Calcium Taste Avoidance in Drosophila

• Published in: Neuron (Cambridge, Mass.) Mass.), 2018-01, Vol.97 (1), p.67-74.e4
• Main Authors: Lee, Youngseok, Poudel, Seeta, Kim, Yunjung, Thakur, Dhananjay, Montell, Craig
• Format: Article
• Language: English
• Subjects: Animals; Behavior; Bitter taste; Calcium; chemoreceptor; Drosophila; Drosophila melanogaster - physiology; Drosophila Proteins - metabolism; Feeding; Feeding Behavior - physiology; Food; gustatory; Insects; ionotropic receptor; labellum; Mammals; Neurons; PPK23; Preferences; Receptors, Ionotropic Glutamate - metabolism; Sodium chloride; Sour taste; Sucrose; Sugar; Tastants; Taste; Taste Perception - physiology; Taste receptors
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2017.11.038

Many animals, ranging from vinegar flies to humans, discriminate a wide range of tastants, including sugars, bitter compounds, NaCl, and sour. However, the taste of Ca2+ is poorly understood, and it is unclear whether animals such as Drosophila melanogaster are endowed with this sense. Here, we examined Ca2+ taste in Drosophila and showed that high levels of Ca2+ are aversive. The repulsion was mediated by two mechanisms—activation of a specific class of gustatory receptor neurons (GRNs), which suppresses feeding and inhibition of sugar-activated GRNs, which normally stimulates feeding. The distaste for Ca2+, and Ca2+-activated action potentials required several members of the variant ionotropic receptor (IR) family (IR25a, IR62a, and IR76b). Consistent with the Ca2+ rejection, we found that high concentrations of Ca2+ decreased survival. We conclude that gustatory detection of Ca2+ represents an additional sense of taste in Drosophila and is required for avoiding toxic levels of this mineral. •Vinegar flies taste Ca2+ and reject foods that contain high levels•Ca2+ suppresses feeding through opposing effects on two classes of taste neurons•Members of the ionotropic receptor (IR) family are required for sensing Ca2+ in food•Flies taste and avoid foods with high levels of Ca2+ to avoid Ca2+ toxicity Lee et al. establish flies as a model to characterize calcium taste. They show that high calcium is aversive, identify taste neurons and receptors required for calcium avoidance, and demonstrate that avoidance of foods with excessive calcium promotes survival.