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Fernández-Chiappe F, Ocker GK, Younger MA. Prospects on non-canonical olfaction in the mosquito and other organisms: why co-express? CURRENT OPINION IN INSECT SCIENCE 2025; 67:101291. [PMID: 39471910 DOI: 10.1016/j.cois.2024.101291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Revised: 10/22/2024] [Accepted: 10/23/2024] [Indexed: 11/01/2024]
Abstract
The Aedes aegypti mosquito utilizes olfaction during the search for humans to bite. The attraction to human body odor is an innate behavior for this disease-vector mosquito. Many well-studied model species have olfactory systems that conform to a particular organization that is sometimes referred to as the 'one-receptor-to-one-neuron' organization because each sensory neuron expresses only a single type of olfactory receptor that imparts the neuron's chemical selectivity. This sensory architecture has become the canon in the field. This review will focus on the recent finding that the olfactory system of Ae. aegypti has a different organization, with multiple olfactory receptors co-expressed in many of its olfactory sensory neurons. We will discuss the canonical organization and how this differs from the non-canonical organization, examine examples of non-canonical olfactory systems in other species, and discuss the possible roles of receptor co-expression in odor coding in the mosquito and other organisms.
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Affiliation(s)
- Florencia Fernández-Chiappe
- Department of Biology, Boston University, Boston, MA 02143, USA; Center for Systems Neuroscience, Boston University, Boston, MA 02143, USA
| | - Gabriel K Ocker
- Center for Systems Neuroscience, Boston University, Boston, MA 02143, USA; Department of Mathematics and Statistics, Boston University, Boston, MA 02143, USA
| | - Meg A Younger
- Department of Biology, Boston University, Boston, MA 02143, USA; Center for Systems Neuroscience, Boston University, Boston, MA 02143, USA.
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2
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Baik LS, Talross GJS, Gray S, Pattisam HS, Peterson TN, Nidetz JE, Hol FJH, Carlson JR. Mosquito taste responses to human and floral cues guide biting and feeding. Nature 2024; 635:639-646. [PMID: 39415007 PMCID: PMC11578787 DOI: 10.1038/s41586-024-08047-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 09/12/2024] [Indexed: 10/18/2024]
Abstract
The taste system controls many insect behaviours, yet little is known about how tastants are encoded in mosquitoes or how they regulate critical behaviours. Here we examine how taste stimuli are encoded by Aedes albopictus mosquitoes-a highly invasive disease vector-and how these cues influence biting, feeding and egg laying. We find that neurons of the labellum, the major taste organ of the head, differentially encode a wide variety of human and other cues. We identify three functional classes of taste sensilla with an expansive coding capacity. In addition to excitatory responses, we identify prevalent inhibitory responses, which are predictive of biting behaviour. Certain bitter compounds suppress physiological and behavioural responses to sugar, suggesting their use as potent stop signals against appetitive cues. Complex cues, including human sweat, nectar and egg-laying site water, elicit distinct response profiles from the neuronal repertoire. We identify key tastants on human skin and in sweat that synergistically promote biting behaviours. Transcriptomic profiling identifies taste receptors that could be targeted to disrupt behaviours. Our study sheds light on key features of the taste system that suggest new ways of manipulating chemosensory function and controlling mosquito vectors.
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Affiliation(s)
- Lisa S Baik
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Gaëlle J S Talross
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Sydney Gray
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Himani S Pattisam
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Taylor N Peterson
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - James E Nidetz
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Felix J H Hol
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - John R Carlson
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA.
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3
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Zhang R, Ng R, Wu ST, Su CY. Targeted deletion of olfactory receptors in D. melanogaster via CRISPR/Cas9-mediated LexA knock-in. J Neurogenet 2024; 38:122-133. [PMID: 39529229 PMCID: PMC11617259 DOI: 10.1080/01677063.2024.2426014] [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] [Received: 09/20/2024] [Accepted: 11/01/2024] [Indexed: 11/16/2024]
Abstract
The study of olfaction in Drosophila melanogaster has greatly benefited from genetic reagents such as olfactory receptor mutant lines and GAL4 reporter lines. The CRISPR/Cas9 gene-editing system has been increasingly used to create null receptor mutants or replace coding regions with GAL4 reporters. To further expand this toolkit for manipulating fly olfactory receptor neurons (ORNs), we generated null alleles for 11 different olfactory receptors by using CRISPR/Cas9 to knock in LexA drivers, including multiple lines for receptors which have thus far lacked knock-in mutants. The targeted neuronal types represent a broad range of antennal ORNs from all four morphological sensillum classes. Additionally, we confirmed their loss-of-function phenotypes, assessed receptor haploinsufficiency, and evaluated the specificity of the LexA knock-in drivers. These receptor mutant lines have been deposited at the Bloomington Drosophila Stock Center for use by the broader scientific community.
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Affiliation(s)
- Runqi Zhang
- Department of Neurobiology, University of California San Diego, La Jolla, USA
| | - Renny Ng
- Department of Neurobiology, University of California San Diego, La Jolla, USA
| | - Shiuan-Tze Wu
- Department of Neurobiology, University of California San Diego, La Jolla, USA
| | - Chih-Ying Su
- Department of Neurobiology, University of California San Diego, La Jolla, USA
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4
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Ali MZ, Anushree, Ahsan A, Ola MS, Haque R, Ahsan J. Ionotropic receptors mediate olfactory learning and memory in Drosophila. INSECT SCIENCE 2024; 31:1249-1269. [PMID: 38114448 DOI: 10.1111/1744-7917.13308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 10/16/2023] [Accepted: 10/27/2023] [Indexed: 12/21/2023]
Abstract
Phenylacetaldehyde (PAH), an aromatic compound, is present in a diverse range of fruits including overripe bananas and prickly pear cactus, the two major host fruits for Drosophila melanogaster. PAH acts as a potent ligand for the ionotropic receptor 84a (IR84a) in the adult fruit fly and it is detected by the IR84a/IR8a heterotetrameric complex. Its role in the male courtship behavior through IR84a as an environmental aphrodisiac is of additional importance. In D. melanogaster, two distinct kinds of olfactory receptors, that is, odorant receptors (ORs) and ionotropic receptors (IRs), perceive the odorant stimuli. They display unique structural, molecular, and functional characteristics in addition to having different evolutionary origins. Traditionally, olfactory cues detected by the ORs such as ethyl acetate, 1-butanol, isoamyl acetate, 1-octanol, 4-methylcyclohexanol, etc. classified as aliphatic esters and alcohols have been employed in olfactory classical conditioning using fruit flies. This underlines the participation of OR-activated olfactory pathways in learning and memory formation. Our study elucidates that likewise ethyl acetate (EA) (an OR-responsive odorant), PAH (an IR-responsive aromatic compound) too can form learning and memory when associated with an appetitive gustatory reinforcer. The association of PAH with sucrose (PAH/SUC) led to learning and formation of the long-term memory (LTM). Additionally, the Orco1, Ir84aMI00501, and Ir8a1 mutant flies were used to confirm the exclusive participation of the IR84a/IR8a complex in PAH/SUC olfactory associative conditioning. These results highlight the involvement of IRs via an IR-activated pathway in facilitating robust olfactory behavior.
