Constantine Alexander's blog

'Selfish' DNA in animal mitochondria offers possible tool to study aging

This roundworm has been found to have "selfish" mitochondrial DNA - a biological oddity never before discovered in an animal. (Photo courtesy of Oregon State University)

Researchers at Oregon State University have discovered, for the first time in any animal species, a type of "selfish" mitochondrial DNA that is actually hurting the organism and lessening its chance to survive – and bears a strong similarity to some damage done to human cells as they age.

The findings, just published in the journal PLoS One, are a biological oddity previously unknown in animals. But they may also provide an important new tool to study human aging, scientists said.

Such selfish mitochondrial DNA has been found before in plants, but not animals. In this case, the discovery was made almost by accident during some genetic research being done on a nematode, Caenorhabditis briggsae – a type of small roundworm.

"We weren't even looking for this when we found it, at first we thought it must be a laboratory error," said Dee Denver, an OSU associate professor of zoology. "Selfish DNA is not supposed to be found in animals. But it could turn out to be fairly important as a new genetic model to study the type of mitochondrial decay that is associated with human aging."

DNA is the material that holds the basic genetic code for living organisms, and through complex biological processes guides beneficial cellular functions. Some of it is also found in the mitochondria, or energy-producing "powerhouse" of cells, which at one point in evolution was separate from the other DNA.

The mitochondria generally act for the benefit of the cell, even though it is somewhat separate. But the "selfish" DNA found in some plant mitochondria – and now in animals – has major differences. It tends to copy itself faster than other DNA, has no function useful to the cell, and in some cases actually harms the cell. In plants, for instance, it can affect flowering and sometimes cause sterility.

"We had seen this DNA before in this nematode and knew it was harmful, but didn't realize it was selfish," said Katie Clark, an OSU postdoctoral fellow. "Worms with it had less offspring than those without, they had less muscle activity. It might suggest that natural selection doesn't work very well in this species."

That's part of the general quandary of selfish DNA in general, the scientists said. If it doesn't help the organism survive and reproduce, why hasn't it disappeared as a result of evolutionary pressure? Its persistence, they say, is an example of how natural selection doesn't always work, either at the organism or cellular level. Biological progress is not perfect.

In this case, the population sizes of the nematode may be too small to eliminate the selfish DNA, researchers said.

What's also interesting, they say, is that the defects this selfish DNA cause in this roundworm are surprisingly similar to the decayed mitochondrial DNA that accumulates as one aspect of human aging. More of the selfish DNA is also found in the worms as they age.

Further study of these biological differences may help shed light on what can cause the mitochondrial dysfunction, Denver said, and give researchers a new tool with which to study the aging process.

Citation: Clark KA, Howe DK, Gafner K, Kusuma D, Ping S, et al. (2012) Selfish Little Circles: Transmission Bias and Evolution of Large Deletion-Bearing Mitochondrial DNA in Caenorhabditis briggsae Nematodes. PLoS ONE 7(7): e41433. doi:10.1371/journal.pone.0041433

Contact: Dee Denver
denvedee@cgrb.oregonstate.edu
541-737-3698
Oregon State University

 

 

Developing Policy on Moving Threatened Species Called "A Grand Challenge for Conservation"

Managed relocation—the act of purposely relocating a threatened species, population, or genotype to an area that is foreign to its natural history—is a controversial response to the threat of extinction resulting from climate change. An article in the August 2012 issue of BioScience by Mark W. Schwartz and his colleagues reports on the findings of the Managed Relocation Working Group, an interdisciplinary group of scientists, researchers, and policymakers whose goals were to examine the conditions that might justify the use of managed relocation and to assess the research being conducted on the topic. The authors note that although traditional management strategies are not likely to address the effects of climate change adequately, guidelines and protocols for managed relocation are poorly developed. "Developing a functional policy framework for managed relocation is a grand challenge for conservation," they assert.

