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Alkaline taste sensation through the alkaliphile chloride channel in Drosophila

Abstract

The sense of taste is an important sentinel governing what should or should not be ingested by an animal, with high pH sensation playing a critical role in food selection. Here we explore the molecular identities of taste receptors detecting the basic pH of food using Drosophilamelanogaster as a model. We identify a chloride channel named alkaliphile (Alka), which is both necessary and sufficient for aversive taste responses to basic food. Alka forms a high-pH-gated chloride channel and is specifically expressed in a subset of gustatory receptor neurons (GRNs). Optogenetic activation of alka-expressing GRNs is sufficient to suppress attractive feeding responses to sucrose. Conversely, inactivation of these GRNs causes severe impairments in the aversion to high pH. Altogether, our discovery of Alka as an alkaline taste receptor lays the groundwork for future research on alkaline taste sensation in other animals.

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Fig. 1: Behavioral and electrophysiological taste responses to alkaline foods depend on alka1.
Fig. 2: alka regulates the aversive feeding and physiological responses to foods containing Na2CO3.
Fig. 3: Expression pattern of alka in the fly labellum.
Fig. 4: Alka forms a high-pH-activated Cl channel in HEK293 cells.
Fig. 5: The P276 residue is essential for the conductance of Alka.
Fig. 6: Alka is sufficient to be an alkaline taste sensor in vivo.
Fig. 7: Effects on feeding responses due to activating or suppressing alka-expressing GRNs.

Data availability

All relevant data have been presented in this paper and its supplementary information. Any other related information is available upon request from Y.V.Z. In addition, we deposited the raw confocal videos for double-labeling experiments, including Fig. 3h (https://doi.org/10.6084/m9.figshare.22029284), Fig. 3i (https://doi.org/10.6084/m9.figshare.22029131), Fig. 3k (https://doi.org/10.6084/m9.figshare.22029488) and Fig. 3l (https://doi.org/10.6084/m9.figshare.22029350) in figshare, a publicly accessible repository. Source data are provided with this paper.

References

  1. Yarmolinsky, D. A., Zuker, C. S. & Ryba, N. J. Common sense about taste: from mammals to insects. Cell 139, 234–244 (2009).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  2. Liman, E. R., Zhang, Y. V. & Montell, C. Peripheral coding of taste. Neuron 81, 984–1000 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  3. Kiwull-Schone, H., Kiwull, P., Manz, F. & Kalhoff, H. Food composition and acid-base balance: alimentary alkali depletion and acid load in herbivores. J. Nutr. 138, 431S–434S (2008).

    Article  PubMed  Google Scholar 

  4. Huang, A. L. et al. The cells and logic for mammalian sour taste detection. Nature 442, 934–938 (2006).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  5. Tu, Y. H. et al. An evolutionarily conserved gene family encodes proton-selective ion channels. Science 359, 1047–1050 (2018).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  6. Mi, T., Mack, J. O., Lee, C. M. & Zhang, Y. V. Molecular and cellular basis of acid taste sensation in Drosophila. Nat. Commun. 12, 3730 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  7. Kloehn, N. W. & Brogden, W. J. The alkaline taste; a comparison of absolute thresholds for sodium hydroxide on the tip and mid-dorsal surfaces of the tongue. Am. J. Psychol. 61, 90–93 (1948).

    Article  CAS  PubMed  Google Scholar 

  8. Liljestrand, G. & Zotterman, Y. The alkaline taste. Acta Physiol. Scand. 35, 380–389 (1956).

    Article  CAS  PubMed  Google Scholar 

  9. Paje, F. & Mossakowski, D. pH-preferences and habitat selection in carabid beetles. Oecologia 64, 41–46 (1984).

    Article  CAS  PubMed  Google Scholar 

  10. Milius, M. et al. A new method for electrophysiological identification of antennal pH receptor cells in ground beetles: the example of Pterostichus aethiops (Panzer, 1796) (Coleoptera, Carabidae). J. Insect Physiol. 52, 960–967 (2006).

    Article  CAS  PubMed  Google Scholar 

  11. Clyne, P. J., Warr, C. G. & Carlson, J. R. Candidate taste receptors in Drosophila. Science 287, 1830–1834 (2000).

    Article  CAS  PubMed  Google Scholar 

  12. Dahanukar, A., Foster, K., van der Goes van Naters, W. M. & Carlson, J. R. A Gr receptor is required for response to the sugar trehalose in taste neurons of Drosophila. Nat. Neurosci. 4, 1182–1186 (2001).

