How water-walking insects defy gravity; Replicating machines, DNA style; Lost (and found) in space; First potential receptor for plant hormone gibberellin; Malnutrition at sea; Acidifying oceans could doom seashells and corals sooner than expected

Porous material has huge, handed holes; Understanding antibodies; The Dune thing; Diatoms delve deep for nutrients to stay alive; Human protein interactions go large scale; Corrupting the bacterial quorum; Quicksand won't suck you right in

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VOL.437 NO.7059 DATED 29 SEPTEMBER 2005

* Animal behaviour: How water-walking insects defy gravity
* Robotics: Replicating machines, DNA style
* Astrophysics: Lost (and found) in space
* Botany: First potential receptor for plant hormone gibberellin
* Oceanography: Malnutrition at sea
* Climate: Acidifying oceans could doom seashells and corals sooner
than expected
* Materials: Porous material has huge, handed holes
* Virology: Understanding antibodies
* Physical sciences: The Dune thing
* Ecology: Diatoms delve deep for nutrients to stay alive
* Cell biology: Human protein interactions go large scale
* Microbiology: Corrupting the bacterial quorum
* And finally... Quicksand won't suck you right in
* Mention of papers to be published at the same time with the same
* Geographical listing of authors

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[1] Animal behaviour: How water-walking insects defy gravity (pp733-736)

Ponds and puddles might appear flat to the human eye, but to a tiny insect
they can be a rugged and treacherous terrain. Researchers have now shown
that water-walking insects use a unique mode of propulsion to climb the
steeply sloping meniscus at the edge of a puddle, despite it being a steep,
slippery wall of water.

Using high-speed video, David Hu and John Bush captured the
meniscus-climbing action of three water-walking insect species. As the
researchers report in this week's Nature, the two-millimetre-long insects
adopt a special posture to create capillary forces that drive them up the
slope at almost thirty body lengths per second , without any need to move
their legs during the journey.

They do this by virtue of their 'wetting' front and rear legs, which can
pull at the surface of the water and raise it into a tiny peak. Meanwhile,
the central pair of legs presses down on the water, forming dimples in its
surface. Because the insects are so small, these perturbations create
capillary forces that suck them up the slope, similar to the way in which
water is sucked up a thin tube by the force of its own surface tension.

John Bush (Massachusetts Institute of Technology, Cambridge, MA, USA)
Tel: +1 857 991 9280; E-mail: [email protected]

[2] Robotics: Replicating machines, DNA style (p636)

Welcome the robots that can copy themselves - and fix any mistakes they
might make. Electromechanical engineers have created a set of machines that
can fashion copies of themselves from randomly circulating components, much
as DNA copies itself from the chemical building blocks floating around in
biological cells.

The system starts with a single template string made up of two different
colours in a certain sequence, explain its creators Joseph M. Jacobson and
colleagues in a Brief Communication in this week's Nature. The string floats
around on a cushion of air - along the same lines as an air-hockey table -
surrounded by loose, randomly moving building blocks of the two colours.

When two blocks come into contact, they can latch together. But the strings
are also fitted with an electronics package that checks the colour of the
neighbouring block, and can trigger them to unlatch if the sequence is not
correct. Thus, over time, the number of strings matching the original
template can grow exponentially, limited only by the supply of building
blocks. If the process can be sufficiently miniaturized, the authors hope it
could prove valuable in automating industrial assembly processes.

Joseph M. Jacobson (Massachusetts Inst of Technology, Cambridge, MA, USA)
Tel: +1 617 253 7209; E-mail: [email protected]

[3] Astrophysics: Lost (and found) in space (pp707-710)

Dark matter - the mysterious stuff that seems to comprise most of the matter
in the Universe - was recently suggested to be even more mysterious, because
of its apparent absence from some galaxies. But it may be there after all,
say Avishai Dekel and colleagues in this week's Nature. They have
investigated the claim, made a few years ago, that the slow speeds of
outlying stars in elliptical galaxies are inconsistent with the presence
there of dark matter. The researchers show that these stars can have low
velocities even if the galaxies contain large amounts of dark matter.