Moving a species to a higher elevation, for instance, may allow it to survive rising temperatures or an elevated sea level, but doing do in an ethically acceptable way is fraught with both legal and political complications. Unforeseen environmental consequences of such an action may be severe—the species might become invasive in its new location, for example. Some question the appropriateness of conserving a single species at the expense of possibly disrupting an entire ecosystem. What is more, lax regulation of managed relocation may open the door to exploitative movement of species. Regulation is often dispersed among states, the federal government, and various agencies, which may have conflicting agendas, and most relevant policies and laws were not written with climate change in mind.

The current state of ecological knowledge is such that predicting accurately the effects of any particular proposed relocation is difficult and likely to remain so for the foreseeable future. This makes it hard to know which species are most likely to benefit from managed relocation. Even so, ad hoc managed relocation projects are already under way in the United States and the United Kingdom.

Schwartz and colleagues recommend action by government agencies to develop and adopt best practices for managed relocation. They urge a transparent approach, with integrated research and international involvement of scientists, policymakers, resource managers, and other stakeholders. The BioScience authors provide a list of key questions that identify the main areas of possible contention. What is needed, they write, is more research to make better predictions; clearly written policies to define the responsibilities of various parties, to enable management and to limit abuse; and stakeholder involvement to minimize social conflict.

Reference: Managed Relocation: Integrating the Scientific, Regulatory, and Ethical Challenges, Mark W. Schwartz, Jessica J. Hellmann, Jason M. McLachlan, Dov F. Sax, Justin O. Borevitz, Jean Brennan, Alex E. Camacho, Gerardo Ceballos, Jamie R. Clark, Holly Doremus, Regan Early, Julie R. Etterson, Dwight Fielder, Jaqueline L. Gill, Patrick Gonzalez, Nancy Green, Lee Hannah, Dale W. Jamieson, Debra Javeline, Ben A. Minteer, Jay Odenbaugh, Stephen Polasky, David M. Richardson, Terry L. Root, Hugh D. Safford, Osvaldo Sala, Stephen H. Schneider, Andrew R. Thompson, John W. Williams, Mark Vellend, Pati Vitt, and Sandra Zellmer

• Download Developing Policy on Moving Threatened Species Called A Grand Challenge for Conservation

Contact:Timothy M. Beardsley, Editor in Chief, BioScience, American Insitute of Biological Sciences (AIBS), 1900 Campus Commons Drive, Suite 200, Reston, VA 20191. USA.

 

 

 

North American freshwater fishes race to extinction

Rate of loss of species exceeds that of terrestrial animals

North American freshwater fishes are going extinct at an alarming rate compared with other species, according to an article in the September issue of BioScience. The rate of extinctions increased noticeably after 1950, although it has leveled off in the past decade. The number of extinct species has grown by 25 percent since 1989.

The article, by Noel M. Burkhead of the US Geological Survey, examines North American freshwater fish extinctions from the end of the 19th Century to 2010, when there were 1213 species in the continent, or about 9 percent of the Earth's freshwater fish diversity. At least 57 North American species and subspecies, and 3 unique populations, have gone extinct since 1898, about 3.2 percent of the total. Freshwater species generally are known to suffer higher rates of extinction than terrestrial vertebrates.

Extinctions in fishes are mostly caused by loss of habitat and the introduction of nonindigenous species. In North America, there are more freshwater fish species in a typical drainage to the east of the Great Continental Divide than to the west, where a greater proportion of species have gone extinct or are found nowhere else.

Estimating the number of extinctions relies on scrutiny of historical records and careful estimation procedures, since the last populations of a species are often recognized as such only in hindsight—there is typically a lag of several years from the last observation of a species and its estimated year of extinction. Estimates are complicated by the fact that, on average, 6.7 new species are discovered each year, and occasionally a species thought to have gone extinct is "rediscovered." Nonetheless, Burkhead concludes that between 53 and 86 species of North American freshwater fishes are likely to have gone extinct by 2050, and that the rate of extinction is now at least 877 times the background extinction rate over geological time.

Reference: Extinction Rates in North American Freshwater Fishes, 1900-2010. Noel M. Burkhead

Contact: Tim Beardsley
tbeardsley@aibs.org
703-674-2500 x326
American Institute of Biological Sciences

 

1.5 million years of climate history revealed after scientists solve mystery of the deep

Study successfully reconstructed temperature from the deep sea to reveal how global ice volume has varied over the glacial-interglacial cycles of the past 1.5 million years

1.5 million years of climate history revealed after scientists solve mystery of the deep Study successfully reconstructed temperature from the deep sea to reveal how global ice volume has varied over the glacial-interglacial cycles of the past 1.5 million years

Tabular iceberg. The production of tabular icebergs is a major mechanism of mass loss from the Antarctic Ice Sheet. Icebergs are calved during both rapid ice-shelf collapse and as part of the normal transfer of mass through the ice sheet to the surrounding ocean.

Scientists have announced a major breakthrough in understanding the Earth's climate machine by reconstructing highly accurate records of changes in ice volume and deep-ocean temperatures over the last 1.5 million years.

The study, which is reported in the journal Science, offers new insights into a decades-long debate about how the shifts in the Earth's orbit relative to the sun have taken the Earth into and out of an ice-age climate.

Being able to reconstruct ancient climate change is a critical part of understanding why the climate behaves the way it does. It also helps us to predict how the planet might respond to man-made changes, such as the injection of large quantities of carbon dioxide into the atmosphere, in the future.

Unfortunately, scientists trying to construct an accurate picture of how such changes caused past climatic shifts have been thwarted by the fact that the most readily available marine geological record of ice-ages – changes in the ratio of oxygen isotopes (Oxygen 18 to Oxygen 16) preserved in tiny calcareous deep sea fossils called foraminifera – is compromised.

This is because the isotope record shows the combined effects of both deep sea temperature changes, and changes in the amount of ice volume. Separating these has in the past proven difficult or impossible, so researchers have been unable to tell whether changes in the Earth's orbit were affecting the temperature of the ocean more than the amount of ice at the Poles, or vice-versa.

The new study, which was carried out by researchers in the University of Cambridge Department of Earth Sciences, appears to have resolved this problem by introducing a new set of temperature-sensitive data. This allowed them to identify changes in ocean temperatures alone, subtract that from the original isotopic data set, and then build what they describe as an unprecedented picture of climatic change over the last 1.5 million years – a record of changes in both oceanic temperature and global ice volume.

Included in this is a much fuller representation of what happened during the "Mid-Pleistocene Transition" (MPT) - a major change in the Earth's climate system which took place sometime between 1.25 million and 600 thousand years ago. Before the MPT, the alternation between glacial periods of extreme cold, and warmer interglacials, happened at intervals of approximately 41,000 years. After the MPT, the major cycles became much longer, regularly taking 100,000 years. The second pattern of climate cycles is the one we are in now. Interestingly, this change occurred with little or no orbital forcing.

"Previously, we didn't really know what happened during this transition, or on either side of it," Professor Harry Elderfield, who led the research team, said. "Before you separate the ice volume and temperature signals, you don't know whether you're seeing a climate record in which ice volume changed dramatically, the oceans warmed or cooled substantially, or both."

"Now, for the first time, we have been able to separate these two components, which means that we stand a much better chance of understanding the mechanisms involved. One of the reasons why that is important, is because we are making changes to the factors that influence the climate now. The only way we can work out what the likely effects of that will be in detail is by finding analogues in the geological past, but that depends on having an accurate picture of the past behaviour of the climate system."

Researchers have developed more than 30 different models for how these features of the climate might have changed in the past, in the course of a debate which has endured for more than 60 years since pioneering work by Nobel Laureate Harold Urey in 1946. The new study helps resolve these problems by introducing a new dataset to the picture - the ratio of magnesium (Mg) to calcium (Ca) in foraminifera. Because it is easier for magnesium to be incorporated at higher temperatures, larger quantities of magnesium in the tiny marine fossils imply that the deep sea temperature was higher at that point in geological time.

The Mg/Ca dataset was taken from the fossil record contained in cores drilled on the Chatham Rise, an area of ocean east of New Zealand. It allowed the Cambridge team to map ocean temperature change over time. Once this had been done, they were able to subtract that information from the oxygen isotopic record. "The calculation tells us the difference between what water temperature was doing and what the ice sheets were doing across a 1.5 million year period," Professor Elderfield explained.

The resulting picture shows that ice volume has changed much more dramatically than ocean temperatures in response to changes in orbital geometry. Glacial periods during the 100,000-year cycles have been characterised by a very slow build-up of ice which took thousands of years, the result of ice volume responding to orbital change far more slowly than the ocean temperatures reacted. Ocean temperature change, however, reached a lower limit, probably because the freezing point of sea water put a restriction on how cold the deep ocean could get.

In addition, the record shows that the transition from 41,000-year cycles to 100,000-year cycles, the characteristic changeover of the MPT, was not as gradual as previously thought. In fact, the build-up of larger ice sheets, associated with longer glacials, appears to have begun quite suddenly, around 900,000 years ago. The pattern of the Earth's response to orbital forcing changed dramatically during this "900,000 year event", as the paper puts it.

The research team now plan to apply their method to the study of deep-sea temperatures elsewhere to investigate how orbital changes affected the climate in different parts of the world.

"Any uncertainty about the Earth's climate system fuels the sense that we don't really know how the climate is behaving, either in response to natural effects or those which are man-made," Professor Elderfield added. "If we can understand how earlier changes were initiated and what the impacts were, we stand a much better chance of being able to predict and prepare for changes in the future."

This research has been supported by funding from the Natural Environment Research Council, The Royal Society, The Leverhulme Trust, The European Union & the University of Cambridge.

Contact: Tom Kirk
thomas.kirk@admin.cam.ac.uk
01-223-332-300
University of Cambridge

 

 

Researchers combine remote sensing technologies for highly detailed look at coastal change

Jekyll Island, Georgia, USA.

Shifting sands and tides make it difficult to measure accurately the amount of beach that's available for recreation, development and conservation, but a team of University of Georgia researchers has combined several remote sensing technologies with historical data to create coastal maps with an unsurpassed level of accuracy.

In a study published in the August issue of the journal Tourism Management, they apply their technique to Georgia's Jekyll Island and unveil a new website that allows developers, conservationists and tourists access to maps and data on beach availability, tidal ranges and erosion.

"Policymakers, coastal managers and conservationists can use this information to help make more informed decisions about managing coastal resources," said lead author Byungyun Yang, a recent graduate of the geography doctoral program and current research associate at the UGA Center for Remote Sensing and Mapping Science, part of the Franklin College of Arts and Sciences. "Tourists can easily access the same data with their computers or smartphones to help plan their trip to the beach."

Beach area is typically measured using the same costly and time-consuming land-based survey techniques that are used to plan roads, subdivisions and other projects. The UGA researchers' technique, on the other hand, combines LiDAR (light detection and ranging) data with high-resolution satellite imagery to provide an exceptional level of detail and accuracy. By shooting hundreds of thousands of pulses of light at a surface and then measuring the time it takes for the reflected light to be detected by a sensor, LiDAR provides three-dimensional elevation data with a level of accuracy that is six inches in diameter, or about the size of a grapefruit. High-resolution satellite images similar to those available through Google Earth provide two-dimensional images with a pixel size of approximately three feet by three feet, allowing the researchers to discern coastal features such as sand dunes.

By combining the sources of remote sensing data with historical shoreline maps dating to 1857, the scientists created detailed maps that precisely delineate the boundary between the ocean and the land. Historical tidal data were used to create models of how Jekyll Island would fare under various calculations of sea-level rise and under tropical storm and hurricane storm surge conditions.

"With this high-resolution data, we can model which areas are going to flood with much greater accuracy," said study co-author Tommy Jordan, associate director of CRMS. "We can see things like small indentations and the spaces between the dunes and simulate where the water would go."

The researchers note that the island has changed significantly over the past 155 years. In a pattern common in barrier islands, its northern portions have eroded while its beach area in the southern region has increased.

