101
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Dehydration prompts increased activity and blood feeding by mosquitoes. Sci Rep 2018; 8:6804. [PMID: 29717151 PMCID: PMC5931509 DOI: 10.1038/s41598-018-24893-z] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 04/11/2018] [Indexed: 11/27/2022] Open
Abstract
Current insights into the mosquito dehydration response rely on studies that examine specific responses but ultimately fail to provide an encompassing view of mosquito biology. Here, we examined underlying changes in the biology of mosquitoes associated with dehydration. Specifically, we show that dehydration increases blood feeding in the northern house mosquito, Culex pipiens, which was the result of both higher activity and a greater tendency to land on a host. Similar observations were noted for Aedes aegypti and Anopheles quadrimaculatus. RNA-seq and metabolome analyses in C. pipiens following dehydration revealed that factors associated with carbohydrate metabolism are altered, specifically the breakdown of trehalose. Suppression of trehalose breakdown in C. pipiens by RNA interference reduced phenotypes associated with lower hydration levels. Lastly, mesocosm studies for C. pipiens confirmed that dehydrated mosquitoes were more likely to host feed under ecologically relevant conditions. Disease modeling indicates dehydration bouts will likely enhance viral transmission. This dehydration-induced increase in blood feeding is therefore likely to occur regularly and intensify during periods when availability of water is low.
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102
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Hoffstaetter LJ, Bagriantsev SN, Gracheva EO. TRPs et al.: a molecular toolkit for thermosensory adaptations. Pflugers Arch 2018; 470:745-759. [PMID: 29484488 PMCID: PMC5945325 DOI: 10.1007/s00424-018-2120-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 01/03/2018] [Accepted: 02/05/2018] [Indexed: 12/19/2022]
Abstract
The ability to sense temperature is crucial for the survival of an organism. Temperature influences all biological operations, from rates of metabolic reactions to protein folding, and broad behavioral functions, from feeding to breeding, and other seasonal activities. The evolution of specialized thermosensory adaptations has enabled animals to inhabit extreme temperature niches and to perform specific temperature-dependent behaviors. The function of sensory neurons depends on the participation of various types of ion channels. Each of the channels involved in neuronal excitability, whether through the generation of receptor potential, action potential, or the maintenance of the resting potential have temperature-dependent properties that can tune the neuron's response to temperature stimuli. Since the function of all proteins is affected by temperature, animals need adaptations not only for detecting different temperatures, but also for maintaining sensory ability at different temperatures. A full understanding of the molecular mechanism of thermosensation requires an investigation of all channel types at each step of thermosensory transduction. A fruitful avenue of investigation into how different molecules can contribute to the fine-tuning of temperature sensitivity is to study the specialized adaptations of various species. Given the diversity of molecular participants at each stage of sensory transduction, animals have a toolkit of channels at their disposal to adapt their thermosensitivity to their particular habitats or behavioral circumstances.
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Affiliation(s)
- Lydia J Hoffstaetter
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520-8026, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520-8026, USA
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520-8026, USA
| | - Sviatoslav N Bagriantsev
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520-8026, USA
| | - Elena O Gracheva
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520-8026, USA.
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520-8026, USA.
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520-8026, USA.
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103
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Ahn JE, Chen Y, Amrein H. Molecular basis of fatty acid taste in Drosophila. eLife 2017; 6:30115. [PMID: 29231818 PMCID: PMC5747521 DOI: 10.7554/elife.30115] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 12/08/2017] [Indexed: 01/01/2023] Open
Abstract
Behavioral studies have established that Drosophila appetitive taste responses towards fatty acids are mediated by sweet sensing Gustatory Receptor Neurons (GRNs). Here we show that sweet GRN activation requires the function of the Ionotropic Receptor genes IR25a, IR76b and IR56d. The former two IR genes are expressed in several neurons per sensillum, while IR56d expression is restricted to sweet GRNs. Importantly, loss of appetitive behavioral responses to fatty acids in IR25a and IR76b mutant flies can be completely rescued by expression of respective transgenes in sweet GRNs. Interestingly, appetitive behavioral responses of wild type flies to hexanoic acid reach a plateau at ~1%, but decrease with higher concentration, a property mediated through IR25a/IR76b independent activation of bitter GRNs. With our previous report on sour taste, our studies suggest that IR-based receptors mediate different taste qualities through cell-type specific IR subunits.
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Affiliation(s)
- Ji-Eun Ahn
- Department of Molecular and Cellular Medicine, Health Science Center, Texas A&M University, College Station, Texas, United States
| | - Yan Chen
- Department of Molecular and Cellular Medicine, Health Science Center, Texas A&M University, College Station, Texas, United States
| | - Hubert Amrein
- Department of Molecular and Cellular Medicine, Health Science Center, Texas A&M University, College Station, Texas, United States
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104
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Enjin A. Humidity sensing in insects-from ecology to neural processing. CURRENT OPINION IN INSECT SCIENCE 2017; 24:1-6. [PMID: 29208217 DOI: 10.1016/j.cois.2017.08.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 08/13/2017] [Accepted: 08/24/2017] [Indexed: 05/29/2023]
Abstract
Humidity is an omnipresent climatic factor that influences the fitness, reproductive behavior and geographic distribution of animals. Insects in particular use humidity cues to navigate the environment. Although the sensory neurons of this elusive sense were first described more than fifty years ago, the transduction mechanism of humidity sensing (hygrosensation) remains unknown. Recent work has uncovered some of the key molecules involved, opening up for novel approaches to study hygrosensory transduction. In this review, I will discuss this progress made toward understanding hygrosensation in insects.