Dark matter is so-called because it can't be seen directly. But astronomers
have inferred that it permeates galaxies because the motions of stars seem
to show that they are being gravitationally attracted by something more than
all the other visible stars and dust. Over four-fifths of the mass in the
Universe seems to be made of this stuff. No one knows what it consists of,
but it doesn't seem to be any of the known forms of matter.

Elliptical galaxies, some of which are probably formed by the merging of
smaller galaxies, ought in this picture to contain just as much dark matter
as any other galaxy. But the paths of the slow-moving stars that have been
seen in elliptical galaxies don't seem to bear the imprint of dark matter's
gravitational tug, which was expected to speed them up. Dekel and colleagues
have now performed computer simulations of the merging events in which
elliptical galaxies are formed, and they find that these processes can
produce stars in elongated orbits that move slowly even when the merged
galaxies contain their usual complement of dark matter. So it may still be
unexplained - but it does seem to be there after all.

Avishai Dekel (Hebrew University, Jerusalem, Israel)
Tel: +972 2 6584100; E-mail: [email protected]

[4] Botany: First potential receptor for plant hormone gibberellin
(pp693-698; N&V)

The plant hormone gibberellin plays an essential role in plant germination,
stem elongation and flower development. But until now, no one had isolated a
receptor for this critical hormone. This week, Makoto Matsuoka and
colleagues provide evidence that the GID1 gene in rice encodes an unknown
soluble protein receptor for this hormone.

The researchers describe a mutant variety of rice that cannot produce
fertile flowers, among other abnormalities. By comparing its DNA with that
from other varieties of rice, they show that abnormalities in the GID1 gene
disrupt the plant's ability to sense gibberellin. In another part of the
experiment, they show that overexpression of the gene product results in
long, spindly plants - the expected result from oversensitivity to the
hormone. The results of the study, which highlight the first soluble
gibberellin receptor, appear this week in Nature.

"The successful hunt carried out by [Ueguchi-Tanaka et al.] not only takes
the plant hormone debate further, but the enhanced molecular understanding
of gibberellin signalling may also presage a new green revolution," write
Dario Bonetta and Peter McCourt in a related News and Views article.

Makoto Matsuoka (Nagoya University, Aichi, Japan)
Tel: +81 52 789 5218; E-mail: [email protected]

Peter McCourt (University of Toronto, Canada)
Tel: +1 416 978 0523; E-mail: [email protected]

[5] Oceanography: Malnutrition at sea (pp687-692; N&V)

How does life in the oceans get its nutrients? Conventional thinking on this
issue is literally knocked sideways by findings reported this week in Nature
by Jaime Palter and co-workers. They show that, while the availability of
nutrients for plankton growth is normally considered to depend on the
vertical circulation of water masses, horizontal water movements can also
exert a crucial influence. Understanding the factors that limit plankton
growth - and thus the base of the oceanic food web - is vitally important
for predicting, for example, changes in fish stocks.

Palter and colleagues find that water a few hundred metres below the surface
of the subtropical North Atlantic Ocean (east of the Gulf of Mexico) can
become depleted in nutrients because of an influx of nutrient-poor water
from a region along the north edge of this part of the ocean. The
subtropical North Atlantic contains a circulating current called a gyre.
Nutrients, on which plankton growth depends, are delivered to the gyre by
vertical, conveyor-belt circulation of water, driven in part by winds at the
ocean surface. The upwelling water tends to be rich in the chemical
compounds such as nitrate and phosphate that organisms need for growth.

The new findings, however, reveal that this nutrient supply can be
undermined by water penetrating into the gyre from the north thanks to a
process called North Atlantic Subtropical Mode Water (STMW) formation. From
January to around April each year, there is a 'bloom' of plankton in the
region of STMW formation, which eats up all the nutrients in that part of
the ocean. This water, the researchers show, can consequently have much
lower nutrient concentrations than those typical of the subtropical North
Atlantic. The depleted water then gets carried southwards into the
subtropical gyre, introducing low nutrient levels that can be seen at least
2,000 kilometres to the south. A related News & Views article by Marina Lévy
accompanies this research.

