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This press release is copyright Nature.
VOL.439 NO.7078 DATED 16 FEBRUARY 2006
This press release contains:
* Summaries of newsworthy papers:
* Astrophysics: Now you see it, now you don't
* Neurobiology: Monkey brains weigh up good and bad
* Climate: Continental-scale river flow increases as plants sweat less
* Planetary science: Near-Sun origin of iron meteorites
* Synthetic biology: Bottom's up to gene control
* Plant biology: Inbreeding prophylactic exposed
* Green chemistry: Ionic liquids are a gas
* Evolution: Uncoiling snake evolution
* And finally...Invading cane toads make long-legged leap into new territory
* Geographical listing of authors
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[1] Astrophysics: Now you see it, now you don't (pp 817-820)
Some stars emit radio waves fairly steadily, while some compact neutron
stars flash like beacons in the sky. But others brighten and dim
erratically, without any discernible pattern to the outbursts, according to
Maura McLaughlin in research published by Nature this week.
The team have discovered a new class of astrophysical objects, which they
call rotating radio transients (RRATs). These emit short bursts of radio
waves, lasting just 2 to 30 milliseconds, interspersed with 'dark' spells of
several minutes to hours. The researchers say that the radio signals from
these objects are typically detectable for less than a second in total each
day.
The researchers have discovered eleven such objects in a four-year survey
conducted to look for transient radio sources of this kind. Although the
bright events are so short, they nevertheless show signs of periodicity for
ten of the objects, repeating in cycles of 0.4 to 7 seconds. In other words,
the objects are rather like lighthouses that are plagued by frequent, random
and prolonged power cuts.
What causes these shutdowns? McLaughlin and colleagues aren't sure what
RRATs are yet, beyond supposing that they are a kind of rotating neutron
star. But they seem to be plentiful: the researchers estimate that there
should be many more of them in our Galaxy than there are regularly pulsing
neutron stars. It's just that, because they are 'dark' most of the time,
they can only be seen by looking hard and long.
CONTACT
Maura McLaughlin (University of Manchester, Jodrell Bank Observatory,
Macclesfield, UK)
Tel: +1 215 886 9735 (until 18th Feb) then + 44 1477 572672; E-mail:
[email protected] <mailto:[email protected]>
OR
Andrew Lyne (University of Manchester, Jodrell Bank, Macclesfield, UK)
Co-author
Tel: +44 1477 571321; E-mail: [email protected] <mailto:[email protected]>
[2] Neurobiology: Monkey brains weigh up good and bad (pp 865-870)
Researchers studying monkeys' brains have discovered distinct groups of
nerve cells responsible for determining whether a stimulus is 'good' or
'bad'. These cells seem to function as part of the pathway that allows the
brain to learn whether certain images are pleasant or unpleasant, and to
respond appropriately.
Daniel Salzman and his colleagues trained rhesus monkeys (Macaca mulatta) to
ascribe 'good' or 'bad' values to certain visual stimuli, by presenting
different images to the monkeys and following them with either a tasty drink
or an unpleasant puff of air in the face. While doing this, they scanned
neurons in a brain region called the amygdala, known to be involved in
processing emotions.
The researchers then swapped the stimuli around, so that previously 'good'
stimuli were now associated with the unpleasant outcome, and vice versa. As
they report this week in Nature, the activity of amygdala neurons changed as
the monkeys got to grips with the new arrangement, so that the 'good'
neurons now became activated in response to the new 'good' stimuli. The
presence of neurons that signify either 'good' or 'bad' visual stimuli may
therefore underlie the process by which we learn how to respond to the world
around us, the researchers conclude.
CONTACT
Daniel Salzman (Columbia University, New York, NY, USA)
Tel: +1 212 543 6931 x400; E-mail: [email protected]
<mailto:[email protected]>
[3] Climate: Continental-scale river flow increases as plants sweat less (pp
835-838; N&V)
Changes in plant water use caused by higher concentrations of atmospheric
carbon dioxide (CO2) are contributing to increasing global river runoff,
according to new research by Nicola Gedney and colleagues published in this
week's Nature.
Despite increasing water consumption by humans, there has been a general
upward trend in continental-scale river runoff over the past century. In
this study, the researchers use a mechanistic land-surface model and a
statistical 'fingerprinting' method to investigate plausible contributors to
the observed increases in runoff. They find that reduced plant transpiration
due to CO2-induced stomatal closure has a significant effect on runoff
trends. As plants transpire (or sweat) less, they draw less water from the
soil. The researchers conclude that as CO2 concentrations rise in the
future, reduced plant water usage is likely to increase both the
availability of freshwater and the risk of flooding.