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Affiliation(s)
- Md Zeeshan Ali
- Department of Biotechnology, Central University of South Bihar, Gaya, Bihar, India
| | - Anushree
- Department of Biotechnology, Central University of South Bihar, Gaya, Bihar, India
| | - Aarif Ahsan
- Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan, USA
| | - Mohammad Shamsul Ola
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Rizwanul Haque
- Department of Biotechnology, Central University of South Bihar, Gaya, Bihar, India
| | - Jawaid Ahsan
- Department of Biotechnology, Central University of South Bihar, Gaya, Bihar, India
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5
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Ferguson ST, Bakis I, Edwards ND, Zwiebel LJ. Olfactory sensitivity differentiates morphologically distinct worker castes in Camponotus floridanus. BMC Biol 2023; 21:3. [PMID: 36617574 PMCID: PMC9827628 DOI: 10.1186/s12915-022-01505-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 12/08/2022] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Camponotus floridanus ant colonies are comprised of a single reproductive queen and thousands of sterile female offspring that consist of two morphologically distinct castes: smaller minors and larger majors. Minors perform most of the tasks within the colony, including brood care and food collection, whereas majors have fewer clear roles and have been hypothesized to act as a specialized solider caste associated with colony defense. The allocation of workers to these different tasks depends, in part, on the detection and processing of local information including pheromones and other chemical blends such as cuticular hydrocarbons. However, the role peripheral olfactory sensitivity plays in establishing and maintaining morphologically distinct worker castes and their associated behaviors remains largely unexplored. RESULTS We examined the electrophysiological responses to general odorants, cuticular extracts, and a trail pheromone in adult minor and major C. floridanus workers, revealing that the repertoire of social behaviors is positively correlated with olfactory sensitivity. Minors in particular display primarily excitatory responses to olfactory stimuli, whereas major workers primarily manifest suppressed, sub-solvent responses. The notable exception to this paradigm is that both minors and majors display robust, dose-dependent excitatory responses to conspecific, non-nestmate cuticular extracts. Moreover, while both minors and majors actively aggress non-nestmate foes, the larger and physiologically distinct majors display significantly enhanced capabilities to rapidly subdue and kill their adversaries. CONCLUSIONS Our studies reveal the behavioral repertoire of minors and majors aligns with profound shifts in peripheral olfactory sensitivity and odor coding. The data reported here support the hypothesis that minors are multipotential workers with broad excitatory sensitivity, and majors are dedicated soldiers with a highly specialized olfactory system for distinguishing non-nestmate foes. Overall, we conclude that C. floridanus majors do indeed represent a physiologically and behaviorally specialized soldier caste in which caste-specific olfactory sensitivity plays an important role in task allocation and the regulation of social behavior in ant colonies.
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Affiliation(s)
- S. T. Ferguson
- grid.152326.10000 0001 2264 7217Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235 USA
| | - I. Bakis
- grid.152326.10000 0001 2264 7217Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235 USA
| | - N. D. Edwards
- grid.152326.10000 0001 2264 7217Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235 USA
| | - L. J. Zwiebel
- grid.152326.10000 0001 2264 7217Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235 USA
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6
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Wang Y, Fang G, Xu P, Gao B, Liu X, Qi X, Zhang G, Cao S, Li Z, Ren X, Wang H, Cao Y, Pereira R, Huang Y, Niu C, Zhan S. Behavioral and genomic divergence between a generalist and a specialist fly. Cell Rep 2022; 41:111654. [DOI: 10.1016/j.celrep.2022.111654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 07/03/2022] [Accepted: 10/21/2022] [Indexed: 11/18/2022] Open
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7
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Xu P, Choo YM, Leal WS. Odorant inhibition in mosquito olfaction mediated by inverse agonists. Biochem Biophys Res Commun 2022; 609:156-162. [PMID: 35430419 PMCID: PMC10540603 DOI: 10.1016/j.bbrc.2022.04.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 04/05/2022] [Indexed: 11/02/2022]
Abstract
The insect repellent methyl salicylate elicits excitatory responses upon interaction with CquiOR32, an odorant receptor (OR) from the southern house mosquito, Culex quinquefasciatus. By contrast, eucalyptol binds to CquiOR32 to generate electrophysiological and behavioral inhibitory responses. In an attempt to identify CquiOR32 variants displaying more robust inhibitory responses for more accurate current-voltage analysis, we sequenced 31 CquiOR32 clones. In the Xenopus oocyte recording system, CquiOR32V2/CquiOrco-expressing oocytes yielded eucalyptol-elicited outward (inhibitory) currents relatively larger than methyl salicylate-generated inward (excitatory) currents. Rescuing experiments showed that two of the amino acid substitutions in CquiOR32V2 located in a predicted transmembrane helix of the receptor are determinants of the outward/inward ratios. These findings, along with co-stimulus assays, suggest that odorant and inhibitor may bind to the same binding pocket. Current-voltage relationships obtained with standard perfusion buffer and those devoid of Na+ or Cl- indicated that both excitatory and inhibitory currents are mediated, at least in part, by cation. We then concluded that eucalyptol is an inverse agonist, which shifts the open ⇔ closed equilibrium of the receptor toward the closed conformation, thus reducing the spontaneous activity. By contrast, the binding of methyl salicylate shifts the equilibrium towards the open conformation and, consequently, leads to an increase in cation influx.
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Affiliation(s)
- Pingxi Xu
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA, 95616, USA
| | - Young-Moo Choo
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA, 95616, USA
| | - Walter S Leal
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA, 95616, USA.
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8
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Khan M, Hartmann AH, O’Donnell MP, Piccione M, Pandey A, Chao PH, Dwyer ND, Bargmann CI, Sengupta P. Context-dependent reversal of odorant preference is driven by inversion of the response in a single sensory neuron type. PLoS Biol 2022; 20:e3001677. [PMID: 35696430 PMCID: PMC9232122 DOI: 10.1371/journal.pbio.3001677] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 06/24/2022] [Accepted: 05/16/2022] [Indexed: 11/18/2022] Open
Abstract
The valence and salience of individual odorants are modulated by an animal’s innate preferences, learned associations, and internal state, as well as by the context of odorant presentation. The mechanisms underlying context-dependent flexibility in odor valence are not fully understood. Here, we show that the behavioral response of Caenorhabditis elegans to bacterially produced medium-chain alcohols switches from attraction to avoidance when presented in the background of a subset of additional attractive chemicals. This context-dependent reversal of odorant preference is driven by cell-autonomous inversion of the response to these alcohols in the single AWC olfactory neuron pair. We find that while medium-chain alcohols inhibit the AWC olfactory neurons to drive attraction, these alcohols instead activate AWC to promote avoidance when presented in the background of a second AWC-sensed odorant. We show that these opposing responses are driven via engagement of distinct odorant-directed signal transduction pathways within AWC. Our results indicate that context-dependent recruitment of alternative intracellular signaling pathways within a single sensory neuron type conveys opposite hedonic valences, thereby providing a robust mechanism for odorant encoding and discrimination at the periphery.