Jaime Palter (Duke University, Durham, NC, USA)
Tel: +1 919 684 6227; E-mail: [email protected]

Marina Lévy (Institut Pierre Simon LaPlace, Paris, France)
Tel: +33 1 44 27 2707; E-mail: [email protected]

[6] Climate: Acidifying oceans could doom seashells and corals sooner than
expected (pp681-686)

As carbon dioxide in the atmosphere dissolves into the Earth's oceans, the
water becomes more acidic and the concentration of carbonate ions is
reduced, threatening to prevent certain marine life and corals from growing
their chalky shells. Research in this week's Nature predicts that if carbon
dioxide emission from burning fossil fuels continues at its present rate,
oceanic ecosystems could be badly hit within decades, not centuries as
previously suggested.

James C. Orr and colleagues used computer models to predict carbonate ion
concentrations in the ocean over the next century. These carbonate ions are
taken up by many sea creatures to form aragonite, a form of calcium
carbonate used to make their shells and external skeletons. But the
scientists' projections suggest that Southern Ocean waters, as well as parts
of the subarctic Pacific Ocean, will be depleted of aragonite by 2100
because of rising carbon dioxide levels.

The authors assessed the biological impact of these predictions by exposing
a species of swimming snail, known as a pteropod, to conditions that
simulated Southern Ocean surface waters in 2100. They found that the snails'
shells dissolved markedly within 48 hours of exposure to these conditions.
The scientists say that these creatures may not be able to adapt quickly
enough to survive in such conditions, and their demise could affect the fish
and whales that feed on them. Similar changes could also affect cold water
corals that provide an important habitat for fish.

James C. Orr (Laboratoire des Sciences du Climat et de l'Environnement,
Gif-sur-Yvette, France)
Tel: +33 1 69 08 77 23; E-mail: [email protected]

[7] Materials: Porous material has huge, handed holes (pp716-719; N&V)

Porous metal oxides are widely used as catalysts to speed up chemical
reactions, and a family of germanium oxides reported in this week's Nature
could prove to be the most versatile yet.

Xiaodong Zou and colleagues found that their germanium oxides contained
larger pores than other metal oxides, potentially allowing chemicals to
sneak inside more easily to undergo reactions. Unusually for a metal oxide,
the walls of the pores are crystalline, which should boost its chemical
activity. It also allowed the scientists to accurately work out the pores'

This revealed that the channels twisted either clockwise or anticlockwise,
like the thread of a nut. By blocking off one set of channels, the
scientists created a material where all the channels spiralled in the same
direction. This could be a useful environment for making chiral molecules,
such as those found in therapeutic drugs, which can come in left- or
right-handed forms depending on the spatial arrangement of their atoms. A
related News & Views article by Hermann Gies accompanies this research.

Xiaodong Zou (Stockholm University, Sweden)
Tel: +46 8 16 23 80; E-mail: [email protected]

Hermann Gies (Ruhr-Universität Bochum, Germany)
Tel: +49 234 322 3512; E-mail: [email protected]

[8] Virology: Understanding antibodies (pp764-768)

Researchers in this week's Nature report on an antibody involved in stopping
West Nile virus at a cellular level before it has a chance to take hold.
They study how the antibody binds to the virus and inhibits infection, after
the virus has attached itself to the cell surface. The findings could help
in the development of vaccines for associated viruses such as Japanese
encephalitis, yellow fever and dengue viruses - the latter infects about 50
million people each year and currently has no authorised vaccine.
West Nile virus is a bird pathogen, but since it was first reported in the
United States in 1999, there have been more than 16,000 reported cases of
human infection, with more than 650 deaths. As West Nile virus is a
flavivirus, the findings should be useful for developing vaccine strategies
against other members of this family - some of which are even more damaging
to humans.

Daved Fremont and colleagues analysed the interaction of an antibody, E16,
with amino acids belonging to one surface protein of the virus. The team
found that E16 waits until the virus has attached itself to the host cell's
surface, then sneakily prevents the fusion process by blocking the
virus-triggered conformational changes in the host cell. Until now,
researchers had assumed that protective antibodies simply blocked the
initial attachment. This work shows E16 can block infection regardless of
the method of entry into the cell, making it a key candidate for improved
vaccine design strategies.