Until now, this effect has been neglected in projections of future water
resources. Although laboratory experiments have shown that the stomatal
openings of many plant species reduce in the presence of elevated CO2
levels, it was unclear whether this would have any significance for the
global water cycle. This analysis suggests that raised CO2 levels may
already influence the water balance at the land surface. In an accompanying
News and Views article, Damon Matthews describes the findings as "an
important step forward in our understanding of the diverse and complex ways
in which human activities are affecting the global climate system".
CONTACT
Nicola Gedney (Met Office, Wallingford, UK)
Tel: +44 1491 692530; E-mail: [email protected]
<mailto:[email protected]>
Damon Matthews (University of Calgary, Calgary, Canada)
Tel: +1 403 220 5593; E-mail: [email protected]
<mailto:[email protected]>
[4] Planetary science: Near-Sun origin of iron meteorites (pp 821-824)
Most iron meteorites come from the asteroid belt, a pile of rubble that
orbits the Sun between Mars and Jupiter. But in this week's Nature,
astronomers suggest that they originally formed much closer to the Sun.
William Bottke and colleagues use a blend of computer models to show that
the parent bodies of iron meteorites coalesced in the same region that
contains the terrestrial planets (Mercury, Venus, Earth and Mars). These
bodies were then melted by heat given off during the decay of radioactive
elements they contained.
Collisions and scattering sent this material spinning out towards the region
between Mars and Jupiter. This suggests that some asteroids may even be
remnants of the long-lost precursor material that formed the Earth.
CONTACT
William Bottke (Southwest Research Institute, Boulder, CO, USA)
Tel: +1 303 546 6066; E-mail: [email protected]
<mailto:[email protected]>
[5] Synthetic biology: Bottom's up to gene control (pp 856-860)
Biologists are all abuzz about synthetic biology, which involves designing
and building new biological parts and systems from their individual
components. A study in this week's Nature shows one way that this might be
possible.
James Collins and his team engineered a region of bacterial DNA so that they
could artificially turn on one gene, and turn off another, by adding
chemicals to the bacterial cells. They tested gene expression under several
different conditions, and used this information to build a mathematical
model that mirrored the behaviour of this gene network.
Crucially, the team then showed that predictions made by the model about how
the genes would act under certain experimental conditions closely matched
how the network really behaved in bacteria, where many other genes and
proteins could potentially complicate the situation.
The authors say their findings demonstrate that models of relatively simple
processes in the cell can be used to predict the behaviour of larger, more
complex ones - a so-called 'bottom-up' approach.
CONTACT
James Collins (Boston University, Boston, MA, USA)
Tel: +1 617 353 0390; E-mail: [email protected] <mailto:[email protected]>
[6] Plant biology: Inbreeding prophylactic exposed (pp 805-810)
A study in this week's Nature reveals how certain plants prevent inbreeding
by blocking fertilization by their own 'self' pollen or pollen from closely
related plants.
Because plants largely rely on wind or animals to distribute pollen, they
use a variety of mechanisms to control mating. Researchers know that the
female parts of many plant species make a potentially toxic molecule -
called S-RNase - in the structures within the flower that receive the pollen
and which only kills 'self' pollen. Bruce McClure and his colleagues show
how this selectivity is achieved.
When S-RNase is taken up by sexually compatible pollen, it is stowed safely
away inside a cellular compartment and one of the proteins needed for its
release is degraded. But in the case of incompatible 'self' pollen, the
protein responsible for releasing S-RNase remains active and S-RNase is
freed from its cellular cage. This allows S-RNase to exert its toxic effects
on the pollen, thus causing the plant to reject it.
CONTACT
Bruce McClure (University of Missouri-Columbia, Columbia, MO, USA)
Tel: +1 573 884 5716; E-mail: [email protected]
<mailto:[email protected]>
[7] Green chemistry: Ionic liquids are a gas (pp831-834; N&V)
Ionic liquids have been advocated as 'green' solvents for industrial
chemistry, because they were thought not to evaporate at all, and thus to
release no toxic fumes. But that's not quite so, according to Luís Rebelo
and colleagues in this week's Nature. They show that some ionic liquids do
indeed evaporate, and can therefore be distilled.
This does not undermine the green credentials of these liquids, which are
composed of charged ions rather than neutral molecules like most ordinary
liquids. The various ionic liquids that Rebelo and colleagues have
investigated do have very low volatility - very little vapour escapes from
the surface of the liquid. But if heated to between 200 and 300 *C, the
liquids will evaporate and then condense again when cooled.
That is a good thing, the researchers say, because it means that
distillation can be used to purify the liquids. This will allow them to be
recycled when they are used as solvents. The belief that such distillation
was not possible has prevented the use of ionic liquids in some applications
where they would otherwise be beneficial.