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Affiliation(s)
- Munzareen Khan
- Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Anna H. Hartmann
- Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Michael P. O’Donnell
- Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Madeline Piccione
- Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Anjali Pandey
- Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Pin-Hao Chao
- Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Noelle D. Dwyer
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | | | - Piali Sengupta
- Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
- * E-mail:
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9
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Xu P, Choo YM, An S, Leal GM, Leal WS. Mosquito odorant receptor sensitive to natural spatial repellents and inhibitory compounds. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2022; 144:103763. [PMID: 35364281 PMCID: PMC10540633 DOI: 10.1016/j.ibmb.2022.103763] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 03/17/2022] [Accepted: 03/27/2022] [Indexed: 06/14/2023]
Abstract
Previously, we have identified an odorant receptor (OR) from the southern house mosquito Culex quinquefasciatus, CquiOR32, which responded to both odorants (agonists) and inhibitory compounds (antagonists). CquiOR32/CquiOrco-expressing oocytes responded to methyl salicylate and other odorants with inward (regular) currents but gave currents in the reverse direction when challenged with eucalyptol and other inhibitors. To determine whether hitherto unknown ORs show this intrareceptor inhibition, we have now examined two other receptors in the same cluster, CquiOR27 and CquiOR28. We cloned and tested four variants of CquiOR28, but none of the 250 compounds in our panel of odorants, including an Orco ligand candidate (OLC12), elicited inward or upward deflections of the current traces. By contrast, CquiOR27/CquiOrco-expressing oocytes gave robust, dose-dependent inward currents when challenged with γ-octalactone and other odorants. On the other hand, octylamine and other phenolic compounds elicited dose-dependent currents in the reverse direction. When stimulatory and inhibitory compounds were presented in binary mixtures, γ-octalactone-elicited inward currents were attenuated in a dose-dependent manner according to the concentration of octylamine. As part of our chemical ecology approach, we tested the repellency activity of the most potent ligands in the surface landing and feeding assay and a newly reported hand-in cage assay. Protection elicited by γ-octalactone did not differ significantly from that of DEET at the same dose. In the hand-in cage assay, a cream formulation of γ-octalactone showed 97.0 ± 1.3% protection, with 47.6 ± 8.3% and 1.4 ± 0.7% landings per trial in the hands covered with a control and γ-octalactone cream, respectively (N = 8, p = 0.0078, Wilcoxon matched-pairs signed-rank test).
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Affiliation(s)
- Pingxi Xu
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA, 95616, USA
| | - Young-Moo Choo
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA, 95616, USA
| | - Sunny An
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA, 95616, USA
| | - Gabriel M Leal
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA, 95616, USA
| | - Walter S Leal
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA, 95616, USA.
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10
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Liu F, Chen Z, Ye Z, Liu N. The Olfactory Chemosensation of Hematophagous Hemipteran Insects. Front Physiol 2021; 12:703768. [PMID: 34434117 PMCID: PMC8382127 DOI: 10.3389/fphys.2021.703768] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 07/09/2021] [Indexed: 11/13/2022] Open
Abstract
As one of the most abundant insect orders on earth, most Hemipteran insects are phytophagous, with the few hematophagous exceptions falling into two families: Cimicidae, such as bed bugs, and Reduviidae, such as kissing bugs. Many of these blood-feeding hemipteran insects are known to be realistic or potential disease vectors, presenting both physical and psychological risks for public health. Considerable researches into the interactions between hemipteran insects such as kissing bugs and bed bugs and their human hosts have revealed important information that deepens our understanding of their chemical ecology and olfactory physiology. Sensory mechanisms in the peripheral olfactory system of both insects have now been characterized, with a particular emphasis on their olfactory sensory neurons and odorant receptors. This review summarizes the findings of recent studies of both kissing bugs (including Rhodnius prolixus and Triatoma infestans) and bed bugs (Cimex lectularius), focusing on their chemical ecology and peripheral olfactory systems. Potential chemosensation-based applications for the management of these Hemipteran insect vectors are also discussed.
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Affiliation(s)
- Feng Liu
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States.,Department of Biological Sciences, Vanderbilt University, Nashville, TN, United States
| | - Zhou Chen
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States.,Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, United States
| | - Zi Ye
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States.,Department of Biological Sciences, Vanderbilt University, Nashville, TN, United States
| | - Nannan Liu
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States
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11
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Kolesov DV, Ivanova VO, Sokolinskaya EL, Kost LA, Balaban PM, Lukyanov KA, Nikitin ES, Bogdanov AM. Impacts of OrX and cAMP-insensitive Orco to the insect olfactory heteromer activity. Mol Biol Rep 2021; 48:4549-4561. [PMID: 34129187 DOI: 10.1007/s11033-021-06480-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 06/05/2021] [Indexed: 11/24/2022]
Abstract
Insect odorant receptors (ORs) have been suggested to function as ligand-gated cation channels, with OrX/Orco heteromers combining ionotropic and metabotropic activity. The latter is mediated by different G proteins and results in Orco self-activation by cyclic nucleotide binding. In this contribution, we co-express the odor-specific subunits DmOr49b and DmOr59b with either wild-type Orco or an Orco-PKC mutant lacking cAMP activation heterologously in mammalian cells. We show that the characteristics of heteromers strongly depend on both the OrX type and the coreceptor variant. Thus, methyl acetate-sensitive Or59b/Orco demonstrated 25-fold faster response kinetics over o-cresol-specific Or49b/Orco, while the latter required a 10-100 times lower ligand concentration to evoke a similar electrical response. Compared to wild-type Orco, Orco-PKC decreased odorant sensitivity in both heteromers, and blocked an outward current rectification intrinsic to the Or49b/Orco pair. Our observations thus provide an insight into insect OrX/Orco functioning, highlighting their natural and artificial tuning features and laying the groundwork for their application in chemogenetics, drug screening, and repellent design.
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Affiliation(s)
- Danila V Kolesov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | - Violetta O Ivanova
- Institute of Higher Nervous Activity and Neurophysiology, Moscow, Russia
| | | | - Liubov A Kost
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia
| | - Pavel M Balaban
- Institute of Higher Nervous Activity and Neurophysiology, Moscow, Russia
| | | | - Evgeny S Nikitin
- Institute of Higher Nervous Activity and Neurophysiology, Moscow, Russia
| | - Alexey M Bogdanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia.
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12
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Widespread Inhibition, Antagonism, and Synergy in Mouse Olfactory Sensory Neurons In Vivo. Cell Rep 2021; 31:107814. [PMID: 32610120 DOI: 10.1016/j.celrep.2020.107814] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 05/05/2020] [Accepted: 06/03/2020] [Indexed: 12/12/2022] Open
Abstract
Sensory information is selectively or non-selectively enhanced and inhibited in the brain, but it remains unclear whether and how this occurs at the most peripheral level. Using in vivo calcium imaging of mouse olfactory bulb and olfactory epithelium in wild-type and mutant animals, we show that odors produce not only excitatory but also inhibitory responses in olfactory sensory neurons (OSNs). Heterologous assays indicate that odorants can act as agonists to some but inverse agonists to other odorant receptors. We also demonstrate that responses to odor mixtures are extensively suppressed or enhanced in OSNs. When high concentrations of odors are mixed, widespread antagonism suppresses the overall response amplitudes and density. In contrast, a mixture of low concentrations of odors often produces synergistic effects and boosts the faint odor inputs. Thus, odor responses are extensively tuned by inhibition, antagonism, and synergy at the most peripheral level, contributing to robust sensory representations.
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13
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Üçpunar HK, Grunwald Kadow IC. Flies Avoid Current Atmospheric CO 2 Concentrations. Front Physiol 2021; 12:646401. [PMID: 33927640 PMCID: PMC8076854 DOI: 10.3389/fphys.2021.646401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 03/22/2021] [Indexed: 11/23/2022] Open
Abstract
CO2 differs from most other odors by being ubiquitously present in the air animals inhale. CO2 levels of the atmosphere, however, are subject to change. Depending on the landscape, temperature, and time of the year, CO2 levels can change even on shortest time scales. In addition, since the 18th century the CO2 baseline keeps increasing due to the intensive fossil fuel usage. However, we do not know whether this change is significant for animals, and if yes whether and how animals adapt to this change. Most insects possess olfactory receptors to detect the gaseous molecule, and CO2 is one of the key odorants for insects such as the vinegar fly Drosophila melanogaster to find food sources and to warn con-specifics. So far, CO2 and its sensory system have been studied in the context of rotting fruit and other CO2-emitting sources to investigate flies’ response to significantly elevated levels of CO2. However, it has not been addressed whether flies detect and potentially react to atmospheric levels of CO2. By using behavioral experiments, here we show that flies can detect atmospheric CO2 concentrations and, if given the choice, prefer air with sub-atmospheric levels of the molecule. Blocking the synaptic release from CO2 receptor neurons abolishes this choice. Based on electrophysiological recordings, we hypothesize that CO2 receptors, similar to ambient temperature receptors, actively sample environmental CO2 concentrations close to atmospheric levels. Based on recent findings and our data, we hypothesize that Gr-dependent CO2 receptors do not primarily serve as a cue detector to find food sources or avoid danger, instead they function as sensors for preferred environmental conditions.
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Affiliation(s)
- Habibe K Üçpunar
- Department of Physiology, School of Medicine, Ankara Medipol University, Ankara, Turkey
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14
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Sawant A, Ebbinghaus BN, Bleckert A, Gamlin C, Yu WQ, Berson D, Rudolph U, Sinha R, Hoon M. Organization and emergence of a mixed GABA-glycine retinal circuit that provides inhibition to mouse ON-sustained alpha retinal ganglion cells. Cell Rep 2021; 34:108858. [PMID: 33730586 PMCID: PMC8030271 DOI: 10.1016/j.celrep.2021.108858] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 12/07/2020] [Accepted: 02/19/2021] [Indexed: 12/04/2022] Open
Abstract
In the retina, amacrine interneurons inhibit retinal ganglion cell (RGC) dendrites to shape retinal output. Amacrine cells typically use either GABA or glycine to exert synaptic inhibition. Here, we combined transgenic tools with immunohistochemistry, electrophysiology, and 3D electron microscopy to determine the composition and organization of inhibitory synapses across the dendritic arbor of a well-characterized RGC type in the mouse retina: the ON-sustained alpha RGC. We find mixed GABA-glycine receptor synapses across this RGC type, unveiling the existence of "mixed" inhibitory synapses in the retinal circuit. Presynaptic amacrine boutons with dual release sites are apposed to ON-sustained alpha RGC postsynapses. We further reveal the sequence of postsynaptic assembly for these mixed synapses: GABA receptors precede glycine receptors, and a lack of early GABA receptor expression impedes the recruitment of glycine receptors. Together our findings uncover the organization and developmental profile of an additional motif of inhibition in the mammalian retina.
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Affiliation(s)
- Abhilash Sawant
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA
| | - Briana N Ebbinghaus
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA
| | - Adam Bleckert
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Clare Gamlin
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Wan-Qing Yu
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - David Berson
- Department of Neuroscience, Brown University, Providence, RI, USA
| | - Uwe Rudolph
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Champaign, IL, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Champaign, IL, USA
| | - Raunak Sinha
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA
| | - Mrinalini Hoon
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA.
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15
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Wicher D, Miazzi F. Functional properties of insect olfactory receptors: ionotropic receptors and odorant receptors. Cell Tissue Res 2021; 383:7-19. [PMID: 33502604 PMCID: PMC7873100 DOI: 10.1007/s00441-020-03363-x] [Citation(s) in RCA: 84] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 11/19/2020] [Indexed: 10/27/2022]
Abstract
The majority of insect olfactory receptors belong to two distinct protein families, the ionotropic receptors (IRs), which are related to the ionotropic glutamate receptor family, and the odorant receptors (ORs), which evolved from the gustatory receptor family. Both receptor types assemble to heteromeric ligand-gated cation channels composed of odor-specific receptor proteins and co-receptor proteins. We here present in short the current view on evolution, function, and regulation of IRs and ORs. Special attention is given on how their functional properties can meet the environmental and ecological challenges an insect has to face.
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Affiliation(s)
- Dieter Wicher
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knoell-Str. 8, 07745, Jena, Germany.
| | - Fabio Miazzi
- Research Group Predators and Toxic Prey, Max Planck Institute for Chemical Ecology, Hans-Knoell-Str. 8, 07745, Jena, Germany
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16
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Xin S, Zhang W. Construction and analysis of the protein-protein interaction network for the olfactory system of the silkworm Bombyx mori. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2020; 105:e21737. [PMID: 32926465 DOI: 10.1002/arch.21737] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 08/21/2020] [Accepted: 08/24/2020] [Indexed: 06/11/2023]
Abstract
Olfaction plays an essential role in feeding and information exchange in insects. Previous studies on the olfaction of silkworms have provided a wealth of information about genes and proteins, yet, most studies have only focused on a single gene or protein related to the insect's olfaction. The aim of the current study is to determine key proteins in the olfactory system of the silkworm, and further understand protein-protein interactions (PPIs) in the olfactory system of Lepidoptera. To achieve this goal, we integrated Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and network analyses. Furthermore, we selected 585 olfactory-related proteins and constructed a (PPI) network for the olfactory system of the silkworm. Network analysis led to the identification of several key proteins, including GSTz1, LOC733095, BGIBMGA002169-TA, BGIBMGA010939-TA, GSTs2, GSTd2, Or-2, and BGIBMGA013255-TA. A comprehensive evaluation of the proteins showed that glutathione S-transferases (GSTs) had the highest ranking. GSTs also had the highest enrichment levels in GO and KEGG. In conclusion, our analysis showed that key nodes in the biological network had a significant impact on the network, and the key proteins identified via network analysis could serve as new research targets to determine their functions in olfaction.
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Affiliation(s)
- Shanghong Xin
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Wenjun Zhang
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
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17
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Abstract
Odor receptors of the mammalian olfactory system have long been known to be activated in combinatorial fashion by odorants. A large-scale study now reveals that inhibition of receptors by odorants is comparably prevalent and combinatorial.
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Affiliation(s)
- Douglas Rioux
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA
| | - John R Carlson
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA.
