Flowering Plants May Be Considerably Older Than Previously Thought

ScienceDaily (Mar. 17, 2010) — Flowering plants may be considerably older than previously thought, says a new analysis of the plant family tree.


A new analysis of the land plant family tree suggests that flowering plants may have lived much earlier than previously thought. (Credit: Wikimedia Commons)

Previous studies suggest that flowering plants, or angiosperms, first arose 140 to 190 million years ago. Now, a paper to be published in the Proceedings of the National Academy of Sciences pushes back the age of angiosperms to 215 million years ago, some 25 to 75 million years earlier than either the fossil record or previous molecular studies suggest.

"If you just looked at the fossil record, you would say that angiosperms originated in the early Cretaceous or late Jurassic," said Michael Donoghue of Yale University. "Most molecular divergence times have shown that they might be older than that," added Yale biologist Jeremy Beaulieu. "But we actually find that they might be Triassic in origin," said Beaulieu. "No one has found a result like that before."

If confirmed, the study could bolster the idea that early angiosperms promoted the rise of certain insects. Modern insects like bees and wasps rely on flowers for nectar and pollen. "The fossil record suggests that a lot of these insect groups originated before angiosperms appeared," said Stephen Smith of the National Evolutionary Synthesis Center. This study shifts the oldest angiosperms back farther in time towards the origin of groups like bees and flies, the scientists say. "If you take our dates and superimpose them on the evolutionary tree for these insect groups, all of a sudden you get a match," said Beaulieu.

To trace the origins of flowering plants, the researchers used genetic comparisons of living plants and clues from fossils to reconstruct the relationships among more than 150 terrestrial plant species. Though their results contradict previous age estimates for angiosperms, they support estimates for other plant groups. "Many of the dates that we get correspond really well to the known fossil record, at least for the origin of land plants and the origin of vascular plants and seed plants," said Donoghue. "But we got a much older date for the origin of angiosperms -- one that's really out of whack with the fossil record," Smith added.

This disconnect between molecular and fossil estimates is not unheard of, the authors explained. "We see the same kind of discrepancy in other groups too, like mammals and birds," said Donoghue.

Why the mismatch between different approaches to dating the tree of life?

One possibility, the researchers explained, is that the first flowering plants weren't diverse or abundant enough to leave their mark in the fossil record. "We would expect there to be a time lag between the time of origin and when they became abundant enough to get fossilized," said Smith. "The debate would just be how long."

"Imagine a long fuse burning and then KABOOM! There's a big explosion. Maybe angiosperms were in that fuse state," said Donoghue. "But it's hard to imagine flowering plants would have had a big impact on the origin of major insect groups if that were the case," he added.

Another possibility, the researchers allow, is that the molecular methods may be amiss. "If the angiosperms originated 215 million years ago, then why don't we find them in the fossil record for almost 80 million years?" said Beaulieu. "It could also suggest that our dates are wrong."

"We've done the best analysis we know how to do with the current tools and information," said Donoghue. To improve on previous studies, the researchers used a method that allows for variable rates of evolution across the plant family tree. "Rates of molecular evolution in plants seem to be correlated with changes in life history," he explained. "Older methods assume that rates of molecular evolution don't change too radically from one branch of the evolutionary tree to another. But this newer method can accommodate some fairly major rate shifts." Although researchers have come up with some savvy statistical tricks to account for rate shifts, Donoghue explained, the problem hasn't entirely disappeared.

"As we develop better molecular methods, people would like it if the molecular dates reconciled with the fossil record. Then everybody would be happy," said Donoghue. "But instead the gap is getting wider," he said. "And in the end, that might actually be interesting."

The team's findings will be published early online in the March 15 issue of Proceedings of the National Academy of Sciences.

Read more here!!

Move Over Predators: Plants Can Control the Food Chain Too -- From the Bottom Up

ScienceDaily (Mar. 25, 2010) — Forget top-to-bottom only. New Cornell University evolutionary biology research published in the journal Science shows how plants at the bottom of the food chain have evolved mechanisms that influence ecosystem dynamics as well.

"The ecology and interactions of most organisms is dictated by their evolutionary history," said Anurag Agrawal, associate professor of ecology and evolutionary biology (EEB), the study's senior author.