Daved Fremont (Washington University, St Louis, MO, USA)
Tel: +1 314 747 6547; E-mail: [email protected]

[9] Physical sciences: The Dune thing (pp720-723)

Moving sand dunes - known as barchans - are fundamentally unstable,
according to research published in Nature this week. Barchans are
crescent-shaped dunes that move faster than most other dune types over
desert surfaces.

The dynamic processes responsible for the evolution of barchan dune fields,
however, remain poorly understood. Using a combination of data from a
three-year field study and a simple theoretical model, Bruno Andreotti and
colleagues now show that that dune collisions and changes in wind direction
destabilize the dunes, generating surface waves that can produce new
barchans of a smaller size by breaking the horns of the large dunes. The
creation of these new dunes prevents dune fields from merging into a single
giant dune, and therefore plays a fundamental role in the development of
barchan dune patterns.

Bruno Andreotti (Ecole Supérieure de Physique et Chimie Industrielles,
Paris, France)
Tel: +33 1 40 79 58 09; E-mail: [email protected]

[10] Ecology: Diatoms delve deep for nutrients to stay alive (pp728-732)

During spring, the North Atlantic Ocean teems with tiny diatoms -
unicellular photosynthetic plankton that fashion cell walls from silicate
minerals dissolved in the water. But researchers had been unsure how these
tiny creatures keep thriving in such huge numbers during periods when
silicate is not readily available at the ocean surface.

The answer is that they 'mine' it from deeper waters, reports a team
led by John Allen in this week's Nature. Silicate periodically rises from
the deep at ocean 'fronts' such as the Iceland-Faeroes Front (IFF), one of
the boundaries between Atlantic and Arctic waters. As long as there are
enough other nutrients, such as nitrate, to sustain the diatoms, this
replenishment enables them to keep growing, the team reports.

This discovery, made by sampling and studying waters from the IFF,
shows that the ocean fronts are more dynamic regions than experts realized,
the authors add. This could potentially help to explain how plankton supply
so much carbon to deep-water ecosystems when they die off. Allen's team also
notes that similar frontal systems could supply other nutrients, such as
phosphate or iron, from the deep.

John Allen (National Oceanography Centre, Southampton, UK)
No telephone number at present - please use the following email address
while we try to find a contact phone number: E-mail: [email protected]

[11] Cell biology: Human protein interactions go large scale (DOI:

***This paper will be published electronically on Nature's website on 28
September 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 29 September, but at a later date.***

Now that all of the 22,000 protein-coding human genes have been sequenced,
researchers want to know which of these proteins interact with each other.
Marc Vidal and colleagues have taken an initial step towards addressing this
issue and report their findings in Nature this week.

They analysed the interactions between 8,100 proteins and detected 2,800
interactions, revealing more than 300 new connections to over 100
disease-associated proteins. Seventy-eight per cent of the interactions
could be verified using a second, different biochemical method.
The authors concluded from a literature search that 85 per cent of the
identified interactions are novel while comparison with curated databases
suggests that 96% of the identified interactions are novel. The study may
also yield insight into the way protein interactions change throughout
evolution, the authors say. They found that proteins of the same
evolutionary level are more likely to interact with each other. For example,
human-specific proteins are more likely to interact with each other than
with proteins found in all multicellular animals.

There is still a long way to go towards establishing a complete interaction
database of all human proteins. The study identifies one per cent of the
entire human 'interactome,' the authors estimate.
CONTACT: Marc Vidal (Dana Farber Cancer Institute, Boston, MA, USA)
Tel: +1 617 632 5180; E-mail: [email protected]

[12] Microbiology: Corrupting the bacterial quorum (pp750-753)

In a process known as quorum sensing, bacteria communicate with each other
using chemical signalling molecules called autoinducers. This type of
communication allows the microbes to synchronize their behaviour and thus
respond as a multicellular organism. One autoinducer, known as AI-2, is a
universal molecule that many species of bacteria use to communicate for this

But a paper appearing in Nature this week shows that some species of
bacteria can interfere with AI-2-directed communication, thereby hindering
other species' ability to respond to the chemical signal. The authors,
Karina Xavier and Bonnie Bassler, say that the findings could have
implications for human health relating to the maintenance of beneficial
microorganisms in the gut and the prevention of bacterial diseases.

