Current Biology . . . Li quietly revealed the fruit fly temperature and sweet taste perception integration mechanism.

Sweet perception is essential for the survival of many animals, because it can guide animals to eat foods rich in nutrients and energy.from invertebrate Drosophila to vertebrate mammals such as us, there are abundant sweet taste receptors and corresponding taste sensing cells.animal preference for sweet food can be influenced by other perceptions, such as food texture, smell and temperature.the Craig Montell team at the University of California, Santa Barbara, has found that the multi dendritic mechanical sensing neurons at the end of the feeding organ (proboscis) of fruit flies can sense the hardness of food and thus inhibit their preference for sweet food.the temperature of food can also affect the perception of sweetness. In our daily life experience, we will find that the sweetness of frozen sweets becomes lighter. The cellular molecular mechanism behind this remains to be further explored.on April 23, 2020, Craig Montell team (the first author is Dr. Li Jingran) published an article in Current Biology Magazine: temperature and sweet taste integration in drophila, and found that low temperature indirectly inhibits the sweet taste perception mediated feeding pathway of Drosophila through direct stimulation of bitter and mechanical neurons.in order to study the effect of food temperature on the sweetness preference of Drosophila melanogaster, the researchers used the behavioral experiment of per (proboscis extension reflex), a commonly used method to quickly identify the response of Drosophila to food preference.adding 0.5 μ l sucrose solution to the refrigeration probe can realize the fine regulation of the food temperature of Drosophila melanogaster. It is found that the acceptance of sucrose solution decreases with the decrease of temperature in the temperature range of 23 ℃ (room temperature) to 17 ℃. In fact, Drosophila can even distinguish the temperature difference of 2 ℃ and make behavioral response.the primary sensory nervous system of chemicals in Drosophila has been studied clearly in the last 20 years. A typical gustatory receptor (sensilla) on the fly's mouth contains five neurons, of which four have a clear division of labor, sensing different compounds, such as bitter substances, sweet substances, acids, salts and osmotic pressure, and the other is a mechanical sensitive neuron.next, the researchers screened different types of taste neurons and found that when bitter sensory neurons (gr66a-gal4 labeling) and mechanical sensing neurons (r41e11-gal4 labeling) were blocked, the inhibition of low temperature on the feeding desire of Drosophila melanogaster was basically relieved. When the sweet sensing neurons (gr64f-gal4 labeling) were blocked, the flies lost the sweet food Reaction.then, the researchers wanted to know the physiological response of these taste neurons to temperature. Through in vivo calcium imaging technology, firstly, they were surprised to find that there was no significant difference in the response of fruit fly's sweet taste sensing neurons to 17 degree sucrose solution and 23 degree sucrose solution, which was different from that of trpm5 ion channel found in mammals more than a decade ago, which revealed that the temperature was autonomously regulated by high temperature activation The mechanism of sweetness perception is different.for the first time, researchers found that low temperature stimulation can activate bitter taste and mechanical sensing neurons. Through tip recording, they found that the decrease of temperature (23 ℃ to 17 ℃) can cause the release of bitterness and mechanical action potential, which further confirmed the ability of these two types of neurons which can inhibit eating behavior to perceive temperature changes. Combined with behavioral results, the researchers studied the effects of cold stimulation on taste and mechanical action potential We propose a working model in which low-temperature sweets inhibit sweet preference by activating bitterness and mechanical sensing neurons.finally, the researchers screened a number of potential mutants of cold sensing receptors or channels. The results showed that a classic visual pathway photosensitive protein, rhodopsin 6 (RH6), was not affected by low temperature, and its preference for sucrose solution was exciting. Meanwhile, RH6 was detected in bitter neurons. In addition, the ability to sense low temperature (23 to 17 degrees) in Drosophila melanogaster with RH6 mutation also showed a defect in the ability to sense low temperature (23 degrees to 17 degrees), and the retrieval experiment further proved the low temperature sensing effect of RH6 protein in bitter neurons.in conclusion, in this work, the researchers found that: 1) fruit flies can recognize and avoid low-temperature sweets.2) hypothermia indirectly inhibited the sweet perception mediated eating pathway through direct stimulation of bitter and mechanical neurons.3) a visual protein plays an important role in the perception of low temperature in bitter neurons.about the author: Li Jingran, female, postdoctoral of University of California, Santa Barbara (2016 to present). with Drosophila as the main model animal, the research interest is to answer some basic scientific questions in the field of neurobiology, such as the relationship between the neural loop of flies and the regulation of metabolic development, the molecular and cellular mechanism of peripheral primary sensory system and the regulatory mechanism of animal behavior. original link: plate maker: Ke