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This press release is copyright Nature. Vol.441 No.7093 Dated 01 June 2006
Solely for the purpose of soliciting informed comment on Nature papers, you may show relevant parts of this document, and the papers to which it refers, to independent specialists - but you must ensure in advance that they understand and accept Nature’s embargo conditions.
This press release contains:
* Summaries of newsworthy papers:
Climate science: From greenhouse to icehouse
Planetary science: Explaining the hot pole of Enceladus
Palaeontology: Flores tools bear hallmarks of 'Hobbit' lineage
Maps: New subsidence map of New Orleans
Virology: Hide-and-seek
Protein engineering: OK Computer
Ecology: Grasses grow better in a mix
Organic chemistry: Giving life a hand?
And finally… Fish show the value of being different to the rest
* Mention of papers to be published at the same time with the same embargo
* Geographical listing of authors
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[1] [2] & [3] Climate science: From greenhouse to icehouse (pp 601-605; 606-609; 610-613; N&V)
The environmental history of the Arctic is revealed in a trio of papers published in this week's Nature.
The Arctic plays a vital role in keeping the Earth cool, because its white snow and sea ice reflect sunlight back out into space. Yet no long-term sedimentary records have previously been recovered directly from the central Arctic to constrain past environmental conditions.
Now, the Arctic Coring Expedition (ACEX) has delivered a cylinder of sediment more than 400 metres long from the Lomonosov ridge on the Arctic seabed by using ice-breaking ships and a floating drilling rig. The sediments inside the core hold a record of the climate in that region over the past 56 million years.
Appy Sluijs and colleagues report that before 55 million years ago, the surface waters of the Arctic Ocean were as warm as 18 degrees Celsius, and were completely free of ice. Then, in an event known as the Palaeocene/Eocene thermal maximum, Arctic temperatures soared to 23 degrees Celsius, more than 10 degrees Celsius higher than previous predictions. Other sediment cores from around the world record the same event, thought to have been triggered by a massive release of carbon from either volcanoes or underwater stores of methane.
But climate models cannot account for temperatures quite this high, even if they assume extreme levels of carbon dioxide. The scientists suggest that other mechanisms, such as stratospheric clouds or ocean mixing by hurricanes, could have played an additional role in keeping the seas relatively warm.
Henk Brinkhuis and colleagues report that around 49 million years ago, after sea temperatures had cooled to around 10 degrees Celsius, a freshwater fern called Azolla flourished in the Arctic Ocean. This confirms previous models of an intensified hydrological cycle at the time. The fern's later disappearance from the record coincides with a sea temperature rise, suggesting that the inflow of warmer, saltier waters from adjacent oceans had restarted.
Since the Palaeocene/Eocene thermal maximum, the Earth has experienced an overall cooling trend. In an overview of the ACEX discoveries, Kathryn Moran and colleagues report on the whole sedimentary record, which captures the transition from a warm ‘greenhouse’ world to a cooler ‘icehouse’ world. Evidence for ice-rafted debris dated to about 45 million years ago suggests that initial Northern Hemisphere cooling may have occurred earlier than previously thought. This suggests that climate changes at both poles went hand in hand.
"In all this, there's a particular challenge for those involved in climate modelling," comments Heather M. Stoll in a related News and Views article. "If they can incorporate the processes causing the hot poles in the past, we will have even greater confidence in their predictions for the future."
CONTACT
Appy A Sluijs (Utrecht University, Netherlands) Paper [1]
Tel: +31 30 253 2638; E-mail: [email protected] <mailto:[email protected]>
Henk HB Brinkhuis (Utrecht University, Netherlands) Paper [2]
Tel: +33 30 253 7691; E-mail: [email protected] <mailto:[email protected]>
Kathryn Moran (University of Rhode Island, Narragansett, RI, USA) Paper [3]
Tel: +1 401 874 6421; E-mail: [email protected] <mailto:[email protected]>
Heather M Stoll (Williams College, Williamstown, MA, USA) N&V Author
Tel: +1 413 597 4541; E-mail: [email protected] <mailto:[email protected]>
[4] Planetary science: Explaining the hot pole of Enceladus (pp 614-616)
The Cassini spacecraft mission has found that one of Saturn’s moons, Enceladus, has a peculiarly 'active' south pole. There, water vapour appears to be streaming out of huge cracks in the ice that covers Enceladus's surface, suggesting that there is liquid water beneath. Francis Nimmo and Robert Pappalardo explain in Nature this week why Enceladus's south pole seems to be so warm.
Planetary scientists have assumed that the heat comes, in effect, from Saturn itself: because the moon is so near this giant planet, Saturn's gravity tugs on the fabric of Enceladus and heats it. Jupiter's moon Io is turned into a fiery, volcanic world by the same effect, called tidal heating. But why does this happen only at Enceladus's south pole?
The researchers think that a plume of relatively warm ice at any point within the moon's icy shell could have caused the moon to reorient itself so that the warm region becomes the new south pole. This happens because the warmer ice expands and becomes less dense, and the resulting uneven distribution of mass shifts the rotational axis of the moon.
But the warm, mushroom-shaped blob - or diapir - might not actually be within the ice shell at all: it could be in Enceladus's rocky core. Or there could be diapirs in both regions. If the diapir is indeed in the ice, then Nimmo and Pappalardo say that the soft part of this shell, below a hard, frigid crust, would have to be at least 0.5 kilometres thick. If it's in the rocky core, then there cannot be a subsurface layer of liquid water between this and the ice shell, since that would lubricate the interface and prevent reorientation from occurring. These and other predictions may make it possible to test the idea of reorientation once more observations of Enceladus have been made.
CONTACT
Francis F Nimmo (University of California, Santa Cruz, CA, USA)
Tel: +1 831 459 1783; E-mail: [email protected] <mailto:[email protected]>
[5] Palaeontology: Flores tools bear hallmarks of 'Hobbit' lineage (pp 624-628)
Homo floresiensis - the tiny, Hobbit-like species that survived until 12,000 years ago on the remote Indonesian island of Flores - probably knew how to make stone tools, despite having a brain only the size of a grapefruit. A cache of far older tools found nearby shows a strikingly similar style to the ones found alongside H. floresiensis, meaning that the tiny species probably inherited a tradition of making them.
Some palaeontologists had argued that H. floresiensis would not have had the brainpower to make stone tools, and that the various flints found alongside their remains at Liang Bua cave must instead have been made by modern humans. But an analysis by Adam Brumm and colleagues in this week's Nature shows that the tools come from a much older tradition, meaning that they were probably made by people who evolved on the island, rather than the modern humans who subsequently landed there.
Brumm and his team make their claim on the basis of more than 500 artefacts found some 50 kilometres from Liang Bua and dating from more than 800,000 years ago. Despite being hundreds of millennia older than the Liang Bua tools, the flint blades were made in the same way, suggesting that H. floresiensis inherited their skills from their ancestors, H. erectus, who lived on Flores before them.
CONTACT
Adam R Brumm (Australian National University, Canberra, Australia)
Tel: +61 2 6125 7613 wk; E-mail: [email protected] <mailto:[email protected]>
[6] Maps: New subsidence map of New Orleans (pp 587-588)
A new map showing the extent of subsidence in the city of New Orleans before Hurricane Katrina struck is unveiled in a Brief Communication in this week’s Nature. It is well known that ground subsidence in New Orleans makes the city vulnerable to flooding, and this study reveals that parts of the city sank rapidly in the three years before the hurricane hit in August 2005.
Researchers led by Timothy Dixon analysed a series of radar images captured by Canada’s RADARSAT satellite. Using a technique known as ‘synthetic aperture radar’ measurement, which focuses on ground structures that reflect radar, they report widespread subsidence between 2002 and 2005. The team propose that ground disturbance was mainly in the vertical direction, and suggest that much of New Orleans is sinking by about six millimetres, on average, every year.
Dixon and colleagues also found that there was substantial subsidence beneath those sections of the Mississippi floodbank system that were breached by the floods following Hurricane Katrina. They point out that weakness in the levees, indicated by their rapid sinking, could explain why they were overtopped during the peak of the storm.
CONTACT
Timothy T H Dixon (University of Miami, FL, USA)
Tel: +1 305 421 4660; E-mail: [email protected] <mailto:[email protected]>
[7] Virology: Hide-and-seek (AOP)
DOI: 10.1038/nature04836
***This paper will be published electronically on Nature's website on 31 May at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 01 June, but at a later date.***
Scientists have identified a microRNA responsible for allowing the herpes simplex virus to lay low in sensory neurons without inducing cell death. Although the gene responsible has already been identified, scientists were puzzled by not being able to identify its encoded protein.
Herpes simplex virus can cause latent infections in the peripheral nervous system, from which it can be reactivated repeatedly. Here, in a paper published online this week by Nature, Nigel Fraser and colleagues show that the viral latency gene, LAT, encodes a microRNA. This microRNA downregulates a signalling pathway that would otherwise cause cell death. Latency was lost and cell death occurred when cells were infected with an altered portion of the gene that could not make the microRNA.
The authors argue that this finding offers new insights into the host-virus interaction and co-evolution.
CONTACT
Nigel W Fraser (University of Pennsylvania, Philadelphia, PA, USA)
Tel: +1 215 898 3847; E-mail: [email protected] <mailto:[email protected]>
[8] Protein engineering: OK Computer (pp 656-659)
One of the great remaining problems in computational protein design involves the redesign of a DNA-modifying protein so that it recognizes, and alters, a new DNA sequence. For example, changing the specificity of a nuclease - a protein that cuts DNA at a specific site - could be beneficial for a range of biotechnological and medical applications.
In this week’s Nature, David Baker and colleagues have shown that it is possible to modify the sequence specificity of a ‘homing endonuclease’ called I-MsoI. They used a computational approach to screen a virtual library of mutant proteins and predicted which amino acids needed to be changed to re-engineer this enzyme so that it recognized, and cleaved, a new DNA sequence. The mutant protein was highly active and was able to cleave the new DNA sequence, but did not modify the original sequence. The authors hope to redesign this and other DNA-modifying enzymes to alter a range of DNA sequences, so that they could specifically target almost any sequence in the genome. These computationally designed proteins may be useful in a range of medical and biotechnological applications, including gene therapeutic and other targeted genomics applications.
CONTACT
David D Baker (University of Washington, Seattle, WA, USA)
Tel: +1 206 543 1295; E-mail: [email protected] <mailto:[email protected]>
[9] Ecology: Grasses grow better in a mix (pp 629-632)
A decade-long study by David Tilman and his colleagues, which is to be published in this week’s Nature, shows that ecosystems containing more species are more stable and productive - a finding with implications for agriculture and conservation.
There is a long-standing debate about whether biologically diverse ecosystems are more stable, and hence whether farmlands and forests depleted of biodiversity by human activity become more vulnerable and/or less productive. The team reports the findings of the longest study conducted to date that tests this idea experimentally. They established 168 plots containing between one and 16 perennial grassland species and measured the biomass they produced.
They found that the productivity of plots containing more species was more constant over time and was dependent on root mass. The results suggest that a reliable and efficient supply of animal fodder or biofuels would be best achieved by a diversity of plants rather than monocultures.
CONTACT
David DT Tilman (University of Minnesota, St. Paul, MN, USA)
Tel: +1 612 625 5743; E-mail: [email protected] <mailto:[email protected]>
[10] Organic chemistry: Giving life a hand? (pp 621-623)
A new way to control the handedness of molecules - whether their chemical structure is 'left-handed' or 'right-handed' - is presented in this week's Nature by Donna Blackmond and colleagues. As well as having potentially useful industrial applications, for example in pharmaceutical chemistry, the result also hints at why the chemistry of life has a preference for a particular ‘handedness’.
Chiral molecules can adopt two different structures that are mirror images of one another, like a left and right hand. Because these two alternative forms of chiral drug molecules can have very different biochemical or physiological effects, controlling the chirality of drugs is hugely important. This sensitivity of biology to molecular handedness stems from the fact that key biomolecules, particularly the amino acids that make up proteins, are themselves chiral - those in our cells are all left-handed. But no one knows why life evolved to use only left-handed amino acids.
Blackmond and colleagues have found a way to obtain very high selectivity for one chiral product or its mirror image in a chemical reaction catalysed by an amino acid. Under the right conditions, certain amino acids will form two types of crystal, one with an equal mixture of the two forms and one consisting of just one chiral form - leaving an excess of the other form in solution. In this way, a mixture that starts with only a small excess of one form over the other becomes spontaneously separated. The researchers say that a process like this might have operated in the chemical mixtures from which life emerged, which are believed to have contained a variety of amino acids.
CONTACT
Donna DG Blackmond (Imperial College London, UK)
Tel: +44 20 7594 1193; E-mail: [email protected] <mailto:[email protected]>
[11] And finally… Fish show the value of being different to the rest (pp 633-636)
It’s good to be different, suggests a study of the evolutionary effects of colour variation in fish. A study of male guppies (Poecilia reticulata) shows that those with rare colour patterns tend to escape the attentions of predators more easily.