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Affiliation(s)
- Anders Enjin
- Department of Biology, Lund University, Lund, Sweden.
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105
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A simple high throughput assay to evaluate water consumption in the fruit fly. Sci Rep 2017; 7:16786. [PMID: 29196744 PMCID: PMC5711950 DOI: 10.1038/s41598-017-16849-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 11/19/2017] [Indexed: 12/21/2022] Open
Abstract
Water intake is essential for survival and thus under strong regulation. Here, we describe a simple high throughput system to monitor water intake over time in Drosophila. The design of the assay involves dehydrating fly food and then adding water back separately so flies either eat or drink. Water consumption is then evaluated by weighing the water vessel and comparing this back to an evaporation control. Our system is high throughput, does not require animals to be artificially dehydrated, and is simple both in design and implementation. Initial characterisation of homeostatic water consumption shows high reproducibility between biological replicates in a variety of experimental conditions. Water consumption was dependent on ambient temperature and humidity and was equal between sexes when corrected for mass. By combining this system with the Drosophila genetics tools, we could confirm a role for ppk28 and DopR1 in promoting water consumption, and through functional investigation of RNAseq data from dehydrated animals, we found DopR1 expression in the mushroom body was sufficient to drive consumption and enhance water taste sensitivity. Together, we provide a simple high throughput water consumption assay that can be used to dissect the cellular and molecular machinery regulating water homeostasis in Drosophila.
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106
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Tauber JM, Brown EB, Li Y, Yurgel ME, Masek P, Keene AC. A subset of sweet-sensing neurons identified by IR56d are necessary and sufficient for fatty acid taste. PLoS Genet 2017; 13:e1007059. [PMID: 29121639 PMCID: PMC5697886 DOI: 10.1371/journal.pgen.1007059] [Citation(s) in RCA: 44] [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: 07/11/2017] [Revised: 11/21/2017] [Accepted: 10/08/2017] [Indexed: 01/10/2023] Open
Abstract
Fat represents a calorically potent food source that yields approximately twice the amount of energy as carbohydrates or proteins per unit of mass. The highly palatable taste of free fatty acids (FAs), one of the building blocks of fat, promotes food consumption, activates reward circuitry, and is thought to contribute to hedonic feeding underlying many metabolism-related disorders. Despite a role in the etiology of metabolic diseases, little is known about how dietary fats are detected by the gustatory system to promote feeding. Previously, we showed that a broad population of sugar-sensing taste neurons expressing Gustatory Receptor 64f (Gr64f) is required for reflexive feeding responses to both FAs and sugars. Here, we report a genetic silencing screen to identify specific populations of taste neurons that mediate fatty acid (FA) taste. We find neurons identified by expression of Ionotropic Receptor 56d (IR56d) are necessary and sufficient for reflexive feeding response to FAs. Functional imaging reveals that IR56d-expressing neurons are responsive to short- and medium-chain FAs. Silencing IR56d neurons selectively abolishes FA taste, and their activation is sufficient to drive feeding responses. Analysis of co-expression with Gr64f identifies two subpopulations of IR56d-expressing neurons. While physiological imaging reveals that both populations are responsive to FAs, IR56d/Gr64f neurons are activated by medium-chain FAs and are sufficient for reflexive feeding response to FAs. Moreover, flies can discriminate between sugar and FAs in an aversive taste memory assay, indicating that FA taste is a unique modality in Drosophila. Taken together, these findings localize FA taste within the Drosophila gustatory center and provide an opportunity to investigate discrimination between different categories of appetitive tastants. Fat represents a calorically potent food source that yields approximately twice the amount of energy as carbohydrates or proteins per unit of mass. Dietary lipids are comprised of both triacylglycerides and FAs, and growing evidence suggests that it is the free FAs that are detected by the gustatory system. The highly palatable taste of FAs promotes food consumption, activates reward centers in mammals, and is thought to contribute to hedonic feeding that underlies many metabolism-related disorders. Despite a role in the etiology of metabolic diseases, little is known about how dietary fats are detected by the gustatory system to promote feeding. We have identified a subset of sugar-sensing neurons in the fly that also responds to medium-chain FAs and are necessary and sufficient for behavioral response to FAs. Further, we find that despite being sensed by shared neuronal populations, flies can differentiate between the taste of sugar and FAs, fortifying the notion that FAs and sugar represent distinct taste modalities in flies.
