How this happened is unclear. But the researchers show that not only did a grouping of grasses pass genes multiple times over millions of years, but that some of the genes that were transferred became integral cogs to the plants' photosynthetic machinery, a critical distinguishing feature in C4 plants, which dominate in hot, tropical climes and now make up 20 percent of the Earth's vegetational covering.

"As far as we know, this is the first case where nuclear genes that have been transmitted between plants have been incorporated into the primary metabolism and contributed to the evolution of a new trait, in this case C4 photosynthesis," said Pascal-Antoine Christin, a postdoctoral researcher in the Department of Ecology and Evolutionary Biology at Brown.

In a paper published in Current Biology, the researchers from Brown, Sheffield, and other universities in the United States, United Kingdom, and France investigated the ancestry of two genes encoding enzymes important in C4 photosynthesis - phosphoenolpyruvate carboxylase (ppc) and phosphoenolpyruvate carboxykinase (pck) - and these enzymes' historical presence and function in a common and well-studied grass, Alloteropsis.

The biologists initially studied the genes in closely related species, three C4 plants (Alloteropsis angusta, Alloteropsis cimicina, and Alloteropsis semialata) and one C3 plant (Alloteropsis eckloniana).

The goal was to learn the evolutionary history of the ppc and pck genes, which were present in their C3 common ancestor and were thought to have been adapted to aid in photosynthesis in the offspring C4 plants.

"People were wondering how these genes evolved. The global assumption was that an ancestor had the genes, but they weren't involved in photosynthesis, and so were later modified to become C4 photosynthetic agents," said Christin, the paper's corresponding author.

To test the hypothesis, the scientists took a wider view, surveying C4 plants in which the ppc enzyme was integral to photosynthesis and plants where the enzyme was present but had no photosynthetic role.

They figured the ppc enzymes used in C4 photosynthesis would be closely related to the non-photosynthetic genes from closely related C3 plants, given their common ancestry.

Instead, the ppc genes involved in C4 photosynthesis were closely related to ppc genes of other C4 species with no close relation in the phylogeny, or family tree. Closer analysis also revealed these plants sharing photosynthetic ppc enzymes had diverged as many as 20 million years ago; the new finding is that despite these ancestral divergences, they exchanged genes.

In all, the researchers documented four instances in which the ppc enzyme or the pck enzyme found in the Alloteropsis C4 plants popped up in other C4 clades - Andropogoneae, Cenchrinae and Melinidinae. These clades include such diverse species as corn, foxtail millet, and guinea grass.

"We've long understood how evolutionary adaptations are passed from parents to offspring. Now we've discovered in plants that they can be passed between distant cousins without direct contact between the species," added Colin Osborne, an evolutionary biologist from the University of Sheffield and a corresponding author on the paper.

"What is so exciting here is that these genes are moving from plant to plant in a way we have not seen before," said Erika Edwards, assistant professor of biology at Brown and the second author on the paper. "There is no host-parasite relationship between these plants, which is usually what we see in this kind of gene movement."

Scientists call this evolutionary event "lateral gene transfer." The question, then, how are the plants passing their genes? The best guess at this point is that genetic material carried airborne in pollen grains land on a different species and a small subset of genes somehow get taken up by the host plant during fertilization. Such "illegitimate pollination events," as Edwards described it, have been seen in the laboratory.

"There are reproductive mishaps that occur. In some cases, these could turn out to be highly advantageous," she said.

Christin, Osborne and Edwards think gene-swapping among plants continues today. "Is it good? Bad? I don't know," Christin said. "It's good for the plants. It means that plants can adapt to new environments by taking genes from others."

"It's like a short cut," Edwards added, "that could present itself as a mechanism for rapid evolution."

Contributing authors include Guillaume Besnard, from the Universite Paul Sabatier in Toulouse; Susanna Boxall, Richard Gregory and James Hartwell, from the University of Liverpool; and Elizabeth Kellogg from the University of Missouri-St. Louis. The Swiss National Science Foundation, the Natural Environment Research Council's Molecular Genomics Facilities (U.K.) and a European Commission Marie Curie fellowship supported the research.

]]> Tue, 21 FEB 2012 08:57:39 AEST Washington (UPI) Feb 17, 2012 - Biologists have observed a theory of species evolution known as the founder effect in action for the first time, U.S. university researchers reported.

The founder effect, first outlined by German evolutionary biologist Ernst Mayr in 1942, says that when a small group of individuals from a genetically diverse population of some species migrates away and "founds" a new colony, the founders' genes play a dominant evolutionary role in the new population for generation after generation.

Biologists, including scientists who did postdoctoral work the University of California, said they wanted to see if the founder effect was real -- it had never been observed in action because evolution takes place so slowly.

They visited heavily forested Iron Cay, a Bahamas island spared the ravages of 2004's Hurricane Frances, and took brown anole lizard couples from the island at random to seven tiny treeless islands nearby where no lizards remained after the Category 4 hurricane.

On each island they released a single lizard pair, they said.

The Iron Cay lizards long ago evolved long hind legs to run swiftly along broad tree branches to avoid predators, the researchers reported.

But on the seven islands slammed by Frances, the anole lizards that drowned had short hind legs, better suited for darting in and out of the short, tangled, scrubby bushes that thrived there, the San Francisco Chronicle reported, citing the researchers.

If the founder effect held up, succeeding generations of the transplanted lizards would maintain their long hind legs, even though the original lizard residents had short legs, the researchers postulated.

The researchers returned to the islands every year to observe and measure the legs on each new generation of lizards, which now populate the islands.

After five or six generations, the founder effect appeared to hold up, with the new generations still sporting the long hind legs of their ancestors, the scientists reported.

But they saw another evolutionary force emerge, they said.

The lizards' long legs began shortening as each generation adapted to the scrub-bush environment, they said.

The scientists realized they were also witnessing Charles Darwin's natural selection, a key mechanism of evolution, they said.

"In this case, we've seen both the founder effect and natural selection operating right before our eyes -- for the first time," Jason Kolbe, a postdoctoral fellow at U.C. Berkeley and U.C. Davis and now at the University of Rhode Island, wrote in the American Association for the Advancement of Science journal Science Express.

]]> Tue, 21 FEB 2012 08:57:39 AEST Yaounde (AFP) Feb 18, 2012 - Poachers have slaughtered some 200 elephants in a national park in northern Cameroon, about a third of the population, and the massacre is still going on, according to a wildlife protection group.

The International Fund for Animal Welfare (IFAW) said a gang of Sudanese poachers had killed the free roaming elephants in the Bouba Ndjida National Park in northern Cameroon, near the border with Chad, in an unprecedented attack.

"At least 100 elephant carcasses have been found in the park in the past month and ongoing shooting is making it impossible to conduct a further, detailed assessment of the situation," IFAW said on its website.

"It is understood that more carcasses are expected to be found in unexplored regions of Bouba Ndjida."

The organisation said many orphaned elephant calves had been spotted abandoned following the shootings and concerns were high the babies may soon die of hunger and thirst.

"Their deaths will only compound the impact of the poaching spree on the Cameroons threatened elephant populations," it said.

IFAW official Celine Sissler-Bienvenu said it was common for armed gangs of poachers to cross from Sudan during the dry season to kill elephants for their ivory.

"But this latest massacre is massive and has no comparison to those of the preceding years," she said.

"The ivory is smuggled out of West and Central Africa for markets in Asia and Europe, and the money it raises funds arms purchases for use in regional conflicts, particularly ongoing unrest in Sudan and in the Central African Republic," Sissler-Bienvenu added.

IFAW said Britain, France, the European Union and the United States had voiced alarm and called on the Cameroon authorities to take urgent action to stop the killing.

Sissler-Bienvenu said the only answer was to end demand for ivory especially in Asia and to ensure conservation officials in range states were provided with skills and the equipment necessary to counter professional gangs of poachers.

"Since 2009 IFAW has provided anti-poaching assessment, training and support to rangers and conservation officials in central African countries which face severe challenges in the fight to end the bloody and cruel illegal ivory trade," she said.

"What these countries now need is the commitment of the international community to financially support these highly skilled and motivated trainees to be able to meet the task of protecting elephants."

]]> Tue, 21 FEB 2012 08:57:39 AEST Washington DC (SPX) Feb 17, 2012 - Analysis of chromosome number variation among species of a North American group of prickly pear cacti (nopales) showed that the most widespread species encountered are of hybrid origin.

Those widespread species likely originated from hybridization among closely related parental species from western and southeastern North America. This study was published in the open access journal Comparative Cytogenetics.

The prickly pear cacti (of the genus Opuntia) are endemic to the Americas. The genus is well known for the taxonomic difficulties it poses, as a result of hybridization and morphological variation, as well as lack of intense study.

Studies of chromosomal differences among species have been beneficial with regards to recognition and determination of hybrid origins of many taxa.

Those studies of the differences in chromosome number have shown that a majority of species of the genus have undergone genome duplication (also known as polyploidy).

This study suggests that a group of well-known prickly pear species occurring primarily in the United States are mostly derived from hybridization and genome duplication, which occurred as a result of the genetic separation of closely related parent species through habitat fragmentation during different times of the Pleistocene.

Those closely related species, which were restricted to the southern United States, after thousands of years of separation, came back in contact and formed the common hybrids in the group, which in turn became dominant and more successful in distribution over their progenitors.

Their progenitors remained confined to the southern part of their distribution likely as a result of their non-adaptability to adverse environmental conditions, which hybrid taxa were more than able to cope with. This scenario results in the distribution pattern of species that we see today.

This study underscores that genome duplication has had an important effect on the evolution of prickly pear cacti and that understanding patterns in chromosome numbers can be used, in part, to infer the historical biogeography of certain plant groups.

]]> Tue, 21 FEB 2012 08:57:39 AEST Tel Aviv, Israel (SPX) Feb 17, 2012 - Since Charles Darwin first put forth the theory of evolution, scientists have been trying to unlock the mysteries of genetics. But research on the genome - the organism's entire hereditary package encoded in DNA and RNA - has been less extensive. There is a tendency to think of the genome as a static and passive container of information, says Dr. Ehud Lamm of Tel Aviv University's Cohn Institute for the History and Philosophy of Science and Ideas.

In the Proceedings of the 23rd Annual Workshop on the History and Philosophy of Science, Dr. Lamm has introduced a critical new paradigm that redefines the genome as a dynamic structure that can impact genes themselves.

"When you try to explain human society by reducing it to individuals, you neglect the fact that people are also shaped by their social environment. The picture is bidirectional," he says, explaining that the relationship between genes and genomes is comparable. "Genomes have a physiology - and genes are a manifestation of this."

His reconception of the genome could change both biological discourse and research. Focusing on notions such as genomic response to stress factors, his theoretical work has the potential to provide deeper insight into how organisms develop and evolve.

Changing genetic research
Historically, genetic research has relegated understanding of the genome to the background, says Dr. Lamm. Past theories that regarded the capacity of the genome to respond to its environment were largely dismissed. But the concept of the genome as a mere collection of genes is a hindrance to research, he says.

Based on current empirical knowledge from the fields of genetics, epigenetics, and genomics as well as "thought experiments," a tool used by scientists and philosophers to analyze situations and experimental conditions, Dr. Lamm is bringing to light the consequences of a new perspective on the genome.

From its embryonic development and continuing throughout our lives, the three-dimensional structure of the genome is changing constantly. The subtle relationship between genes and genomes impacts properties such as recessivity and dominance - a result of the developmental system rather than an intrinsic genetic property - and the process of how genes are inherited.

Lamm calls mechanisms that are involved in genomic changes "genomic epigenetic mechanisms" (GEMs) and highlights their importance for understanding the evolution of both genomes and organisms. Some GEMs are activated under conditions of ecological or genomic stress and can lead to changes that are subsequently inherited, contributing to the evolutionary process.

Although research into genomic structure and dynamics is ongoing, existing information can be used to reassess central notions in evolutionary biology.

Ultimately, the mechanisms of the genome impact how, when, and in what way genetic material acts, as well as the physiology of cells themselves.

Building a new conceptual framework
So far, no useful theoretical framework exists to help scientists conceptualize the genome and the genes as a developmental system. Dr. Lamm hopes to provide it.

"The time is ripe to start thinking about how the genome and genes work as a system. With a gene-centric point of view, central concepts in genetics are problematic, most critically the gene concept itself. Considering the genome in addition to the gene might fill the gaps," concludes Dr. Lamm. With better conceptual tools, scientists can become more adept at thinking about these crucial biological systems.

]]> Tue, 21 FEB 2012 08:57:39 AEST Yerevan (AFP) Feb 16, 2012 - The authorities in Armenia on Thursday offered cash rewards to hunters who kill wolves after increasing reports of attacks on rural villages exacerbated by recent cold weather and heavy snow.

"Because of the heavy snowfall, wolves began to appear more frequently in populated areas and it became necessary to deal with them," Armenian Environmental Protection Minister Aram Harutiunian told a news conference.

The authorities will pay around $260 (200 euros) to hunters who kill a wolf -- a significant amount in impoverished regions of the ex-Soviet republic.

Harutiunian said that he envisaged a cull of around 200 wolves from an estimated total population of between 500 and 700, which he said would not threaten the animals with extinction in the country.

"We believe that this way we can ease the situation and it will not affect the wolf population," he said.

But local environmentalists condemned the planned cull, saying that deforestation and illegal hunting had reduced wolves' natural sources of food in the wild, causing them to scavenge in populated areas.

"Instead of destroying wolves, it is better to stop the illegal and uncontrolled hunting of wild animals," environmentalist Srbuhi Harutiunian told AFP.

]]> Tue, 21 FEB 2012 08:57:39 AEST Houston TX (SPX) Feb 16, 2012 - In a study of the molecular underpinnings of plants' pest resistance, Rice University biologists have shown that plants both anticipate daytime raids by hungry insects and make sophisticated preparations to fend them off.

"When you walk past plants, they don't look like they're doing anything," said Janet Braam, an investigator on the new study, which appears this week in the Proceedings of the National Academy of Sciences. "It's intriguing to see all of this activity down at the genetic level. It's like watching a besieged fortress go on full alert."

Braam, professor and chair of Rice's Department of Biochemistry and Cell Biology, said scientists have long known that plants have an internal clock that allows them to measure time regardless of light conditions. For example, some plants that track the sun with their leaves during the day are known to "reset" their leaves at night and move them back toward the east in anticipation of sunrise.

In recent years, scientists have begun to apply powerful genetic tools to the study of plant circadian rhythms. Researchers have found that as many as one-third of the genes in Arabidopsis thaliana - a widely studied species in plant biology - are activated by the circadian cycle. Rice biochemist Michael Covington found that some of these circadian-regulated genes were also connected to wounding responses.

"We wondered whether some of these circadian-regulated genes might allow plants to anticipate attacks from insects, in much the same way that they anticipate the sunrise," said Covington, now at the University of California, Davis.

Danielle Goodspeed, a graduate student in biochemistry and cell biology, designed a clever experiment to answer the question. She used 12-hour light cycles to entrain the circadian clocks of both Arabidopsis plants and cabbage loopers, a type of caterpillar that eats Arabidopsis.

Half of the plants were placed with caterpillars on a regular day-night cycle, and the other half were placed with "out-of-phase" caterpillars whose internal clocks were set to daytime mode during the hours that the plants were in nighttime mode.

"We found that the plants whose clocks were in phase with the insects were relatively resistant, whereas the plants whose clocks were out of phase were decimated by the insects feeding on them," Goodspeed said.

Wassim Chehab, a Rice faculty fellow in biochemistry and cell biology, helped Goodspeed design a follow-up experiment to understand how plants used their internal clocks to resist insect attacks. Chehab and Goodspeed examined the accumulation of the hormone jasmonate, which plants use to regulate the production of metabolites that interfere with insect digestion.

They found that Arabidopsis uses its circadian clock to increase jasmonate production during the day, when insects like cabbage loopers feed the most. They also found that the plants used their internal clocks to regulate the production of other chemical defenses, including those that protect against bacterial infections.

"Jasmonate defenses are employed by virtually all plants, including tomatoes, rice and corn," Chehab said. "Understanding how plants regulate these hormones could be important for understanding why some pests are more damaging than others, and it could help suggest new strategies for insect resistance."

]]> Tue, 21 FEB 2012 08:57:39 AEST Chicago IL (SPX) Feb 15, 2012 - Following one of Earth's five greatest mass extinctions, tiny marine organisms called graptoloids did not begin to rapidly develop new physical traits until about 2 million years after competing species became extinct.

This discovery, based on new research, challenges the widely held assumption that a period of explosive evolution quickly follows for survivors of mass extinctions.

In the absence of competition, the common theory goes, surviving species hurry to adapt, evolving new physical attributes to take advantage of newly opened niches in the ecosystem. But that's not what researchers found in graptoloid populations that survived a mass extinction about 445 million years ago.

"What we found is more consistent with a different theory, which says you might expect an evolutionary lag as the ecosystem reforms itself and new interspecies relationships form," said University at Buffalo geology professor Charles E. Mitchell, who led the research.

The research provides insight on how a new mass extinction, possibly one resulting from man-made problems such as deforestation and climate change, might affect life on Earth today.

"How would it affect today's plankton? How would it affect groups of organisms in general?" asked the paper's lead author, David W. Bapst, a PhD candidate at the University of Chicago, who studied with Mitchell as an undergraduate.

"The general motivation behind this work is understanding how extinction and evolution of form relate to each other, and the fossil record is the only place where we can do these sort of experiments across long spans of time," Bapst said.