In food webs, predators help suppress populations of prey by eating them; that frees species lower in the food chain, such as plants, to flourish, a dynamic called a "trophic cascade." Most trophic cascade studies have focused on the ability of predators to increase plant biomass by eating herbivores. Such studies typically find strong trophic cascades in aquatic environments, where big fish eat minnows, which eat the tiny algae-eating crustaceans called daphnia.

Agrawal, first author Kailen Mooney, who is a former Cornell postdoctoral researcher and now assistant professor at the University of California-Irvine, and colleagues studied trophic cascades in 16 milkweed species, famed for their interactions with monarch butterflies, and also fed upon by aphids.

Plants have evolved three main strategies for increasing their biomass as much as they can against the forces that limit their growth, said the researchers: They grow as quickly as possible; develop direct defenses, such as toxins or prickly leaves, against herbivores; and attract such predators as ladybugs that eat their pests.

But plants do not have the resources to develop all three defenses. Since Darwin, evolutionary biologists have hypothesized that over millions of years of evolution, plant species are subject to trade-offs, developing some defense strategies in lieu of others; a key finding of the new study is that these evolutionary trade-offs drive how modern ecosystems are structured.

In the case of milkweed, some favored fast growth and the ability to attract predators while putting less energy into resisting herbivores.

The study found that one of the major factors leading to greater milkweed biomass (or growth) is the production of volatile compounds called sesquiterpenes, which attract such predators as aphid-eating ladybugs. But surprisingly, the plants' biomass increases regardless of whether ladybugs or other aphid predators are present.

The reason, the researchers suggest, is because the trait to produce sesquiterpenes appears genetically linked to faster growth; the strategy here is to replace leaves faster than they can be eaten. At the same time, milkweed species that put more energy into growing faster put less energy into resisting such pests as aphids.

"Because no species can do everything, milkweeds that grow fast necessarily have lower resistance to aphids," said Agrawal. "Thus species that grow fast benefit the most from predators" of aphids.

The findings have implications for agriculture, as conventional strategies for controlling pests often involve spraying insecticides, said Agrawal. "By including the evolutionary history in our understanding of natural pest management, we gain insight into plant strategies that have stood the test of time, and this may provide hints for breeding crops with traits that ensure robust lines of defense," he added.

*Science, March 26, 2010.

Co-authors include Andre Kessler, assistant professor, and postdoctoral researcher Rayko Halitschke, both in EEB at Cornell.

The study was funded by the National Science Foundation, Cornell Center for a Sustainable Future and University of California-Irvine's School of Biological Sciences.

Read more here!

Evolution More Rapid Than Darwin Thought

ScienceDaily (Mar. 22, 2010) — Evolution can proceed much more rapidly than has long been thought. This is shown by Magnus Karlsson, a doctoral candidate at Linnaeus University in Kalmar, in his dissertation about the impact of genetics and the environment on the color patterns of pygmy grasshoppers.

It has been the accepted view among evolutionary biologists since Darwin published his Origin of Species in 1859 that measurable evolutionary changes occur slowly, often taking hundreds of generations. This view may now be about to change.

Pygmy grasshoppers exist in many different color variants and in many types of environment. Through a series of experiments and studies in nature, Magnus Karlsson discovered that the distribution between the color variants of pygmy grasshoppers differs across different environments. In recently burnt over areas, a very high proportion of the grasshoppers are black. In unburnt areas, on the other hand, the black variant is unusual. What's more, the proportion of black grasshoppers changes very rapidly between generations in the burnt areas, whereas the proportion in unburnt areas remains the same over the same period of time.

Magnus Karlsson presents data that show that the pygmy grasshoppers' color changes by natural selection. He believes that the primary cause of these changes is birds and other animals that hunt using their vision. The black grasshoppers are simply less visible against the burnt background, so they survive more often. But as the environment changes and becomes more complex, the advantage of being dark diminishes, and other color variants can once again increase in number.

In his experiments, Magnus Karlsson has also shown that the color pattern of the pygmy grasshopper is genetically conditioned and is passed on from parent to offspring. On the other hand, various environmental factors, such as crowdedness or the substrate the grasshoppers grow up on, do not affect their color. In other words, there is no indication that the grasshoppers themselves can change their color depending on what environment they are surrounded by. Therefore, the great differences that exist between burnt and unburnt environments are the result of unusually rapid evolutionary change.

But it is not only that evolution sometimes proceeds rapidly; variation itself also offers major advantages. In groups consisting of many different color variants, survival is higher than in groups with less color variation. This means quite simply that variable groups may find it easier to adapt to environmental changes and that they are more productive.

The practical significance of Magnus Karlsson's discoveries is broad and just as varied as his grasshoppers. He believes this new knowledge can be used in planning preservation projects for threatened species and to improve yields in agriculture.

"But the most important part of the dissertation is that I have shown that evolution sometimes proceeds incredibly rapidly. This is huge," says Magnus Karlsson.

His dissertation is titled Evolution in Changing Environments Revealed by Fire Melanism in Pygmy Grasshoppers.

Read more here!

First Ever Southern Tyrannosaur Dinosaur Discovered

ScienceDaily (Mar. 26, 2010) — Scientists from Cambridge, London and Melbourne have found the first ever evidence that tyrannosaur dinosaurs existed in the southern continents. They identified a hip bone found at Dinosaur Cove in Victoria, Australia as belonging to an ancestor of Tyrannosaurus rex.
Tyrannosaurus rex. (Credit: iStockphoto)

The find sheds new light on the evolutionary history of this group of dinosaurs. It also raises the crucial question of why it was only in the north that tyrannosaurs evolved into the giant predators like T. rex.

The 30cm-long pubis bone from Dinosaur Cove looks like a rod with two expanded ends, one of which is flattened and connects to the hip and the other looks like a 'boot'.

According to Dr Roger Benson of the Department of Earth Sciences at the University of Cambridge, who identified the find: "The bone is unambiguously identifiable as a tyrannosaur because these dinosaurs have very distinctive hip bones."

The discovery lays to rest the belief held by some scientists that tyrannosaurs never made it to the southern continents.

"This is an exciting discovery because tyrannosaur fossils had only ever been found in the northern hemisphere before and some scientists thought tyrannosaurs never made it down south.

"Although we only have one bone, it shows that 110 million years ago small tyrannosaurs like ours might have been found worldwide. This find has major significance for our knowledge of how this group of dinosaurs evolved." says Dr Benson.

Dr Paul Barrett, Palaeontologist at the Natural History Museum, London and member of the research team commented: "The absence of tyrannosauroids from the southern continents was becoming more and more anomalous as representatives of other 'northern' dinosaur groups started to show up in the south. This find shows that tyrannosauroids were able to reach these areas early in their evolutionary history and also hints at the possibility that others remain to be discovered in Africa, South America and India."

The bone would have come from an animal about three metres long and weighing around 80 kg, similar to a human, and would have had the large head and small arms that make tyrannosaurs so distinctive.

The newly identified dinosaur, known as NMV P186069, was much smaller than T. rex, which was 12 metres long and weighed around four tonnes. Giant size like this only evolved late in the tyrannosaur lineage.

Compared with T. rex, which lived about 70 million years ago at the end of Cretaceous period, NMV P186069 lived earlier during the Cretaceous, around 110 million years ago.

During the time of the dinosaurs the continents gradually went from a single supercontinent towards something like their present-day arrangement. This tyrannosaur is from the mid-stages of this continental break-up, when the southern continents of South America, Antarctica, Africa and Australia had separated from the northern continents, but had not separated from each other.

While answering the question of whether or not tyrannosaurs lived in both the southern and northern hemispheres, the new find leaves another, deeper mystery: why did tyrannosaurs evolve into giant predators such as T. rex only in the northern hemisphere?

According to Dr Benson: "It is difficult to explain why different groups succeeded in the north and the south if they originally existed in both places. What we need to know now is just how diverse the early radiation of tyrannosaurs was, why they went extinct, leaving only giant-sized, short-armed species like T. rex, and how successful they might have been in the southern hemisphere. We can only answer these questions with new discoveries."

About the excavation: Dinosaur Cove is in south-east Australia, where the Otway ranges meet the sea to the west of Cape Otway, along the Great Ocean road. The fossil-bearing rock layers consist of sand-, silt- and mudstones around 106 million years old.

The site was excavated during the 1980s and 1990s. Work at the site was challenging: access involved either climbing down dangerous cliffs or landing a boat or helicopter on rock platforms at low tide, and the hardness of the rock meant heavy mining equipment and dynamite was required to uncover the fossil-bearing rock layers. Swedish mining company Atlas Copco donated some of the equipment used and the excavation was funded by the National Geographic Society.

Read more here!

Prolonged Climatic Stress Main Reason for Mass Extinction 65 Million Years Ago, Paleontologist Says

ScienceDaily (Mar. 27, 2010) — Long-term climate fluctuations were probably the main reason for the extinction of the dinosaurs and other creatures 65 million years ago. This conclusion was reached by PD Dr. Michael Prauss, paleontologist at Freie Universitaet Berlin, based on his latest research results.

According to new research from a German paleontologist, long-term climate fluctuations -- not a giant meteorite impact -- were likely the main reason for the extinction of the dinosaurs and other creatures 65 million years ago. (Credit: iStockphoto/Adrian Chesterman)

Prauss thus challenges the almost 30-year-old theory that a meteorite impact at the Mexican Yucatan peninsula was the single cause for one of the five largest mass extinctions in Earth history, which has most recently been reiterated in a publication in the journal Science. According to Prauss, the impact was only one in a chain of catastrophic events that caused substantial environmental perturbations, probably largely controlled by the intermittent activity of the Deccan volcanism near the then-Indian continent, that continued over several million years and peaked at the Cretaceous-Paleogen boundary.

"The resulting chronic stress, to which of course the meteorite impact was a contributing factor, is likely to have been fundamental to the crisis in the biosphere and finally the mass extinction," says Michael Prauss. In a research project funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) and in collaboration with Prof. Dr. Gerta Keller, paleontologist at Princeton University, U.S.A., Prauss analyzed several drill cores and rock sections covering the extended Cretaceous-Paleogene boundary interval at Brazos River, Texas, USA. The investigated region is located about 1000 km northwest of the Chicxulub impact crater and is well known among geologic scientists for its exceptionally complete preservation of Upper Cretaceous sediments.

Based on an analysis of the appearance and distribution of organic-walled microfossils such as Algal cysts, pollen, and spores of terrestrial plants, Prauss shows that significant and persistent variations in the ecosystem of the Upper Cretaceous started long before the meteorite impact. Among others, these are reflected by fluctuations in sea-level and marine algae productivity.

Prauss also considers it highly problematic to equate the meteorite impact with the position of the Cretaceous-Paleogene boundary: "The actual impact took place well before the geochemically and micropaleontologically defined Cretaceous Paleogene boundary." He supports his assertion with the position of the so-called fern spike, an episodic, significant increase in the proportion of fern spores caused by the pioneering phase of ferns in repopulating landscapes of destroyed ecosystems. In all sections of the investigated area the fern spike occurs well before important stratigraphic evidence for the Paleogene.

The new results contradict a publication by Schulte et al. (2010) in the March 5 issue of Science. Schulte et al. summarize the Cretaceous-Paleogene issue only to arrive at the 30-year-old theory of the impact as the sole cause of mass extinction. The occurrence of substantial fluctuations within the ecosystem of the Upper Cretaceous before the impact is disputed and the impact event is equated in time with the biostratigraphic Cretaceous-Paleogene boundary. "In the light of the new data, both of these points have to be refuted," says Prauss.

Read more!

How Did Flowering Plants Evolve to Dominate Earth?

ScienceDaily (Dec. 1, 2009) — To Charles Darwin it was an 'abominable mystery' and it is a question which has continued to vex evolutionists to this day: when did flowering plants evolve and how did they come to dominate plant life on earth? A new study in Ecology Letters reveals the evolutionary trigger which led to early flowering plants gaining a major competitive advantage over rival species, leading to their subsequent boom and abundance
.

Colorful tulips and other spring flowers in the Keukenhof Gardens, the Netherlands. How did flowering plants come to dominate plant life on earth? (Credit: iStockphoto/Monika Lewandowska)

The study, by Dr Tim Brodribb and Dr Taylor Field of the University of Tasmania and University of Tennessee, used plant physiology to reveal how flowering plants, including crops, were able to dominate land by evolving more efficient hydraulics, or 'leaf plumbing', to increase rates of photosynthesis.

