Biologists seeking elusive proof of natural selection at the single-gene level have a powerful new tool at their disposal. Chris Toomajian, postdoctoral researcher in molecular and computational biology in the USC College of Letters, Arts and Sciences, led a group that sought to replace the standard neutral model, a common but unrealistic test for natural selection, with a statistical method based on hard genomic data.
The group’s research will be published online April 25 by Public Library of Science. "Do we now have enough data to see the standard neutral model wasn’t appropriate?" Toomajian asked. "We know something more now about how the population has been structured."
The standard neutral model makes improbable assumptions about population structure, such as assigning each individual an equal chance of reproducing.
Co-author Magnus Nordborg, associate professor of molecular and computational biology in USC College, predicted that earlier research would need to be revisited because the model makes it too easy to infer selection at any given gene. "Once you start looking at enough cases then you realize that, oops, it’s all under selection. I think a lot of that research is going to end up in the trash can," Nordborg said.
The group’s method can be applied to any organism, including humans. The PLoS paper focused on the weed Arabidopsis thaliana, and in particular on the FRIGIDA (FRI) gene, known to influence flowering time. A. thaliana was once a plant that bloomed annually. But two versions of FRI that appeared thousands of years ago enabled the plant to flower year-round, helping it out-compete other plants.
Toomajian and his group showed that these two versions, also called gene variants, are too common to have spread solely by chance. "We’ve shown that for one gene with an important role in that [flowering] process, there’s good evidence that there’s natural selection changing the behavior of the plants," Toomajian said. Why the variants were selected remains unclear, though some have suggested that the plant evolved under pressure from the spread of agriculture. Toomajian’s group identified the gene variants through a comparison of 96 plants over 1,102 short fragments of the genome.
Each variant was assigned a score based on the similarity of two plants around the FRI gene relative to their similarity at other regions in the genome. The higher the score, the less likely it is that a variant could have arisen and spread randomly. The scoring formula accounts for the greater similarity expected in related plants.
Nordborg said that while natural selection is well documented at the whole-organism level, researchers consider biochemical proof of selection "the Holy Grail" of population genetics. "What has proven very difficult is to connect specific molecular changes to selection," Nordborg said. The PLoS paper, along with other recent studies based on intrinsic genomic comparisons, brings biology closer to this goal.
Carl Marziali | EurekAlert!
Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University
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...
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...
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...
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...
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...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Power and Electrical Engineering
16.01.2017 | Information Technology
16.01.2017 | Power and Electrical Engineering