The molecular basis for water taste in Drosophila. Nature

Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, CA, USA.
Nature (Impact Factor: 41.46). 04/2010; 465(7294):91-5. DOI: 10.1038/nature09011
Source: PubMed


The detection of water and the regulation of water intake are essential for animals to maintain proper osmotic homeostasis. Drosophila and other insects have gustatory sensory neurons that mediate the recognition of external water sources, but little is known about the underlying molecular mechanism for water taste detection. Here we identify a member of the degenerin/epithelial sodium channel family, PPK28, as an osmosensitive ion channel that mediates the cellular and behavioural response to water. We use molecular, cellular, calcium imaging and electrophysiological approaches to show that ppk28 is expressed in water-sensing neurons, and that loss of ppk28 abolishes water sensitivity. Moreover, ectopic expression of ppk28 confers water sensitivity to bitter-sensing gustatory neurons in the fly and sensitivity to hypo-osmotic solutions when expressed in heterologous cells. These studies link an osmosensitive ion channel to water taste detection and drinking behaviour, providing the framework for examining the molecular basis for water detection in other animals.

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Available from: Makoto Hiroi, Aug 13, 2014
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    • "), (22) Gr5a-GAL4 (Wang et al., 2004), (23) Gr66a- GAL4 (Scott et al., 2001), (24) Ir76b-GAL4 (Zhang et al., 2013), (25) ppk28-GAL4 (Cameron et al., 2010), (26) Ir76b-QF (Zhang et al., 2013), (27) QUAS-mtdTomato::3xHA (Potter et al., 2010), (28) lexAop-CD2::GFP (Lai & Lee, 2006), (29) 13xLexAop2- IVS-FRT-stop-FRT-spGFP11::CD4::HA-T2A-Brp D3 ::mCherry (attP2) (Karuppudurai et al., 2014), (30) UAS-Syb::spGFP1-10 (Karuppudurai et al., 2014). To label single cells by the FLP-out recombination method, wandering larvae, or early pupae were treated with 39 ° C heat shock for 20 min (for UAS-FRT-CD2, y -FRT-CD8::GFP ), 5 min (for 20xUAS-IVS-FRT-stop-FRT- spGFP1-10::CD4::HA ) or 0 – 2 min (for 13xLexAop2-IVS-FRT- stop-FRT-spGFP11::CD4::HA-T2A-Brp D3 ::mCherry (attP2) ), and then kept at 25 ° C until dissection. "
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    ABSTRACT: Although the gustatory system provides animals with sensory cues important for food choice and other critical behaviors, little is known about neural circuitry immediately following gustatory sensory neurons (GSNs). Here, we identify and characterize a bilateral pair of gustatory second-order neurons in Drosophila. Previous studies identified GSNs that relay taste information to distinct subregions of the primary gustatory center (PGC) in the gnathal ganglia (GNG). To identify candidate gustatory second-order neurons (G2Ns) we screened ∼5,000 GAL4 driver strains for lines that label neural fibers innervating the PGC. We then combined GRASP (GFP reconstitution across synaptic partners) with presynaptic labeling to visualize potential synaptic contacts between the dendrites of the candidate G2Ns and the axonal terminals of Gr5a-expressing GSNs, which are known to respond to sucrose. Results of the GRASP analysis, followed by a single cell analysis by FLPout recombination, revealed a pair of neurons that contact Gr5a axon terminals in both brain hemispheres, and send axonal arborizations to a distinct region outside the PGC but within the GNG. To characterize the input and output branches, respectively, we expressed fluorescence-tagged acetylcholine receptor subunit (Dα7) and active-zone marker (Brp) in the G2Ns. We found that G2N input sites overlaid GRASP-labeled synaptic contacts to Gr5a neurons, while presynaptic sites were broadly distributed throughout the neurons' arborizations. GRASP analysis and further tests with the Syb-GRASP method suggested that the identified G2Ns receive synaptic inputs from Gr5a-expressing GSNs, but not Gr66a-expressing GSNs, which respond to caffeine. The identified G2Ns relay information from Gr5a-expressing GSNs to distinct regions in the GNG, and are distinct from other, recently identified gustatory projection neurons, which relay information about sugars to a brain region called the antennal mechanosensory and motor center (AMMC). Our findings suggest unexpected complexity for taste information processing in the first relay of the gustatory system.
    Journal of neurogenetics 05/2015; DOI:10.3109/01677063.2015.1054993 · 1.27 Impact Factor
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    • "Previous studies had revealed excellent correspondence between stimulus-evoked electrophysiological responses in sensory neurons and calcium responses in their cell bodies and axon termini in olfactory and gustatory receptor neurons of fruit flies (de Bruyne et al., 2001; Suh et al., 2004; Pelz et al., 2006; Kwon et al., 2007; Cameron et al., 2010). Although we do not know the correlation between the calcium signals observed in the axons of subgroup-D JO neurons and their action potential responses, the tonic calcium response of subgroup-D JO neurons to vibrations of middle-range frequencies, a pulse song, and the anterior deflection observed in this study strongly suggests these signals would be transmitted to their downstream neural circuits. "
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    ABSTRACT: The fruit fly Drosophila melanogaster responds behaviorally to sound, gravity, and wind. Johnston's organ (JO) at the antennal base serves as a sensory organ in the fruit fly to detect these mechanosensory stimuli. Among the five anatomically defined subgroups of sensory neurons in JO, subgroups A and B detect sound vibrations and subgroups C and E respond to static deflections, such as gravity and wind. The functions of subgroup-D JO neurons, however, remain unknown. In this study, we used molecular-genetic methods to explore the physiologic properties of subgroup-D JO neurons. Both vibrations and static deflection of the antennal receiver activated subgroup-D JO neurons. This finding clearly revealed that zone D in the antennal mechanosensory and motor center (AMMC), the projection target of subgroup-D JO neurons, is a primary center for antennal vibrations and deflection in the fly brain. We anatomically identified two types of interneurons downstream of subgroup-D JO neurons, AMMC local neurons (AMMC LNs), and AMMC D1 neurons. AMMC LNs are local neurons whose projections are confined within the AMMC, connecting zones B and D. On the other hand, AMMC D1 neurons have both local dendritic arborizations within the AMMC and descending projections to the thoracic ganglia, suggesting that AMMC D1 neurons are likely to relay information of the antennal movement detected by subgroup-D JO neurons from the AMMC directly to the thorax. Together, these findings provide a neural basis for how JO and its brain targets encode information of complex movements of the fruit fly antenna.
    Frontiers in Physiology 05/2014; 5:179. DOI:10.3389/fphys.2014.00179 · 3.53 Impact Factor
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    • "Frontiers in Behavioral Neuroscience January 2014 | Volume 8 | Article 6 | 1 BEHAVIORAL NEUROSCIENCE et al., 2004; Al-Anzi et al., 2006; Moon et al., 2006; Dahanukar et al., 2007; Benton et al., 2009; Cameron et al., 2010; Weiss et al., 2011; Miyamoto et al., 2012; Zhang et al., 2013 "
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    ABSTRACT: The sensation of bitter substances can alert an animal that a specific type of food is harmful and should not be consumed. However, not all bitter compounds are equally toxic and some may even be beneficial in certain contexts. Thus, taste systems in general may have a broader range of functions than just in alerting the animal. In this study we investigate bitter sensing and processing in Drosophila larvae using quinine, a substance perceived by humans as bitter. We show that behavioral choice, feeding, survival, and associative olfactory learning are all directly affected by quinine. On the cellular level, we show that 12 gustatory sensory receptor neurons that express both GR66a and GR33a are required for quinine-dependent choice and feeding behavior. Interestingly, these neurons are not necessary for quinine-dependent survival or associative learning. On the molecular receptor gene level, the GR33a receptor, but not GR66a, is required for quinine-dependent choice behavior. A screen for gustatory sensory receptor neurons that trigger quinine-dependent choice behavior revealed that a single GR97a receptor gene expressing neuron located in the peripheral terminal sense organ is partially necessary and sufficient. For the first time, we show that the elementary chemosensory system of the Drosophila larva can serve as a simple model to understand the neuronal basis of taste information processing on the single cell level with respect to different behavioral outputs.
    Frontiers in Behavioral Neuroscience 01/2014; 8:6. DOI:10.3389/fnbeh.2014.00006 · 3.27 Impact Factor
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