"Flowering plants are the most abundant and ecologically successful group of plants on earth," said Brodribb. "One reason for this dominance is the relatively high photosynthetic capacity of their leaves, but when and how this increased photosynthetic capacity evolved has been a mystery."

Using measurements of leaf vein density and a linked hydraulic-photosynthesis model, Brodribb and Field reconstructed the evolution of leaf hydraulic capacity in seed plants. Their results revealed that an evolutionary transformation in the plumbing of angiosperm leaves pushed photosynthetic capacity to new heights.

The reason for the success of this evolutionary step is that under relatively low atmospheric C0₂ conditions, like those existing at present, water transport efficiency and photosynthetic performance are tightly linked. Therefore adaptations that increase water transport will enhance maximum photosynthesis, exerting substantial evolutionary leverage over competing species.

The evolution of dense leaf venation in flowering plants, around 140-100 million years ago, was an event with profound significance for the continued evolution of flowering plants. This step provided a 'cretaceous productivity stimulus package' which reverberated across the biosphere and led to these plants playing the fundamental role in the biological and atmospheric functions of the earth.

"Without this hydraulic system we predict leaf photosynthesis would be two-fold lower then present," concludes Brodribb. "So it is significant to note that without this evolutionary step land plants would not have the physical capacity to drive the high productivity that underpins modern terrestrial biology and human civilisation."

Read more here!

Plodding Amoeba Flips Into Free-Swimming Flagellate: Naegleria Genome Sheds Light on Transition from Prokaryotes to Eukaryotes

ScienceDaily (Mar. 5, 2010) — In the long evolutionary road from bacteria to humans, a major milestone occurred some 1.5 billion years ago when microbes started building closets for all their stuff, storing DNA inside a nucleus, for example, or cramming all the energy machinery inside mitochondria.

Top: N. gruberi flagellate-stage (microtubules are highlighted in green, basal bodies in red, and DNA is stained blue). Bottom: N. gruberi, amoeba-stage. (Credit: Photos by Lillian Fritz-Laylin, UC Berkeley)

Scientists have now sequenced the genome of a weird, single-celled organism called Naegleria gruberi that is telling biologists about that transition from prokaryotes, which function just fine with all their proteins floating around in a soup, to eukaryotes, which neatly compartmentalize those proteins?

The sequence, produced by the Department of Energy Joint Genome Institute (JGI), and an analysis by scientists from the University of California, Berkeley, Lancaster University in the United Kingdom and institutions elsewhere in the United States and the U.K. are published in the March 5 issue of the journal Cell.

"In a sense, analyzing the Naegleria genome shows us what it would be like to be on this planet more than a billion years ago, and what kind of organisms were around then and what they might have looked like," said Simon E. Prochnik, a JGI and UC Berkeley bioinformaticist and coauthor of the Cell paper.

Naegleria is a common soil amoeba -- the sequenced organism was isolated from the mud in a grove of eucalyptus trees on the UC Berkeley campus -- that, under stress, quickly grows two flagella, like sperm tails, that it uses to swim around. It has a third identity, a hard cyst, that can persist in the soil until conditions become damp and warm enough for it to turn into an amoeba.

"This one-celled organism hunts and eats bacteria as an amoeba, swims around looking for a better environment as a flagellate, and then hunkers down and waits for good times as a cyst," Prochnik said. "It is a very rare process to go from amoeba to flagellate like this."

Not surprisingly, the organism is packed with genes that help support these three personalities, he said. He and his colleagues report that this amoeboflagellate contains 15,727 genes coding for proteins, while humans have 23,000 protein-coding genes.

"Naegleria has a lot of genes because it has a complicated lifestyle; most single-celled organisms -- in particular, parasites -- have a simpler lifestyle, and therefore have fewer genes," Prochnik said. "These single-celled organisms are highly versatile, containing all the genetic information necessary to survive in a wide range of environments and under a wide range of stresses."

