Science - USA (2020-05-22)

842 22 MAY 2020 • VOL 368 ISSUE 6493 sciencemag.org SCIENCE

PHOTO: MARTYN WILLIAMS/ALAMY STOCK PHOTO

RESEARCH | IN OTHER JOURNALS

CANCER IMMUNOLOGY

Vaccine potential of

dendritic cells

The ability of dendritic
cells (DCs) to process and
present antigens to the
immune system makes them
intriguing candidates for
the development of cancer
immunotherapies. Zhou et
al. investigated whether the
CD103+ tissue-resident con-
ventional DC1 (cDC1) subset
could control tumors in mouse
models. DCs were grown and
activated in cell culture using
an immunostimulant called
polyinosinic:polycytidylic acid
(poly I:C). The cells were then
loaded with tumor antigens
and injected into mice to
assess their vaccine potential.
The authors found that in
vitro–generated CD103+ cDC1s
restrained melanoma and
osteosarcoma tumor growth.
Tumors could be further hin-
dered if the in vitro–generated
cDC1s were combined with
immune checkpoint blockade
treatment. —PNK
J. Immunother. Cancer 8 , e000474
(2020).

HIGH PRESSURE

Diffuse density

determination

Liquid iron at extreme pressure

and temperature powers Earth’s

magnetic field, but its proper-

ties are not well constrained.

Kuwayama et al. used diffuse

x-ray scattering to determine

the density of molten iron

at conditions near those of

Earth’s outer core. The authors

developed a new data analysis

method to obtain these values,

which can be combined with

shock-wave observations to

determine the thermal equa-

tion of liquid state for iron. The

results help to constrain the

amounts of alloying elements in

Earth’s core and provide a new

strategy for measuring liquid

density at high pressures. —BG

Phys. Rev. Lett. 124 , 165701 (2020).

OPTOMECHANICS

The coolest of vibrations

Shifts in the resonance fre-

quency of micrometer-sized

mechanical resonators provide

a platform for high-resolu-

tion sensing and detection

applications. To exploit opto-

mechanical resonators for

quantum technologies, the

temperature of the system

needs to be very low, ideally

well below an occupancy of just

one phonon, so that the system

is in its ground state. From

there, selection and control

of the transitions between

quantized energy levels provide

for quantum-enhanced preci-

sion measurement. Qiu et al.

demonstrate laser cooling of a

crystalline silicon optomechani-

cal resonator to its zero-point

energy. With a mean thermal

phonon occupancy of just

~0.09 quantum, corresponding

to ~92% ground state prob-

ability and –7.4 decibels of the

zero-point energy, the stage is

now set for exquisite quantum-

sensing applications as well as

fundamental tests of quantum

mechanics. —ISO

Phys. Rev. Lett. 124 , 173601 (2020).

DEVELOPMENTAL BIOLOGY

Atlas of gastrulation

We marvel at the progression

of a single cell into a complex

organism, and microscopy has

long been used to visualize

early developmental events.

More recently, molecular

networks and cellular lin-

eages have been constructed

by measuring cells’ gene

expression profile through

single-cell RNA sequencing

(scRNA-seq). Sladitschek et

al. combined scRNA-seq and

light-sheet imaging of the

ascidian Phallusia mammillata

to reveal gene expression in

all cells of the embryo up to

the formation of the multilay-

ered gastrula. Every cell was

followed for all cell divisions in

18 cell lineages. The result is a

map of cell spatial position and

lineage history that reveals

embryonic bilateral symmetry

and interembryonic variabil-

ity, as well as the patterned

expression of cell adhesion

molecules. This resource can

be used to examine any num-

ber of molecular mechanisms

and developmental events

occurring in the gastrulat-

ing embryo and can serve as

model for the spatiotemporal

map. —BAP

Cell 10.1016/j.cell.2020.03.055

(2020).

SOIL MICROBIOME

Rehydrating peatland

microbiomes

P

eatlands are good at storing carbon but are

destabilized when they dry out. This happens

because oxygen penetrates the dry peat to

promote aerobic degradation, releasing carbon

and nutrients. Destruction of the mossy overlay

follows, which in an intact functioning bog supplies a

continuous accumulation of organic matter. Rewetting

might restore dried-out peatlands, but whether func-

tioning bog communities that draw down carbon are

restored depends on whether microbial communities

are restored. Emsens et al. surveyed the micro-

bial communities of undrained, dry, and rewetted

peatlands. Microbial communities differed between

undrained and dry peatland. Rewetted peatlands

showed recovery of microbial communities, although

loss of organic matter during extended dry times

seemed to limit microbiome recovery. —PJH

ISME J. 10.1038/s41396-020-0639-x (2020).

After short periods of drought, rehydration of peat bogs

allows recovery of their microbial communities.

Published by AAAS