How Some Animals Feel the Rough Texture of Food-ScienceDaily

Professor Craig Montell of the University of California, Santa Barbara and postdoctoral fellow Chaolan Lee Current biology It provides a first explanation of how a particular animal feels the texture of food based on its graininess and smoothness. In fruit flies, they found that mechanical sensory channels relay this information about the texture of food.

A channel called TMEM63 is part of a class of receptors that appear in organisms from plants to humans. As a result, new discoveries may help shed some of our own taste nuances.

“We all appreciate that texture affects the attractiveness of food,” said Montel, a prominent professor of molecular, cellular and developmental biology at Dagan. “But this is something we don’t really understand.”

Li and Montell focused on fruit flies to investigate the molecular and cellular mechanisms behind the effect of graininess on food palatability. “We found that, like us, they have food preferences that are influenced by the characteristics of this texture,” Montel said. They devised a taste test that added small particles of various sizes to sweet foods and found that flies prefer particles of a particular size.

In a previous work, Montel and his group unraveled the nuances of play in the sense of taste. In 2016, they found a channel that allowed flies to sense the hardness and viscosity of food through the movement of small bristles on the tongue and labellum. Recently, they discovered a mechanism by which low temperatures reduce palatability.

Researchers are now trying to identify the receptors needed to sense the graininess. They considered the particles to be mechanically activated channels that were triggered when the flies’ taste hairs were lightly bent. However, the inactivation of known receptors did not affect food preferences based on smoothness and graininess.

The authors then examined the protein TMEM63. “FlyTMEM63 is part of a class of mechanosensors that are conserved from plants to humans, but their role in animals was unknown,” Montel said.

Li and Montell inactivated the gene encoding TMEM63 and compared the behavior of mutant flies with wild-type animals, solely on the suspicion that they might convey information about graininess.

After refraining from food from animals for several hours, researchers measured interest in different sugar solutions mixed with particles of different sizes. They measured the animal’s interest in the presented food using the amount of flies that stretched the tengu. Li and Montell found that without TMEM63, flies could not distinguish between a solution of pure sugar water and a solution containing small silica spheres about 9 micrometers in diameter, which is the level of roughness that flies prefer.

When they added chemicals to make the sugar solution unpleasant-a mild acid, caffeine or a moderate amount of salt-microspheres reversed the aversion of flies. However, it is not a fly that lacks TMEM63. Restoring the gene encoding this channel on the label of the mutant fly regained the ability of the animal to detect the grainy condition.

“Before this study, it was not known that flies could even distinguish foods based on their graininess,” Montel said. “We found that the mechanically sensitive channel was TMEM63, which revealed one role for this protein in animals.”

The TMEM63 channel functions in a single polyjuvenile neuron (md-L) on each of the two labels at the end of the fly tengu. Neurons sense the movement of most gustatory bristles on the label. Slight movement of the bristles in interaction with food particles activates TMEM63 channels, stimulating neurons that relay sensations to the brain. Because one neuron is connected to many bristles, it may not be able to convey the position data of individual particles, only the graininess of Gestalt.

By applying a light force to these bristles (mimicking the action of small particles in a sandy solution), Montel and Lee can activate md-L neurons. However, the same procedure had no effect on flies that knocked out TMEM63. Interestingly, both groups of animals were able to detect large forces on the bristles, which could be caused by hard or viscous foods.

Montel’s team has previously shown that another channel, called TMC, is also expressed in md-L neurons and is important for detecting these greater forces. Both TMEM63 and TMC relay texture information about food and may even activate the same neurons. However, the Li and Montell results reveal that the two channels have different roles.

Textures can provide a lot of information about food. It may indicate freshness or spoilage. For example, fruits are often eaten when they start to spoil. “Animals use all possible sensory information to assess food preference,” Montel said. “This includes not only its chemical composition, but also its color, odor, temperature, and various texture features.

“The 9 micrometer particle size that flies enjoy most is the size that corresponds to some of their favorite foods, such as budding yeast and particles of their favorite fruits,” he explained.

Montel suggested that TMEM63 almost certainly has many other roles in animals. “This protein is conserved in humans,” Montel said. “I don’t know if it plays a role in human texture sensations, but some mechanically sensitive channels probably do.”