    Article  CAS  PubMed  Google Scholar 

  13. Wang, Z., Singhvi, A., Kong, P. & Scott, K. Taste representations in the Drosophila brain. Cell 117, 981–991 (2004).

    Article  CAS  PubMed  Google Scholar 

  14. Slone, J., Daniels, J. & Amrein, H. Sugar receptors in Drosophila. Curr. Biol. 17, 1809–1816 (2007).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  15. Jiao, Y., Moon, S. J. & Montell, C. A Drosophila gustatory receptor required for the responses to sucrose, glucose, and maltose identified by mRNA tagging. Proc. Natl Acad. Sci. USA 104, 14110–14115 (2007).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  16. Zhang, Y. V., Ni, J. & Montell, C. The molecular basis for attractive salt-taste coding in Drosophila. Science 340, 1334–1338 (2013).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  17. Jaeger, A. H. et al. A complex peripheral code for salt taste in Drosophila. eLife 7, e37167 (2018).

    Article  PubMed  PubMed Central  Google Scholar 

  18. Dweck, H. K. M., Talross, G. J. S., Luo, Y., Ebrahim, S. A. M. & Carlson, J. R. Ir56b is an atypical ionotropic receptor that underlies appetitive salt response in Drosophila. Curr. Biol. 32, 1776–1787 (2022).

    Article  CAS  PubMed  Google Scholar 

  19. Rimal, S. et al. Mechanism of acetic acid gustatory repulsion in Drosophila. Cell Rep. 26, 1432–1442 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  20. Ganguly, A. et al. Requirement for an otopetrin-like protein for acid taste in Drosophila. Proc. Natl Acad. Sci. USA 118, e2110641118 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  21. Sanchez-Alcaniz, J. A. et al. An expression atlas of variant ionotropic glutamate receptors identifies a molecular basis of carbonation sensing. Nat. Commun. 9, 4252 (2018).

    Article  PubMed  PubMed Central  Google Scholar 

  22. Shim, J. et al. The full repertoire of Drosophila gustatory receptors for detecting an aversive compound. Nat. Commun. 6, 8867 (2015).

    Article  CAS  PubMed  Google Scholar 

  23. Sung, H. Y. et al. Heterogeneity in the Drosophila gustatory receptor complexes that detect aversive compounds. Nat. Commun. 8, 1484 (2017).

    Article  PubMed  PubMed Central  Google Scholar 

  24. Montell, C. Drosophila sensory receptors—a set of molecular Swiss army knives. Genetics 217, 1–34 (2021).

  25. Ahn, J. E., Chen, Y. & Amrein, H. Molecular basis of fatty acid taste in Drosophila. eLife 6, e30115 (2017).

    Article  PubMed  PubMed Central  Google Scholar 

  26. Brown, E. B. et al. Ir56d-dependent fatty acid responses in Drosophila uncover taste discrimination between different classes of fatty acids. eLife 10, e67878 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  27. Luo, R. et al. Molecular basis and homeostatic regulation of Zinc taste. Protein Cell 13, 462–469 (2022).

    Article  PubMed  Google Scholar 

  28. Lee, Y., Poudel, S., Kim, Y., Thakur, D. & Montell, C. Calcium taste avoidance in Drosophila. Neuron 97, 67–74 (2018).

    Article  CAS  PubMed  Google Scholar 

  29. Wisotsky, Z., Medina, A., Freeman, E. & Dahanukar, A. Evolutionary differences in food preference rely on Gr64e, a receptor for glycerol. Nat. Neurosci. 14, 1534–1541 (2011).

    Article  CAS  PubMed  Google Scholar 

  30. Freeman, E. G. & Dahanukar, A. Molecular neurobiology of Drosophila taste. Curr. Opin. Neurobiol. 34, 140–148 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  31. Scott, K. et al. A chemosensory gene family encoding candidate gustatory and olfactory receptors in Drosophila. Cell 104, 661–673 (2001).

    Article  CAS  PubMed  Google Scholar 

  32. Benton, R., Vannice, K. S., Gomez-Diaz, C. & Vosshall, L. B. Variant ionotropic glutamate receptors as chemosensory receptors in Drosophila. Cell 136, 149–162 (2009).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  33. Venkatachalam, K. & Montell, C. TRP channels. Annu Rev. Biochem. 76, 387–417 (2007).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  34. Zhang, J. et al. Sour sensing from the tongue to the brain. Cell 179, 392–402 (2019).

    Article  CAS  PubMed  Google Scholar 

  35. Lynch, J. W. Molecular structure and function of the glycine receptor chloride channel. Physiol. Rev. 84, 1051–1095 (2004).

    Article  CAS  PubMed  Google Scholar 

  36. Remnant, E. J. et al. Evolution, expression, and function of nonneuronal ligand-gated chloride channels in Drosophila melanogaster. G3 6, 2003–2012 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  37. Knipple, D. C. & Soderlund, D. M. The ligand-gated chloride channel gene family of Drosophila melanogaster. Pestic. Biochem. Physiol. 97, 140–148 (2010).

    Article  CAS  Google Scholar 

  38. Ffrench-Constant, R. H., Mortlock, D. P., Shaffer, C. D., MacIntyre, R. J. & Roush, R. T. Molecular cloning and transformation of cyclodiene resistance in Drosophila: an invertebrate γ-aminobutyric acid subtype A receptor locus. Proc. Natl Acad. Sci. USA 88, 7209–7213 (1991).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  39. Henderson, J. E., Soderlund, D. M. & Knipple, D. C. Characterization of a putative γ-aminobutyric acid (GABA) receptor β subunit gene from Drosophila melanogaster. Biochem. Biophys. Res. Commun. 193, 474–482 (1993).

    Article  CAS  PubMed  Google Scholar 

  40. Harvey, R. J. et al. Sequence of a Drosophila ligand-gated ion-channel polypeptide with an unusual amino-terminal extracellular domain. J. Neurochem. 62, 2480–2483 (1994).

    Article  CAS  PubMed  Google Scholar 

  41. Cully, D. F., Paress, P. S., Liu, K. K., Schaeffer, J. M. & Arena, J. P. Identification of a Drosophila melanogaster glutamate-gated chloride channel sensitive to the antiparasitic agent avermectin. J. Biol. Chem. 271, 20187–20191 (1996).

    Article  CAS  PubMed  Google Scholar 

  42. Gengs, C. et al. The target of Drosophila photoreceptor synaptic transmission is a histamine-gated chloride channel encoded by ort (hclA). J. Biol. Chem. 277, 42113–42120 (2002).

    Article  CAS  PubMed  Google Scholar 

  43. Gisselmann, G., Pusch, H., Hovemann, B. T. & Hatt, H. Two cDNAs coding for histamine-gated ion channels in D. melanogaster. Nat. Neurosci. 5, 11–12 (2002).

    Article  CAS  PubMed  Google Scholar 

  44. Schnizler, K. et al. A novel chloride channel in Drosophila melanogaster is inhibited by protons. J. Biol. Chem. 280, 16254–16262 (2005).

    Article  CAS  PubMed  Google Scholar 

  45. Feingold, D., Starc, T., O’Donnell, M. J., Nilson, L. & Dent, J. A. The orphan pentameric ligand-gated ion channel pHCl-2 is gated by pH and regulates fluid secretion in Drosophila Malpighian tubules. J. Exp. Biol. 219, 2629–2638 (2016).

    PubMed  Google Scholar 

  46. Redhai, S. et al. An intestinal zinc sensor regulates food intake and developmental growth. Nature 580, 263–268 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  47. Frenkel, L. et al. Organization of circadian behavior relies on glycinergic transmission. Cell Rep. 19, 72–85 (2017).

    Article  CAS  PubMed  Google Scholar 

  48. Dambly-Chaudiere, C. et al. The paired box gene pox neuro: a determinant of poly-innervated sense organs in Drosophila. Cell 69, 159–172 (1992).

    Article  CAS  PubMed  Google Scholar 

  49. Zhang, Y. V., Aikin, T. J., Li, Z. & Montell, C. The basis of food texture sensation in Drosophila. Neuron 91, 863–877 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  50. Stocker, R. F. The organization of the chemosensory system in Drosophila melanogaster: a review. Cell Tissue Res. 275, 3–26 (1994).

