Blue is an indicator of first star's supernova explosions: More than 13 billion years old

Artist's conception of evolution of metal-poor and "metal-rich" supernovae at different phases and simulated light curves from shock breakout (ultraviolet) through plateau (red, green and blue colors) to exponential decay. Both shock breakout and "plateau" phases are shorter, bluer, and fainter for metal-poor supernova in comparison with "metal-rich" supernova.

An international collaboration led by the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) have discovered that the color of supernovae during a specific phase could be an indicator for detecting the most distant and oldest supernovae in the Universe -- more than 13 billion years old.

For 100 million years after the big bang, the Universe was dark and filled with hydrogen and helium. Then, the first stars appeared, and heavier elements (referred to as "metals," meaning anything heavier than helium) were created by thermonuclear fusion reactions within stars.

These metals were spread around the galaxies by supernova explosions. Studying first generation supernovae provides a glimpse into what the Universe looked like when the first stars, galaxies, and supermassive black holes formed, but to date it has been difficult to distinguish a first generation supernova from an ordinary supernova.

A new study published in The Astrophysical Journal, led by Kavli IPMU Project Researcher Alexey Tolstov, identified characteristic changes between these supernovae types after experimenting with supernovae models based on extremely metal-poor stars with virtually no metals. These stars make good candidates because they preserve their chemical abundance at the time of their formation.

"The explosions of first generation of stars have a great impact on subsequent star and galaxy formation. But first, we need a better understanding of how these explosions look like to discover this phenomenon in the near future. The most difficult thing here is the construction of reliable models based on our current studies and observations. Finding the photometric characteristics of metal poor supernovae, I am very happy to make one more step to our understanding of the early Universe." said Tolstov.

Similar to all supernovae, the luminosity of metal-poor supernovae show a characteristic rise to a peak brightness followed by a decline. The phenomenon starts when a star explodes with a bright flash, caused by a shock wave emerging from the surface of the progenitor stars after the core collapse phase. Shock breakout is followed by a long ''plateau'' phase of almost constant luminosity lasting several months, before a slow exponential decay.

An international collaboration led by the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) have discovered that the color of supernovae during a specific phase could be an indicator for detecting the most distant and oldest supernovae in the Universe -- more than 13 billion years old. For 100 million years after the big bang, the Universe was dark and filled with hydrogen and helium. Then, the first stars appeared, and heavier elements (referred to as "metals," meaning anything heavier than helium) were created by thermonuclear fusion reactions within stars.

The team calculated light curves of metal-poor supernova, produced by blue supergiant stars, and "metal-rich" red supergiant stars. Both shock breakout and "plateau" phases are shorter, bluer, and fainter for metal-poor supernova in comparison with "metal-rich" supernova. The team concluded the color blue could be used as an indicator of a low-metallicity progenitor. The expanding universe makes it difficult to detect first star and supernova radiation, which shift into the near-infrared wavelength.

Read more at Science Daily

'Frankenstein' galaxy surprises astronomers

At left, in optical light, UGC 1382 appears to be a simple elliptical galaxy. But spiral arms emerged when astronomers incorporated ultraviolet and deep optical data (middle). Combining that with a view of low-density hydrogen gas (shown in green at right), scientists discovered that UGC 1382 is gigantic.

About 250 million light-years away, there's a neighborhood of our universe that astronomers had considered quiet and unremarkable. But now, scientists have uncovered an enormous, bizarre galaxy possibly formed from the parts of other galaxies.

A new study to be published in the Astrophysical Journal reveals the secret of UGC 1382, a galaxy that had originally been thought to be old, small and typical. Instead, scientists using data from NASA telescopes and other observatories have discovered that the galaxy is 10 times bigger than previously thought and, unlike most galaxies, its insides are younger than its outsides, almost as if it had been built using spare parts.

"This rare, 'Frankenstein' galaxy formed and is able to survive because it lies in a quiet little suburban neighborhood of the universe, where none of the hubbub of the more crowded parts can bother it," said study co-author Mark Seibert of the Observatories of the Carnegie Institution for Science, Pasadena, California. "It is so delicate that a slight nudge from a neighbor would cause it to disintegrate."