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18
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Pfister P, Smith BC, Evans BJ, Brann JH, Trimmer C, Sheikh M, Arroyave R, Reddy G, Jeong HY, Raps DA, Peterlin Z, Vergassola M, Rogers ME. Odorant Receptor Inhibition Is Fundamental to Odor Encoding. Curr Biol 2020; 30:2574-2587.e6. [PMID: 32470365 DOI: 10.1016/j.cub.2020.04.086] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 03/31/2020] [Accepted: 04/28/2020] [Indexed: 11/18/2022]
Abstract
Most natural odors are complex mixtures of volatile components, competing to bind odorant receptors (ORs) expressed in olfactory sensory neurons (OSNs) of the nose. To date, surprisingly little is known about how OR antagonism shapes neuronal representations in the detection layer of the olfactory system. Here, we investigated its prevalence, the degree to which it disrupts OR ensemble activity, and its conservation across phylogenetically related ORs. Calcium imaging microscopy of dissociated OSNs revealed significant inhibition, often complete attenuation, of responses to indole-a commonly occurring volatile associated with both floral and fecal odors-by a set of 36 tested odorants. To confirm an OR mechanism for the observed inhibition, we performed single-cell transcriptomics on OSNs exhibiting specific response profiles to a diagnostic panel of odorants and identified three paralogous receptors-Olfr740, Olfr741, and Olfr743-which, when tested in vitro, recapitulated OSN responses. We screened ten ORs from the Olfr740 gene family with ∼800 perfumery-related odorants spanning a range of chemical scaffolds and functional groups. Over half of these compounds (430) antagonized at least one of the ten ORs. OR activity fitted a mathematical model of competitive receptor binding and suggests normalization of OSN ensemble responses to odorant mixtures is the rule rather than the exception. In summary, we observed OR antagonism occurred frequently and in a combinatorial manner. Thus, extensive receptor-mediated computation of mixture information appears to occur in the olfactory epithelium prior to transmission of odor information to the olfactory bulb.
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Affiliation(s)
- Patrick Pfister
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Benjamin C Smith
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Barry J Evans
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Jessica H Brann
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Casey Trimmer
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Mushhood Sheikh
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Randy Arroyave
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Gautam Reddy
- Department of Physics, UC San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA
| | - Hyo-Young Jeong
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Daniel A Raps
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Zita Peterlin
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Massimo Vergassola
- Department of Physics, UC San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA
| | - Matthew E Rogers
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA.
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19
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Yan H, Jafari S, Pask G, Zhou X, Reinberg D, Desplan C. Evolution, developmental expression and function of odorant receptors in insects. J Exp Biol 2020; 223:jeb208215. [PMID: 32034042 PMCID: PMC7790194 DOI: 10.1242/jeb.208215] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Animals rely on their chemosensory system to discriminate among a very large number of attractive or repulsive chemical cues in the environment, which is essential to respond with proper action. The olfactory sensory systems in insects share significant similarities with those of vertebrates, although they also exhibit dramatic differences, such as the molecular nature of the odorant receptors (ORs): insect ORs function as heteromeric ion channels with a common Orco subunit, unlike the G-protein-coupled olfactory receptors found in vertebrates. Remarkable progress has recently been made in understanding the evolution, development and function of insect odorant receptor neurons (ORNs). These studies have uncovered the diversity of olfactory sensory systems among insect species, including in eusocial insects that rely extensively on olfactory sensing of pheromones for social communication. However, further studies, notably functional analyses, are needed to improve our understanding of the origins of the Orco-OR system, the mechanisms of ORN fate determination, and the extraordinary diversity of behavioral responses to chemical cues.
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Affiliation(s)
- Hua Yan
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
- Center for Smell and Taste (UFCST), University of Florida, Gainesville, FL 32610, USA
| | - Shadi Jafari
- Department of Molecular Biology, Umeå University, 901 87 Umeå, Sweden
- Department of Biology, New York University, New York, NY 10003, USA
| | - Gregory Pask
- Department of Biology, Bucknell University, Lewisburg, PA 17837, USA
| | - Xiaofan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, 510642 Guangzhou, China
| | - Danny Reinberg
- Howard Hughes Medical Institute (HHMI), Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
| | - Claude Desplan
- Department of Biology, New York University, New York, NY 10003, USA
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20
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Young BD, Escalon JA, Mathew D. Odors: from chemical structures to gaseous plumes. Neurosci Biobehav Rev 2020; 111:19-29. [PMID: 31931034 DOI: 10.1016/j.neubiorev.2020.01.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 01/07/2020] [Accepted: 01/07/2020] [Indexed: 10/25/2022]
Abstract
We are immersed within an odorous sea of chemical currents that we parse into individual odors with complex structures. Odors have been posited as determined by the structural relation between the molecules that compose the chemical compounds and their interactions with the receptor site. But, naturally occurring smells are parsed from gaseous odor plumes. To give a comprehensive account of the nature of odors the chemosciences must account for these large distributed entities as well. We offer a focused review of what is known about the perception of odor plumes for olfactory navigation and tracking, which we then connect to what is known about the role odorants play as properties of the plume in determining odor identity with respect to odor quality. We end by motivating our central claim that more research needs to be conducted on the role that odorants play within the odor plume in determining odor identity.
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Affiliation(s)
- Benjamin D Young
- Philosophy and Neuroscience, University of Nevada, 1664 N Virginia St, Reno, NV 89557, United States.
| | | | - Dennis Mathew
- Biology and Neuroscience, University of Nevada, Reno, United States.
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21
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Verschut TA, Carlsson MA, Hambäck PA. Scaling the interactive effects of attractive and repellent odours for insect search behaviour. Sci Rep 2019; 9:15309. [PMID: 31653955 PMCID: PMC6814803 DOI: 10.1038/s41598-019-51834-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 10/09/2019] [Indexed: 11/09/2022] Open
Abstract
Insects searching for resources are exposed to a complexity of mixed odours, often involving both attractant and repellent substances. Understanding how insects respond to this complexity of cues is crucial for understanding consumer-resource interactions, but also to develop novel tools to control harmful pests. To advance our understanding of insect responses to combinations of attractive and repellent odours, we formulated three qualitative hypotheses; the response-ratio hypothesis, the repellent-threshold hypothesis and the odour-modulation hypothesis. The hypotheses were tested by exposing Drosophila melanogaster in a wind tunnel to combinations of vinegar as attractant and four known repellents; benzaldehyde, 1-octen-3-ol, geosmin and phenol. The responses to benzaldehyde, 1-octen-3-ol and geosmin provided support for the response-ratio hypothesis, which assumes that the behavioural response depends on the ratio between attractants and repellents. The response to phenol, rather supported the repellent-threshold hypothesis, where aversion only occurs above a threshold concentration of the repellent due to overshadowing of the attractant. We hypothesize that the different responses may be connected to the localization of receptors, as receptors detecting phenol are located on the maxillary palps whereas receptors detecting the other odorants are located on the antennae.