    Article  CAS  PubMed  Google Scholar 

  51. Shanbhag, S. R., Park, S. K., Pikielny, C. W. & Steinbrecht, R. A. Gustatory organs of Drosophila melanogaster: fine structure and expression of the putative odorant-binding protein PBPRP2. Cell Tissue Res. 304, 423–437 (2001).

    Article  CAS  PubMed  Google Scholar 

  52. Dusek, M., Chapuis, G., Meyer, M. & Petricek, V. Sodium carbonate revisited. Acta Crystallogr. B 59, 337–352 (2003).

    Article  PubMed  Google Scholar 

  53. Khanna, A. & Kurtzman, N. A. Metabolic alkalosis. Respir. Care 46, 354–365 (2001).

    CAS  PubMed  Google Scholar 

  54. Lee, T. & Luo, L. Mosaic analysis with a repressible cell marker for studies of gene function in neuronal morphogenesis. Neuron 22, 451–461 (1999).

    Article  CAS  PubMed  Google Scholar 

  55. Moon, S. J., Kottgen, M., Jiao, Y., Xu, H. & Montell, C. A taste receptor required for the caffeine response in vivo. Curr. Biol. 16, 1812–1817 (2006).

    Article  CAS  PubMed  Google Scholar 

  56. Fujii, S. et al. Drosophila sugar receptors in sweet taste perception, olfaction, and internal nutrient sensing. Curr. Biol. 25, 621–627 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  57. Ganguly, A. et al. A molecular and cellular context-dependent role for Ir76b in detection of amino acid taste. Cell Rep. 18, 737–750 (2017).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  58. Cameron, P., Hiroi, M., Ngai, J. & Scott, K. The molecular basis for water taste in Drosophila. Nature 465, 91–95 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  59. Chen, Z., Wang, Q. & Wang, Z. The amiloride-sensitive epithelial Na+ channel PPK28 is essential for Drosophila gustatory water reception. J. Neurosci. 30, 6247–6252 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  60. Thistle, R., Cameron, P., Ghorayshi, A., Dennison, L. & Scott, K. Contact chemoreceptors mediate male-male repulsion and male-female attraction during Drosophila courtship. Cell 149, 1140–1151 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  61. Betz, H. Glycine receptors: heterogeneous and widespread in the mammalian brain. Trends Neurosci. 14, 458–461 (1991).

    Article  CAS  PubMed  Google Scholar 

  62. Duran, C., Thompson, C. H., Xiao, Q. & Hartzell, H. C. Chloride channels: often enigmatic, rarely predictable. Annu. Rev. Physiol. 72, 95–121 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  63. Germann, A. L. et al. Activation and modulation of recombinant glycine and GABAA receptors by 4-halogenated analogues of propofol. Br. J. Pharm. 173, 3110–3120 (2016).

    Article  CAS  Google Scholar 

  64. Huang, X., Chen, H., Michelsen, K., Schneider, S. & Shaffer, P. L. Crystal structure of human glycine receptor-α3 bound to antagonist strychnine. Nature 526, 277–280 (2015).

    Article  CAS  PubMed  Google Scholar 

  65. Schmidt, T., Situ, A. J. & Ulmer, T. S. Structural and thermodynamic basis of proline-induced transmembrane complex stabilization. Sci. Rep. 6, 29809 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  66. Gödde, J. & Krefting, E. R. Ions in the receptor lymph of the labellar taste hairs of the fly Protophormia terraenovae. J. Insect Physiol. 35, 107–111 (1989).

    Article  Google Scholar 

  67. Larsson, M. C. et al. Or83b encodes a broadly expressed odorant receptor essential for Drosophila olfaction. Neuron 43, 703–714 (2004).

    Article  CAS  PubMed  Google Scholar 

  68. Eliason, J., Afify, A., Potter, C. & Matsumura, I. A GAL80 collection to inhibit GAL4 transgenes in Drosophila olfactory sensory neurons. G3 8, 3661–3668 (2018).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  69. Klapoetke, N. C. et al. Independent optical excitation of distinct neural populations. Nat. Methods 11, 338–346 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  70. Umezaki, Y., Yasuyama, K., Nakagoshi, H. & Tomioka, K. Blocking synaptic transmission with tetanus toxin light chain reveals modes of neurotransmission in the PDF-positive circadian clock neurons of Drosophila melanogaster. J. Insect Physiol. 57, 1290–1299 (2011).

    Article  CAS  PubMed  Google Scholar 

  71. Venken, K. J., Simpson, J. H. & Bellen, H. J. Genetic manipulation of genes and cells in the nervous system of the fruit fly. Neuron 72, 202–230 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  72. Brand, A. H. & Perrimon, N. Targeted gene expression as a means of altering cell fates and generating dominant phenotypes. Development 118, 401–415 (1993).

    Article  CAS  PubMed  Google Scholar 

  73. Adrogue, H. E. & Adrogue, H. J. Acid–base physiology. Respir. Care 46, 328–341 (2001).

    CAS  PubMed  Google Scholar 

  74. Murayama, T., Takayama, J., Fujiwara, M. & Maruyama, I. N. Environmental alkalinity sensing mediated by the transmembrane guanylyl cyclase GCY-14 in C. elegans. Curr. Biol. 23, 1007–1012 (2013).

    Article  CAS  PubMed  Google Scholar 

  75. Wang, X., Li, G., Liu, J., Liu, J. & Xu, X. Z. TMC-1 mediates alkaline sensation in C. elegans through nociceptive neurons. Neuron 91, 146–154 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  76. Ye, X. & Randall, D. J. The effect of water pH on swimming performance in rainbow trout (Salmo gairdneri, Richardson). Fish Physiol. Biochem. 9, 15–21 (1991).

    Article  CAS  PubMed  Google Scholar 

  77. St John, S. J. & Boughter, J. D. Jr Orosensory responsiveness to and preference for hydroxide-containing salts in mice. Chem. Senses 34, 487–498 (2009).

  78. Massie, H. R., Williams, T. R. & Colacicco, J. R. Changes in pH with age in Drosophila and the influence of buffers on longevity. Mech. Ageing Dev. 16, 221–231 (1981).

    Article  CAS  PubMed  Google Scholar 

  79. Shanbhag, S. & Tripathi, S. Epithelial ultrastructure and cellular mechanisms of acid and base transport in the Drosophila midgut. J. Exp. Biol. 212, 1731–1744 (2009).

    Article  CAS  PubMed  Google Scholar 

  80. Deshpande, S. A. et al. Acidic food pH increases palatability and consumption and extends Drosophila lifespan. J. Nutr. 145, 2789–2796 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  81. Liu, W. et al. Symbiotic bacteria attenuate Drosophila oviposition repellence to alkaline through acidification. Insect Sci. 28, 403–414 (2021).

    Article  CAS  PubMed  Google Scholar 

  82. Moon, S. J., Lee, Y., Jiao, Y. & Montell, C. A Drosophila gustatory receptor essential for aversive taste and inhibiting male-to-male courtship. Curr. Biol. 19, 1623–1627 (2009).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  83. Koh, T. W. et al. The Drosophila IR20a clade of ionotropic receptors are candidate taste and pheromone receptors. Neuron 83, 850–865 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  84. Min, S., Ai, M., Shin, S. A. & Suh, G. S. Dedicated olfactory neurons mediating attraction behavior to ammonia and amines in Drosophila. Proc. Natl Acad. Sci. USA 110, E1321–E1329 (2013).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  85. Zhang, Y. V., Raghuwanshi, R. P., Shen, W. L. & Montell, C. Food experience-induced taste desensitization modulated by the Drosophila TRPL channel. Nat. Neurosci. 16, 1468–1476 (2013).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  86. Kang, K. et al. Analysis of Drosophila TRPA1 reveals an ancient origin for human chemical nociception. Nature 464, 597–600 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  87. Kim, S. H. et al. Drosophila TRPA1 channel mediates chemical avoidance in gustatory receptor neurons. Proc. Natl Acad. Sci. USA 107, 8440–8445 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  88. Ullrich, F. et al. Identification of TMEM206 proteins as pore of PAORAC/ASOR acid-sensitive chloride channels. eLife 8, e49187 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  89. Yang, J. et al. PAC, an evolutionarily conserved membrane protein, is a proton-activated chloride channel. Science 364, 395–399 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  90. Nonaka, T. & Wong, D. T. W. Saliva diagnostics. Annu. Rev. Anal. Chem. 15, 107–121 (2022).