Seibert and Lea Hagen, a graduate student at Pennsylvania State University, University Park, came upon this galaxy by accident. They had been looking for stars forming in run-of-the-mill elliptical galaxies, which do not spin and are more three-dimensional and football-shaped than flat disks. Astronomers originally thought that UGC 1382 was one of those.

But while looking at images of galaxies in ultraviolet light through data from NASA's Galaxy Evolution Explorer (GALEX), a behemoth began to emerge from the darkness.

"We saw spiral arms extending far outside this galaxy, which no one had noticed before, and which elliptical galaxies should not have," said Hagen, who led the study. "That put us on an expedition to find out what this galaxy is and how it formed."

Researchers then looked at data of the galaxy from other telescopes: the Sloan Digital Sky Survey, the Two Micron All-Sky Survey (2MASS), NASA's Wide-field Infrared Survey Explorer (WISE), the National Radio Astronomy Observatory's Very Large Array and Carnegie's du Pont Telescope at Las Campanas Observatory. After GALEX revealed previously unseen structures to the astronomers, optical and infrared light observations from the other telescopes allowed the researchers to build a new model of this mysterious galaxy.

As it turns out, UGC 1382, at about 718,000 light-years across, is more than seven times wider than the Milky Way. It is also one of the three largest isolated disk galaxies ever discovered, according to the study. This galaxy is a rotating disk of low-density gas. Stars don't form here very quickly because the gas is so spread out.

But the biggest surprise was how the relative ages of the galaxy's components appear backwards. In most galaxies, the innermost portion forms first and contains the oldest stars. As the galaxy grows, its outer, newer regions have the youngest stars. Not so with UGC 1382. By combining observations from many different telescopes, astronomers were able to piece together the historical record of when stars formed in this galaxy -- and the result was bizarre.

"The center of UGC 1382 is actually younger than the spiral disk surrounding it," Seibert said. "It's old on the outside and young on the inside. This is like finding a tree whose inner growth rings are younger than the outer rings."

The unique galactic structure may have resulted from separate entities coming together, rather than a single entity that grew outward. In other words, two parts of the galaxy seem to have evolved independently before merging -- each with its own history.

At first, there was likely a group of small galaxies dominated by gas and dark matter, which is an invisible substance that makes up about 27 percent of all matter and energy in the universe (our own matter is only 5 percent). Later, a lenticular galaxy, a rotating disk without spiral arms, would have formed nearby. At least 3 billion years ago, the smaller galaxies may have fallen into orbit around the lenticular galaxy, eventually settling into the wide disk seen today.

Read more at Science Daily

Homo erectus walked as we do

The shapes of the fossil and modern footprints are nearly indistinguishable.

Fossil bones and stone tools can tell us a lot about human evolution, but certain dynamic behaviours of our fossil ancestors -- things like how they moved and how individuals interacted with one another -- are incredibly difficult to deduce from these traditional forms of paleoanthropological data. Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, along with an international team of collaborators, have recently discovered multiple assemblages of Homo erectus footprints in northern Kenya that provide unique opportunities to understand locomotor patterns and group structure through a form of data that directly records these dynamic behaviours. Using novel analytical techniques, they have demonstrated that these H. erectus footprints preserve evidence of a modern human style of walking and a group structure that is consistent with human-like social behaviours.

Habitual bipedal locomotion is a defining feature of modern humans compared with other primates, and the evolution of this behaviour in our clade would have had profound effects on the biologies of our fossil ancestors and relatives. However, there has been much debate over when and how a human-like bipedal gait first emerged in the hominin clade, largely because of disagreements over how to indirectly infer biomechanics from skeletal morphologies. Likewise, certain aspects of group structure and social behaviour distinguish humans from other primates and almost certainly emerged through major evolutionary events, yet there has been no consensus on how to detect aspects of group behaviour in the fossil or archaeological records.