The research on graptoloids is scheduled to appear in the online Early Edition of the Proceedings of the National Academy of Sciences.

Other team members included Peter C. Bullock and Michael J. Melchin of St. Francis Xavier University in Nova Scotia, and H. David Sheets of Canisius College in Buffalo, N.Y. The National Science Foundation and Natural Sciences and Engineering Research Council of Canada supported the study.

Graptoloids are an extinct zooplankton that lived in colonies. Because the animals evolved quickly and had a wide geographic range, their fossil record is rich - a trove of information on how species diversify.

Bapst, Mitchell and their colleagues examined two different groups of graptoloids in their study: neograptines and diplograptines. Each kind lived during the Ordovician mass extinction that began about 445 million years ago, but only neograptines survived.

Before the extinction event, diplograptine species were dominant, outnumbering neograptine species. Diplograptines also varied more in their morphology, building colonies of many different shapes.

With diplograptines gone after the Ordovician mass extinction, neograptines had a chance to recover in an environment free of competitors.

According to the popular ecological release hypothesis, a popular theory, these circumstances should have led to a burst of adaptive radiation. In other words, without competition, the neograptines should have diversified rapidly, developing new physical traits - new colonial architectures - to take advantage of ecological niches that the diplograptines once filled.

But that's not what the researchers found.

To test the adaptive radiation idea, they analyzed the colony forms of 183 neograptine and diplograptine species that lived before, during or after the Ordovician mass extinction - a total of 9 million years of graptoloid history.

This wealth of data enabled the team to track graptoloid evolution with more precision than past studies could. What the researchers discovered looked nothing like adaptive radiation.

Almost immediately following the Ordovician mass extinction, new neograptine species proliferated, as expected. But according to the study, these new species displayed only small changes in form or morphology, not the burst of innovation the release hypothesis predicts. In fact, graptoloids had been evolving new physical traits at a more intensive pace before the extinction event.

Limited morphological innovation among neograptines continued for approximately 2 million years after the extinction, Bapst said.

The lag supports a type of evolution that argues that interactions between co-evolving species help foster diversification. Because such relationships likely take time to develop in a recovering ecosystem, an evolutionary lag of the kind the graptoloid study detected should occur in the wake of a mass extinction.

Another possible explanation is that newly appeared graptoloid species may have differed in ways outside of physical traits, a phenomenon that biologists refer to as non-adaptive radiations. A third possibility is that graptoloids may have experienced evolutionary lag due to their complex mode of growth.

Besides investigating how neograptines fared after the extinction event, the team also analyzed whether colony form alone could explain why neograptines survived the mass extinction while diplograptines disappeared. The scientists concluded that this was unlikely, suggesting a role for other factors such as possible differences in the preferred habitat of the two groups.

]]> Tue, 21 FEB 2012 08:57:39 AEST Jaipur, India (AFP) Feb 15, 2012 - An entire village inside a north Indian nature reserve has been moved to make more room for local tigers in a bid to protect the country's dwindling big cat population, an official said Wednesday.

The village of Umri was relocated from Rajasthan state's Sariska tiger reserve last week, according to R.S. Shekhawat, the field director of the national park.

"The process took place with the cooperation of the families. It will help in securing a proper habitat for big cats, so both the governments of the state and the centre (federal government) are working in this direction," he told AFP.

He said the authorities compensated the affected families with either a lump sum payment of 1 million rupees ($20,274) or a combination of land and cash to build their new homes.

India is home to half of the world's rapidly shrinking wild tiger population but has been struggling to halt the big cat's decline in the face of poachers, international smuggling networks and loss of habitat.

The Sariska national park is in the Aravalli mountain range and located about 167 kilometres (104 miles) from the national capital New Delhi.

Currently home to just five tigers, officials in the desert park are working on relocating more villagers in the months ahead, Shekhawat said.

"We expect to relocate all families in different villages inside the reserve by 2013," he said.

India has employed a series of measures recently to stem the decline in the number of tigers.

Last month officials announced that armed commandos would be deployed in the jungles of southern India to prevent poachers from capturing and killing the big cats.

India has seen its tiger population plummet from an estimated 40,000 animals in 1947, when it gained independence from British colonial rule, to just 1,706 in 2011.