    Article  Google Scholar 

  91. Dibattista, M., Pifferi, S., Boccaccio, A., Menini, A. & Reisert, J. The long tale of the calcium activated Cl(−) channels in olfactory transduction. Channels 11, 399–414 (2017).

    Article  PubMed  PubMed Central  Google Scholar 

  92. Huang, W. et al. Increased intracellular Cl(−) concentration improves airway epithelial migration by activating the RhoA/ROCK pathway. Theranostics 10, 8528–8540 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  93. Zheng, Y. et al. Identification of two novel Drosophila melanogaster histamine-gated chloride channel subunits expressed in the eye. J. Biol. Chem. 277, 2000–2005 (2002).

    Article  CAS  PubMed  Google Scholar 

  94. Li, Q. & Montell, C. Mechanism for food texture preference based on grittiness. Curr. Biol. 31, 1850–1861.e6 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  95. Chu, B., Chui, V., Mann, K. & Gordon, M. D. Presynaptic gain control drives sweet and bitter taste integration in Drosophila. Curr. Biol. 24, 1978–1984 (2014).

    Article  CAS  PubMed  Google Scholar 

  96. Potter, C. J., Tasic, B., Russler, E. V., Liang, L. & Luo, L. The Q system: a repressible binary system for transgene expression, lineage tracing, and mosaic analysis. Cell 141, 536–548 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  97. Shearin, H. K., Macdonald, I. S., Spector, L. P. & Stowers, R. S. Hexameric GFP and mCherry reporters for the Drosophila GAL4, Q, and LexA transcription systems. Genetics 196, 951–960 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

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Acknowledgements

We thank S. Chan and P. Nguyen for their technical contributions to this study. We also thank the Bloomington Drosophila Research Center for fly stocks and the Drosophila Genome Research Center for DNA clones. We appreciate the laboratories of D.R. Reed, M. Hakan Ozdener and I. Matsumoto at the Monell Chemical Senses Center for sharing equipment and facilities. Our work was supported by the National Institute on Deafness and other Communication Disorders grants R01 DC018592 (Y.V.Z.) and R01 DC007864 (C.M.), the Ambrose Monell Foundation (Y.V.Z.) and the National Key Research and Development Program of China Project 2018YFA0108001 (Z.-Q.T.).

Author information

Authors and Affiliations

Authors

Contributions

Y.V.Z. conceived of this work. T.M., J.O.M., W.K., Q.L. and L.Y. carried out the molecular genetics and feeding experiments. T.M. and Z.-Q.T. performed patch-clamp analyses. W.K., P.J., L.Y. and Y.V.Z. conducted immunohistochemistry and tip-recording assays. T.M., J.O.M., W.K., C.M. and Y.V.Z. interpreted the data and composed the paper. Y.V.Z. oversaw the project.

Corresponding author

Correspondence to Yali V. Zhang.

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The authors declare no competing interests.

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Nature Metabolism thanks the anonymous reviewers for their contribution to the peer review of this work. Primary Handling Editor: Ashley Castellanos-Jankiewicz, in collaboration with the Nature Metabolism team.

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Extended data

Extended Data Fig. 1 Screening for receptors or ion channels required for the feeding responses to alkaline food.

a, We tested a wide array of receptor and ion channel candidates, a representative sample of which is shown in the bar graph. These include the gustatory receptor (Gr) family, such as Gr66a and Gr33a; the ionotropic glutamate receptor (Ir) family, such as Ir76b and Ir25a; the transient-receptor-potential (trp) ion channel family, such as trpl and trpA1; the otopetrin family, such as otopla; the transmembrane channel-like (tmc); and genes with unknown functions, such as CG12344. n = 10 trials. b, Feeding responses to neutral versus alkaline foods among control flies and mutant flies of the fly LGCC family. n = 10 trials. Mean ± s.e.m., one-way ANOVA with Tukey’s posthoc tests, ****p < 0.0001.