Bonnie Bassler (Princeton University, NJ, USA)
Tel: +1 609 258 2857; E-mail: [email protected]

[13] And finally... Quicksand won't suck you right in (p635)

Paradoxically, quicksand is easy to sink into but very hard to escape from.
Researchers simulating the way this mixture of fine sand, clay and salt
water behaves find that quicksand liquefies when perturbed, explaining why
it is so easy to sink into.

The more it moves, the more liquid it becomes, report Daniel Bonn and his
colleagues in a Brief Communication in this week's Nature. This explains why
moving too much only makes things worse, because it helps you sink in

Once the quicksand has liquefied, the sand settles at the bottom, making it
so dense that it is impossible for material of the same density as a human
to become completely submerged. "Any unfortunate victim should sink halfway
into the quicksand," say the authors, "but could then take solace from the
knowledge that there would be no risk of being sucked beneath the surface."
But this reassurance comes at a price: pulling out a foot takes a force
equivalent to that needed to lift a medium-sized car.

Daniel Bonn (University of Amsterdam, The Netherlands)
No telephone number at present - please use the following email address
while we try to find a contact phone number: E-mail: [email protected]


[14] Isotope-induced partial localization of core electrons in the
homonuclear molecule N2 (pp711-715)

[15] Trace element signature of subduction-zone fluids, melts and
supercritical liquids at 120-180 km depth pp724-727)

[16] Ca21/calmodulin is critical for brassinosteroid biosynthesis and
plant growth (pp741-745)

[17] Phosphatidylserine-dependent engulfment by macrophages of nuclei
from erythroid precursor cells (pp754-758)

[18] A non-haem iron centre in the transcription factor NorR senses
nitric oxide (pp759-763)


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.

Hobart, Tasmania: 6

Liege: 6
Namur: 11

Ottawa: 14

Taichung, Taiwan: 4
Taipei, Taiwan: 4

Rijeka: 14

Gif-sur-Yvette: 6
Meudon: 3
Paris: 3, 6, 9, 13
Plouzane: 6
Toulouse: 6

Berlin: 14
Bremerhaven: 6
Dresden: 14
Hamburg: 6
Wuerzburg: 14

Jerusalem: 3, 15

La Spezia: 10

Nagoya: 4
Osaka: 17
Sendai: 14
Tokyo: 4, 17
Tsukuba: 4
Yokohama: 6

Agadir: 9

Amsterdam: 13

Stockholm: 7

Bern: 6
Zurich: 15

Exeter: 6
Fife: 10
Portaferry: 10
Southampton: 6, 10
Thurso: 10

Tempe: 7
Los Angeles: 6
Pasadena: 14
Sacramento: 11
San Marcos: 6
Santa Cruz: 3
Boulder: 6
Atlanta: 18
Rockville: 8
Beverly: 11
Boston: 11
Cambridge: 1, 2, 3
Woburn: 11
Woods Hole: 6
St. Louis: 8
New Jersey
Princeton: 6, 12
New York
Mahopac: 7
North Carolina
Beaufort: 5
Durham: 5
University Park: 6
Houston: 11
Pullman: 16
Seattle: 6

For North America and Canada
Katie McGoldrick, Nature Washington
Tel: +1 202 737 2355; E-mail: [email protected]

For Japan, Korea, China, Singapore and Taiwan
Rinoko Asami, Nature Tokyo
Tel: +81 3 3267 8751; E-mail: [email protected]

For the UK/Europe/other countries not listed above
Ruth Francis, Nature London
Tel: +44 20 7843 4562; E-mail [email protected]

Katharine Mansell, Nature London
Tel: +44 20 7843 4658; E-mail: [email protected]

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Published: 28 Sep 2005

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