In 2009, a set of 1.5-million-year-old hominin footprints was discovered at a site near the town of Ileret, Kenya. Continued work in this region by scientists from the Max Planck Institute for Evolutionary Anthropology, and an international team of collaborators, has revealed a hominin trace fossil discovery of unprecedented scale for this time period -- five distinct sites that preserve a total of 97 tracks created by at least 20 different presumed Homo erectus individuals. Using an experimental approach, the researchers have found that the shapes of these footprints are indistinguishable from those of modern habitually barefoot people, most likely reflecting similar foot anatomies and similar foot mechanics. "Our analyses of these footprints provide some of the only direct evidence to support the common assumption that at least one of our fossil relatives at 1.5 million years ago walked in much the same way as we do today," says Kevin Hatala, of the Max Planck Institute for Evolutionary Anthropology and The George Washington University.

Based on experimentally derived estimates of body mass from the Ileret hominin tracks, the researchers have also inferred the sexes of the multiple individuals who walked across footprint surfaces and, for the two most expansive excavated surfaces, developed hypotheses regarding the structure of these H. erectus groups. At each of these sites there is evidence of several adult males, implying some level of tolerance and possibly cooperation between them. Cooperation between males underlies many of the social behaviours that distinguish modern humans from other primates. "It isn't shocking that we find evidence of mutual tolerance and perhaps cooperation between males in a hominin that lived 1.5 million years ago, especially Homo erectus, but this is our first chance to see what appears to be a direct glimpse of this behavioural dynamic in deep time," says Hatala.

From Science Daily

Is Lightning Hotter Than the Sun?

What's five times hotter than the sun and capable of sending a DeLorean back to the future?

Yep, the answer is a bolt of lightning, which can reach temperatures of roughly 30,000 kelvins (53,540 degrees Fahrenheit). The sun, on the other hand, is eclipsed in this case — its surface temperature is just 6,000 kelvins (10,340 degrees Fahrenheit). It's one amazing piece of science trivia, but what exactly does it all mean?

First, it's important to realize that the sun's surface is actually its coolest layer. Dive down to its core, and you'd encounter plasma temperatures of about 15 million kelvins (about 27 million degrees Fahrenheit). Things also heat up just above the sun's surface, as its atmosphere exceeds temperatures of 500,000 kelvins (about 900,000 degrees Fahrenheit).

"Power is the rate at which energy is used or transferred," explains University of Washington physics professor Robert H. Holzworth. "So power is energy per second, and the energy per second in lighting can be very high, but it only lasts a really, really, short time, like tens of microseconds. So the total energy isn't like the total energy from the sun, obviously, but the rate the energy dissipates can be very large. It's one of the most powerful natural phenomena on Earth."

But just where does all that energy come from?

"Ultimately that energy comes from the sun," Holzworth says. "The sun heats up the surface, which results in differential heating. One area is warmer than another, and warm air rises since it's less dense. When you have moisture in the air, that parcel of air can go up much higher than it would otherwise. That's the basis of very strong convection."

At this point, Holzworth explained, ice forms in the parcel of rising air.

"You can get very efficient charge transfer, so that you get positive and negative charges separated by the bouncing ice," Holzworth says. "It turns out that when you have ice collisions, there's some likelihood that, at certain places in the cloud, smaller ice formations such as snowflakes are going to get charged positive, leaving behind negative charge on the hail stones or the soft hail."

The lighter, positively charged ice particles continue to rise toward the top of the clouds. Meanwhile, the heavier, negatively charged ice particles plummet, thus separating the charge in a process known as gravity separation.

This process creates a strong electric field, which in turn ionizes the air around the cloud, separating air molecules into positive ions and electrons. Electrons move far more easily in ionized air. Once a channel of ionized air is established from cloud to ground (or between two points in a cloud), high-temperature current flows in the form of a lightning stroke that neutralizes the charge separation.

Richard E. Orville, director of Texas A&M University's atmospheric sciences department, equates the breakdown of an electrical buildup to an incident he witnessed in eighth grade involving a screwdriver and an electrical socket.

"There was a fellow sitting in front of me, and for some reason he had a screwdriver in his hand," Orville said. "He stuck it in the wall socket and received a very big discharge. Of course that's because you had an excess of electricity in a plug just waiting to be tapped, which we do every day when we plug in a device. So in this case, you've got a buildup of electrical charge in the base of a cloud, and breakdown occurs when the electric field gets high enough."

So while it wouldn't be accurate to say a bolt of lightning is hotter than the sun itself, these flashes of electrical energy do reach higher temperatures than the surface of the sun.

From Discovery News

New Dwarf Planet Discovered in Outer Solar System

Artist rendering of the orbit of newly found RR245 (orange line). Objects as bright or brighter than RR245 are labeled. The Minor Planet Center describes the object as the 18th largest in the Kuiper Belt.

Astronomers have found another Pluto-like dwarf planet located about 20 times farther away from the sun than Neptune.

The small planet, designed 2015 RR245, is estimated to be about 435 miles in diameter and flying in an elliptical, 700-year orbit around the sun.

At closest approach, RR245 will be about 3.1 billion miles from the sun, a milestone it is expected to next reach in 2096.

At its most distant point, the icy world is located about 7.5 billion miles away.

It was found by a joint team of astronomers using the Canada-France-Hawaii Telescope (CFHT) on Maunakea, Hawaii, in images taken in September 2015 and analyzed in February. The discovery was announced on Monday in the Minor Planet Electronic Circular.

The Minor Planet Center describes RR245 as the 18th largest object in the Kuiper Belt.

"The vast majority of the dwarf planets like RR245 were destroyed or thrown from the solar system in the chaos that ensued as the giant planets moved out to their present positions," the CFHT said. "RR245 is one of the few dwarf planets that has survived to the present day — along with Pluto and Eris, the largest known dwarf planets."

Observations of RR245 will continue. Once its precise orbit is known the dwarf planet will get an official name. As discoverers, the Outer Solar System Origins Survey team has naming rights.

Read more at Discovery News

Skeleton With Alien-Like Skull Found

Archaeologists in Mexico have unearthed the 1,600 year old skeleton of a woman with an elongated, "alien-like" skull and stone-encrusted teeth.

Found at a town called San Juan Evangelista, near the ancient ruins of Teotihuacan some 30 miles from Mexico City, the skeleton belongs to an upper class woman who died at around 35-40 years of age.

According to a statement by the National Anthropology and History Institute (INAH), the woman was buried with offerings. Archaeologists led by Veronica Ortega found 19 jars near the bones. They estimate the burial dates between 350-400 AD.

Dubbed "The Woman of Tlailotlacan," the skeleton features a skull that was deliberately deformed.

"It shows signs of erect tabular deformation which was achieved by a very extreme compression," anthropologist Jorge Velasco Archer said.

Tabular or flat-head deformations required compressing the child's frontal and occipital bones with boards or pads. The meaning of skull shaping wasn't just aesthetic but also religious and social.

The Maya themselves told Gonzalo Fernández de Oviedo, a Spanish chronicler, that head shaping was made to look "noble and handsome and better able to carry loads."

Velasco Archer noted that this type of cranial deformation is more likely found in the southern part of Mesoamerica rather than in the Mexican central region where Teotihuacan is located.

Encrusted with two round pyrite stones, the skull's front teeth confirmed the woman was a foreigner in Teotihuacan. The dental decoration technique is typical of Mayan regions in southern Mexico and Central America.

The woman also wore a prosthetic lower tooth made of a green stone known as serpentine.

"Tartar formation on the serpentine prosthetic teeth shows the woman used it for a long time," Velasco Archer said.

Analysis is ongoing to determine how the false tooth stood in place and whether some kind of cement was used.

Read more at Discovery News

Monkey-Made Nut Processing Site Found

A monkey-operated cashew nut processing site, dating to at least 700 years ago, has just been discovered in Brazil.

The findings, outlined in the journal Current Biology, document the earliest evidence for tool use by monkeys outside of Africa. Humans might have even first learned about cashew nuts from the industrious little primates.

"One of the ways that modern hunter gatherers gain information about the landscape is to observe the behavior of other animals -- alarm calls by monkeys can signal a predator threat that also affects humans, for example," lead author Michael Haslam, a senior research fellow in primate archaeology at the University of Oxford, told Discovery News.

"It's speculative," he added, "but noisy and prominent cashew processing by capuchin monkeys was unlikely to have been missed by ancient Brazilians."

The following three videos show the capuchins at work:

Haslam and his colleagues observed capuchin monkeys busily using stones as hand-held hammers and anvils to pound open cashew nuts, which are actually seeds within a hard fruit that grows on the brightly colored cashew apple. Pulp inside the apple is edible as well, but is hard to transport, explaining why the apples are not often found outside of Latin America.

To establish the antiquity of capuchin cashew processing at the site -- Serra da Capivara National Park in northeast Brazil -- the researchers conducted an excavation that recovered many capuchin stone tools. Small pieces of charcoal found with the large tool cache were radiocarbon dated to at least 700 years ago. This means that the tools predate the arrival of Europeans in the New World.

A capuchin cashew-processing stone covered with residue from the nuts.

The researchers estimate that around 100 generations of capuchins have processed cashews at the same site over the past seven centuries. The number could even be much higher. The monkeys are thought to have originated in Africa before traveling, perhaps unintentionally on floating vegetation, to the New World some 40 million years ago. The cashew trees, on the other hand, are native to Brazil. At Serra da Capivara, the trees date to about 8,500–7200 years ago.

Senior author Tiago Falótico, a postdoctoral research fellow at the University of São Paulo Institute of Psychology, said, "Cashews nuts are not a primary food source, but capuchins have a great preference for it when it is present. Some of the individuals even discarded apparently good cashew apples just to eat the nut."

He continued, "We know that cashew nuts are very energetic and balanced across carbohydrates, fat, and protein, characteristics that makes cashew nuts a good food choice."

Researchers Lydia Luncz and Tiago Falótico, who is standing under a cashew tree. Both are at the study site, Serra da Capivara National Park in northeast Brazil.

As for how the monkeys first learned how to process cashews, the researchers suggest that shelled edibles once helped save the capuchins from starvation.

Co-author Eduardo Ottoni, a professor in the Institute of Psychology at the University of São Paulo, explained that "robust" capuchins split off from slenderer built ones as they left the Amazon forest and reached the Atlantic forest.

"That involved crossing much drier areas where hard-shelled fruit was probably a key resource, hence their robust jaws," Ottoni said. "In such a context, stone-aided nut cracking was arguably very useful."

Capuchins do not just use tools to process cashews. Ottoni said that some select even heavier stones to bust open hard palm nuts in certain regions. The Serra da Capivara monkeys use different stones to dig plant roots and tubers.

They also use sticks as probes to dislodge prey -- mostly lizards -- from rock cracks. They use sticks to pull spiders out of their burrows and to collect honey. Each tool is carefully selected for size, weight and usefulness to the particular task.

Other monkeys, such as macaques, are also adept at using tools. Last year, for example, Amanda Tan from Nanyang Technological University and her team documented how macaques use one-handed hammering with the points of small tools to crack open oysters with precision at Piak Nam Yai and Thao Islands in Laem Son National Park, Thailand.

Read more at Discovery News

99-Million-Year-Old Fanged Spiders Stuck in Amber

About 99 million years ago, two bizarre spiders — each sporting hard, armored plates on their bodies and horns on their fangs — became mummified in sticky tree resin that turned into amber.

They remained there until recently, when scientists discovered the chunk of amber and analyzed the spiders locked inside.

These ancient, extinct spiders are part of a spider family called Tetrablemmidae, a group whose males often have horns on their heads and fangs, said study lead author Paul Selden, a professor of invertebrate paleontology at the University of Kansas.

But the newly identified species has rather "complex" horns that have two prongs at their tips, which is peculiar, even for a Tetrablemmid spider, Selden said.

"The new fossil is an adult male and takes these horns to an extreme," Selden told Live Science in an email. "Nevertheless, the new species can be firmly placed within the modern family and is similar to species living in Southeast Asia and China today."

Both of the amber fossils came from a mine in northern Burma (also known as Myanmar). Selden met with a dealer who was selling the polished specimens in China, and the scientist and his colleagues purchased those that were of scientific interest, he said.

Tetrablemmid spiders usually have six or fewer eyes, but the researchers couldn't find any on the Cretaceous-age specimens, likely because those body parts didn't preserve well, he said. However, the mummies look somewhat similar to the modern Tetrablemmid spiders in the genus Sinamma, which live in southwest China. Sinamma species have eyes on the upper part of the head, so the newfound species likely did too, the researchers said.

"What caught my eye about this spider was the enormous projection on its head, most likely bearing eyes, and the bizarre horns on its fangs," Selden said.

Selden and his colleagues named the new species Electroblemma bifida. The genus name refers to the Greek "elektron," or amber, and "blemma" or appearance, a common suffix used for tetrablemmid spiders. The species name refers to the two-pronged tip at the end of the horns on this spider's fangs, the researchers said.

In general, Tetrablemmid spiders have armor-like hard plates covering their bodies that protect them from predators, such as spider-hunting wasps, Selden said. These spiders are usually tiny, only about a quarter inch (0.6 centimeters) long. The mummified specimens are slightly smaller, with one measuring 0.06 inches (1.58 millimeters) long.

Read more at Discovery News

Dawn maps Ceres craters where ice can accumulate

At the poles of Ceres, scientists have found craters that are permanently in shadow (indicated by blue markings). Such craters are called "cold traps" if they remain below about minus 240 degrees Fahrenheit (minus 151 degrees Celsius). These shadowed craters may have been collecting ice for billions of years because they are so cold. This image was created using data from NASA's Dawn spacecraft.

Scientists with NASA's Dawn mission have identified permanently shadowed regions on the dwarf planet Ceres. Most of these areas likely have been cold enough to trap water ice for a billion years, suggesting that ice deposits could exist there now.

"The conditions on Ceres are right for accumulating deposits of water ice," said Norbert Schorghofer, a Dawn guest investigator at the University of Hawaii at Manoa. "Ceres has just enough mass to hold on to water molecules, and the permanently shadowed regions we identified are extremely cold -- colder than most that exist on the moon or Mercury."

Permanently shadowed regions do not receive direct sunlight. They are typically located on the crater floor or along a section of the crater wall facing toward the pole. The regions still receive indirect sunlight, but if the temperature stays below about minus 240 degrees Fahrenheit (minus 151 degrees Celsius), the permanently shadowed area is a cold trap -- a good place for water ice to accumulate and remain stable. Cold traps were predicted for Ceres but had not been identified until now.

In this study, Schorghofer and colleagues studied Ceres' northern hemisphere, which was better illuminated than the south. Images from Dawn's cameras were combined to yield the dwarf planet's shape, showing craters, plains and other features in three dimensions. Using this input, a sophisticated computer model developed at NASA's Goddard Space Flight Center, Greenbelt, Maryland, was used to determine which areas receive direct sunlight, how much solar radiation reaches the surface, and how the conditions change over the course of a year on Ceres.

The researchers found dozens of sizeable permanently shadowed regions across the northern hemisphere. The largest one is inside a 10-mile-wide (16-kilometer) crater located less than 40 miles (65 kilometers) from the north pole.

Taken together, Ceres' permanently shadowed regions occupy about 695 square miles (1,800 square kilometers). This is a small fraction of the landscape -- much less than 1 percent of the surface area of the northern hemisphere.

The team expects the permanently shadowed regions on Ceres to be colder than those on Mercury or the moon. That's because Ceres is quite far from the sun, and the shadowed parts of its craters receive little indirect radiation.