The researchers compared the Naegleria genome to the genomes of 16 other eukaryotes, ranging from humans and fungi to green plants and other unicellular eukaryotes, shedding light on the set of perhaps 4,000 genes that may have been part of the first, most primitive eukaryotes, according to UC Berkeley graduate student Lillian Fritz-Laylin, first author of the paper. The number of genes surprised the researchers, because previous genome comparisons that included parasites came up with a much lower number. That may be because parasites live off their host and have been able to shed many genes that are critical for a free-living organism, they said.

"Now that our analysis focuses on data from free-living organisms, including Naegleria, that haven't lost all these genes and functions, we can make a broader comparison, and we find a lot more proteins were probably present in the eukaryotic ancestor than we previously thought," Fritz-Laylin said.

"This is the first genome comparison that includes not only Naegleria, but representatives of all six sequenced groups of eukaryotes," Prochnik said. Naegleria is part of a diverse group that includes a cousin, Naegleria fowleri, that can fatally infect swimmers. The other eurkaryotic groups are animals and fungi; plants and green algae; chromalveolata, which include diatoms, red tide and malaria; amoebozoa, which include various single-celled amoebae; and the diverse group that includes parasites like giardia.

Among other things, Naegleria's genes shed light on how cells move, how they signal one another and how they metabolize nutrients.

As an amoeba, Naegleria pushes out little feet, called pseudopods, that propel it in its hunt for food. Yet, once the food disappears, the amoeba creates flagella from scratch and uses them to swim about in search of new hunting grounds.

What is interesting, Fritz-Laylin said, is that pseudopods and flagella use different proteins for movement. Amoebae make use of actin, which provides the internal scaffolding for the cell and for the pseudopods that help amoebae explore their environment. Flagella, on the other hand, are made mostly of the protein tubulin. Because Naegleria has both types of movement, the organism can help scientists understand the origins of these parallel systems during the evolution of eukaryotes.

Scientists can starve populations of Naegleria in its amoeba form and have seen it switch quickly and simultaneously to its flagellar form. This suggests that the switch from an actin-based system to a microtubule-based system of movement is very highly regulated and synchronized across a population.

"The sequence helped us identify the genes associated with each type of motility," she said. "Although this has been done for flagellar motility, it had not been done for amoeboid motility."

The genome also reveals versatility in how Naegleria produces energy. The organism can use oxygen to burn nutrients -- glucose, amino acids or fatty acids -- for energy or, in the absence of oxygen, utilize other nutrients and possibly produce hydrogen as a byproduct.

Like the recently sequenced, free-living alga Chlamydomonas, Naegleria likely uses its metabolic flexibility to survive the intermittent hypoxia common to muddy environments, the researchers concluded. Prochnik suggests that Naegleria could help biologists understand hydrogen production that, in other organisms, might be used to produce energy.

Fritz-Laylin noted that, while the genome will be a boon to the small number of biologists who study the organism, it also will help in understanding the evolution of more complicated organisms.

"By comparing diverse organisms like Naegleria from all over the family tree of eukaryotes we can begin to understand where we come from," she said.

Other co-authors of the paper are Michael L. Ginger of the School of Health and Medicine at Lancaster University; Meredith L. Carpenter, Alex Paredez, W. Zacheus Cande and Daniel S. Rokhsar of UC Berkeley; Rochak Neupane of UC Berkeley's Center for Integrative Genomics; Alan Kuo, Jarrod Chapman, Shengqiang Shu, Asaf Salamov, Erika Lindquist, Hank Tu, Harris Shapiro, Susan Lucas and Igor V. Grigoriev of JGI; Joel B. Dacks of the University of Alberta Edmonton in Alberta, Canada; Jonathan Pham, Michael Cipriano and Scott C. Dawson of UC Davis; Joel Mancuso of Gatan Inc. in Pleasanton, Calif.; Mark C. Field of the University of Cambridge, U.K.; and Chandler Fulton of Brandeis University in Waltham, Mass.

Rokhsar is the program head for computational genomics at JGI and a professor of molecular and cell biology and of physics at UC Berkeley.

Funding for the project came primarily from the Department of Energy.

Read More Here!

