Ir56d-dependent fatty acid responses in Drosophila uncover taste discrimination between different classes of fatty acids.
Ir56d-dependent fatty acid responses in Drosophila uncover taste discrimination between different classes of fatty acids.
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DOI：
10.7554/elife.67878
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发表时间：
2021-05-05
期刊：
影响因子：
7.7
通讯作者：
Keene AC
中科院分区：
文献类型：
--
作者：
Brown EB;Shah KD;Palermo J;Dey M;Dahanukar A;Keene AC
化学感觉系统对于评估食物的热值和潜在毒性至关重要。虽然动物可以区分成千上万种气味，但人们对味觉系统的辨别能力知之甚少。脂肪和糖代表了高热量和有吸引力的食物来源，有助于享乐性进食。尽管脂肪和糖的营养价值不同，但味觉系统区分不同有益味道的能力被认为是有限的。在果蝇中，表达嗜离子受体56d （IR56d）的味觉神经元是对中链脂肪酸己酸的反射性行为反应所必需的。在这里，我们测试了苍蝇是否可以区分不同种类的脂肪酸使用厌恶记忆试验。我们的结果表明，果蝇能够区分中链脂肪酸与短链脂肪酸和长链脂肪酸，但不能区分其他中链脂肪酸。虽然IR56d神经元对短链、中链和长链脂肪酸有广泛的反应，但IR56d的遗传缺失选择性地破坏了对中链脂肪酸的反应。此外，IR56d+ GR64f+神经元对于中链脂肪酸的喙延伸反应（PER）是必需的，但IR56d和GR64f神经元对于短链和长链脂肪酸的PER都是不需要的，这表明参与了一种或多种其他类型的神经元。综上所述，这些发现表明，IR56d是中链脂肪酸味觉的选择性必需，脂肪酸的识别是通过共享神经元群体中的差异受体激活来实现的。我们的研究揭示了味觉系统在味觉类别中编码味觉身份的能力。
Chemosensory systems are critical for evaluating the caloric value and potential toxicity of food. While animals can discriminate between thousands of odors, much less is known about the discriminative capabilities of taste systems. Fats and sugars represent calorically potent and attractive food sources that contribute to hedonic feeding. Despite the differences in nutritional value between fats and sugars, the ability of the taste system to discriminate between different rewarding tastants is thought to be limited. In Drosophila, taste neurons expressing the ionotropic receptor 56d (IR56d) are required for reflexive behavioral responses to the medium-chain fatty acid, hexanoic acid. Here, we tested whether flies can discriminate between different classes of fatty acids using an aversive memory assay. Our results indicate that flies are able to discriminate medium-chain fatty acids from both short- and long-chain fatty acids, but not from other medium-chain fatty acids. While IR56d neurons are broadly responsive to short-, medium-, and long-chain fatty acids, genetic deletion of IR56d selectively disrupts response to medium-chain fatty acids. Further, IR56d+ GR64f+ neurons are necessary for proboscis extension response (PER) to medium-chain fatty acids, but both IR56d and GR64f neurons are dispensable for PER to short- and long-chain fatty acids, indicating the involvement of one or more other classes of neurons. Together, these findings reveal that IR56d is selectively required for medium-chain fatty acid taste, and discrimination of fatty acids occurs through differential receptor activation in shared populations of neurons. Our study uncovers a capacity for the taste system to encode tastant identity within a taste category.