NUCLEAR PHYSICS
A proton-shedding
nucleus
A stable atomic nucleus
contains a careful balance of
the number of protons and
neutrons. For unstable nuclei
that have a pronounced excess
of protons, a rare radioactive
process called proton emis-
sion, in which one or more
protons are ejected from the
nucleus, is the preferred road to
stability. Although one to three
proton emissions have been
observed in several nuclides,
only one nuclide has been
observed to decay through a
four-proton emission. Jin et al.
now add^18 Mg to that short list.
The researchers created the
previously unobserved nuclide(^18) Mg by smashing a beam of
(^20) Mg against a target and then
detected^18 Mg through its decay
to^14 O and four protons. —JS
Phys. Rev. Lett. 127 , 262502 (2021).
156 14 JANUARY 2022 • VOL 375 ISSUE 6577 science.org SCIENCE
CREDITS: (FROM LEFT TO RIGHT BIOPHOTO ASSOCIATES/SCIENCE SOURCE; PAVEL1964/ISTOCKPHOTO
RESEARCH | IN SCIENCE JOURNALS
toxicity. Thus, pro–IL-12 is a safe
therapy that could have a large
clinical impact for patients with
cancer. —DAE
Sci. Immunol. 6 , eabi6899 (2021).
CELL BIOLOGY
Ancient origin
of cell death
Gasdermins are cell death
proteins in mammals that form
membrane pores in response to
pathogen infection. Johnson et
al. report that diverse bacteria
encode structural and func-
tional homologs of mammalian
gasdermins. Like their mam-
malian counterparts, bacterial
gasdermins are activated by
caspase-like proteases, oligomer-
ize into large membrane pores,
and defend against pathogen—in
this case, bacteriophage—infec-
tion. Proteolytic activation occurs
through the release of a short
inhibitory peptide, and many
bacterial gasdermins are lipidated
to facilitate membrane pore
formation. Pyroptotic cell death,
a central component of mam-
malian innate immunity, thus has
a shared origin with an ancient
antibacteriophage defense sys-
tem. —SMH
Science, abj8432, this issue p. 221
PLANT SCIENCE
mRNA migration through
plasmodesmata
In plants, certain transcription
factors are produced in one cell
but transported, sometimes
AQUATIC ECOLOGY
Wastewater degrades
food webs
Urban wastewater has profound
effects on aquatic ecosystems
downstream, adding nutrients
along with harmful pollutants.
Mor et al. examined these
effects across entire food webs,
comparing bottom-up (increased
primary production due to added
nutrients) and top-down (loss of
predators) effects. Observations
from 10 streams showed that
stream reaches exposed to
effluent had higher primary
production but lower energy
transfer to consumers compared
with paired upstream controls.
They also found reduced species
richness and narrower trophic
niches in predators downstream
from effluent. Thus, wastewater
pollution has both direct (abiotic)
and indirect (biotic) impacts on
aquatic communities. —BEL
Ecology 10.1002/ecy.3587 (2021).
as messenger RNA (mRNA),
through plasmodesmata,
channels between neighboring
plant cells, where they act. This
system helps to manage stem
cell development. Kitagawa
et al. have identified part of
the machinery that manages
this cell-to-cell transport.
Transport of the mRNA encod-
ing the KNOTTED1 homeobox
transcription factor depends
on Ribosomal RNA-Processing
Protein 44 (AtRRP44A), a sub-
unit of the RNA exosome. —PJH
Science, abm0840, this issue p. 177
2D MATERIALS
Following a crossover
Superfluidity in fermionic sys-
tems occurs through the pairing
of fermions into bosons, which
can undergo condensation.
Depending on the strength of the
interactions between fermions,
the pairs range from large and
overlapping to tightly bound.
The crossover between these
two limits has been explored in
ultracold Fermi gases. Liu et al.
observed the crossover in an
electronic system consisting of
two layers of graphene separated
by an insulating barrier and
placed in a magnetic field. In this
two-dimensional system, the
pairs were excitons formed from
an electron in one layer and a
hole in the other. The research-
ers used magnetic field and layer
separation to tune the interac-
tions and detected the signatures
of superfluidity through transport
measurements. —JS
Science, abg1110, this issue p. 205
Plasmodesmata, seen here in blue in a false-color transmission electron micrograph,
mediate the transmission of molecules as large as mRNA between plant cells.
IN OTHER JOURNALS Edited byCaroline Ash
andJesse Smith
EVOLUTION
Dining out on transparency
S
everal butterflies mimic the coloration of poisonous species
without being toxic themselves. Mimics benefit from predator
avoidance without the cost of carrying the requisite metabolic
machinery. Pinna et al. observed that some toxic butterflies
with transparent wing patches have mimics too. The ques-
tion is, what is being mimicked: camouflage, toxic potential, both,
or some other advantage? Close examination of the diversity of
microstructures of these patches indicated how they are precisely
fine-tuned to bird predator perception and revealed convergent
structural evolution among mimicking species. Transparent mimics
avoid being spotted by hungry birds, but when they are,
they are thought to be unpalatable because of their wing
patterns and thus are rejected for lunch. —CA
eLife 10 , e69080 (2021).
Despite their transparency offering
camouflage, glasswing butterflies may
still mimic the wing patterns of toxic
relatives to provide additional protection.