To arrive at their findings, senior author Kristin Scott, Ph.D., and her research team made use of a powerful genetics technique that enables fruit fly researchers to tightly control which genes are expressed in a cell and which remain silent. The team first homed in on a class of taste neurons, called E409, found on taste pegs in the fruit flys labellum. These neurons had not been characterized before and were not already associated with known taste receptors for sweet and bitter. They then labeled the neurons with a fluorescent protein and found that their projections extended to separate parts of the taste area of the brain in comparison to the sweet and bitter neurons. Next, the researchers tested the E409 neurons response to an array of compounds and found that substances high in carbon dioxide, such as beer, yeast, and carbonated water, elicited heightened neuron activity as opposed to substances low in carbon dioxide. Finally, they found that fruit flies were attracted to solutions with high carbon dioxide concentrations, while those whose E409 neurons were shut off were not.
Because fruit flies are also able to smell carbon dioxide, the team also wanted to learn if the two senses influenced one another. Under normal conditions, when fruit flies smell carbon dioxide in the air, they are repelled by it. Scott and her team showed that fruit flies that had their E409 neurons sh
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NIH/National Institute on Deafness and Other Communication Disorders