Featured Research

from universities, journals, and other organizations

Transistor in the fly antenna: Insect odorant receptors regulate their own sensitivity

Date:
March 18, 2013
Source:
Max Planck Institute for Chemical Ecology
Summary:
Highly developed antennae containing different types of olfactory receptors allow insects to use minute amounts of odors for orientation. Scientists have now provided experimental proof that the extremely sensitive olfactory system of fruit flies is based on self-regulation of odorant receptors. Even a below threshold odor stimulation increases the sensitivity of the receptor, and if a second odor pulse arrives, a neural response will be elicited.

The antennae of the fruit fly Drosophila melanogaster, shown schematically in dark yellow. Dark red: odor molecules. Right: The odorant receptors studied are protein dimers consisting of the odorant receptor Or22a and the co-receptor Orco; they mediate very sensitive responses to odor molecules. Above: State of sensitization weak ion flow caused by cAMP; below: signals are “switched through” in the receptor system resulting in opening of the ion channel and electric signal transduction.
Credit: Graphics: Dieter Wicher, Max Planck Institute for Chemical Ecology / Animation: Moves Like Nature, Kimberly Falk

Highly developed antennae containing different types of olfactory receptors allow insects to use minute amounts of odors for orientation towards resources like food, oviposition sites or mates. Scientists at the Max Planck Institute for Chemical Ecology in Jena, Germany, have now used mutant flies and for the first time provided experimental proof that the extremely sensitive olfactory system of fruit flies − they are able to detect a few thousand odor molecules per milliliter of air, whereas humans need hundreds of millions − is based on self-regulation of odorant receptors.

Related Articles


Even fewer molecules below the response threshold are sufficient to amplify the sensitivity of the receptors, and binding of molecules shortly afterwards triggers the opening of an ion channel that controls the fly's reaction and flight behavior. This means that a below threshold odor stimulation increases the sensitivity of the receptor, and if a second odor pulse arrives within a certain time span, a neural response will be elicited.

Results of the research are published in the online journal PLOS ONE.

A sensitive sense of smell is vital

It is amazing how many fruit flies (Drosophila melanogaster) find their way to a rotting apple. It is known that insects are able to detect the slightest concentrations of odor molecules, especially pheromones, but also "food signals."

Dieter Wicher, Shannon Olsson, Bill Hansson and their colleagues at the Max Planck Institute for Chemical Ecology were looking for answers to the question why insects can trace odor molecules so easily and at such low concentrations in comparison to other animals. They focused their attention on odorant receptor proteins in the antenna, the insects' nose. These insect proteins are pretty young from an evolutionary perspective and their molecular constituents may be the basis for the insects' highly sensitive sense of smell.

Receptor system Or22a-Orco

Insect odorant receptors form a receptor system that consists of the actual receptor protein and an ion channel. After binding of an odor molecule, receptor protein and ion channel trigger the neural electrical response. This mechanism was recently described in the receptor system Or22a-Orco (Wicher et al., Nature 452, 2008); Sato et al., Nature 452, 2008). Apart from functioning as so-called ionotropic receptors, which enable ion flow through membranes after binding of odor molecules, odorant receptors also elicit intracellular signals. These stimulate the formation of cyclic adenosine monophosphate (cyclic AMP or cAMP), which activates an ion flow through the co-receptor Orco. The role and relevance of this weak and slow electrical current, however, was until now unclear.

Drosophila mutant Orco mut

Merid N. Getahun, a PhD student from Ethiopia, and his colleagues have conducted numerous experiments on Drosophila olfactory neurons. They injected tiny amounts of compounds that stimulate, inhibit or imitate cAMP formation directly into the sensory hairs housing olfactory sensory neurons on the fly antenna. The researchers tested the flies' responses to ethyl butyrate, which has a fruity odor similar to pineapple, and measured activity in the sensory neurons by using glass microelectrodes. As a control, they used genetically modified fruit flies where the co-receptor Orco had been inactivated. "The fact that these mutants are no more able to respond to cAMP or the inhibition/activation of the involved key enzymes, such as protein kinase C and phospholipase C, shows that the highly sensitive olfactory system in insects is regulated intracellularly by their own odorant receptors," says Dieter Wicher, the leader of the research group. The combination of odorant receptor and co-receptor Orco can be compared to a transistor, Wicher continues: A weak basic current is sufficient to release the main electric current that activates the neuron. The process can also be seen as a short-term memory situated in the insect nose. A very weak stimulus does not elicit a response when it first occurs, but if it reoccurs within a certain time span it will release the electrical response according to the principle "one time is no time, but two is a bunch." [JWK/AO]


Story Source:

The above story is based on materials provided by Max Planck Institute for Chemical Ecology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Merid N. Getahun, Shannon B. Olsson, Sofia Lavista-Llanos, Bill S. Hansson, Dieter Wicher. Insect Odorant Response Sensitivity Is Tuned by Metabotropically Autoregulated Olfactory Receptors. PLoS ONE, 2013; 8 (3): e58889 DOI: 10.1371/journal.pone.0058889

Cite This Page:

Max Planck Institute for Chemical Ecology. "Transistor in the fly antenna: Insect odorant receptors regulate their own sensitivity." ScienceDaily. ScienceDaily, 18 March 2013. <www.sciencedaily.com/releases/2013/03/130318132635.htm>.
Max Planck Institute for Chemical Ecology. (2013, March 18). Transistor in the fly antenna: Insect odorant receptors regulate their own sensitivity. ScienceDaily. Retrieved November 24, 2014 from www.sciencedaily.com/releases/2013/03/130318132635.htm
Max Planck Institute for Chemical Ecology. "Transistor in the fly antenna: Insect odorant receptors regulate their own sensitivity." ScienceDaily. www.sciencedaily.com/releases/2013/03/130318132635.htm (accessed November 24, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Monday, November 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Winter Can Cause Depression — Here's How To Combat It

Winter Can Cause Depression — Here's How To Combat It

Newsy (Nov. 23, 2014) Millions of American suffer from seasonal depression every year. It can lead to adverse health effects, but there are ways to ease symptoms. Video provided by Newsy
Powered by NewsLook.com
Ebola-Hit Sierra Leone's Late Cocoa Leaves Bitter Taste

Ebola-Hit Sierra Leone's Late Cocoa Leaves Bitter Taste

AFP (Nov. 23, 2014) The arable district of Kenema in Sierra Leone -- at the centre of the Ebola outbreak in May -- has been under quarantine for three months as the cocoa harvest comes in. Duration: 01:32 Video provided by AFP
Powered by NewsLook.com
Anglerfish Rarely Seen In Its Habitat Will Haunt You

Anglerfish Rarely Seen In Its Habitat Will Haunt You

Newsy (Nov. 22, 2014) For the first time Monterey Bay Aquarium recorded a video of the elusive, creepy and rarely seen anglerfish. Video provided by Newsy
Powered by NewsLook.com
Birds Around the World Take Flight

Birds Around the World Take Flight

Reuters - Light News Video Online (Nov. 22, 2014) An imperial eagle equipped with a camera spreads its wings over London. It's just one of the many birds making headlines in this week's "animal roundup". Jillian Kitchener reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins