• UCSBgauchos twitter avatar
    Gilbertson Earns Big West Player of the Week Honor https://t.co/P0wmPtDjNT
    1 hour 30 min ago
  • ucsantabarbara twitter avatar
    When secrets are exposed, can life ever be the same? That question is at the heart of @ucsbTD's “Lydia." https://t.co/r1KKTmmB5N
    7 hours 7 min ago
  • ArtsandLectures twitter avatar
    RT @KCRWinSB: Extreme sports, mountain culture & exotic locations are a few highlights of the @BanffMtnFest. Don't miss it! https://t.co/sR…
    7 hours 8 min ago
  • ArtsandLectures twitter avatar
    .@DrSidMukherjee on the powerful documentary Cancer: The Emperor of All Maladies with @kenburns & @katiecouric https://t.co/p7pRHUrhGr
    7 hours 18 min ago
  • ArtsandLectures twitter avatar
    Fearless foodies, we're prepping for @AltonBrownLive with a giveaway! Find out how you can win #AltonBrown swag!… https://t.co/7xWh29cuct
    7 hours 34 min ago
  • UCSBgauchos twitter avatar
    WWP: Gauchos Begin Barbara Kalbus Invitational Against No. 8 Michigan https://t.co/p3U6s9Pswr
    7 hours 47 min ago
  • UCSB_GradPost twitter avatar
    Maria Vazquez on seeing the big picture and grad school life lessons https://t.co/8ghZtxLgvN #UCSB #ucsbgradpost
    8 hours 53 min ago
  • UCSBgauchos twitter avatar
    Gauchos Host Riverside in Final Home Game Thursday https://t.co/FPzQSdg2Ae
    9 hours 14 min ago
  • UCSBengineering twitter avatar
    Cryptographer Stefano Tessaro receives early career recognition from the Alfred P. Sloan Foundation https://t.co/iQi8qUA6uS
    9 hours 37 min ago
  • AS_UCSB twitter avatar
    Eager to make your mark on campus? Pop into our winter recruitment fair to learn how to get involved with your A.S.… https://t.co/Cp0VIE7bEq
    9 hours 58 min ago
  • brenucsb twitter avatar
    RT @CoraKammeyer: So cool to hear @GlobalEcoGuy speak at @brenucsb about the work @calacademy is doing to explore+explain+sustain our awe-i…
    11 hours 27 min ago
  • ArtsandLectures twitter avatar
    @mrjoshz @benshapiro oops, not an A&L event. Daily Nexus says it was put on by UCSB College Republicans: https://t.co/z8KDFjpXTv
    12 hours 6 min ago
  • brenucsb twitter avatar
    .@GlobalEcoGuy: Museums are the most trusted institutions in the nation w/ high approval ratings from Dems & Republicans alike #BrenTalks
    13 hours 3 min ago
  • ArtsandLectures twitter avatar
    Looking forward to another collaboration #theemperorofallmaladies #thegene https://t.co/BEzznCTSdN
    13 hours 5 min ago
  • brenucsb twitter avatar
    @GlobalEcoGuy: Museums serve ~ 1 billion visitors a year, more than all the sports stadiums & theme parks in the nation combined #BrenTalks
    13 hours 6 min ago

The Bitter and the Sweet: Fruit Flies Reveal an Interaction Between the Two

The study explains how fruit flies respond to sugar when bitter compounds are added
Wednesday, August 21, 2013 - 17:00
Santa Barbara, CA

Figure 3adj.jpg

OBP49a protein

The red shows expression of the OBP49a protein in accessory (thecogen) cells in gustatory sensilla, which are distributed on the labella.

Pacman1.jpeg

Pac-Man

Bitter-containing foods, such as coffee beans, reduce the attractive taste of sugar. This concept is depicted by a Pac-Man, comprised of coffee beans, eating up sugar cubes.

Fruit flies have a lot to teach us about the complexity of food. Like these tiny little creatures, most animals are attracted to sugar but are deterred from eating it when bitter compounds are added.

A new study conducted by Craig Montell, Duggan Professor of Neuroscience in the Department of Molecular, Cellular and Developmental Biology, explains a breakthrough in understanding how sensory input impacts fruit flies' decisions about sweet taste. The findings were published today in the journal Neuron.

It is generally well known that the addition of bitter compounds inhibits attraction to sugars. However, until now the cellular and molecular mechanisms underlying an important aspect of this ubiquitous animal behavior were poorly understood.

When animals encounter bitterness in foods, two factors cause them to stop eating. First, bitter compounds bind to proteins called bitter gustatory receptors (GRs), which inhibits feeding. The second — and more elusive — factor involves inhibition of the sugar response. This is the focus of Montell's research.

At the center of the team's discovery is the function of an odorant-binding protein (OPB) in the gustatory system. These proteins are usually but not exclusively resident in the olfactory system. Montell's team found definitive evidence that an OBP, synthesized and released from non-neuronal cells, not only binds bitter tastants, but also moves and binds to the surface of nearby gustatory receptor neurons (GRNs) that contain sugar-activated GRs.

This unanticipated process inhibits the activity of these GRNs and reduces the fruit flies' attraction to sugars. These results not only reveal an unexpected role for an OBP in taste, but also identify the first molecular player (OBP49a) involved in the integration of opposing attractive and aversive gustatory stimuli in fruit flies.

The researchers used two different fruit flies, wild-type and mutants missing the OBP49a protein, to demonstrate that bitter compounds suppress feeding behavior by binding to the OBP49a protein. As expected, wild-type flies find bitter aversive and prefer the lower concentration of sucrose when the higher concentration of sucrose is laced with bitter tastants such as quinine.

The same was not true of the mutant flies, which do not express OBP49a. Their avoidance behavior was impaired because the bitter compounds did not inhibit the sweet response by binding to OPB49. However, loss of OBP49a did not affect gustatory behavior or action potentials in sugar- or bitter-activated GRNs when the GRNs were presented with just one type of tastant.

"We showed that the OBP49a protein was in very close proximity or even touching the sugar GRs," said Montell. "If the bitter compound weren't present, there would be normal sugar activation. We found that decreased behavioral avoidance to a sucrose/aversive mixture in the mutant flies was due to a deficit in the sugar-activated GRNs and not due to effects on GRNs activated by bitter compounds."

OBP49a is the first molecule shown to promote the inhibition of the sucrose-activated GRNs by aversive chemicals in fruit flies. The findings demonstrate at least one important cellular mechanism through which bitter and sweet taste integration occurs in the taste receptor neurons. However, the findings do not exclude the possibility that suppression of sweet by bitter compounds could also take place through the integration of separate bitter and sweet inputs in the brain.

"As we get a better understanding of aversive and attractive chemosensory behaviors in flies, it helps us understand how insect pests can be controlled," said Montell. "This is a step toward understanding the behaviors of related insects that spread disease. Molecules related to the OBPs and GRs in fruit flies are also in ticks and mosquitos that spread parasites and viruses."

Craig Montell

Neuron

Contact Info: 

Julie Cohen
julie.cohen@ia.ucsb.edu
(805) 893-7220

Topics: