RESEARCH HIGHLIGHTS
Selections from the
scientific literature
ECO LO GY
The choices city dwellers make
when deciding which plants
to cultivate in their gardens or
yards could affect the function
and health of the wider plant
ecosystem.
Sonja Knapp at the
Helmholtz Centre for
Environmental Research in
Halle, Germany, and her group
compared the characteristics
and diversity of plants in 137
residential yards with those of
a nearby nature reserve. They
found that yard plant species
were more closely related
to each other, shorter-lived,
faster-growing and more likely
to be self-pollinating.
As yard plants spread into
natural habitats, the ability of
those ecosystems to respond to
environmental change could
be reduced, the authors say.
Ecology http://dx.doi.org/
10.1890/11-0392.1 (2012)
A NIMAL B EHAVIO UR
M. KONRAD/IST AUSTRIA
Licking ants fight
fungal infection
Healthy ants that rub up against
infected counterparts or even
lick pathogenic fungal spores
off them may be immunizing
themselves and, ultimately,
protecting their whole colony.
Sylvia Cremer at the Institute
of Science and Technology
Austria in Klosterneuburg and
her colleagues infected ants
MARKA/SUPERSTOCK
A look at backyard
biodiversity
G EOLOGY
Hot tuff not so tough
Tuffs are volcanic rocks commonly used as
building materials despite their notorious
weakness — and at least one popular tuff could
pose an even greater hazard in the event of a fire.
Michael Heap at the University of Strasbourg
in France and his colleagues examined three
types of tuff commonly used in buildings in
the Neapolitan region of Italy (pictured). Two
exhibited no reduction in strength after thermal
stressing, but the most commonly used one,
(Lasius neglectus; pictured)
with fluorescently labelled
fungal spores (Metarhizium
anisopliae) and released them
among healthy members of
their colony. The authors
found that spores frequently
transferred to healthy
ants, resulting in low-level
infection. Genetic analysis
revealed that these minor
infections upregulated a set of
immune-system genes
that bolstered the ants’
anti-fungal defences.
Computer modelling
suggests that this ‘social
immunization’ actively
stimulates the ants’ immune
systems, allowing the colony
as a whole to fight infection.
PLoS Biol. 10, e1001300 (2012)
known as Neapolitan yellow tuff, lost 80% of its
compressive strength as temperatures reached
1,000 °C. This is explained by the fact that
Neapolitan yellow tuff contains zeolite minerals
that are sensitive to heat.
The team suggests that the results be
considered in establishing regional fire codes
and recommends similar tests for building tuff
in other regions.
Geology 40, 311–314 (2012)
M OL ECU L A R B I OLOGY
MicroRNAs boost
gene variation
Small RNA molecules that
regulate and stabilize the
expression of certain genes
in humans may also promote
and preserve variations in
gene expression between
individuals and ethnic groups.
Jian Lu and Andrew Clark
at Cornell University in
Ithaca, New York, examined
the expression profiles of
protein-coding genes that are
influenced by microRNAs
(miRNAs) and were obtained
from multiple human
populations. The authors
compared these profiles with
© 2012 Macmillan Publishers Limited. All rights reserved
those of genes not targeted by
miRNAs. Expression of some
of the miRNA-regulated genes
varied little across populations,
or between humans,
chimpanzees and macaques.
However, most differed from
one individual to another and
between ethnic groups.
Genome Res. http://dx.doi.org/
10.1101/gr.132514.111 (2012)
N A NOT ECH NOLOGY
Lasers sort
particles by size
Gold nanoparticles have a
range of biomedical uses,
from detecting tumours to
delivering drugs. However,
their size is important because
RESEARCH HIGHLIGHTS THIS WEEK
Nano Lett. http://dx.doi.
org/10.1021/nl204378r (2012)
GENETICS
Fewer imprinted
genes at re-count
Most mammalian cells have
one maternal and one paternal
copy of most genes, but some
genes carry a molecular
signature or ‘imprint’ that
silences one copy. Tomas
Babak at Stanford University
in California and his team
mapped the imprinted genes
in mouse brains and found far
fewer than recent estimates
had suggested.
In 2010, two studies found
more than 1,300 imprinted
genes in the mouse brain, ten
times more than traditional
counts. The increase was
attributed to improved
RNA-sequencing technology.
When Babak et al. repeated
the experiments, they found
only 13% of the imprinted
genes first identified by the
2010 studies and uncovered
statistical weaknesses that
resulted in many false-positive
signals. Using a different
analytical approach, the
authors identified roughly
50 new candidate imprinted
genes.
