SCIENCE science.org 15 APRIL 2022 • VOL 376 ISSUE 6590 260-B
RESEARCHECOSYSTEM ECOLOGY
Declining nitrogen in
natural ecosystems
Nitrogen (N) availability is key to
the functioning of ecosystems
and the cycling of nutrients and
energy through the biosphere.
However, there is growing
evidence that N availability is
decreasing in many terrestrial
ecosystems. The consequences
of declining N availability will
be widespread. For example, a
decreased concentration of N in
leaves reduces the availability
of N for insects, contributing
to population declines that
may then cascade through
higher trophic levels. Mason
et al. reviewed the extent of
this phenomenon, and the
anthropogenic factors that
might be driving it (including
climate change and increasing
atmospheric carbon dioxide),
and discuss how its damag-
ing effects might be mitigated.
—AMS
Science, abh3767, this issue p. 261
LIPIDOMICS
Greasing the skin
In multicellular organisms, cells
are parts of communities in
which an individual contributes
to the collective phenotype of
the community. Understanding
the “social” organization of these
cell communities is instrumental
to dissecting their physiology
and the pathological conse-
quences of their abnormalities.
Capolupo et al. investigated
the lipid metabolism and gene
expression of individual human
skin cells and found that specific
lipid compositions drive cell
specialization. Specifically, the
authors found that sphingolipids
determine the transcriptional
programs of fibroblasts populat-
ing different layers of the human
skin. These results reveal an
unexpected role for membrane
lipids in the establishment of cell
identity and tissue architecture.
—LZ
Science, abh1623, this issue p. 262
NEUROIMMUNOLOGY
Give a nod to Nod2 in
gut–brain cross-talk
Nod2 is a pattern recognition
receptor (PRR) that helps the
immune system recognize
fragments of bacterial cell walls
called muropeptides. Previous
work in mice has shown that
Nod2 may also play a role in
various metabolic and neuro-
logic pathologies. Gabanyi et al.
report that Nod2 is expressed
throughout the brain in reporter
mice, including in the hypothala-
mus (see the Perspective by
Adamantidis). When Nod2 was
knocked out specifically in inhibi-
tory GABAergic neurons, mice,
particularly older female mice,
exhibited altered temperature
regulation and feeding behavior.
Moreover, muropeptides could
reach the brain and regulate
neurons once there. This work
suggests that the brain may
sense changes in gut bacteria
as a measure of food intake
and could serve as the basis for
future neurologic and metabolic
therapies. —STS
Science, abj3986, this issue p. 263;
see also abo7933, p. 248SIGNAL TRANSDUCTION
mTORC1 as fatty liver
disease target
Inappropriate accumulation of
fat in the liver causes serious life-
threatening disease in humans.
In mice, Gosis et al. explored
the potential beneficial effects
of controlling lipid metabolism
by preventing signaling by the
mTORC1 (mechanistic target of
rapamycin complex 1) pro-
tein kinase complex (see the
Perspective by Ginsberg and
Mani). The authors inhibited
some, but not all, signaling by
mTORC1 by depleting the follicu-
lin protein in the liver. Such mice
had increased lipid consump-
tion and decreased lipogenesis
and were protected when fed
a diet that normally induces
nonalcoholic fatty liver disease.These effects appear to result in
part from activation of the TFE3
transcription factor. Similar
strategies might thus be useful
in treating liver disease. —LBR
Science, abf8271, this issue p. 264;
see also abp8276, p. 297MATERIALS SCIENCE
Asymmetrical
crystal growth
The shapes of crystalline
materials reflect the growth
rates of different faces, such
as elongation in the fastest-
growing direction. In the absence
of impurities, boundary walls,
or guiding macromolecules,
one would expect symmetrical
faces to grow at the same rate.
Avrahami et al. examined crystal
growth and arrangement in
developing coccoliths, micro-
scopic calcite crystal arrays
produced by the unicellular alga
Calcidiscus leptoporus (see the
Perspective by Prywer). The
authors found that the {104}
faces connected by symmetry
relations did not show the same
growth rates, thus leading to
symmetry breaking in growth
and the formation of complex
growth habits. This asymmetri-
cal growth is not caused by guide
macromolecules, but rather is
solely controlled by the diffusion
of ions. —MSL
Science, abm1748, this issue p. 312;
see also abo2781, p. 240CATA LYS I S
Promoting copper
catalysts with C60
Ethylene glycol, a commodity
chemical used as a feedstock and
antifreeze agent, is synthesized
industrially from dimethyl oxalate
(DMO) by hydrogenation over
precious-metal palladium cata-
lysts at high pressures (typically
20 bars). Copper–chromium
catalysts supported on silica
as an alternative have required
even higher pressures. Zheng
et al. show that the addition offullerene (C60) onto copper-silica
allows DMO hydrogenation to be
performed at ambient pressures
with high yield (98%) and without
deactivation after 1000 hours
(see the Perspective by Gravel
and Doris). The use of C60 to sta-
bilize electron-deficient copper
species that enhance hydrogen
adsorption could likely be applied
to other hydrogenation reactions
catalyzed by copper. —PDS
Science, abm9257, this issue p. 288;
see also abo3155, p. 242CORONAVIRUS
SARS-CoV-2 spikes
the STING pathway
The lungs of patients with
severe COVID-19 disease
are damaged by inflamma-
tion and contain syncytial (or
fused) pneumocytes. Liu et al.
uncovered a mechanism by
which severe acute respira-
tory syndrome coronavirus 2
(SARS-CoV-2)–induced cell
fusion may contribute to exces-
sive lung inflammation. Cultured
epithelial cells expressing the
SARS-CoV-2 spike protein
fused with cells expressing
ACE, the spike protein recep-
tor. The fused cells exhibited
DNA damage and micronuclei,
which led to the activation of
the cytosolic DNA sensor cGAS
and the adaptor protein STING
and the expression of type I
interferon–encoding and inter-
feron-stimulated genes. —JFF
Sci. Signal. 15 , eabg8744 (2022).INFAMMATORY DISEASE
Troublemakers in the IBD
enteric virome
The diverse set of DNA and
RNA viruses that comprise the
enteric virome are a com-
monly overlooked component
of the complete gut microbiota
ecosystem. Adiliaghdam et al.
compared the composition and
immunomodulatory function of
the enteric virome from inflam-
matory bowel disease (IBD)Edited by Michael FunkALSO IN SCIENCE JOURNALS