CRMS director, study co-author and geography professor Marguerite Madden noted that balancing the interests of tourism, conservation and development can be challenging, but said that access to high-quality data can help ensure that stakeholders make well-informed decisions.

"Now all of the interested parties—developers, land managers, the Jekyll Island Authority, the state and the people who enjoy and live on the island—have access to the same maps, images and other data," Madden said.

Contact: Byungyun Yang
yys0910@gmail.com
706-224-1546
University of Georgia

 

 

Solar power day and night

KIT controls fluctuation of renewable energies by using modern storage systems

		The new energy module of KIT generates, stores, and distributes electricity. In addition, it balances fluctuating renewable energies. Montage: PCE/KIT

Energy storage systems are one of the key technologies for the energy turnaround. With their help, the fluctuating supply of electricity based on photovoltaics and wind power can be stored until the time of consumption. At Karlsruhe Institute of Technology (KIT), several pilot plants of solar cells, small wind power plants, lithium-ion batteries, and power electronics are under construction to demonstrate how load peaks in the grid can be balanced and what regenerative power supply by an isolated network may look like in the future.

"High-performance batteries on the basis of lithium ions can already be applied reasonably in the grid today," says Dr. Andreas Gutsch, coordinator of the Competence E project. As stationary storage systems, they can store solar or wind power until it is retrieved by the grid. "When applied correctly, batteries can also balance higher load and production peaks and, hence, make sense from an economic point of view."

The Competence E project is presently developing several pilot systems consisting of photovoltaics and wind power plants coupled to a lithium-ion battery. Over a development phase of two years, a worldwide battery screening was made. "Now, we know which lithium-ion cells are suited best for stationary storage systems," says Gutsch. The first stage of the modular systems will be constructed on KIT Campus North by the end of 2012. It will have a capacity of 50 kW.

A newly developed, gear-free wind generator that is particularly suited for weak wind regions will complement electricity production by the photovoltaics system in the winter months in particular. The first stage will be able to cover electricity consumption of a medium-sized company throughout the year. In the long term, the know-how obtained will be used to develop smaller storage systems for private households as well as larger systems for industry.

Apart from the battery, the key component of the stationary energy storage system is an adapted power electronics unit for charging and discharging the battery within two hours only. Hence, the stationary storage system can be applied as an interim storage system for peak load balancing. During times of weak loads, solar energy and wind electricity are fed into the battery. At times of peak load, the energy from the photovoltaics system, wind generator, and battery is fed into the grid. Apart from load management, night discharge is of significant economic importance, because consumption of photovoltaics energy by other electric devices of the user can be increased considerably. The battery is charged in the afternoon and discharged during darkness until the next morning.

"Controlling the interaction of solar cells, wind generator, storage systems, and the grid is the central challenge," Gutsch explains. System control always has to reliably and precisely interfere with the multitude of operation states. Only this will ensure a good service life and performance of the lithium-ion batteries in the long term and, hence, economic efficiency of the complete system. "Such a system can be controlled 24 h a day and 365 days a year with detailed battery know-how. Only then will economically efficient and safe operation be guaranteed for decades," emphasizes Gutsch. After first functional tests, concrete application systems of variable power will be produced in cooperation with industry.

In spite of the high costs of lithium-ion batteries, this technology may be worthwhile today already, in particular in regions that do not have any stable grids. Smaller and larger islands, for example, are often supplied with electricity by diesel generators. In Africa and India, large areas are not supplied with electricity at all. A photovoltaics system with a coupled lithium-ion battery can be applied profitably, if appropriate system design and load profile are chosen. With decreasing costs of system components, we will achieve "battery parity" in Germany, in analogy to the "grid parity" already reached for photovoltaics-based electricity consumption by the private customer.

Karlsruhe Institute of Technology (KIT) is a public corporation according to the legislation of the state of Baden-Württemberg. It fulfills the mission of a university and the mission of a national research center of the Helmholtz Association. KIT focuses on a knowledge triangle that links the tasks of research, teaching, and innovation.

Contact: Monika Landgraf
presse@kit.edu
49-721-608-47414
Helmholtz Association of German Research Centres