CONTACT
Luis Rebelo (New University of Lisbon, Oeiras, Portugal)
Tel: +351 214469441; E-mail: [email protected]
<mailto:[email protected]>
Peter Wasserscheid (University of Erlangen, Erlangen, Germany)
E-mail: [email protected]
<mailto:[email protected]>
[8] Evolution: Uncoiling snake evolution (pp 839-842)
The discovery of fossilized snake skulls raises questions on snake evolution
in this week's Nature. The well-preserved fossils together form an almost
complete skull and mandible, and belong to the extinct snake Yurlunggur,
which lived 25-12 million years ago.
John Scanlon unearthed the fossils at the Riversleigh World Heritage site in
Australia. Yurlunggur belongs to a group of snakes called madtsoiids, which
lived in Australia until the Pleistocene. The genus had previously only been
known from fossils of its vertebrae, because archaic snake skulls are often
crushed by sediment. The freshwater carbonate deposits in the Riversleigh
area provide ideal conditions for fossil preservation, and it's believed
that the finding may include more than one new species.
This discovery has enabled the author to draw links between Yurlunggur and
the best-known species from this era, Wonambi naracoortensis. These links
support the view thatmadtsoiids represent perhaps the most primitive snake
lineage.
CONTACT
John Scanlon (Riversleigh Fossil Centre, Mount Isa, Australia)
Tel: +61 7 4749 1555; E-mail: [email protected]
<mailto:[email protected]>
[9] And finally... Invading cane toads make long-legged leap into new
territory (pp 830)
The introduction of cane toads (Bufo marinus) to Australia more than 70
years ago, initially to combat insect pests on sugar cane crops, has turned
into an ecological disaster. The toads, which now have a range covering more
than a million square kilometres of the continent, are toxic and pose a real
threat to native species. What's more, the problem is growing all the time -
new research shows that toads at the forefront of the invasion have longer
legs than those in older populations, meaning that they can encroach ever
faster on new territory.
Richard Shine and colleagues stationed themselves at the invasion front 60
kilometres east of Darwin, in the north of the country, and waited for the
toads - which can travel almost 2 kilometres in a single night - to arrive.
When they did, they found that the first to arrive had longer legs than
those that arrived later.
Toads in older, established populations in Queensland have shorter legs, the
researchers report in a Brief Communication in this week's Nature, showing
that evolution is favouring longer-legged toads among those leading the
charge into new territory. This is consistent with the fact that the
invasion is gaining pace - from the 1940s to the 1960s, the toads advanced
by around 10 kilometres per annum; today their invasion front claims more
than 50 kilometres each year.
CONTACT
Richard Shine (The University of Sydney, Sydney, Australia)
Tel: +61 2 9351 3772; E-mail: [email protected]
<mailto:[email protected]>
ALSO IN THIS ISSUE...
[10] A spin triplet supercurrent through the half-metallic ferromagnet
CrO2 (pp 825-827)
[11] Scale invariance and universality of force networks in static
granular matter (pp 828-830)
[12] Proteorhodopsin lateral gene transfer between marine planktonic
Bacteria and Archaea (pp847-850)
[13] Copy number polymorphism in Fcgr3 predisposes to glomerulonephritis
in rats and humans (pp 851-855)
[14] The primate amygdala represents the positive and negative value of
visual stimuli during learning (pp 865-870)
[15] Crystal structures of catalytic complexes of the oxidative DNA/RNA
repair enzyme AlkB
(pp 879-884)
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.
ARGENTINA
Cordoba: 6
AUSTRALIA
Adelaide: 8
Epping: 1
Mount Isa: 8
Sydney: 9
CANADA
Calgary: 3
Mississauga: 5
Vancouver: 1
DENMARK
Copenhagen: 12
FRANCE
Nice: 4
GERMANY
Erlangen: 7
Garching: 10
ITALY
Capoterra: 1
Monserrato: 1
MEXICO
Mexico City: 6
THE NETHERLANDS
Amsterdam: 11
Delft: 10
Leiden: 11
PORTUGAL
Oeiras: 7
UK
Belfast: 7
Exeter: 3
London: 13
Macclesfield: 1
Oxford: 11, 13
Reading: 3
Wallingford: 3
Winfrith Newburgh: 3
USA
Alabama
Tuscaloosa: 10
California
La Jolla: 5
Colorado
Boulder: 4, 7
Georgia
Athens: 6
Massachusetts
Boston: 5
Cambridge: 12
Missouri
Columbia: 6
New Jersey
Monmouth Junction: 15
New York
Ithaca: 1
New York: 1, 14, 15
North Carolina
Chapel Hill: 5
Rhode Island
Providence: 10
PRESS CONTACTS...
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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
Ruth Francis, Nature London
Tel: +44 20 7843 4562; E-mail [email protected]
<mailto:[email protected]>
Zoe Corbyn, Nature London
Tel: +44 20 7843 4658; E-mail: [email protected]
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