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Affiliation(s)
- John M. Tauber
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL, United States of America
| | - Elizabeth B. Brown
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL, United States of America
| | - Yuanyuan Li
- Department of Biological Sciences, Binghamton University, Binghamton, NY, United States of America
| | - Maria E. Yurgel
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL, United States of America
| | - Pavel Masek
- Department of Biological Sciences, Binghamton University, Binghamton, NY, United States of America
| | - Alex C. Keene
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL, United States of America
- * E-mail:
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107
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Lee MJ, Sung HY, Jo H, Kim HW, Choi MS, Kwon JY, Kang K. Ionotropic Receptor 76b Is Required for Gustatory Aversion to Excessive Na+ in Drosophila. Mol Cells 2017; 40:787-795. [PMID: 29081083 PMCID: PMC5682255 DOI: 10.14348/molcells.2017.0160] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 08/23/2017] [Indexed: 12/31/2022] Open
Abstract
Avoiding ingestion of excessively salty food is essential for cation homeostasis that underlies various physiological processes in organisms. The molecular and cellular basis of the aversive salt taste, however, remains elusive. Through a behavioral reverse genetic screening, we discover that feeding suppression by Na+-rich food requires Ionotropic Receptor 76b (Ir76b) in Drosophila labellar gustatory receptor neurons (GRNs). Concentrated sodium solutions with various anions caused feeding suppression dependent on Ir76b. Feeding aversion to caffeine and high concentrations of divalent cations and sorbitol was unimpaired in Ir76b-deficient animals, indicating sensory specificity of Ir76b-dependent Na+ detection and the irrelevance of hyperosmolarity-driven mechanosensation to Ir76b-mediated feeding aversion. Ir76b-dependent Na+-sensing GRNs in both L- and s-bristles are required for repulsion as opposed to the previous report where the L-bristle GRNs direct only low-Na+ attraction. Our work extends the physiological implications of Ir76b from low-Na+ attraction to high-Na+ aversion, prompting further investigation of the physiological mechanisms that modulate two competing components of Na+-evoked gustation coded in heterogeneous Ir76b-positive GRNs.
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Affiliation(s)
- Min Jung Lee
- Samsung Medical Center, Department of Anatomy and Cell Biology, School of Medicine, Sungkyunkwan University, Suwon 16419,
Korea
- Dong-A ST Research Institute, Yongin 17073,
Korea
| | - Ha Yeon Sung
- Department of Biological Sciences, Sungkyunkwan University, Suwon 16419,
Korea
| | - HyunJi Jo
- Samsung Medical Center, Department of Anatomy and Cell Biology, School of Medicine, Sungkyunkwan University, Suwon 16419,
Korea
| | - Hyung-Wook Kim
- College of Life Sciences, Sejong University, Seoul 05006,
Korea
| | - Min Sung Choi
- Department of Biological Sciences, Sungkyunkwan University, Suwon 16419,
Korea
| | - Jae Young Kwon
- Department of Biological Sciences, Sungkyunkwan University, Suwon 16419,
Korea
| | - KyeongJin Kang
- Samsung Medical Center, Department of Anatomy and Cell Biology, School of Medicine, Sungkyunkwan University, Suwon 16419,
Korea
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108
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van Giesen L, Garrity PA. More than meets the IR: the expanding roles of variant Ionotropic Glutamate Receptors in sensing odor, taste, temperature and moisture. F1000Res 2017; 6:1753. [PMID: 29034089 PMCID: PMC5615767 DOI: 10.12688/f1000research.12013.1] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/27/2017] [Indexed: 11/20/2022] Open
Abstract
The ionotropic receptors (IRs) are a branch of the ionotropic glutamate receptor family and serve as important mediators of sensory transduction in invertebrates. Recent work shows that, though initially studied as olfactory receptors, the IRs also mediate the detection of taste, temperature, and humidity. Here, we summarize recent insights into IR evolution and its potential ecological significance as well as recent advances in our understanding of how IRs contribute to diverse sensory modalities.
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Affiliation(s)
- Lena van Giesen
- National Center for Behavioral Genomics and Volen Center for Complex Systems Department of Biology, Brandeis University, Waltham, Massachusetts, USA
| | - Paul A Garrity
- National Center for Behavioral Genomics and Volen Center for Complex Systems Department of Biology, Brandeis University, Waltham, Massachusetts, USA
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109
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Marin E, Costa M. Sensory Neurobiology: Wet Fly Fishing. Curr Biol 2017; 27:R839-R842. [PMID: 28898645 DOI: 10.1016/j.cub.2017.07.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A neuron responding to moist air and its ionotropic receptor have been identified in Drosophila melanogaster. Moreover, second-order neurons integrate temperature and humidity information before reaching higher brain centres.
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Affiliation(s)
- Elizabeth Marin
- Department of Zoology, University of Cambridge, CB2 3EJ, UK; Department of Biology, Bucknell University, Lewisburg, PA 17837, USA
| | - Marta Costa
- Department of Zoology, University of Cambridge, CB2 3EJ, UK.
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