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Affiliation(s)
- Thomas A Verschut
- Department of Ecology, Environment and Plant Sciences, Stockholm University, 106 91, Stockholm, Sweden. .,Department of Zoology, Stockholm University, 106 91, Stockholm, Sweden.
| | - Mikael A Carlsson
- Department of Zoology, Stockholm University, 106 91, Stockholm, Sweden
| | - Peter A Hambäck
- Department of Ecology, Environment and Plant Sciences, Stockholm University, 106 91, Stockholm, Sweden
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22
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Qin S, Li Q, Tang C, Tu Y. Optimal compressed sensing strategies for an array of nonlinear olfactory receptor neurons with and without spontaneous activity. Proc Natl Acad Sci U S A 2019; 116:20286-20295. [PMID: 31548382 PMCID: PMC6789560 DOI: 10.1073/pnas.1906571116] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
There are numerous different odorant molecules in nature but only a relatively small number of olfactory receptor neurons (ORNs) in brains. This "compressed sensing" challenge is compounded by the constraint that ORNs are nonlinear sensors with a finite dynamic range. Here, we investigate possible optimal olfactory coding strategies by maximizing mutual information between odor mixtures and ORNs' responses with respect to the bipartite odor-receptor interaction network (ORIN) characterized by sensitivities between all odorant-ORN pairs. For ORNs without spontaneous (basal) activity, we find that the optimal ORIN is sparse-a finite fraction of sensitives are zero, and the nonzero sensitivities follow a broad distribution that depends on the odor statistics. We show analytically that sparsity in the optimal ORIN originates from a trade-off between the broad tuning of ORNs and possible interference. Furthermore, we show that the optimal ORIN enhances performances of downstream learning tasks (reconstruction and classification). For ORNs with a finite basal activity, we find that having inhibitory odor-receptor interactions increases the coding capacity and the fraction of inhibitory interactions increases with the ORN basal activity. We argue that basal activities in sensory receptors in different organisms are due to the trade-off between the increase in coding capacity and the cost of maintaining the spontaneous basal activity. Our theoretical findings are consistent with existing experiments and predictions are made to further test our theory. The optimal coding model provides a unifying framework to understand the peripheral olfactory systems across different organisms.
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Affiliation(s)
- Shanshan Qin
- Center for Quantitative Biology, Peking University, Beijing 100871, China
| | - Qianyi Li
- Integrated Science Program, Yuanpei College, Peking University, Beijing 100871, China
| | - Chao Tang
- Center for Quantitative Biology, Peking University, Beijing 100871, China;
- School of Physics, Peking University, Beijing 100871, China
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - Yuhai Tu
- Physical Sciences Department, IBM T. J. Watson Research Center, Yorktown Heights, NY 10598
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23
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Xu P, Choo YM, Chen Z, Zeng F, Tan K, Chen TY, Cornel AJ, Liu N, Leal WS. Odorant Inhibition in Mosquito Olfaction. iScience 2019; 19:25-38. [PMID: 31349189 PMCID: PMC6660600 DOI: 10.1016/j.isci.2019.07.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 04/22/2019] [Accepted: 07/03/2019] [Indexed: 01/03/2023] Open
Abstract
How chemical signals are integrated at the peripheral sensory system of insects is still an enigma. Here we show that when coexpressed with Orco in Xenopus oocytes, an odorant receptor from the southern house mosquito, CquiOR32, generated inward (regular) currents when challenged with cyclohexanone and methyl salicylate, whereas eucalyptol and fenchone elicited inhibitory (upward) currents. Responses of CquiOR32-CquiOrco-expressing oocytes to odorants were reduced in a dose-dependent fashion by coapplication of inhibitors. This intrareceptor inhibition was also manifested in vivo in fruit flies expressing the mosquito receptor CquiOR32, as well in neurons on the antennae of the southern house mosquito. Likewise, an orthologue from the yellow fever mosquito, AaegOR71, showed intrareceptor inhibition in the Xenopus oocyte recording system and corresponding inhibition in antennal neurons. Inhibition was also manifested in mosquito behavior. Blood-seeking females were repelled by methyl salicylate, but repellence was significantly reduced when methyl salicylate was coapplied with eucalyptol. We found dual inhibitory/excitatory odorant receptors (ORs) in mosquitoes Inhibitory and endogenous ORs coexpressed in flies showed lateral inhibition The bipolar nature of these inhibitory ORs was displayed in electrophysiology The duality excitation/inhibition was also manifested in mosquito behavior
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Affiliation(s)
- Pingxi Xu
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA 95616, USA
| | - Young-Moo Choo
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA 95616, USA
| | - Zhou Chen
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36489, USA
| | - Fangfang Zeng
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA 95616, USA
| | - Kaiming Tan
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA 95616, USA
| | - Tsung-Yu Chen
- Center for Neuroscience, Department of Neurology, University of California-Davis, Davis, CA 95616, USA
| | - Anthony J Cornel
- Department of Entomology and Nematology, University of California-Davis, Davis, CA 95616, USA
| | - Nannan Liu
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36489, USA
| | - Walter S Leal
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA 95616, USA.
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24
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Kadakia N, Emonet T. Front-end Weber-Fechner gain control enhances the fidelity of combinatorial odor coding. eLife 2019; 8:e45293. [PMID: 31251174 PMCID: PMC6609331 DOI: 10.7554/elife.45293] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 06/26/2019] [Indexed: 11/13/2022] Open
Abstract
We showed previously (Gorur-Shandilya et al., 2017) that Drosophila olfactory receptor neurons (ORNs) expressing the co-receptor Orco scale their gain inversely with mean odor intensity according to Weber-Fechner's law. Here, we show that this front-end adaptation promotes the reconstruction of odor identity from dynamic odor signals, even in the presence of confounding background odors and rapid intensity fluctuations. These enhancements are further aided by known downstream transformations in the antennal lobe and mushroom body. Our results, which are applicable to various odor classification and reconstruction schemes, stem from the fact that this adaptation mechanism is not intrinsic to the identity of the receptor involved. Instead, a feedback mechanism adjusts receptor sensitivity based on the activity of the receptor-Orco complex, according to Weber-Fechner's law. Thus, a common scaling of the gain across Orco-expressing ORNs may be a key feature of ORN adaptation that helps preserve combinatorial odor codes in naturalistic landscapes.
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Affiliation(s)
- Nirag Kadakia
- Department of Molecular, Cellular and Developmental BiologyYale UniversityNew HavenUnited States
| | - Thierry Emonet
- Department of Molecular, Cellular and Developmental BiologyYale UniversityNew HavenUnited States
- Department of PhysicsYale UniversityNew HavenUnited States
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25
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Si G, Kanwal JK, Hu Y, Tabone CJ, Baron J, Berck M, Vignoud G, Samuel ADT. Structured Odorant Response Patterns across a Complete Olfactory Receptor Neuron Population. Neuron 2019; 101:950-962.e7. [PMID: 30683545 DOI: 10.1016/j.neuron.2018.12.030] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 10/29/2018] [Accepted: 12/20/2018] [Indexed: 11/15/2022]
Abstract
Odor perception allows animals to distinguish odors, recognize the same odor across concentrations, and determine concentration changes. How the activity patterns of primary olfactory receptor neurons (ORNs), at the individual and population levels, facilitate distinguishing these functions remains poorly understood. Here, we interrogate the complete ORN population of the Drosophila larva across a broadly sampled panel of odorants at varying concentrations. We find that the activity of each ORN scales with the concentration of any odorant via a fixed dose-response function with a variable sensitivity. Sensitivities across odorants and ORNs follow a power-law distribution. Much of receptor sensitivity to odorants is accounted for by a single geometrical property of molecular structure. Similarity in the shape of temporal response filters across odorants and ORNs extend these relationships to fluctuating environments. These results uncover shared individual- and population-level patterns that together lend structure to support odor perceptions.
