In the first detailed genetic study of fly taste receptors, UC Berkeley neuroscientist Kristin Scott and her colleagues showed that fruit flies have receptors devoted to sweet and bitter tastes just like humans. While human taste receptors are limited to the tongue, the receptors in flies are mounted on bristles scattered all over the body, including the legs, the wings, the food-sucking proboscis and the egg-laying ovipositor.
"Taste neurons basically tell the fly whether food is good or bad to eat," said Scott, an assistant professor of molecular and cell biology at UC Berkeley. "It's pretty amazing that after hundreds of millions of years of evolution, flies and humans still use the same logic for taste detection."
Tracing the taste receptor nerve cells into the brain, Scott and her team showed that fly brains contain a map both of the location on the body and the type or quality of the taste.
Though no one has mapped the taste areas inside mammal or human brains, other senses typically are mapped in the brain by location or quality, but not both. Odors, for example, are perceived by the brain according to what, not where, they are. Touch, on the other hand, is mapped to the brain according to its location on the skin.
"We think there are body maps as well as quality maps in the fly brain because flies need to know where the food is located in order to react properly," Scott said. "If a fly tastes sugar with its leg, it automatically extends its proboscis and eats. If it detects sugar with its proboscis, it just eats."
Scott noted that flies, like mammals, probably also have sour and salt taste receptors, but these have yet to be characterized in any animal. Mammals have a fifth taste receptor, umami, which means "savory" in Japanese
Contact: Robert Sanders
University of California - Berkeley