Unselfish Molecules May Have Helped Give Birth to the Genetic Material of Life

ScienceDaily (Mar. 8, 2010) — One of the biggest questions facing scientists today is how life began. How did non-living molecules come together in that primordial ooze to form the polymers of life? Scientists at the Georgia Institute of Technology have discovered that small molecules could have acted as "molecular midwives" in helping the building blocks of life's genetic material form long chains and may have assisted in selecting the base pairs of the DNA double helix.New research suggests that small molecules could have acted as "molecular midwives" in helping the building blocks of life's genetic material form long chains and may have assisted in selecting the base pairs of the DNA double helix. (Credit: iStockphoto)

The research appears in the online early edition of the Proceedings of the National Academy of Sciences beginning March 8, 2010.

"Our hypothesis is that before there were protein enzymes to make DNA and RNA, there were small molecules present on the pre-biotic Earth that helped make these polymers by promoting molecular self-assembly," said Nicholas V. Hud, professor in the School of Chemistry and Biochemistry at the Georgia Institute of Technology. "We've found that the molecule ethidium can assist short oligonucleotides in forming long polymers and can also select the structure of the base pairs that hold together two strands of DNA."

One of the biggest problems in getting a polymer to form is that, as it grows, its two ends often react with each other instead of forming longer chains. The problem is known as strand cyclization, but Hud and his team discovered that using a molecule that binds between neighboring base pairs of DNA, known as an intercalator, can bring short pieces of DNA and RNA together in a manner that helps them create much longer molecules.

"If you have the intercalator present, you can get polymers. With no intercalator, it doesn't work, it's that simple," said Hud.

Hud and his team also tested how much influence a midwife molecule might have had on creating DNA's Watson-Crick base pairs (A pairs with T, and G pairs with C). They found that the midwife used could determine the base pairing structure of the polymers that formed. Ethidium was most helpful for forming polymers with Watson-Crick base pairs. Another molecule that they call aza3 made polymers in which each A base is paired with another A.

"In our experiment, we found that the midwife molecules present had a direct effect on the kind of base pairs that formed. We're not saying that ethidium was the original midwife, but we've shown that the principle of a small molecule working as a midwife is sound. In our lab, we're now searching for the identity of a molecule that could have helped make the first genetic polymers, a sort of 'unselfish' molecule that was not part of the first genetic polymers, but was critical to their formation," said Hud.

The work was supported by the National Aeronautics and Space Administration and the National Science Foundation.

Read More Here

Why birds are NOT descended from dinosaurs

By Daily Mail Reporter
Last updated at 12:02 PM on 10th June 2009

Birds did not descend from dinosaurs, scientists claim after studying how our feathered friends move and breathe.

It has been known for decades that the femur, or thigh bone in birds is largely fixed making birds 'knee runners.'

But researchers from Oregon State University found the bone also stops their lung collapsing, allowing the breathing capacity for flight.

The thigh bone stops a bird's lungs from collapsing, allowing them the breathing capacity to fly unlike dinosaurs like sauropods

Every other animal that has walked on land, including humans, elephants, lizards and theropod dinosaurs - a family that includes the T Rex, had a moveable thigh bone.

The find may force paleontologists to reconsider their long-held belief that modern birds are direct descendants of ancient, meat-eating dinosaurs.

'It's amazing we didn't understand a basic aspect of bird biology,' said US researcher Professor John Ruben.

'A velociraptor did not just spout feathers at some point and fly off into the sunset.

Running and walking is generated mostly at knee and ankle joints in birds

'Birds probably evolved on a parallel path alongside dinosaurs, starting that process before most dinosaur species even existed.'

Characteristics such as feathers, wings and a bird's unique way of moving therefore developed separately.

Dinosaurs and birds both thrived in the Cretaceous period between 145 and 65 million years ago.

The Archaeopteryx, long considered the oldest bird, lived 150million years ago, while dinosaurs emerged earlier around 200million years ago.

However, Professor Ruben said he didn't discount birds and dinosaurs sharing an ancient ancestor such as the small, reptilian 'thecodonts' that roamed Earth 250million years ago.

'It just seems pretty clear now that birds were evolving all along on their own and did not descend directly from the theropod dinosaurs,' he concluded.

There study has been published in The Journal of Morphology.

Read more: http://www.dailymail.co.uk/sciencetech/article-1192019/Why-birds-NOT-descended-dinosaurs.html#ixzz0hnJtScr9