Source data

Extended Data Fig. 2 Generating the alka1 null mutant flies.

a, Genomic composition of the wild-type and mutant alka genes, including the translational start (ATG) and stop (*) codons, exons, and introns. The red arrows indicate the guide RNA (gRNA) target sites (gRNA1 and gRNA2). To screen for the alka1 mutant, we designed three sets of primers, P1, P2, and P3, which flanked the gRNA targeting sites. b, PCR analyses of genomic DNA with the P1, P2, and P3 primers for wild-type (wt) and alka1 mutant flies. c, The predicted topology of the Alka protein comprising four transmembrane segments. The TM2 domain (red) is predicted to line the channel pore. Both the N- and C-terminal ends of the Alka protein reside on the extracellular side. The red arrows show the ablated protein regions in the alka1 mutant.

Extended Data Fig. 3 Electrophysiological responses to NaOH and NaCl.

a, Statistical analyses of the frequencies of spikes produced by L-, I-, and S-type sensilla responding to 10 mM NaOH in wild-type (wt) flies. n = 11 flies. Mean ± s.e.m., one-way ANOVA with Tukey’s posthoc tests, ****p < 0.0001. b, Representative spikes evoked by 10 mM NaCl (pH 7) at S6 sensilla for wt and alka1 mutant flies. The arrow indicates the stimulus onset. c, Statistical analyses of the frequencies of spikes produced by S6 sensilla in response to different concentrations of NaCl for wt and alka1 mutant flies. n = 10 flies. Mean ± s.e.m., unpaired two-tailed Student’s t-tests.

Source data

Extended Data Fig. 4 alka is required to detect alkaline food through the legs.

a–b, Expression of alka-gal4;UAS-mCD8::GFP at the tarsal segment of the fly foreleg. c, PERs to alkaline solutions containing 30 mM sucrose and various concentrations of NaOH among wild-type (wt), alka1, alka1;Ir761, and rescue flies. n = 12 trials. Mean ± s.e.m., two-way ANOVA with Tukey’s posthoc tests, **p = 0.0081, ****p < 0.0001. d, Expression of alka-gal4;UAS-mCD8::GFP in the maxillary palp. e, Expression of alka-gal4;UAS-mCD8::GFP in the antenna. f, No obvious anti-Alka signals were detected in the wt adult brain. g, Relative localization pattern between ppk28-expressing GRNs and taste sensilla. Scale bars: 10 μm (ab, de, g), 50 μm (f).

Source data

Extended Data Fig. 5 Multi-sequence alignment of the full protein sequences among fly Alka and the glycine receptor alpha 1 (GlyRa1) from zebrafish, mice, or humans.

The protein sequence identities between Alka and GlyRa1 in other species are as follows: zebrafish, 30% identity; mouse, 30% identity; human, 30% identity. Identical amino acid residues are labeled in red, whereas similar amino acid residues among at least three species are labeled in yellow and highlighted in bold. The four transmembrane regions (TM1-TM4) are denoted by black bars above their amino acid sequences.

Extended Data Fig. 6 Ion selectivity of Alka and conductance of Alka in response to acidic pH, glycine, or GABA stimuli.

a, Localization of Alka in HEK293 cells expressing Alka that is N-terminally fused with a Myc tag. Scale bar: 5 μm. b, Configuration of the whole-cell patch-clamp recording setup. We used a stimulating pipette (red) to locally apply high-pH solutions to the cells and a patch pipette (blue) to carry out whole-cell recordings. c, Current-voltage (I-V) relationships of Alka-expressed HEK293 cells, which were elicited by voltage ramps from -80 mV to +80 mV. The bath solution contained 150 mM NaF, NaCl, NaBr, or NaI, and the intracellular solution contained 150 mM CsCl. d, Statistical analyses of reversal potentials from experiments in c. n = 11 cells (NaF, NaBr, or NaI); n = 14 cells (NaCl). Mean ± s.e.m., one-way ANOVA with Tukey’s posthoc tests, **p = 0.0012, ****p < 0.0001. e, Relative anion permeability of Alka. n = 11 cells (NaF, NaBr, or NaI); n = 14 cells (NaCl). Mean ± s.e.m., one-way ANOVA with Tukey’s posthoc tests, ***p = 0.0003. f, g, Currents from Alka-expressing cells and control cells without Alka expression responding to the stimuli of acidic isosmotic solutions. n = 11 cells. Mean ± s.e.m., unpaired two-tailed Student’s t-tests. hk, Currents evoked by Alka-expressing cells and control cells without Alka expression in response to the stimuli of glycine (0.001–1 mM) (h,i) or GABA (0.001–1 mM) (j,k). n = 11 cells. Mean ± s.e.m., unpaired two-tailed Student’s t-tests. Cells were clamped at −70 mV. Arrows indicate the onset of stimulus.

