates the classificatory information in receptor signal with a spatiotemporal code that is enriched in odor sensitivity, particularly in its transient. Inspired by this fact, we propose an easily implementable AL-like network and show that it significantly expedites and enhances the identification of odors from slow and noisy artificial polymer sensor responses. The device owes its efficiency to two intrinsic mechanisms: inhibition (which triggers a competition) and integration (due to the dynamical nature of the network). The former functions as a sharpening filter extracting the features of receptor signal that favor odor separation, whereas the latter implements a working memory by accumulating the extracted features in trajectories. This cooperation boosts the odor specificity during the receptor transient, which is essential for fast odor recognition.
Collapse
Affiliation(s)
- Mehmet K Muezzinoglu
- Institute for Nonlinear Science, University of California, San Diego, La Jolla, CA 92093-0402, U.S.A.
| | | | | | | | | |
Collapse
|
159
|
Fuss SH, Ray A. Mechanisms of odorant receptor gene choice in Drosophila and vertebrates. Mol Cell Neurosci 2009; 41:101-12. [PMID: 19303443 DOI: 10.1016/j.mcn.2009.02.014] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 02/27/2009] [Indexed: 01/13/2023] Open
Abstract
Odorant receptors are encoded by extremely large and divergent families of genes. Each receptor is expressed in a small proportion of neurons in the olfactory organs, and each neuron in turn expresses just one odorant receptor gene. This fundamental property of the peripheral olfactory system is widely conserved across evolution, and observed in vertebrates, like mice, and invertebrates, like Drosophila, despite their olfactory receptor gene families being evolutionarily unrelated. Here we review the progress that has been made in these two systems to understand the intriguing and elusive question: how does a single neuron choose to express just one of many possible odorant receptors and exclude expression of all others?
Collapse
Affiliation(s)
- Stefan H Fuss
- Department of Molecular Biology and Genetics, Bogazici University, 34342 Istanbul, Turkey
| | | |
Collapse
|
160
|
The olfactory sensory map in Drosophila. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 628:102-14. [PMID: 18683641 DOI: 10.1007/978-0-387-78261-4_7] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The fruit fly (Drosophila melanogaster) exhibits robust odor-evoked behaviors in response to cues from diverse host plants and pheromonal cues from other flies. Understanding how the adult olfactory system supports the perception of these odorous chemicals and translates them into appropriate attraction or avoidance behaviors is an important goal in contemporary sensory neuroscience. Recent advances in genomics and molecular neurobiology have provided an unprecedented level of detail into how the adult Drosophila olfactory system is organized. Volatile odorants are sensed by two bilaterally symmetric olfactory sensory appendages, the third segment of the antenna and the maxillary palps, which respectively contain approximately 1200 and 120 olfactory sensory neurons (OSNs) each. These OSNs express a divergent family of seven transmembrane domain odorant receptors (ORs) with no homology to vertebrate ORs, which determine the odor specificity of a given OSN. Drosophila was the first animal for which all OR genes were cloned, their patterns of gene expression determined and axonal projections of most OSNs elucidated. In vivo electrophysiology has been used to decode the ligand response profiles of most of the ORs, providing insight into the initial logic of olfactory coding in the fly. This chapter will review the molecular biology, neuroanatomy and function of the peripheral olfactory system of Drosophila.
Collapse
|
161
|
Rodrigues V, Hummel T. Development of the Drosophila olfactory system. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 628:82-101. [PMID: 18683640 DOI: 10.1007/978-0-387-78261-4_6] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The olfactory system throughout the animal kingdom is characterized by a large number of highly specialized neuronal cell types. Olfactory receptor neurons (ORNs) in the peripheral sensory epithelium display two main differentiation features: the selective expression of a single odorant receptor out of a large genomic repertoire of receptor genes and the synaptic connection to a single type of relay neuron in the primary olfactory CNS target area. In the mouse olfactory system, odorant receptors themselves play a central role in the coordination of both types of ORN differentiation. The olfactory system of Drosophila, although similar in structural and functional organization compared to mammals, does not seem to involve odorant receptors in the selection of OR gene expression and target cell recognition, suggesting distinct developmental control mechanisms. In this chapter we summarize recent findings in Drosophila of how gene networks regulate ORN specification and differentiation in the peripheral sensory organs as well as how different cellular interactions and patterning signals organize the class-specific axonal and dendritic connectivity in the CNS target area.
Collapse
Affiliation(s)
- Veronica Rodrigues
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | | |
Collapse
|
162
|
Rains GC, Kulasiri D, Zhou Z, Samarasinghe S, Tomberlin JK, Olson DM. Synthesizing Neurophysiology, Genetics, Behaviour and Learning to Produce Whole-Insect Programmable Sensors to Detect Volatile Chemicals. Biotechnol Genet Eng Rev 2009; 26:179-204. [DOI: 10.5661/bger-26-179] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
163
|
Chapter 3 Mapping and Manipulating Neural Circuits in the Fly Brain. ADVANCES IN GENETICS 2009; 65:79-143. [DOI: 10.1016/s0065-2660(09)65003-3] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
|
164
|
Gerber B, Stocker RF, Tanimura T, Thum AS. Smelling, tasting, learning: Drosophila as a study case. Results Probl Cell Differ 2009; 47:139-185. [PMID: 19145411 DOI: 10.1007/400_2008_9] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Understanding brain function is to account for how the sensory system is integrated with the organism's needs to organize behaviour. We review what is known about these processes with regard to chemosensation and chemosensory learning in Drosophila. We stress that taste and olfaction are organized rather differently. Given that, e.g., sugars are nutrients and should be eaten (irrespective of the kind of sugar) and that toxic substances should be avoided (regardless of the kind of death they eventually cause), tastants are classified into relatively few behavioural matters of concern. In contrast, what needs to be done in response to odours is less evolutionarily determined. Thus, discrimination ability is warranted between different kinds of olfactory input, as any difference between odours may potentially be or become important. Therefore, the olfactory system has a higher dimensionality than gustation, and allows for more sensory-motor flexibility to attach acquired behavioural 'meaning' to odours. We argue that, by and large, larval and adult Drosophila are similar in these kinds of architecture, and that additionally there are a number of similarities to vertebrates, in particular regarding the cellular architecture of the olfactory pathway, the functional slant of the taste and smell systems towards classification versus discrimination, respectively, and the higher plasticity of the olfactory sensory-motor system. From our point of view, the greatest gap in understanding smell and taste systems to date is not on the sensory side, where indeed impressive advances have been achieved; also, a satisfying account of associative odour-taste memory trace formation seems within reach. Rather, we lack an understanding as to how sensory and motor formats of processing are centrally integrated, and how adaptive motor patterns actually are selected. Such an understanding, we believe, will allow the analysis to be extended to the motivating factors of behaviour, eventually leading to a comprehensive account of those systems which make Drosophila do what Drosophila's got to do.
Collapse
Affiliation(s)
- B Gerber
- Universität Würzburg, Biozentrum, Am Hubland, Würzburg, 97074, Germany.
| | | | | | | |
Collapse
|
165
|
Farris SM. Tritocerebral tract input to the insect mushroom bodies. ARTHROPOD STRUCTURE & DEVELOPMENT 2008; 37:492-503. [PMID: 18590832 DOI: 10.1016/j.asd.2008.05.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Revised: 05/20/2008] [Accepted: 05/21/2008] [Indexed: 05/26/2023]
Abstract
Insect mushroom bodies, best known for their role in olfactory processing, also receive sensory input from other modalities. In crickets and grasshoppers, a tritocerebral tract containing afferents from palp mechanosensory and gustatory centers innervates the accessory calyx. The accessory calyx is uniquely composed of Class III Kenyon cells, and was shown by immunohistochemistry to be present sporadically across several insect orders. Neuronal tracers applied to the source of tritocerebral tract axons in several species of insects demonstrated that tritocerebral tract innervation of the mushroom bodies targeted the accessory calyx when present, the primary calyces when an accessory calyx was not present, or both. These results suggest that tritocerebral tract input to the mushroom bodies is likely ubiquitous, reflecting the importance of gustation for insect behavior. The scattered phylogenetic distribution of Class III Kenyon cells is also proposed to represent an example of generative homology, in which the developmental program for forming a structure is retained in all members of a lineage, but the program is not "run" in all branches.
Collapse
Affiliation(s)
- Sarah M Farris
- Department of Biology, West Virginia University, 3139 Life Sciences Building, 53 Campus Drive, Morgantown, WV 26506, USA.
| |
Collapse
|
166
|
Abstract
The mushroom body (MB) of the insect brain has important roles in odor learning and memory and in diverse other brain functions. To elucidate the anatomical basis underlying its function, we studied how the MB of Drosophila is organized by its intrinsic and extrinsic neurons. We screened for the GAL4 enhancer-trap strains that label specific subsets of these neurons and identified seven subtypes of Kenyon cells and three other intrinsic neuron types. Laminar organization of the Kenyon cell axons divides the pedunculus into at least five concentric strata. The alpha', beta', alpha, and beta lobes are each divided into three strata, whereas the gamma lobe appears more homogeneous. The outermost stratum of the alpha/beta lobes is specifically connected with a small, protruded subregion of the calyx, the accessory calyx, which does not receive direct olfactory input. As for the MB extrinsic neurons (MBENs), we found three types of antennal lobe projection neurons, among which two are novel. In addition, we resolved 17 other types of MBENs that arborize in the calyx, lobes, and pedunculus. Lobe-associated MBENs arborize in only specific areas of the lobes, being restricted along their longitudinal axes, forming two to five segmented zones in each lobe. The laminar arrangement of the Kenyon cell axons and segmented organization of the MBENs together divide the lobes into smaller synaptic units, possibly facilitating characteristic interaction between intrinsic and extrinsic neurons in each unit for different functional activities along the longitudinal lobe axes and between lobes. Structural differences between lobes are also discussed.
Collapse
Affiliation(s)
- Nobuaki K Tanaka
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan
| | | | | |
Collapse
|
167
|
SNMP is a signaling component required for pheromone sensitivity in Drosophila. Proc Natl Acad Sci U S A 2008; 105:10996-1001. [PMID: 18653762 DOI: 10.1073/pnas.0803309105] [Citation(s) in RCA: 221] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The only known volatile pheromone in Drosophila, 11-cis-vaccenyl acetate (cVA), mediates a variety of behaviors including aggregation, mate recognition, and sexual behavior. cVA is detected by a small set of olfactory neurons located in T1 trichoid sensilla on the antennae of males and females. Two components known to be required for cVA reception are the odorant receptor Or67d and the extracellular pheromone-binding protein LUSH. Using a genetic screen for cVA-insensitive mutants, we have identified a third component required for cVA reception: sensory neuron membrane protein (SNMP). SNMP is a homolog of CD36, a scavenger receptor important for lipoprotein binding and uptake of cholesterol and lipids in vertebrates. In humans, loss of CD36 is linked to a wide range of disorders including insulin resistance, dyslipidemia, and atherosclerosis, but how CD36 functions in lipid transport and signal transduction is poorly understood. We show that SNMP is required in pheromone-sensitive neurons for cVA sensitivity but is not required for sensitivity to general odorants. Using antiserum to SNMP infused directly into the sensillum lymph, we show that SNMP function is required on the dendrites of cVA-sensitive neurons; this finding is consistent with a direct role in cVA signal transduction. Therefore, pheromone perception in Drosophila should serve as an excellent model to elucidate the role of CD36 members in transmembrane signaling.
Collapse
|
168
|
Laughlin JD, Ha TS, Jones DNM, Smith DP. Activation of pheromone-sensitive neurons is mediated by conformational activation of pheromone-binding protein. Cell 2008; 133:1255-1265. [PMID: 18585358 DOI: 10.1016/j.cell.2008.04.046] [Citation(s) in RCA: 339] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Revised: 04/17/2008] [Accepted: 04/29/2008] [Indexed: 11/29/2022]
Abstract
Detection of volatile odorants by olfactory neurons is thought to result from direct activation of seven-transmembrane odorant receptors by odor molecules. Here, we show that detection of the Drosophila pheromone, 11-cis vaccenyl acetate (cVA), is instead mediated by pheromone-induced conformational shifts in the extracellular pheromone-binding protein, LUSH. We show that LUSH undergoes a pheromone-specific conformational change that triggers the firing of pheromone-sensitive neurons. Amino acid substitutions in LUSH that are predicted to reduce or enhance the conformational shift alter sensitivity to cVA as predicted in vivo. One substitution, LUSH(D118A), produces a dominant-active LUSH protein that stimulates T1 neurons through the neuronal receptor components Or67d and SNMP in the complete absence of pheromone. Structural analysis of LUSH(D118A) reveals that it closely resembles cVA-bound LUSH. Therefore, the pheromone-binding protein is an inactive, extracellular ligand converted by pheromone molecules into an activator of pheromone-sensitive neurons and reveals a distinct paradigm for detection of odorants.
Collapse
Affiliation(s)
- John D Laughlin
- Department of Pharmacology, University of Colorado at Denver and Health Sciences Center, 12801 East 17th Avenue, M/S 8303, P.O. Box 6511, Aurora CO 80045
| | - Tal Soo Ha
- Department of Pharmacology and Department of Neuroscience, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd. Dallas, TX 75390-9111
| | - David N M Jones
- Department of Pharmacology, University of Colorado at Denver and Health Sciences Center, 12801 East 17th Avenue, M/S 8303, P.O. Box 6511, Aurora CO 80045.,Program in Biomolecular Structure, University of Colorado at Denver and Health Sciences Center, 12801 East 17th Avenue, M/S 8303, P.O. Box 6511, Aurora CO 80045
| | - Dean P Smith
- Department of Pharmacology and Department of Neuroscience, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd. Dallas, TX 75390-9111
| |
Collapse
|
169
|
Kreher SA, Mathew D, Kim J, Carlson JR. Translation of sensory input into behavioral output via an olfactory system. Neuron 2008; 59:110-24. [PMID: 18614033 PMCID: PMC2496968 DOI: 10.1016/j.neuron.2008.06.010] [Citation(s) in RCA: 189] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 05/21/2008] [Accepted: 06/11/2008] [Indexed: 11/24/2022]
Abstract
We investigate the logic by which sensory input is translated into behavioral output. First we provide a functional analysis of the entire odor receptor repertoire of an olfactory system. We construct tuning curves for the 21 functional odor receptors of the Drosophila larva and show that they sharpen at lower odor doses. We construct a 21-dimensional odor space from the responses of the receptors and find that the distance between two odors correlates with the extent to which one odor masks the other. Mutational analysis shows that different receptors mediate the responses to different concentrations of an odorant. The summed response of the entire receptor repertoire correlates with the strength of the behavioral response. The activity of a small number of receptors is a surprisingly powerful predictor of behavior. Odors that inhibit more receptors are more likely to be repellents. Odor space is largely conserved between two dissimilar olfactory systems.
Collapse
Affiliation(s)
- Scott A. Kreher
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven CT 06520
| | - Dennis Mathew
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven CT 06520
| | - Junhyong Kim
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104
- Penn Genome Frontiers Institute, University of Pennsylvania, Philadelphia, PA 19104
| | - John R. Carlson
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven CT 06520
| |
Collapse
|
170
|
Hiroi M, Tanimura T, Marion-Poll F. Hedonic taste in Drosophila revealed by olfactory receptors expressed in taste neurons. PLoS One 2008; 3:e2610. [PMID: 18612414 PMCID: PMC2440521 DOI: 10.1371/journal.pone.0002610] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Accepted: 06/04/2008] [Indexed: 01/01/2023] Open
Abstract
Taste and olfaction are each tuned to a unique set of chemicals in the outside world, and their corresponding sensory spaces are mapped in different areas in the brain. This dichotomy matches categories of receptors detecting molecules either in the gaseous or in the liquid phase in terrestrial animals. However, in Drosophila olfactory and gustatory neurons express receptors which belong to the same family of 7-transmembrane domain proteins. Striking overlaps exist in their sequence structure and in their expression pattern, suggesting that there might be some functional commonalities between them. In this work, we tested the assumption that Drosophila olfactory receptor proteins are compatible with taste neurons by ectopically expressing an olfactory receptor (OR22a and OR83b) for which ligands are known. Using electrophysiological recordings, we show that the transformed taste neurons are excited by odor ligands as by their cognate tastants. The wiring of these neurons to the brain seems unchanged and no additional connections to the antennal lobe were detected. The odor ligands detected by the olfactory receptor acquire a new hedonic value, inducing appetitive or aversive behaviors depending on the categories of taste neurons in which they are expressed i.e. sugar- or bitter-sensing cells expressing either Gr5a or Gr66a receptors. Taste neurons expressing ectopic olfactory receptors can sense odors at close range either in the aerial phase or by contact, in a lipophilic phase. The responses of the transformed taste neurons to the odorant are similar to those obtained with tastants. The hedonic value attributed to tastants is directly linked to the taste neurons in which their receptors are expressed.
Collapse
Affiliation(s)
- Makoto Hiroi
- UMR n°1272, Physiologie de l'Insecte: Signalisation and Communication, INRA / UPMC / AgroParisTech, Route de Saint Cyr, Versailles, France
- Department of Biology, Graduate School of Sciences, Kyushu University, Ropponmatsu, Fukuoka, Japan
| | - Teiichi Tanimura
- Department of Biology, Graduate School of Sciences, Kyushu University, Ropponmatsu, Fukuoka, Japan
| | - Frédéric Marion-Poll
- UMR n°1272, Physiologie de l'Insecte: Signalisation and Communication, INRA / UPMC / AgroParisTech, Route de Saint Cyr, Versailles, France
| |
Collapse
|
171
|
Baker TC. Balanced olfactory antagonism as a concept for understanding evolutionary shifts in moth sex pheromone blends. J Chem Ecol 2008. [PMID: 18452043 DOI: 10.1007/s10886-008-9468-9465] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
Abstract
In the sex pheromone communication systems of moths, both heterospecific sex pheromone components and individual conspecific pheromone components may act as behavioral antagonists when they are emitted at excessive rates and ratios. In such cases, the resulting blend composition does not comprise the sex pheromone of a given species. That is, unless these compounds are emitted at optimal rates and ratios with other compounds, they act as behavioral antagonists. Thus, the array of blend compositions that are attractive to males is centered around the characterized female-produced sex pheromone blend of a species. I suggest here that the resulting optimal attraction of males to a sex pheromone is the result of olfactory antagonistic balance, compared to the would-be olfactory antagonistic imbalance imparted by behaviorally active compounds when they are emitted individually or in other off-ratio blends. Such balanced olfactory antagonism might be produced in any number of ways in olfactory pathways, one of which would be mutual, gamma-aminobutyric-acid-related disinhibition by local interneurons in neighboring glomeruli that receive excitatory inputs from pheromone-stimulated olfactory receptor neurons. Such mutual disinhibition would facilitate greater excitatory transmission to higher centers by projection interneurons arborizing in those glomeruli. I propose that in studies of moth sex pheromone olfaction, we should no longer artificially compartmentalize the olfactory effects of heterospecific behavioral antagonists into a special category distinct from olfaction involving conspecific sex pheromone components. Indeed, continuing to impose such a delineation among these compounds may retard advances in understanding how moth olfactory systems can evolve to allow males to exhibit correct behavioral responses (that is, attraction) to novel sex-pheromone-related compositions emitted by females.
Collapse
Affiliation(s)
- Thomas C Baker
- Center for Chemical Ecology, Department of Entomology, Penn State University, University Park, PA 16802, USA.
| |
Collapse
|
172
|
Kazama H, Wilson RI. Homeostatic matching and nonlinear amplification at identified central synapses. Neuron 2008; 58:401-13. [PMID: 18466750 DOI: 10.1016/j.neuron.2008.02.030] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Revised: 01/30/2008] [Accepted: 02/25/2008] [Indexed: 01/27/2023]
Abstract
Here we describe the properties of a synapse in the Drosophila antennal lobe and show how they can explain certain sensory computations in this brain region. The synapse between olfactory receptor neurons (ORNs) and projection neurons (PNs) is very strong, reflecting a large number of release sites and high release probability. This is likely one reason why weak ORN odor responses are amplified in PNs. Furthermore, the amplitude of unitary synaptic currents in a PN is matched to the size of its dendritic arbor. This matching may compensate for a lower input resistance of larger dendrites to produce uniform depolarization across PN types. Consistent with this idea, a genetic manipulation that lowers input resistance increases unitary synaptic currents. Finally, strong stimuli produce short-term depression at this synapse. This helps explain why PN odor responses are transient, and why strong ORN odor responses are not amplified as powerfully as weak responses.
Collapse
Affiliation(s)
- Hokto Kazama
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston MA 02115, USA
| | | |
Collapse
|
173
|
Odor Detection in Insects: Volatile Codes. J Chem Ecol 2008; 34:882-97. [DOI: 10.1007/s10886-008-9485-4] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Revised: 04/23/2008] [Accepted: 04/28/2008] [Indexed: 10/22/2022]
|
174
|
Shiraiwa T. Multimodal chemosensory integration through the maxillary palp in Drosophila. PLoS One 2008; 3:e2191. [PMID: 18478104 PMCID: PMC2364657 DOI: 10.1371/journal.pone.0002191] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Accepted: 04/01/2008] [Indexed: 01/17/2023] Open
Abstract
Drosophila melanogaster has an olfactory organ called the maxillary palp. It is smaller and numerically simpler than the antenna, and its specific role in behavior has long been unclear. Because of its proximity to the mouthparts, I explored the possibility of a role in taste behavior. Maxillary palp was tuned to mediate odor-induced taste enhancement: a sucrose solution was more appealing when simultaneously presented with the odorant 4-methylphenol. The same result was observed with other odors that stimulate other types of olfactory receptor neuron in the maxillary palp. When an antennal olfactory receptor was genetically introduced in the maxillary palp, the fly interpreted a new odor as a sweet-enhancing smell. These results all point to taste enhancement as a function of the maxillary palp. It also opens the door for studying integration of multiple senses in a model organism.
Collapse
Affiliation(s)
- Takashi Shiraiwa
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut, United States of America.
| |
Collapse
|
175
|
Balanced olfactory antagonism as a concept for understanding evolutionary shifts in moth sex pheromone blends. J Chem Ecol 2008; 34:971-81. [PMID: 18452043 DOI: 10.1007/s10886-008-9468-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Revised: 03/21/2008] [Accepted: 03/24/2008] [Indexed: 10/22/2022]
Abstract
In the sex pheromone communication systems of moths, both heterospecific sex pheromone components and individual conspecific pheromone components may act as behavioral antagonists when they are emitted at excessive rates and ratios. In such cases, the resulting blend composition does not comprise the sex pheromone of a given species. That is, unless these compounds are emitted at optimal rates and ratios with other compounds, they act as behavioral antagonists. Thus, the array of blend compositions that are attractive to males is centered around the characterized female-produced sex pheromone blend of a species. I suggest here that the resulting optimal attraction of males to a sex pheromone is the result of olfactory antagonistic balance, compared to the would-be olfactory antagonistic imbalance imparted by behaviorally active compounds when they are emitted individually or in other off-ratio blends. Such balanced olfactory antagonism might be produced in any number of ways in olfactory pathways, one of which would be mutual, gamma-aminobutyric-acid-related disinhibition by local interneurons in neighboring glomeruli that receive excitatory inputs from pheromone-stimulated olfactory receptor neurons. Such mutual disinhibition would facilitate greater excitatory transmission to higher centers by projection interneurons arborizing in those glomeruli. I propose that in studies of moth sex pheromone olfaction, we should no longer artificially compartmentalize the olfactory effects of heterospecific behavioral antagonists into a special category distinct from olfaction involving conspecific sex pheromone components. Indeed, continuing to impose such a delineation among these compounds may retard advances in understanding how moth olfactory systems can evolve to allow males to exhibit correct behavioral responses (that is, attraction) to novel sex-pheromone-related compositions emitted by females.
Collapse
|
176
|
Sato K, Pellegrino M, Nakagawa T, Nakagawa T, Vosshall LB, Touhara K. Insect olfactory receptors are heteromeric ligand-gated ion channels. Nature 2008; 452:1002-6. [PMID: 18408712 DOI: 10.1038/nature06850] [Citation(s) in RCA: 734] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2007] [Accepted: 02/20/2008] [Indexed: 11/09/2022]
Abstract
In insects, each olfactory sensory neuron expresses between one and three ligand-binding members of the olfactory receptor (OR) gene family, along with the highly conserved and broadly expressed Or83b co-receptor. The functional insect OR consists of a heteromeric complex of unknown stoichiometry but comprising at least one variable odorant-binding subunit and one constant Or83b family subunit. Insect ORs lack homology to G-protein-coupled chemosensory receptors in vertebrates and possess a distinct seven-transmembrane topology with the amino terminus located intracellularly. Here we provide evidence that heteromeric insect ORs comprise a new class of ligand-activated non-selective cation channels. Heterologous cells expressing silkmoth, fruitfly or mosquito heteromeric OR complexes showed extracellular Ca2+ influx and cation-non-selective ion conductance on stimulation with odorant. Odour-evoked OR currents are independent of known G-protein-coupled second messenger pathways. The fast response kinetics and OR-subunit-dependent K+ ion selectivity of the insect OR complex support the hypothesis that the complex between OR and Or83b itself confers channel activity. Direct evidence for odorant-gated channels was obtained by outside-out patch-clamp recording of Xenopus oocyte and HEK293T cell membranes expressing insect OR complexes. The ligand-gated ion channel formed by an insect OR complex seems to be the basis for a unique strategy that insects have acquired to respond to the olfactory environment.
Collapse
Affiliation(s)
- Koji Sato
- Department of Integrated Biosciences, The University of Tokyo, Chiba 277-8562, Japan
| | | | | | | | | | | |
Collapse
|
177
|
Haddad R, Khan R, Takahashi YK, Mori K, Harel D, Sobel N. A metric for odorant comparison. Nat Methods 2008; 5:425-9. [DOI: 10.1038/nmeth.1197] [Citation(s) in RCA: 169] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Accepted: 03/13/2008] [Indexed: 11/09/2022]
|
178
|
Turner GC, Bazhenov M, Laurent G. Olfactory Representations by Drosophila Mushroom Body Neurons. J Neurophysiol 2008; 99:734-46. [DOI: 10.1152/jn.01283.2007] [Citation(s) in RCA: 294] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Learning and memory has been studied extensively in Drosophila using behavioral, molecular, and genetic approaches. These studies have identified the mushroom body as essential for the formation and retrieval of olfactory memories. We investigated odor responses of the principal neurons of the mushroom body, the Kenyon cells (KCs), in Drosophila using whole cell recordings in vivo. KC responses to odors were highly selective and, thus sparse, compared with those of their direct inputs, the antennal lobe projection neurons (PNs). We examined the mechanisms that might underlie this transformation and identified at least three contributing factors: excitatory synaptic potentials (from PNs) decay rapidly, curtailing temporal integration, PN convergence onto individual KCs is low (∼10 PNs per KC on average), and KC firing thresholds are high. Sparse activity is thought to be useful in structures involved in memory in part because sparseness tends to reduce representation overlaps. By comparing activity patterns evoked by the same odors across olfactory receptor neurons and across KCs, we show that representations of different odors do indeed become less correlated as they progress through the olfactory system.
Collapse
|
179
|
Sato K, Touhara K. Insect olfaction: receptors, signal transduction, and behavior. Results Probl Cell Differ 2008; 47:121-38. [PMID: 19083129 DOI: 10.1007/400_2008_10] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The insect olfactory system is a suitable model for exploring molecular function of odorant receptors, axonal projection of olfactory receptor neurons onto secondary neurons, and the neural circuit for odor perception. Recent progress in the study of insect olfaction revealed that the heteromeric insect olfactory receptor complex forms a cation nonselective ion channel directly gated by odor or pheromone ligands independent of known G-protein signaling pathways. Despite fundamental differences in transduction machineries between insects and vertebrates, the anatomical and functional features of insect odor-coding strategy are similar and thus justify any consideration of mammalian olfaction in the study of insects. The understanding of the molecular mechanism of insect olfaction will help in the development of insect repellents for controlling insect pest and vector populations for a wide range of pathogens.
Collapse
Affiliation(s)
- K Sato
- Department of Integrated Biosciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8562, Japan
| | | |
Collapse
|
180
|
A family of chemoreceptors in Tribolium castaneum (Tenebrionidae: Coleoptera). PLoS One 2007; 2:e1319. [PMID: 18091992 PMCID: PMC2121604 DOI: 10.1371/journal.pone.0001319] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 11/15/2007] [Indexed: 01/08/2023] Open
Abstract
Chemoperception in invertebrates is mediated by a family of G-protein-coupled receptors (GPCR). To date nothing is known about the molecular mechanisms of chemoperception in coleopteran species. Recently the genome of Tribolium castaneum was sequenced for use as a model species for the Coleoptera. Using blast searches analyses of the T. castaneum genome with previously predicted amino acid sequences of insect chemoreceptor genes, a putative chemoreceptor family consisting of 62 gustatory receptors (Grs) and 26 olfactory receptors (Ors) was identified. The receptors have seven transmembrane domains (7TMs) and all belong to the GPCR receptor family. The expression of the T. castaneum chemoreceptor genes was investigated using quantification real- time RT-PCR and in situ whole mount RT-PCR analysis in the antennae, mouth parts, and prolegs of the adults and larvae. All of the predicted TcasGrs were expressed in the labium, maxillae, and prolegs of the adults but TcasGr13, 19, 28, 47, 62, 98, and 61 were not expressed in the prolegs. The TcasOrs were localized only in the antennae and not in any of the beetles gustatory organs with one exception; the TcasOr16 (like DmelOr83b), which was localized in the antennae, labium, and prolegs of the beetles. A group of six TcasGrs that presents a lineage with the sugar receptors subfamily in Drosophila melanogaster were localized in the lacinia of the Tribolium larvae. TcasGr1, 3, and 39, presented an ortholog to CO2 receptors in D. melanogaster and Anopheles gambiae was recorded. Low expression of almost all of the predicted chemoreceptor genes was observed in the head tissues that contain the brains and suboesophageal ganglion (SOG). These findings demonstrate the identification of a chemoreceptor family in Tribolium, which is evolutionarily related to other insect species.
Collapse
|
181
|
Abstract
Two qualitatively different kinds of neural map have been described: continuous maps exemplified by the visual retinotopic map, and discrete maps exemplified by the olfactory glomerular map. Here, we review developmental mechanisms of retinotopic and olfactory glomerular mapping and discuss underlying commonalities that have emerged from recent studies. These include the use of molecular gradients, axon-axon interactions, and the interplay between labeling molecules and neuronal activity in establishing these maps. Since visual retinotopic and olfactory glomerular maps represent two ends of a continuum that includes many other types of neural map in between, these emerging general principles may be widely applicable to map formation throughout the nervous system.