]]> Tue, 21 FEB 2012 08:57:39 AEST La Jolla CA (SPX) Feb 14, 2012 - Lying around in the sun all day is hazardous not just for humans but also for plants, which have no means of escape. Ultraviolet (UV) radiation from the sun can damage proteins and DNA inside cells, leading to poor growth and even death (as well as carcinogenesis in humans). But plants have evolved some powerful adaptive defenses, including a complex array of protective responses orchestrated by a UV-sensing protein molecule known as UVR8.

Now, scientists from The Scripps Research Institute and the University of Glasgow have put together a detailed picture of UVR8's structure and inner workings.

"It's an ancient molecule that seems to play a fundamental role in plants," said Scripps Research Professor Elizabeth Getzoff.

"Knowing how it works helps us to understand better how plant growth varies with changes in sunlight, for example due to climate shifts; it's also important that we understand its basic light-switch mechanism."

Getzoff was a principal investigator for the study, which is reported February 9 in the journal Science's early online edition, Science Express.

Sunscreen for Plants
Researchers first found evidence of UVR8's protective function in 2002, when they knocked out its gene in the wild mustard plant Arabidopsis, the standard experimental model for plant biologists.

The mutant plants grew poorly when exposed to UV "B" wavelength radiation-the range most responsible for tanning and burning of human skin. When UVR8 is present in Arabidopsis, it can sense UV-B light and switch on a broad protective response involving more than 100 Arabidopsis genes.

"These are genes for DNA-repair enzymes and other protective proteins," said Getzoff. "It's the plant equivalent of putting on sunscreen."

Molecules similar to UVR8 have been found in more ancient plant species such as algae and mosses, suggesting that UVR8 represents a primordial adaptation to UV light, possibly originating before Earth's atmosphere developed a UV-absorbing ozone layer.

John Christie of the University of Glasgow was a visiting scientist in Getzoff's lab in 2010, and suggested a collaboration to find out more about UVR8. Getzoff's lab specializes in finding and analyzing the detailed atomic structures of proteins, while Christie and his colleague Gareth I. Jenkins, a professor of plant cell and molecular biology at the University of Glasgow, are experts on UVR8 biology.

Structures No One Has Seen Before
In the study, Christie and other members of Getzoff's lab produced and purified copies of the UVR8 molecule and chemically induced it to crystallize-to line up in a regular pattern.

Firing X-rays at the crystallized UVR8, evaluating the resulting diffraction pattern, and using related techniques, the scientists were able to determine UVR8's molecular architecture, including the three-dimensional arrangement of its component atoms, to a fine resolution of 1.7 Angstroms-170 trillionths of a meter.

UVR8 was known to be a "dimer" made of two identical protein subunits. The Getzoff lab's structural analysis revealed that these subunits are doughnut-shaped, and normally stick together weakly, like a couple of balloons that have become electrically charged after being rubbed.

The interface connecting these two subunits is spanned by the component amino acids of the protein-including pyramidal structures made of tryptophan amino acids, which serve as the primary sensors of UV-B light. "The absorption of UV-B photons by these tryptophan pyramids leads to the weakening of the electrostatic force that holds the two UVR8 subunits together," said Christie.

As a result of this weakening, the subunits can separate, move singly to the cell nucleus, and begin their orchestration of gene activity. The team's analysis also suggested that within a few hours, the subunits can reassemble into UV-B-sensitive dimers again.

"Other light-sensing proteins require a chemical modification or helper molecule to detect light, but UVR8 is unique in that it has these inbuilt UV-B-sensing tryptophan pyramids-structures that no one has seen before," said Christie.

Molecule with Its Own Light Sensor
To help confirm that UVR8 can sense UV-B light entirely on its own, members of Jenkins's lab altered single amino acids within UVR8 to see how the molecule's light-sensing function changed. Tryptophans in the pyramid structure turned out to be crucial for UV-B detection; in fact, amino-acid substitution of one tryptophan by a phenylalanine shifts the sensitivity of UVR8 to shorter-wavelength UV-C radiation.

"These experiments showed without a doubt that UVR8 contains its own light sensor," said Getzoff.

Getzoff and her colleagues now intend to find out more precisely how the absorption of UV-B causes the disassociation of the UVR8 dimer, and then how the separated subunits interact with other proteins and chromosomes in the nucleus to switch on protective responses in the plant. Both UVR8 and a similar, but not UV-controlled, protein in humans bind to chromosomes to control gene activity.

]]> Tue, 21 FEB 2012 08:57:39 AEST Subscribe to our daily selection of space, military, environment and energy newsletters responseText http://visitor.constantcontact.com/manage/optin/ea?v=0016gbbKsaiGSpQFojVO8ZoHw%3D%3D