Having a catalogue of
imprinted genes is important
for understanding why
imprinting occurs and how it
can go awry.
COMMUNITY
CHOICE
PLoS Genet. 8, e1002600 (2012)
M O L EC UL A R I M AG I N G
Follow the
lymph vessels
Lymph vessels grow as wounds
heal and cancers spread — a
process that can be imaged
in living animals, researchers
demonstrate in mice.
Lymph vessels often sprout
at sites of inflammation,
and their growth has been
linked to tumour metastasis.
Sagrario Ortega at the
Spanish National Cancer
Research Centre in Madrid
and her colleagues genetically
engineered a mouse to express
a luminescent protein under
the control of the gene Vegfr3,
a lymphatic marker.
The team imaged live mice,
tracking vessel growth during
embryo development, wound
healing and inflammation.
They also watched as lymph
vessels grew at the edge of
melanoma tumours and in
lymph nodes infiltrated by
the cancer. This vessel growth
may aid the spread of cancer to
distant organs, the authors say.
Proc. Natl Acad. Sci. USA
http://dx.doi.org/10.1073/
pnas.1115542109 (2012)
M ATER I A L S
A graphene
window on liquids
By using graphene membranes
as viewing ‘windows’,
researchers have filmed
nanocrystals growing in
liquids at atomic resolution.
Studying structures in
liquids at the atomic level
is challenging because the
imaging technique of choice,
transmission electron
microscopy, requires that
samples be in a vacuum to
maximize their interactions
with the electron beam. Airtight capsules can be used
to enclose liquids, but are
thick and made of materials
The most viewed
papers in science
CA NCE R
Small, cancer-resistant mice
Boosting the levels of a tumour-suppressor
protein in mice makes them smaller and
on www.cell.com
more metabolically efficient, as well as
in March
resistant to cancer.
Pier Paolo Pandolfi at Beth Israel Deaconess Medical Center
in Boston, Massachusetts, and his colleagues genetically
engineered mice to have additional copies of Pten, a gene that is
mutated or deleted in many cancers. The mice are smaller than
normal because they have fewer cells. When injected with a
carcinogen, the animals developed tumours later than controls.
The transgenic mice burn energy at a higher rate. Cells from
these mice consume less glucose than normal mouse cells but
generate more ATP — the energy molecule created during
cellular respiration — indicating a more efficient metabolism.
Increasing levels of the PTEN protein could offer a
therapeutic approach to preventing both cancer and obesity.
✪ HIGHLY READ
Cell 149, 49–62 (2012)
that interfere with passing
electrons, resulting in a blurred
picture. Membranes made of
graphene — atomically thin
sheets of carbon atoms — are
both impermeable to liquids
and much more transparent to
electrons.
Paul Alivisatos at the
Lawrence Berkeley National
Laboratory in Berkeley,
California, and his colleagues
used these graphene
windows to create atomicresolution movies of platinum
nanocrystals clumping
together in a liquid.
Science 336, 61–64 (2012)
ZOOLOGY
Vision with no
nervous system
Sponge larvae can detect light
despite lacking a nervous
system or the photosensitive
‘opsin’ proteins found in all
other known animal eyes.
Instead, another pigment called
cryptochrome may underlie
the light-sensing ability of
the sponge Amphimedon
queenslandica (pictured),
report Todd Oakley at the
University of California, Santa
Barbara, and his colleagues.
Cryptochromes mainly
absorb blue light and, in other
animals, have been implicated
in functions from setting
circadian rhythms to sensing
magnetic fields. The authors
identified two cryptochrome
genes in the sponge. One,
Aq-Cry2, is expressed in the
‘ring eyes’ of A. queenslandica
larvae and has an absorbance
peak similar to the wavelengths
that trigger larval activity.
Because eye evolution in
other animals has always
involved opsins, the use of
cryptochrome represents
a separate lineage of eye
evolution, the team suggests.
J. Exp. Biol. 215, 1278–1286
(2012)
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S. LEYS
it affects their optical and
mechanical properties, as
well as their toxicity. Martin
Ploschner and his colleagues at
the University of St Andrews,
UK, report an efficient way to
sort gold nanoparticles by size
using laser light.
The team aimed green and
red lasers at a thin layer of
water containing a mixture
of gold nanoparticles 100 and
130 nanometres in diameter.
The green light’s frequency
matched that of the electrons
in the smaller nanoparticles.
This resonance enhanced
forces acting on the particles,
pushing them in one direction.
The red light interacted with
the larger particles, moving
them in the opposite direction.
The researchers suggest
that the method could sort
nanoparticles more finely than
current methods, which rely
on centrifugation.