Researchers, led by Kimberly Hughes, removed the male guppies from pools within river systems in Trinidad, sorted them into different groupings according to their colour pattern, and then restored them in such a way that certain groups were in a minority in a given pool. Less than three weeks later, they returned to the pools and found that fish with a rare colour pattern had enjoyed greater survival rates.
The researchers, who publish their findings in this week’s Nature, suggest that predators may overlook rare types when hunting, perhaps because they form a ‘search image’ in their minds that means they are more likely to target common variants. This process, together with female preference for distinctive rare males, may explain how the population avoids becoming a uniform group of conformists.
CONTACT
Kimberly A. Hughes (University of Illinois, Urbana, IL, USA)
Tel: +1 217 244 6632; E-mail: [email protected] <mailto:[email protected]>
ALSO IN THIS ISSUE…
[12] Dimensional reduction at a quantum critical point (pp 617-620)
[13] Assembly of the inner rod determines needle length in the type III secretion injectisome (pp 637-640)
[14] Hrr25-dependent phosphorylation state regulates organization of the pre-40S subunit (pp 651-655)
ADVANCE ONLINE PUBLICATION
***These papers will be published electronically on Nature's website on 31 May at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included them on this release to avoid multiple mailings they will not appear in print on 01 June, but at a later date.***
[15] Signal peptide peptidase is required for dislocation from the endoplasmic reticulum (AOP)
DOI: 10.1038/nature04830
[16] Molecular architecture of axonemal microtubule doublets revealed by cryo-electron tomography (AOP) DOI: 10.1038/nature04816
GEOGRAPHICAL LISTING OF AUTHORS…
The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.
AUSTRALIA
Canberra: 5
New South Wales: 5
AUSTRIA
Vienna: 13
CANADA
Toronto: 11
FRANCE
Aix-en-Provence: 1, 3
Bordeaux: 3
Talence: 1, 2
GERMANY
Bremerhaven: 1, 2, 3
Heidelberg: 14
Kiel: 3
INDONESIA
Bandung: 5
ITALY
Milan: 6
Padova: 1, 2, 3
JAPAN
Chikusa: 3
Fukuoka: 1, 2, 3
Ibaraki: 1, 2, 3, 10
Kashiwa: 12
Sapporo: 1, 2, 3
Sendai: 1, 2, 3
Suita: 13
Yamagata: 1, 2, 3
Yokosuka: 1, 2, 3
NETHERLANDS
Leiden : 2, 5
Texel: 1, 2
Utrecht: 1, 2, 3
NORWAY
Allegaten: 3
Tromso: 1, 2, 3
PANAMA
Panama City: 11
RUSSIA
St Petersburg: 3
SWEDEN
Stockholm: 1, 2, 3
SWITZERLAND
Basel: 14
Zurich: 3
UNITED KINGDOM
Aberdeen: 1, 2, 3
Blackpool: 2
Edinburgh: 1, 2, 3, 14
London: 1, 2, 3, 10
Southampton: 1, 2, 3
UNITED STATES OF AMERICA
California
Berkeley: 16
Pasadena: 4
Riverside: 11
Santa Cruz: 4
Stanford: 12
Colorado
Boulder: 4
Connecticut
New Haven: 1, 13
Florida
Miami: 6
Tallahassee: 12
Illinois
Lake Forest: 11
Urbana: 11
Indiana
West Lafayette: 1, 2
Louisiana
Baton Rouge: 6
Maryland
Silver Spring: 6
Massachusetts
Boston: 1, 2, 3
Cambridge: 15
Waltham: 13
Michigan
Ann Arbor: 1, 2, 3
Minnesota
St Paul: 9
Nebraska
Lincoln: 9
New Mexico
Los Alamos: 12
Pennsylvania
Philadelphia: 7
Rhode Island
Narragansett: 1, 2, 3
Texas
Houston: 1, 2, 3
Virginia
Harrisonburg: 1, 2, 3
Reston: 1, 2, 3
Washington
Seattle: 8
PRESS CONTACTS…
For North America and Canada
Katie McGoldrick, Nature Washington
Tel: +1 202 737 2355; E-mail: [email protected] <mailto:[email protected]>
For Japan, Korea, China, Singapore and Taiwan
Rinoko Asami, Nature Tokyo
Tel: +81 3 3267 8751; E-mail: [email protected] <mailto:[email protected]>
For the UK/Europe/other countries not listed above
Helen Jamison, Nature London
Tel: +44 20 7843 4658; E-mail [email protected] <mailto:[email protected]>
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