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Extended Data Fig. 7 Spikes elicited by NaOH in control flies and spikes evoked by sucrose in flies misexpressing Alka or AlkaP276A at the sweet GRNs.

a, Spikes evoked by L7 sensilla responding to high-pH stimuli in alka1;Gr64f-Gal4 or alka1;UAS-alka flies. b, Statistical analyses of the spike frequencies for alka1;UAS-alka and alka1;Gr64f-Gal4 flies. n = 11 flies. Mean ± s.e.m., unpaired two-tailed Student’s t-tests. c, Spikes produced by L7 sensilla responding to 50 mM sucrose in alka1;Gr64f-Gal4/UAS-alka or alka1;Gr64f-Gal4/UAS-alkaP276A flies. d, Statistical analyses of the spike frequencies for alka1;Gr64f-Gal4/UAS-alka and alka1;Gr64f-Gal4/UAS-alkaP276A flies. n = 11 flies. Mean ± s.e.m., unpaired two-tailed Student’s t-tests. Arrows indicate stimulus onset.

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Extended Data Fig. 8 Expression of alka-Gal4 in combination with Orco-Gal80 in the fly labellum and brain.

ab, Expression of alka-Gal4,UAS-mCD8::GFP;Orco-Gal80 in the antenna (a) and the maxillary palp (b). c, Expression of alka-Gal4,UAS-mCD8::GFP;Orco-Gal80 in the labellum. d, GRN projections in the brain of the alka-Gal4,UAS-mCD8::GFP;Orco-Gal80 fly. SEZ, subesophageal zone; AL, antennal lobe. Scale bars: 10 μm (ac), 50 μm (d).

Extended Data Fig. 9 alka-expressing GRNs are required to sense alkaline food.

ab, GFP expression in the labellum of Gr66a-Gal4,UAS-GFP;LexAop-Gal80 (a) or Gr66a-Gal4,UAS-GFP;Gr66a-lexA,LexAop-Gal80 (b). Scale bar: 10 μm. c, Relative localization between the alka-expressing GRNs and S-type taste sensilla in the alka-Gal4,UAS-GFP;Gr66a-lexA,LexAop-Gal80 fly labellum. Scale bar: 10 μm. d, PERs to sweet food (50 mM sucrose), alkaline food (10 mM NaOH mixed with 30 mM sucrose), and bitter food (10 mM caffeine mixed with 30 mM sucrose) for alka-TNT (alka-Gal4,UAS-TNT), alka-TNT;Orco-Gal80 (alka-Gal4,UAS-TNT;Orco-Gal80), alka-TNT;Gr66a-Gal80(alka-Gal4,UAS-TNT;Gr66a-lexA,LexAop-Gal80), Gr66a-TNT(Gr66a-Gal4,UAS-TNT),Gr66a-TNT;Gr66a-Gal80 (Gr66a-Gal4,UAS-TNT;Gr66a-lexA,LexAop-Gal80), ppk23-TNT (ppk23-Gal4,UAS-TNT), ppk28-TNT (ppk28-Gal4,UAS-TNT), and wild-type (wt) flies. n = 11 trials. Mean ± s.e.m., one-way ANOVA with Tukey’s posthoc tests, ****p < 0.0001.

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Supplementary information

Supplementary Information

Supplementary Sections 1 (Antibodies), 2 (Molecular genetics) and 3 (Extended Data video titles).

Reporting Summary

The alka-Gal4 control fly showing persistent sucrose (500 mM) feeding in the presence and absence of an intense red light stimulus (2,000 lux).

The alka-Gal4,UAS-CsChrimson;Orco-Gal80 fly exhibiting normal feeding of sucrose (500 mM) in the absence of red light but a cessation of feeding in response to a moderate red light stimulus (1,200 lux).

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Mi, T., Mack, J.O., Koolmees, W. et al. Alkaline taste sensation through the alkaliphile chloride channel in Drosophila. Nat Metab 5, 466–480 (2023). https://doi.org/10.1038/s42255-023-00765-3

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