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Affiliation(s)
- Guangwei Si
- Department of Physics, Harvard University, Cambridge, MA 02138, USA; Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Jessleen K Kanwal
- Center for Brain Science, Harvard University, Cambridge, MA 02138, USA; Program in Neuroscience, Harvard University, Cambridge, MA 02138, USA
| | - Yu Hu
- Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Christopher J Tabone
- Department of Physics, Harvard University, Cambridge, MA 02138, USA; Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Jacob Baron
- Department of Physics, Harvard University, Cambridge, MA 02138, USA; Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Matthew Berck
- Department of Physics, Harvard University, Cambridge, MA 02138, USA; Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Gaetan Vignoud
- Department of Physics, Harvard University, Cambridge, MA 02138, USA; Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Aravinthan D T Samuel
- Department of Physics, Harvard University, Cambridge, MA 02138, USA; Center for Brain Science, Harvard University, Cambridge, MA 02138, USA.
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26
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Clark DA, Odell SR, Armstrong JM, Turcotte M, Kohler D, Mathis A, Schmidt DR, Mathew D. Behavior Responses to Chemical and Optogenetic Stimuli in Drosophila Larvae. Front Behav Neurosci 2018; 12:324. [PMID: 30622461 PMCID: PMC6308144 DOI: 10.3389/fnbeh.2018.00324] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 12/10/2018] [Indexed: 11/13/2022] Open
Abstract
An animal’s ability to navigate an olfactory environment is critically dependent on the activities of its first-order olfactory receptor neurons (ORNs). While considerable research has focused on ORN responses to odorants, the mechanisms by which olfactory information is encoded in the activities of ORNs and translated into navigational behavior remain poorly understood. We sought to determine the contributions of most Drosophila melanogaster larval ORNs to navigational behavior. Using odorants to activate ORNs and a larval tracking assay to measure the corresponding behavioral response, we observed that larval ORN activators cluster into four groups based on the behavior responses elicited from larvae. This is significant because it provides new insights into the functional relationship between ORN activity and behavioral response. Subsequent optogenetic analyses of a subset of ORNs revealed previously undescribed properties of larval ORNs. Furthermore, our results indicated that different temporal patterns of ORN activation elicit different behavioral outputs: some ORNs respond to stimulus increments while others respond to stimulus decrements. These results suggest that the ability of ORNs to encode temporal patterns of stimulation increases the coding capacity of the olfactory circuit. Moreover, the ability of ORNs to sense stimulus increments and decrements facilitates instantaneous evaluations of concentration changes in the environment. Together, these ORN properties enable larvae to efficiently navigate a complex olfactory environment. Ultimately, knowledge of how ORN activity patterns and their weighted contributions influence odor coding may eventually reveal how peripheral information is organized and transmitted to subsequent layers of a neural circuit.
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Affiliation(s)
- David A Clark
- Department of Biology, University of Nevada, Reno, NV, United States.,Integrated Neuroscience Graduate Program, University of Nevada, Reno, NV, United States
| | - Seth R Odell
- Department of Biology, University of Nevada, Reno, NV, United States.,Integrated Neuroscience Graduate Program, University of Nevada, Reno, NV, United States
| | - Joanna M Armstrong
- Department of Mathematics & Statistics, University of Nevada, Reno, NV, United States
| | - Mariah Turcotte
- Department of Biology, University of Nevada, Reno, NV, United States
| | - Donovan Kohler
- Department of Biology, University of Nevada, Reno, NV, United States
| | - America Mathis
- Department of Biology, University of Nevada, Reno, NV, United States
| | - Deena R Schmidt
- Integrated Neuroscience Graduate Program, University of Nevada, Reno, NV, United States.,Department of Mathematics & Statistics, University of Nevada, Reno, NV, United States
| | - Dennis Mathew
- Department of Biology, University of Nevada, Reno, NV, United States.,Integrated Neuroscience Graduate Program, University of Nevada, Reno, NV, United States
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Low Ca 2+ levels in the culture media support the heterologous expression of insect odorant receptor proteins in HEK cells. J Neurosci Methods 2018; 312:122-125. [PMID: 30476491 DOI: 10.1016/j.jneumeth.2018.11.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 11/22/2018] [Accepted: 11/22/2018] [Indexed: 11/23/2022]
Abstract
BACKGROUND Heterologous expression of insect odorant receptors (ORs) in mammalian or insect cells is challenging due to the insufficient intracellular trafficking of ORs and their ability to form leak ion channels. NEW METHOD We tested whether reducing the Ca2+ levels in the cell culture medium after electroporation by means of a Dulbecco's Modified Eagle Medium (DMEM) without calcium, in a 1:1 ratio with Ham's F12 nutrient mixture, together with 10% fetal calf serum, can improve the success rate of insect OR expression in HEK293 cells. RESULTS We show that a reduced extracellular Ca2+ level supports functional expression of insect ORs by increasing the fraction of cells responding to the co-receptor agonist VUAA1 and by reducing the intracellular Ca2+ base level of transfected cells. COMPARISON WITH EXISTING METHOD(S) A DMEM formula without calcium outperforms standard DMEM in a 1:1 ratio with Ham's F12 mix and 10% serum, when culturing HEK293 cells transiently expressing insect OR proteins. CONCLUSIONS Reducing the extracellular Ca2+ level of HEK293 cell culture media after transfection increases the success of functional insect OR expression.
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Koerte S, Keesey IW, Khallaf MA, Cortés Llorca L, Grosse-Wilde E, Hansson BS, Knaden M. Evaluation of the DREAM Technique for a High-Throughput Deorphanization of Chemosensory Receptors in Drosophila. Front Mol Neurosci 2018; 11:366. [PMID: 30356801 PMCID: PMC6189519 DOI: 10.3389/fnmol.2018.00366] [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: 07/11/2018] [Accepted: 09/18/2018] [Indexed: 11/13/2022] Open
Abstract
In the vinegar fly Drosophila melanogaster, the majority of olfactory receptors mediating the detection of volatile chemicals found in their natural habitat have been functionally characterized (deorphanized) in vivo. In this process, receptors have been assigned ligands leading to either excitation or inhibition in the olfactory sensory neuron where they are expressed. In other, non-drosophilid insect species, scientists have not yet been able to compile datasets about ligand-receptor interactions anywhere near as extensive as in the model organism D. melanogaster, as genetic tools necessary for receptor deorphanization are still missing. Recently, it was discovered that exposure to artificially high concentrations of odorants leads to reliable alterations in mRNA levels of interacting odorant receptors in mammals. Analyzing receptor expression after odorant exposure can, therefore, help to identify ligand-receptor interactions in vivo without the need for other genetic tools. Transfer of the same methodology from mice to a small number of receptors in D. melanogaster resulted in a similar trend, indicating that odorant exposure induced alterations in mRNA levels are generally applicable for deorphanization of interacting chemosensory receptors. Here, we evaluated the potential of the DREAM (Deorphanization of receptors based on expression alterations in mRNA levels) technique for high-throughput deorphanization of chemosensory receptors in insect species using D. melanogaster as a model. We confirmed that in some cases the exposure of a chemosensory receptor to high concentration of its best ligand leads to measureable alterations in mRNA levels. However, unlike in mammals, we found several cases where either confirmed ligands did not induce alterations in mRNA levels of the corresponding chemosensory receptors, or where gene transcript-levels were altered even though there is no evidence for a ligand-receptor interaction. Hence, there are severe limitations to the suitability of the DREAM technique for deorphanization as a general tool to characterize olfactory receptors in insects.
