Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Penn Geneticists Help Show Bitter Taste Perception Is Not Just About Flavors

07.12.2011
Long the bane of picky eaters everywhere, broccoli’s taste is not just a matter of having a cultured palate; some people can easily taste a bitter compound in the vegetable that others have difficulty detecting.

Now a team of Penn researchers has helped uncover the evolutionary history of one of the genes responsible for this trait. Beyond showing the ancient origins of the gene, the researchers discovered something unexpected: something other than taste must have driven its evolution.

The team was led by Penn researchers Sarah Tishkoff, a Penn Integrates Knowledge professor with appointments in the genetics department in Penn’s Perelman School of Medicine and the biology department in the School of Arts and Sciences, and Michael C. Campbell, a postdoctoral fellow in the genetics department at the medical school, and included undergraduate and postdoctoral researchers from both the genetics and biology departments. The team included their collaborator Paul Breslin from the Monell Chemical Senses Center in Philadelphia and Rutgers University and researchers from the Musée de L’Homme in France, the National Institutes of Health and several African universities and research institutes.

Their research was published in the journal Molecular Biology and Evolution.

The researchers were interested in the gene TAS2R38, which codes for a bitter taste receptor protein with the same name. People with a certain version of that gene can taste a compound, phenylthiocarbamide, or PTC, which is chemically similar to naturally occurring bitter compounds, called glucosinolates, present in many foods, including cruciferous vegetables like broccoli and Brussels sprouts. These “tasters” find such foods to have a bitter taste that people with a different version can’t detect. As a result, “nontasters” have been shown to consume fewer cruciferous vegetables.

Modern humans originated in Africa, and populations from that region have the highest levels of genetic diversity globally. Previous studies had looked at variations in the PTC-sensitivity gene, but none had ever studied a large sample of diverse African populations with different cultures, ethnicities or diets.

“Because there is more genetic variation in African populations, you’re likely to see unique variants you may not see elsewhere,” Tishkoff said. “Our study of variation at the TAS2R38 gene in Africa and correlations with taste perception and diet gives us a clue about the evolutionary history of the gene and how natural selection might be influencing the pattern of variation.”

Genes that influence perception are of particular interest to geneticists because those genes are under strong evolutionary pressure; organisms with senses that are well adapted to their environment have better chances to survive and reproduce. PTC-sensitivity’s potential impact on nutrition, or the ability to detect bitter-tasting toxins, would therefore make it an obvious target for natural selection.

By looking at the TAS2R38 gene in 611 Africans from 57 diverse ethnic populations with distinct diets (for example, Pygmy hunter-gatherers and Maasai pastoralists), as well as in 132 non-Africans, the researchers showed that Africans had more variation than non-Africans, including several never-before-seen rare mutations.

The researchers also tested the correlation between genetic variation at this gene and levels of PTC tasting ability in 463 Africans, another first-of-its-kind study. In an experiment that was challenging to carry out across a wide swath of the African continent, participants sampled successively concentrated solutions of PTC and water until they were able to detect the bitter taste. When correlated with the participants’ genetic data, the study revealed that Africans have a broader range of PTC taste sensitivity than typically seen outside of Africa, and that relatively new rare mutations also decrease an individual’s ability to taste PTC.

Comparing different African populations confirmed that the PTC-sensitivity gene is millions of years old, meaning it predates the evolution of modern humans and likely existed in the common ancestor of modern humans and Neanderthals.

The study also revealed something surprising: local diet did not have an effect on the evolution of any of the PTC-sensitivity gene variants.

“Although we typically see a lot of genetic variation among diverse African populations, the frequency of TAS2R38 variants is fairly similar across different ethnicities, cultures and diets,” Campbell said. “This is suggestive that variation at this gene serves some other function beyond oral sensory perception.”

This counter-intuitive discovery is in line with other recent studies, which found receptors similar to TAS2R38 in the lungs, upper airways and gut. If the variations of the TAS2R38 gene have had a heretofore-undiscovered impact on breathing or digesting, alongside tasting, the former traits might be the true focus of natural selection.

“Why are we ‘tasting’ in our guts or in our lungs? There must be something else,” Tishkoff said, “that these taste receptors are doing, and it must be a pretty important physiological process, otherwise these variants wouldn’t be maintained.”

“We now believe the chemical senses play key sentinel roles at points of entry to the body like the mouth, airways and gastro-intestinal tract,” Breslin said. “It is possible that, in addition to detecting bitter-tasting thyroid toxins, products of this gene help to defend against ubiquitous pan-African threats, such as inhaling injurious compounds or growing undesirable bacteria in airway mucus or intestines.”

In addition to Tishkoff and Campbell, the research was conducted by postdoctoral fellows Alessia Ranciaro and Jibril B. Hirbo, both of the genetics department in Penn’s Perelman School of Medicine; undergraduate student Daniel Zinshteyn of the biology department in the School of Arts and Sciences; Breslin; Alain Froment of the Musée de L’Homme; Sabah Omar of Kenya Medical Research Institute; Jean-Marie Bodo of Cameroon’s Ministry of Scientific Research and Innovation; Thomas Nyambo and Godfrey Lema of Tanzania’s Muhimbili University of Health and Allied Sciences; and Dennis Drayna of the NIH’s National Institute on Deafness and Other Communication Disorders.

The research was supported by the National Science Foundation, the National Institutes of Health and a David and Lucile Packard Career Award.

Evan Lerner | EurekAlert!
Further information:
http://www.upenn.edu

More articles from Life Sciences:

nachricht Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

Im Focus: Repairing defects in fiber-reinforced plastics more efficiently

Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Multiregional brain on a chip

16.01.2017 | Power and Electrical Engineering

New technology enables 5-D imaging in live animals, humans

16.01.2017 | Information Technology

Researchers develop environmentally friendly soy air filter

16.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>