Collapse
|
182
|
Benton R, Vannice KS, Vosshall LB. An essential role for a CD36-related receptor in pheromone detection in Drosophila. Nature 2007; 450:289-93. [PMID: 17943085 DOI: 10.1038/nature06328] [Citation(s) in RCA: 375] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Accepted: 10/01/2007] [Indexed: 01/22/2023]
Abstract
The CD36 family of transmembrane receptors is present across metazoans and has been implicated biochemically in lipid binding and transport. Several CD36 proteins function in the immune system as scavenger receptors for bacterial pathogens and seem to act as cofactors for Toll-like receptors by facilitating recognition of bacterially derived lipids. Here we show that a Drosophila melanogaster CD36 homologue, Sensory neuron membrane protein (SNMP), is expressed in a population of olfactory sensory neurons (OSNs) implicated in pheromone detection. SNMP is essential for the electrophysiological responses of OSNs expressing the receptor OR67d to (Z)-11-octadecenyl acetate (cis-vaccenyl acetate, cVA), a volatile male-specific fatty-acid-derived pheromone that regulates sexual and social aggregation behaviours. SNMP is also required for the activation of the moth pheromone receptor HR13 by its lipid-derived pheromone ligand (Z)-11-hexadecenal, but is dispensable for the responses of the conventional odorant receptor OR22a to its short hydrocarbon fruit ester ligands. Finally, we show that SNMP is required for responses of OR67d to cVA when ectopically expressed in OSNs not normally activated by pheromones. Because mammalian CD36 binds fatty acids, we suggest that SNMP acts in concert with odorant receptors to capture pheromone molecules on the surface of olfactory dendrites. Our work identifies an unanticipated cofactor for odorant receptors that is likely to have a widespread role in insect pheromone detection. Moreover, these results define a unifying model for CD36 function, coupling recognition of lipid-based extracellular ligands to signalling receptors in both pheromonal communication and pathogen recognition through the innate immune system.
Collapse
Affiliation(s)
- Richard Benton
- Laboratory of Neurogenetics and Behaviour, The Rockefeller University, 1230 York Avenue, Box 63, New York, New York 10065, USA
| | | | | |
Collapse
|
183
|
Bhandawat V, Olsen SR, Gouwens NW, Schlief ML, Wilson RI. Sensory processing in the Drosophila antennal lobe increases reliability and separability of ensemble odor representations. Nat Neurosci 2007; 10:1474-82. [PMID: 17922008 DOI: 10.1038/nn1976] [Citation(s) in RCA: 240] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Accepted: 08/16/2007] [Indexed: 11/09/2022]
Abstract
Here we describe several fundamental principles of olfactory processing in the Drosophila melanogaster antennal lobe (the analog of the vertebrate olfactory bulb), through the systematic analysis of input and output spike trains of seven identified glomeruli. Repeated presentations of the same odor elicit more reproducible responses in second-order projection neurons (PNs) than in their presynaptic olfactory receptor neurons (ORNs). PN responses rise and accommodate rapidly, emphasizing odor onset. Furthermore, weak ORN inputs are amplified in the PN layer but strong inputs are not. This nonlinear transformation broadens PN tuning and produces more uniform distances between odor representations in PN coding space. In addition, portions of the odor response profile of a PN are not systematically related to their direct ORN inputs, which probably indicates the presence of lateral connections between glomeruli. Finally, we show that a linear discriminator classifies odors more accurately using PN spike trains than using an equivalent number of ORN spike trains.
Collapse
Affiliation(s)
- Vikas Bhandawat
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, Massachusetts 02115, USA
| | | | | | | | | |
Collapse
|
184
|
Ruebenbauer A. Simulation of the neural response to the odour stimulus. J Theor Biol 2007; 248:311-6. [PMID: 17570406 DOI: 10.1016/j.jtbi.2007.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2007] [Revised: 05/08/2007] [Accepted: 05/08/2007] [Indexed: 11/25/2022]
Abstract
The paper is aimed at the description of the newly introduced model used to simulate the neural response to the chemical stimulus. A potential difference across the living cell or tissue depends usually on the chemical excitation of this living entity. The peculiar case of chemical excitation is the odour recognition across animal kingdom, in particular by various insects. A potential difference is characterised by relatively rapid variation with time elapsed since the application of the stimulus. A complete mathematical model giving results similar to the real ones is outlined and discussed in light of the potential application to the various experimental patterns recognition. The saturation effects due to overlapping spikes are discussed in some detail. It is proposed to use semi-invariants as the semi-quantitative method to compare various data sets obtained either in response to various stimuli or to the same stimulus applied to various species.
Collapse
Affiliation(s)
- Agnieszka Ruebenbauer
- Chemical Ecology-Ecotoxicology, Department of Ecology, Lund University, SE-223 62 Solvegatan 37, Lund, Sweden.
| |
Collapse
|
185
|
Ghaninia M, Ignell R, Hansson BS. Functional classification and central nervous projections of olfactory receptor neurons housed in antennal trichoid sensilla of female yellow fever mosquitoes, Aedes aegypti. Eur J Neurosci 2007; 26:1611-23. [PMID: 17880395 PMCID: PMC2121139 DOI: 10.1111/j.1460-9568.2007.05786.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 07/20/2007] [Accepted: 07/26/2007] [Indexed: 11/29/2022]
Abstract
Mosquitoes are highly dependent on their olfactory system for, e.g. host location and identification of nectar-feeding and oviposition sites. Odours are detected by olfactory receptor neurons (ORNs) housed in hair-shaped structures, sensilla, on the antennae and maxillary palps. In order to unravel the function of the olfactory system in the yellow fever vector, Aedes aegypti, we performed single-sensillum recordings from trichoid sensilla on female antennae. These sensilla are divided into four distinct morphological types. Based on the response to a set of 16 odour compounds, we identified 18 different ORN types, housed in 10 sensillum types. The ORNs responded to behaviourally relevant olfactory cues, such as oviposition attractants and sweat-borne compounds, including 4-methylcyclohexanol and indole, respectively. Two ORNs housed in these sensilla, as well as two ORNs housed in an additional sensillum type, did not respond to any of the compounds tested. The ORNs housed in individual sensilla exhibited stereotypical pairing and displayed differences in signalling mode (excitatory and inhibitory) as well as in temporal response patterns. In addition to physiological characterization, we performed anterograde neurobiotin stainings of functionally identified ORNs in order to define the functional map among olfactory glomeruli in the primary olfactory centre, the antennal lobe. The targeted glomeruli were compared with an established 3D map. Our data showed that the ORN types sent their axons to defined antennal lobe glomeruli in a stereotypic pattern.
Collapse
Affiliation(s)
- Majid Ghaninia
- Division of Chemical Ecology, Department of Plant Protection Biology, SLU, Box 44, 230 53, Alnarp, Sweden
| | | | | |
Collapse
|
186
|
Lu T, Qiu YT, Wang G, Kwon JY, Rutzler M, Kwon HW, Pitts RJ, van Loon JJ, Takken W, Carlson JR, Zwiebel LJ. Odor coding in the maxillary palp of the malaria vector mosquito Anopheles gambiae. Curr Biol 2007; 17:1533-44. [PMID: 17764944 PMCID: PMC3113458 DOI: 10.1016/j.cub.2007.07.062] [Citation(s) in RCA: 242] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 07/27/2007] [Accepted: 07/30/2007] [Indexed: 11/25/2022]
Abstract
BACKGROUND Many species of mosquitoes, including the major malaria vector Anopheles gambiae, utilize carbon dioxide (CO(2)) and 1-octen-3-ol as olfactory cues in host-seeking behaviors that underlie their vectorial capacity. However, the molecular and cellular basis of such olfactory responses remains largely unknown. RESULTS Here, we use molecular and physiological approaches coupled with systematic functional analyses to define the complete olfactory sensory map of the An. gambiae maxillary palp, an olfactory appendage that mediates the detection of these compounds. In doing so, we identify three olfactory receptor neurons (ORNs) that are organized in stereotyped triads within the maxillary-palp capitate-peg-sensillum population. One ORN is CO(2)-responsive and characterized by the coexpression of three receptors that confer CO(2) responses, whereas the other ORNs express characteristic odorant receptors (AgORs) that are responsible for their in vivo olfactory responses. CONCLUSIONS Our results describe a complete and highly concordant map of both the molecular and cellular olfactory components on the maxillary palp of the adult female An. gambiae mosquito. These results also facilitate the understanding of how An. gambiae mosquitoes sense olfactory cues that might be exploited to compromise their ability to transmit malaria.
Collapse
Affiliation(s)
- Tan Lu
- Department of Biological Sciences, Center for Molecular Neuroscience, Institute of Chemical Biology and Global Health, and Program in Developmental Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - Yu Tong Qiu
- Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
| | - Guirong Wang
- Department of Biological Sciences, Center for Molecular Neuroscience, Institute of Chemical Biology and Global Health, and Program in Developmental Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - Jae Young Kwon
- Department of Molecular, Cellular, and Developmental, Biology, Yale University, New Haven, Connecticut 06520-8103
| | - Michael Rutzler
- Department of Biological Sciences, Center for Molecular Neuroscience, Institute of Chemical Biology and Global Health, and Program in Developmental Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - Hyung-Wook Kwon
- Department of Biological Sciences, Center for Molecular Neuroscience, Institute of Chemical Biology and Global Health, and Program in Developmental Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - R. Jason Pitts
- Department of Biological Sciences, Center for Molecular Neuroscience, Institute of Chemical Biology and Global Health, and Program in Developmental Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - Joop J.A. van Loon
- Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
| | - John R. Carlson
- Department of Molecular, Cellular, and Developmental, Biology, Yale University, New Haven, Connecticut 06520-8103
| | - Laurence J. Zwiebel
- Department of Biological Sciences, Center for Molecular Neuroscience, Institute of Chemical Biology and Global Health, and Program in Developmental Biology, Vanderbilt University, Nashville, Tennessee 37235
- Correspondence:
| |
Collapse
|
187
|
Wang P, Lyman RF, Shabalina SA, Mackay TFC, Anholt RRH. Association of polymorphisms in odorant-binding protein genes with variation in olfactory response to benzaldehyde in Drosophila. Genetics 2007; 177:1655-65. [PMID: 17720903 PMCID: PMC2147940 DOI: 10.1534/genetics.107.079731] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Adaptive evolution of animals depends on behaviors that are essential for their survival and reproduction. The olfactory system of Drosophila melanogaster has emerged as one of the best characterized olfactory systems, which in addition to a family of odorant receptors, contains an approximately equal number of odorant-binding proteins (OBPs), encoded by a multigene family of 51 genes. Despite their abundant expression, little is known about their role in chemosensation, largely due to the lack of available mutations in these genes. We capitalized on naturally occurring mutations (polymorphisms) to gain insights into their functions. We analyzed the sequences of 13 Obp genes in two chromosomal clusters in a population of wild-derived inbred lines, and asked whether polymorphisms in these genes are associated with variation in olfactory responsiveness. Four polymorphisms in 3 Obp genes exceeded the statistical permutation threshold for association with responsiveness to benzaldehyde, suggesting redundancy and/or combinatorial recognition by these OBPs of this odorant. Model predictions of alternative pre-mRNA secondary structures associated with polymorphic sites suggest that alterations in Obp mRNA structure could contribute to phenotypic variation in olfactory behavior.
Collapse
Affiliation(s)
- Ping Wang
- Department of Genetics, North Carolina State University, Raleigh, North Carolina 27695, USA
| | | | | | | | | |
Collapse
|
188
|
Abstract
The chemical senses-smell and taste-allow animals to evaluate and distinguish valuable food resources from dangerous substances in the environment. The central mechanisms by which the brain recognizes and discriminates attractive and repulsive odorants and tastants, and makes behavioral decisions accordingly, are not well understood in any organism. Recent molecular and neuroanatomical advances in Drosophila have produced a nearly complete picture of the peripheral neuroanatomy and function of smell and taste in this insect. Neurophysiological experiments have begun to provide insight into the mechanisms by which these animals process chemosensory cues. Given the considerable anatomical and functional homology in smell and taste pathways in all higher animals, experimental approaches in Drosophila will likely provide broad insights into the problem of sensory coding. Here we provide a critical review of the recent literature in this field and comment on likely future directions.
Collapse
Affiliation(s)
- Leslie B Vosshall
- Laboratory of Neurogenetics and Behavior, The Rockefeller University, New York, NY 10021-6399, USA.
| | | |
Collapse
|
189
|
Keene AC, Waddell S. Drosophila olfactory memory: single genes to complex neural circuits. Nat Rev Neurosci 2007; 8:341-54. [PMID: 17453015 DOI: 10.1038/nrn2098] [Citation(s) in RCA: 325] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A central goal of neuroscience is to understand how neural circuits encode memory and guide behaviour. Studying simple, genetically tractable organisms, such as Drosophila melanogaster, can illuminate principles of neural circuit organization and function. Early genetic dissection of D. melanogaster olfactory memory focused on individual genes and molecules. These molecular tags subsequently revealed key neural circuits for memory. Recent advances in genetic technology have allowed us to manipulate and observe activity in these circuits, and even individual neurons, in live animals. The studies have transformed D. melanogaster from a useful organism for gene discovery to an ideal model to understand neural circuit function in memory.
Collapse
Affiliation(s)
- Alex C Keene
- Department of Neurobiology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, Massachusetts 01605, USA
| | | |
Collapse
|
190
|
Olsen SR, Bhandawat V, Wilson RI. Excitatory interactions between olfactory processing channels in the Drosophila antennal lobe. Neuron 2007; 54:89-103. [PMID: 17408580 PMCID: PMC2048819 DOI: 10.1016/j.neuron.2007.03.010] [Citation(s) in RCA: 209] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Revised: 03/13/2007] [Accepted: 03/15/2007] [Indexed: 11/28/2022]
Abstract
Each odorant receptor gene defines a unique type of olfactory receptor neuron (ORN) and a corresponding type of second-order neuron. Because each odor can activate multiple ORN types, information must ultimately be integrated across these processing channels to form a unified percept. Here, we show that, in Drosophila, integration begins at the level of second-order projection neurons (PNs). We genetically silence all the ORNs that normally express a particular odorant receptor and find that PNs postsynaptic to the silent glomerulus receive substantial lateral excitatory input from other glomeruli. Genetically confining odor-evoked ORN input to just one glomerulus reveals that most PNs postsynaptic to other glomeruli receive indirect excitatory input from the single ORN type that is active. Lateral connections between identified glomeruli vary in strength, and this pattern of connections is stereotyped across flies. Thus, a dense network of lateral connections distributes odor-evoked excitation between channels in the first brain region of the olfactory processing stream.
Collapse
|
191
|
Tunstall NE, Sirey T, Newcomb RD, Warr CG. Selective pressures on Drosophila chemosensory receptor genes. J Mol Evol 2007; 64:628-36. [PMID: 17541681 DOI: 10.1007/s00239-006-0151-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Accepted: 02/28/2007] [Indexed: 01/06/2023]
Abstract
The evolution and patterns of selection of genes encoding 10 Drosophila odorant receptors (Or) and the sex pheromone receptor Gr68a were investigated by comparing orthologous sequences across five to eight ecologically diverse species of Drosophila. Using maximum likelihood estimates of dN/dS ratios we show that all 11 genes sampled are under purifying selection, indicating functional constraint. Four of these genes (Or33c, Or42a, Or85e, and Gr68a) may be under positive selection, and if so, there is good evidence that 12 specific amino acid sites may be under positive selection. All of these sites are predicted to be located either in loop regions or just inside membrane spanning regions, and interestingly one of the two sites in Gr68a is in a similar position to a previously described polymorphism in Gr5a that causes a shift in sensitivity to its ligand trehalose. For three Ors, possible evidence for positive selection was detected along a lineage. These include Or22a in the lineage leading to D. mauritiana and Or22b in the lineage leading to D. simulans. This is of interest in light of previous data showing a change in ligand response profile for these species in the sensory neuron (ab3A) which expresses both Or22a and Or22b in D. melanogaster. In summary, while the main chemosensory function and/or structural integrity of these 10 Or genes and Gr68a are evolutionarily preserved, positive selection appears to be acting on some of these genes, at specific sites and along certain lineages, and provides testable hypotheses for further functional experimentation.
Collapse
Affiliation(s)
- Narelle E Tunstall
- School of Biological Sciences, Monash University, Wellington Road, Clayton, VIC, Australia
| | | | | | | |
Collapse
|
192
|
Schlief ML, Wilson RI. Olfactory processing and behavior downstream from highly selective receptor neurons. Nat Neurosci 2007; 10:623-30. [PMID: 17417635 PMCID: PMC2838507 DOI: 10.1038/nn1881] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2006] [Accepted: 02/27/2007] [Indexed: 11/09/2022]
Abstract
In both the vertebrate nose and the insect antenna, most olfactory receptor neurons (ORNs) respond to multiple odors. However, some ORNs respond to just a single odor, or at most to a few highly related odors. It has been hypothesized that narrowly tuned ORNs project to narrowly tuned neurons in the brain, and that these dedicated circuits mediate innate behavioral responses to a particular ligand. Here we have investigated neural activity and behavior downstream from two narrowly tuned ORN types in Drosophila melanogaster. We found that genetically ablating either of these ORN types impairs innate behavioral attraction to their cognate ligand. Neurons in the antennal lobe postsynaptic to one of these ORN types are, like their presynaptic ORNs, narrowly tuned to a pheromone. However, neurons postsynaptic to the second ORN type are broadly tuned. These results demonstrate that some narrowly tuned ORNs project to dedicated central circuits, ensuring a tight connection between stimulus and behavior, whereas others project to central neurons that participate in the ensemble representations of many odors.
Collapse
Affiliation(s)
- Michelle L Schlief
- Department of Neurobiology, Harvard Medical School, 220 Longwood Ave., Boston, Massachusetts 02115, USA
| | | |
Collapse
|
193
|
Sukontason K, Methanitikorn R, Chaiwong T, Kurahashi H, Vogtsberger RC, Sukontason KL. Sensilla of the antenna and palp of Hydrotaea chalcogaster (Diptera: Muscidae). Micron 2007; 38:218-23. [PMID: 16978868 DOI: 10.1016/j.micron.2006.07.018] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Revised: 07/07/2006] [Accepted: 07/07/2006] [Indexed: 11/24/2022]
Abstract
Hydrotaea chalcogaster is a fly species of medical and forensic importance in many parts of the world. In this study, we investigated the sensilla of the antenna and palp of the adult female fly using scanning electron microscopy. The antennal scape has one type of sensillum, the sharp-tipped sensillum trichodeum; whereas, the antennal pedicel also possessed this type of sensillum in addition to an unidentified type. Three types of sensilla were found on the flagellum: (1) sensilla basiconica, with both large and small sensilla basiconica showing wall pores, (2) sensilla coeloconica, with a smooth surface, and (3) sensory pits, with wall pores of pegs. The arista is located dorso-laterally on the flagellum and has three segments. Short microtrichia are located around the distal end of its second segment and on the proximal half of the third segment. Both large sharp-tipped sensilla chaetica and small sensilla basiconica with wall pores were observed on the palps. Results of this study contribute to our overall understanding of the ultrastructural morphology of sensilla on the antenna and palp of H. chalcogaster.
Collapse
Affiliation(s)
- Kom Sukontason
- Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
| | | | | | | | | | | |
Collapse
|
194
|
Ray A, van Naters WVDG, Shiraiwa T, Carlson JR. Mechanisms of odor receptor gene choice in Drosophila. Neuron 2007; 53:353-69. [PMID: 17270733 PMCID: PMC1986798 DOI: 10.1016/j.neuron.2006.12.010] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Revised: 10/05/2006] [Accepted: 12/07/2006] [Indexed: 11/24/2022]
Abstract
A remarkable problem in neurobiology is how olfactory receptor neurons (ORNs) select, from among a large odor receptor repertoire, which receptors to express. We use computational algorithms and mutational analysis to define positive and negative regulatory elements that are required for selection of odor receptor (Or) genes in the proper olfactory organ of Drosophila, and we identify an element that is essential for selection in one ORN class. Two odor receptors are coexpressed by virtue of the alternative splicing of a single gene, and we identify dicistronic mRNAs that each encode two receptors. Systematic analysis reveals no evidence for negative feedback regulation, but provides evidence that the choices made by neighboring ORNs of a sensillum are coordinated via the asymmetric segregation of regulatory factors from a common progenitor. We show that receptor gene choice in Drosophila also depends on a combinatorial code of transcription factors to generate the receptor-to-neuron map.
Collapse
Affiliation(s)
- Anandasankar Ray
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | | | | | | |
Collapse
|
195
|
Sweeney LB, Couto A, Chou YH, Berdnik D, Dickson BJ, Luo L, Komiyama T. Temporal target restriction of olfactory receptor neurons by Semaphorin-1a/PlexinA-mediated axon-axon interactions. Neuron 2007; 53:185-200. [PMID: 17224402 DOI: 10.1016/j.neuron.2006.12.022] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Revised: 09/19/2006] [Accepted: 12/01/2006] [Indexed: 11/24/2022]
Abstract
Axon-axon interactions have been implicated in neural circuit assembly, but the underlying mechanisms are poorly understood. Here, we show that in the Drosophila antennal lobe, early-arriving axons of olfactory receptor neurons (ORNs) from the antenna are required for the proper targeting of late-arriving ORN axons from the maxillary palp (MP). Semaphorin-1a is required for targeting of all MP but only half of the antennal ORN classes examined. Sema-1a acts nonautonomously to control ORN axon-axon interactions, in contrast to its cell-autonomous function in olfactory projection neurons. Phenotypic and genetic interaction analyses implicate PlexinA as the Sema-1a receptor in ORN targeting. Sema-1a on antennal ORN axons is required for correct targeting of MP axons within the antennal lobe, while interactions amongst MP axons facilitate their entry into the antennal lobe. We propose that Sema-1a/PlexinA-mediated repulsion provides a mechanism by which early-arriving ORN axons constrain the target choices of late-arriving axons.
Collapse
Affiliation(s)
- Lora B Sweeney
- Howard Hughes Medical Institute, Department of Biological Sciences and Neurosciences Program, Stanford University, Stanford, CA 94305, USA
| | | | | | | | | | | | | |
Collapse
|
196
|
Pelz D, Roeske T, Syed Z, de Bruyne M, Galizia CG. The molecular receptive range of an olfactory receptor in vivo (Drosophila melanogaster Or22a). ACTA ACUST UNITED AC 2007; 66:1544-63. [PMID: 17103386 DOI: 10.1002/neu.20333] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Understanding how odors are coded within an olfactory system requires knowledge about its input. This is constituted by the molecular receptive ranges (MRR) of olfactory sensory neurons that converge in the glomeruli of the olfactory bulb (vertebrates) or the antennal lobe (AL, insects). Aiming at a comprehensive characterization of MRRs in Drosophila melanogaster we measured odor-evoked calcium responses in olfactory sensory neurons that express the olfactory receptor Or22a. We used an automated stimulus application system to screen [Ca(2+)] responses to 104 odors both in the antenna (sensory transduction) and in the AL (neuronal transmission). At 10(-2) (vol/vol) dilution, 39 odors elicited at least a half-maximal response. For these odorants we established dose-response relationships over their entire dynamic range. We tested 15 additional chemicals that are structurally related to the most efficient odors. Ethyl hexanoate and methyl hexanoate were the best stimuli, eliciting consistent responses at dilutions as low as 10(-9). Two substances led to calcium decrease, suggesting that Or22a might be constitutively active, and that these substances might act as inverse agonists, reminiscent of G-protein coupled receptors. There was no difference between the antennal and the AL MRR. Furthermore we show that Or22a has a broad yet selective MRR, and must be functionally described both as a specialist and a generalist. Both these descriptions are ecologically relevant. Given that adult Drosophila use approximately 43 ORs, a complete description of all MRRs appears now in reach.
Collapse
Affiliation(s)
- Daniela Pelz
- Institut für Neurobiologie, Freie Universität Berlin, D-14195 Berlin, Germany
| | | | | | | | | |
Collapse
|
197
|
Endo K, Aoki T, Yoda Y, Kimura KI, Hama C. Notch signal organizes the Drosophila olfactory circuitry by diversifying the sensory neuronal lineages. Nat Neurosci 2007; 10:153-60. [PMID: 17220884 DOI: 10.1038/nn1832] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Accepted: 12/15/2006] [Indexed: 11/09/2022]
Abstract
An essential feature of the organization and function of the vertebrate and insect olfactory systems is the generation of a variety of olfactory receptor neurons (ORNs) that have different specificities in regard to both odorant receptor expression and axonal targeting. Yet the underlying mechanisms that generate this neuronal diversity remain elusive. Here we demonstrate that the Notch signal is involved in the diversification of ORNs in Drosophila melanogaster. A systematic clonal analysis showed that a cluster of ORNs housed in each sensillum were differentiated into two classes, depending on the level of Notch activity in their sibling precursors. Notably, ORNs of different classes segregated their axonal projections into distinct domains in the antennal lobes. In addition, both the odorant receptor expression and the axonal targeting of ORNs were specified according to their Notch-mediated identities. Thus, Notch signaling contributes to the diversification of ORNs, thereby regulating multiple developmental events that establish the olfactory map in Drosophila.
Collapse
Affiliation(s)
- Keita Endo
- Laboratory for Neural Network Development, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minami, Chuo, Kobe, Hyogo 650-0047, Japan
| | | | | | | | | |
Collapse
|
198
|
Ngern-klun R, Sukontason K, Methanitikorn R, Vogtsberger RC, Sukontason KL. Fine structure of Chrysomya nigripes (Diptera: Calliphoridae), a fly species of medical importance. Parasitol Res 2007; 100:993-1002. [PMID: 17216239 DOI: 10.1007/s00436-006-0426-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Accepted: 11/30/2006] [Indexed: 11/30/2022]
Abstract
The fine structure of Chrysomya nigripes Aubertin, a blow fly species of medical importance, is presented using scanning electron microscopy (SEM) to contribute information on the morphology of the adult of this fly species. The surface of the dome-shaped ommatidia exhibits a microscopic granulose appearance. The palpus is equipped with small sensilla basiconica and sensilla chaetica, which provide sensory reception for detecting environmental information. At the apex of the mouthparts, the labellum is endowed with large numbers of sensilla trichodea and basiconic-like sensilla of variable length. The anterior (mesothoracic) spiracle is elliptical in shape and covered with extensively ramified setae except for a small dorsal aperture. The posterior (metathoracic) spiracle is shaped like a rounded isosceles triangle and covered by two valves of unequal size. The larger valve covers the upper approximately 2/3 of the spiracular opening, whereas the smaller valve covers the lower approximately 1/3 of the opening. Extensively ramified setae line and cover the valves over the entire spiracle. SEM analyses of the haltere knob and the prosternal organs, located adjacent to the cervical sclerites, revealed a striking resemblance of the morphological features of their sensilla. Each sensillum emanates from a cuticular ring, is approximately 12-15 mum in length, has a smooth surface, and terminates in a sharp tip. Various types of sensilla were associated with the ovipositor including sensilla trichodea, sensilla basiconica, sensilla placodea and probably sensilla styloconica. The possible function of sensilla distributed in particular regions of the fly integument is discussed.
Collapse
Affiliation(s)
- Radchadawan Ngern-klun
- Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | | | | | | | | |
Collapse
|
199
|
Smith DP. Odor and pheromone detection in Drosophila melanogaster. Pflugers Arch 2007; 454:749-58. [PMID: 17205355 DOI: 10.1007/s00424-006-0190-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Accepted: 11/08/2006] [Indexed: 11/28/2022]
Abstract
Drosophila melanogaster has proven to be a useful model system to probe the mechanisms underlying the detection, discrimination, and perception of volatile odorants. The relatively small receptor repertoire of 62 odorant receptors makes the goal of understanding odor responses from the total receptor repertoire approachable in this system, and recent work has been directed toward this goal. In addition, new work not only sheds light but also raises more questions about the initial steps in odor perception in this system. Odorant receptor genes in Drosophila are predicted to encode seven transmembrane receptors, but surprising data suggest that these receptors may be inverted in the plasma membrane compared to classical G-protein coupled receptors. Finally, although some Drosophila odorant receptors are activated directly by odorant molecules, detection of a volatile pheromone, 11-cis vaccenyl acetate requires an extracellular adapter protein called LUSH for activation of pheromone sensitive neurons. Because pheromones are used by insects to trigger mating and other behaviors, these insights may herald new approaches to control behavior in pathogenic and agricultural pest insects.
Collapse
MESH Headings
- Acetates
- Animals
- Discrimination, Psychological/physiology
- Drosophila Proteins/agonists
- Drosophila Proteins/genetics
- Drosophila Proteins/metabolism
- Drosophila melanogaster/anatomy & histology
- Drosophila melanogaster/genetics
- Drosophila melanogaster/physiology
- Female
- GTP-Binding Proteins/metabolism
- Genes, Insect/physiology
- Humans
- Male
- Nerve Net
- Odorants
- Oleic Acids
- Olfactory Receptor Neurons/cytology
- Olfactory Receptor Neurons/physiology
- Pheromones/physiology
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Odorant/agonists
- Receptors, Odorant/genetics
- Receptors, Odorant/metabolism
- Receptors, Pheromone/agonists
- Receptors, Pheromone/genetics
- Receptors, Pheromone/metabolism
- Sense Organs/anatomy & histology
- Sense Organs/metabolism
- Sexual Behavior, Animal/physiology
- Signal Transduction/drug effects
- Signal Transduction/genetics
- Smell/physiology
Collapse
Affiliation(s)
- Dean P Smith
- Department of Pharmacology and Center for Basic Neuroscience, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9111, USA.
| |
Collapse
|
200
|
Abstract
Odour perception is initiated by specific interactions between odorants and a large repertoire of receptors in olfactory neurons. During the past few years, considerable progress has been made in tracing olfactory perception from the odorant receptor protein to the activity of olfactory neurons to higher processing centres and, ultimately, to behaviour. The most complete picture is emerging for the simplest olfactory system studied--that of the fruitfly Drosophila melanogaster. Comparison of rodent, insect and nematode olfaction reveals surprising differences and unexpected similarities among chemosensory systems.
Collapse
Affiliation(s)
- Cornelia I Bargmann
- Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA.
| |
Collapse
|