"On Ceres, these regions act as cold traps down to relatively low latitudes," said Erwan Mazarico, a Dawn guest investigator at Goddard. "On the moon and Mercury, only the permanently shadowed regions very close to the poles get cold enough for ice to be stable on the surface."

The situation on Ceres is more similar to that on Mercury than the moon. On Mercury, permanently shadowed regions account for roughly the same fraction of the northern hemisphere. The trapping efficiency -- the ability to accumulate water ice -- is also comparable.

By the team's calculations, about 1 out of every 1,000 water molecules generated on the surface of Ceres will end up in a cold trap during a year on Ceres (1,682 days). That's enough to build up thin but detectable ice deposits over 100,000 years or so.

Read more at Science Daily

How plants sense electric fields

The functional potassium channel TPC1 consists of two identical subunits (left in the picture). Potassium ions (blue spheres) are guided through the canal pore when calcium ions that bind to the channel protein (green spheres) and changes in the electric field (flashes) actuate the voltage sensors (red cylinders). When the channel opens, an electrical signal (red current trace) is triggered and cells of the sample plant Arabidopsis thaliana depicted here exchange information.

An international group of researchers has pinpointed the sensor plants use to sense electric fields. A beneficial side effect: Their work could contribute to the understanding of how the Ebola virus enters human cells.

The cells of plants, animals and humans all use electrical signals to communicate with each other. Nerve cells use them to activated muscles. But leaves, too, send electrical signals to other parts of the plant, for example, when they were injured and are threatened by hungry insects.

"We have been asking ourselves for many years what molecular components plants use to exchange information among each other and how they sense the changes in electric voltage," says Professor Rainer Hedrich, Head of the Chair for Molecular Plant Physiology and Biophysics at the University of Würzburg.

Results published in Plant Biology

This question has been intriguing Hedrich since the mid 1980s when he was still a postdoc in the laboratory of Erwin Neher at the Max Planck Institute in Göttingen. "Back then, we used the patch clamp technique to make the first-time discovery of an ion channel in plants which is activated by calcium ions and an electric field." In 2005, other scientists then found the gene underlying this ion channel (name: TCP1). And now it has been Hedrich's team again that has identified that part of the channel which functions as a sensor for electric voltage and activates the channel.

Their detailed findings are published in the journal Plant Biology. Having received attention from the scientific world, the article has been recommended by the " Faculty of 1000" in the meantime. The renowned platform, which evaluates scientific publications, is operated by worldwide leaders in biology and medicine.

Teamwork discovered channel function

The discovery of the voltage sensor was made by international teamwork. Initially, Hedrich got support from Professor Thomas Müller of his own department. The structural biologist created a three-dimensional model of the TPC1 channel protein. This allowed areas in the protein to be localised that are eligible as voltage sensors. "Our model clearly showed that the TCP1 channel is made up of two interconnected, nearly identical protein units each capable of forming a potential voltage sensor," Müller explains.

An analysis of the evolution of the TCP1 gene shed even more light on the matter. The Würzburg scientists Jörg Schulz, Professor of Computation Biology, and Dirk Becker, a team leader at Julius von Sachs Plant Research Institute, found out that the gene first occurs with the evolution of cells that have a nucleus. Since then, all living beings, humans included, seem to have had it. "During the analysis, we noticed that the second unit of the TPC1 protein has hardly changed in millions of years. It is almost identical from simple protozoa to plants and humans," Becker further.

Mutations provided the decisive cue

So they had to look for the voltage sensor in the second protein unit. The work group of Würzburg electrophysiologist Irene Marten then delivered the decisive experimental cue: Plants that carry a mutation in a special subunit of the channel have lost their ability to respond to the electric field.

"Together with the former Würzburg biophysicists Gerald Schönknecht, presently researching at Oklahoma State University in the USA, and Ingo Dreyer, currently at University Talca in Chile, we then developed a mathematical model. This model can explain how the electric switch in the TPC1 channel protein works at the molecular level," Hedrich explains.

Read more at Science Daily