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Affiliation(s)
- Sarah Koerte
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Ian W Keesey
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Mohammed A Khallaf
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Lucas Cortés Llorca
- Department for Molecular Ecology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Ewald Grosse-Wilde
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Bill S Hansson
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Markus Knaden
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
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Neuronal Responses of Antennal Olfactory Sensilla to Insect Chemical Repellents in the Yellow Fever Mosquito, Aedes aegypti. J Chem Ecol 2018; 44:1120-1126. [PMID: 30291492 DOI: 10.1007/s10886-018-1022-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Revised: 09/18/2018] [Accepted: 09/25/2018] [Indexed: 10/28/2022]
Abstract
The yellow fever mosquito, Aedes aegypti, is a vector of many human diseases such as yellow fever, dengue fever, and Zika. As insecticide resistance has been widely reported, chemical repellents have been adopted as alternative options for mosquito and mosquito-borne disease control. This study characterized the responses of olfactory receptor neurons (ORNs) in different types of antennal olfactory sensilla in Ae. aegypti to 48 chemicals that exhibited repellent activity in various insect species. Both excitatory and inhibitory responses were observed from ORNs in response to these chemicals and differential tuning properties were also observed among ORNs. Remarkable excitatory responses were recorded from the ORNs in sensilla SST1, SST2, SBTI, SBTII, and LST2, while inhibitory activities were detected from a neuron in sensillum SST2 in response to several terpene/terpenoid compounds. Moreover, the temporal dynamics of neuronal responses were found to be compound-specific and concentration-dependent. Hierarchical cluster analysis and principal component analysis of the response to each compound across ORNs in seven types of olfactory sensilla in Ae. aegypti revealed that odor reception depended not only on chemical class but also specific chemical structure. Results of this study give new insights into the sensory physiology of Aedes mosquitoes to the chemical repellents and should contribute to the development of new repellent reagents for human protection.
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Jacob VEJM. Current Source Density Analysis of Electroantennogram Recordings: A Tool for Mapping the Olfactory Response in an Insect Antenna. Front Cell Neurosci 2018; 12:287. [PMID: 30233325 PMCID: PMC6135050 DOI: 10.3389/fncel.2018.00287] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 08/13/2018] [Indexed: 11/29/2022] Open
Abstract
The set of chemosensory receptors expressed by the olfactory receptor neurons lying in an insect's antennae and maxillary palps define the ability of this insect to perceive the volatile chemicals of its environment. The main two electrophysiological methods of antennal recordings for studying the range of chemicals that activate chemosensory receptors have limitations. Single-sensillum recording (SSR) samples a subset of olfactory receptor neurons and therefore does not reveal the full capacity of an insect to perceive an odor. Electroantennography (EAG), even if less resolutive than SSRs, is sometimes preferred since it samples the activity of a large number of the olfactory receptor neurons. But, at least in flies, the amplitude of the EAG signal is not directly correlated with the degree of sensitivity of the insect to the olfactory compound. Such dual methodology was also used to study mammalian brains, and the current source density (CSD) analysis was developed to bridge the gap between the cellular and the population recordings. This paper details the use of a similar approach adapted to the study of olfactory responses within insects with bulbous antennae. The EAG was recorded at multiple antennal positions and the CSD that generates the EAG potentials were estimated. The method measures the activation of olfactory receptor neurons (ORNs) across the antennae and thus it quantifies the olfactory sensitivity of the insect. It allows a rapid mapping of olfactory responses and thus can be used to guide further SSRs or to determine that two chemicals are detected by independent ORNs. This study further explored biases resulting from a limited number of recording positions or from an approximation of the antennal geometry that should be considered for interpreting the CSD maps. It also shows that the CSD analysis of EAGs is compatible with a gas chromatograph stimulator for analyzing the response to complex odors. Finally, I discuss the origin of the EAG signal in light of the CSD theory.
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Utashiro N, Williams CR, Parrish JZ, Emoto K. Prior activity of olfactory receptor neurons is required for proper sensory processing and behavior in Drosophila larvae. Sci Rep 2018; 8:8580. [PMID: 29872087 PMCID: PMC5988719 DOI: 10.1038/s41598-018-26825-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 05/14/2018] [Indexed: 11/10/2022] Open
Abstract
Animal responses to their environment rely on activation of sensory neurons by external stimuli. In many sensory systems, however, neurons display basal activity prior to the external stimuli. This prior activity is thought to modulate neural functions, yet its impact on animal behavior remains elusive. Here, we reveal a potential role for prior activity in olfactory receptor neurons (ORNs) in shaping larval olfactory behavior. We show that prior activity in larval ORNs is mediated by the olfactory receptor complex (OR complex). Mutations of Orco, an odorant co-receptor required for OR complex function, cause reduced attractive behavior in response to optogenetic activation of ORNs. Calcium imaging reveals that Orco mutant ORNs fully respond to optogenetic stimulation but exhibit altered temporal patterns of neural responses. These findings together suggest a critical role for prior activity in information processing upon ORN activation in Drosophila larvae, which in turn contributes to olfactory behavior control.
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Affiliation(s)
- Nao Utashiro
- Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Claire R Williams
- Department of Biology, University of Washington, 24 Kincaid Hall, Box 351800, Seattle, WA, 98195, USA.,Molecular and Cellular Biology Program, University of Washington, Seattle, WA, 98195, USA
| | - Jay Z Parrish
- Department of Biology, University of Washington, 24 Kincaid Hall, Box 351800, Seattle, WA, 98195, USA.,Molecular and Cellular Biology Program, University of Washington, Seattle, WA, 98195, USA
| | - Kazuo Emoto
- Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. .,International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
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Tzotzos G, Iley JN, Moore EA. New insights on repellent recognition by Anopheles gambiae odorant-binding protein 1. PLoS One 2018; 13:e0194724. [PMID: 29614080 PMCID: PMC5882127 DOI: 10.1371/journal.pone.0194724] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 03/08/2018] [Indexed: 01/30/2023] Open
Abstract
It is generally recognized that insect odorant binding proteins (OBPs) mediate the solubilisation and transport of hydrophobic odorant molecules and contribute to the sensitivity of the insect olfactory system. However, the exact mechanism by which OBPs deliver odorants to olfactory receptors and their role, if any, as selectivity filters for specific odorants, are still a matter of debate. In the case of Anopheles gambiae, recent studies indicate that ligand discrimination is effected through the formation of heterodimers such as AgamOBP1 and AgamOBP4 (odorant binding proteins 1 and 4 from Anopheles gambiae). Furthermore, AgamOBPs have been reported to be promiscuous in binding more than one ligand simultaneously and repellents such as DEET (N,N-diethyl-3-toluamide) and 6-MH (6-methyl-5-hepten-2-one) interact directly with mosquito OBPs and/or compete for the binding of attractive odorants thus disrupting OBP heterodimerisation. In this paper, we propose mechanisms of action of DEET and 6-MH. We also predict that ligand binding can occur in several locations of AgamOBP1 with partial occupancies and propose structural features appropriate for repellent pharmacophores.
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Affiliation(s)
| | - Jim N. Iley
- School of Life, Health and Chemical Sciences, Open University, Milton Keynes, United Kingdom
| | - Elaine A. Moore
- School of Life, Health and Chemical Sciences, Open University, Milton Keynes, United Kingdom
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