Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


’Fossil genes’ reveal how life sheds form and function


Reading the fossil record, a paleontologist can peer into evolutionary history and see the surface features that plants and animals and, occasionally, microbes have left behind.

Now, scouring the genome of a Japanese yeast, scientists have found a trackway of fossil genes in the making, providing a rare look at how an organism, in response to the demands of its environment, has changed its inner chemistry and lost the ability to metabolize a key sugar.

The finding is a snapshot of evolution at work showing, at the most fundamental level, how traits and features are discarded by virtually all forms of life when they are no longer needed. "Many people think evolution is always happening in a forward direction," that new features are just tacked on, says Sean B. Carroll, a professor of molecular biology at the Howard Hughes Medical Institute at the University of Wisconsin-Madison. "The other side of the coin is that we lose things. Losses as well as gains make up the story of evolution."

Writing Sept. 20, in the Proceedings of the National Academy of Sciences, Carroll and colleagues Chris Todd Hittinger and Antonis Rokas describe the discovery of a set of seven genes caught in the act of fossilization.

In the Japanese yeast, known to scientists as Saccharomyces kudriavzevii, the Wisconsin scientists found the decaying genes that, when intact, are all functionally related and make up a pathway that permits the organism to convert the sugar galactose to energy.

The same pathway, among the most studied in biology, exists not only in yeasts, but also in virtually all other microbes, as well as plants and animals, including humans. Their sole function is devoted to the utilization of galactose, suggesting that the yeast experienced an ecological shift that somehow removed galactose from the organism’s menu, thereby making the galactose-processing genes obsolete.

The relic genes, according to Hittinger, are "full of holes," where numerous DNA bases - the building blocks of all genes - have been edited out through mutation to terminate the physiological message they were responsible for transmitting along the pathway. "Genes become fossilized if there is no use for them," says Rokas. "If you relax the pressure on the genes to zero, mutations will begin to accumulate. This steady bombardment of mutations will erase the genes over time."

However, there is a window of preservation before the genes are wiped completely away, leaving relics as diagnostic as any fossil bone and providing scientists with important clues to biological functions discarded as an organism adapts to its environment.

Indeed, probing the genomes of three other species of yeast that are unable to metabolize galactose, the Wisconsin scientists found the genetic pathway almost completely absent from all three, with only a single remaining gene marking the pathway like a faded signpost. "Evolution repeats itself," Carroll says. "What we see is that three or four times, these genes have been junked in different species. The process of sweeping these genes away is more complete in these other species."

Relic genes, sometimes called pseudo-genes, have been found elsewhere, including humans. Fossil olfactory genes tell the story of how humans came to depend more on sight as color vision displaced a sense of smell that, in the distant past, was far superior to what humans enjoy today.

In the Japanese yeast, the seven fossil genes that make up the eroding pathway are "still in the same place (on the genome) they are in neighboring species," says Carroll. "What we have is a picture of an entire set of genes performing related functions becoming fossilized. "To see this, the change has to be relatively recent. Sometime in the last 5 to 10 million years the pressure (on these genes) started to relax," Carroll explains.

Sean B. Carroll | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Make way for the mini flying machines
21.03.2018 | American Chemical Society

nachricht New 4-D printer could reshape the world we live in
21.03.2018 | American Chemical Society

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

TRAPPIST-1 planets provide clues to the nature of habitable worlds

21.03.2018 | Physics and Astronomy

The search for dark matter widens

21.03.2018 | Materials Sciences

Natural enemies reduce pesticide use

21.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>