SCIENCE science.org 3 DECEMBER 2021 • VOL 374 ISSUE 6572 1212-B
CORONAVIRUS
Understanding the
earliest cases in Wuhan
The earliest symptomatic cases
of COVID-19 in Wuhan, China,
could be informative about
the origins of the pandemic
and suggest ways of detecting
unknown diseases sooner. In
a Perspective, Worobey draws
from diverse sources to put
together a timeline of the earliest
cases of COVID-19, the connec-
tions of these patients to the
Huanan market that sold wild
animals, and the events that led
to the identification of COVID-19
as a new viral pneumonia. This
analysis demonstrates that most
of the first cases were associ-
ated with the market, indicating
that spillover from susceptible
animals was the likely source of
community transmission. —GKA
Science, abm4454, this issue p. 1202
DEVELOPMENTAL BIOLOGY
The nonconserved
primitive streak
In human development, a linear
structure called the primitive
streak appears 14 days after
fertilization. This structure
marks the transition of the
embryo from having radial to
bilateral symmetry. The primitive
streak also gives anterior-pos-
terior and dorsal-ventral spatial
information to cells undergoing
gastrulation and forming the
various body cell types. In a
Review, Sheng et al. present a
phylogenetic and ontogenetic
overview of the primitive streak.
They discuss organismal, cel-
lular, and molecular features of
the primitive streak and how it
functions in amniote gastrula-
tion. The observation that this
structure is not conserved and is
not required for development in
vitro has implications for embry-
onic stem cell–based models
and considerations about human
development research. —BAP
Science, abg1727, this issue p. 1213
CORONAVIRUS
Immune memory after
vaccination
Vaccination against severe acute
respiratory syndrome coronavi-
rus 2 (SARS-CoV-2) has proven
highly effective at preventing
severe COVID-19. However, the
evolution of viral variants and
waning antibody levels over time
raise questions regarding the
longevity of vaccine-induced
immune protection. Goel et al.
examined B and T lymphocyte
responses in individuals who
received SARS-CoV-2 mes-
senger RNA vaccines. They
performed a 6-month longitu-
dinal study of individuals who
never had SARS-CoV-2 infection
compared with people who had
recovered from SARS-CoV-2.
Humoral and cellular immune
memory was observed in vac-
cinated individuals, as were
functional immune responses
against the Alpha (B.1.1.7), Beta
(B.1.351), and Delta (B.1.617.2)
viral variants. Analysis of T cell
activity suggested that robust
cellular immune memory may
prevent hospitalization by limit-
ing the development of severe
disease. —PNK
Science, abm0829, this issue p. 1214METABOLISM
Reversing the chain
The mitochondrial electron
transport chain is a major part
of cellular metabolism and plays
key roles in both cellular respira-
tion and the synthesis of critical
metabolites. Typically, electrons
flow through the electron trans-
port chain in a specific direction,
ending up with oxygen as the ter-
minal electron acceptor. Spinelli
et al. characterized an alterna-
tive path of electron flow through
the transport chain, ending
with fumarate as the electron
acceptor (see the Perspective by
Baksh and Finley). This pathway
operates under conditions of
limited oxygen availability, and
the authors have confirmed its
activity in vivo in a mouse model,observing that the propensity to
use this pathway varied between
organs. —YN
Science, abi7495, this issue p. 1227;
see also abm8098, p. 1196TOPOLOGICAL MATTER
Synthesizing
topological order
Topologically ordered matter
exhibits long-range quantum
entanglement. However, mea-
suring this entanglement in real
materials is extremely tricky.
Now, two groups take a different
approach and turn to synthetic
systems to engineer the topolog-
ical order of the so-called toric
code type (see the Perspective
by Bartlett). Satzinger et al. used
a quantum processor to study
the ground state and excitations
of the toric code. Semeghini et
al. detected signatures of a toric
code–type quantum spin liquid
in a two-dimensional array of
Rydberg atoms held in optical
tweezers. —JS
Science, abi8378, abi8794,
this issue p. 1237, this issue p. 1242;
see also abl8910, p. 1200ORGANIC CHEMISTRY
Radical substitution
Nucleophilic substitution is a
venerable reaction in organic
chemistry. Typically, an incoming
ion delivers two electrons to a
carbon center while a departing
ion takes two electrons away
with it. The one-electron analog
homolytic substitution is used
less often, in part because the
incoming neutral radicals can
self-couple instead of bonding
to the intended target. Liu et al.
report that an iron porphyrin
catalyst can direct homolytic
substitution between primary
and tertiary carbon radicals by
selectively activating the primary
partners. —JSY
Science, abl4322, this issue p. 1258NANOPHOTONICS
Optomechanical
upconversion
Molecules have rich signatures
in their spectra at infrared
wavelengths and are typically
accessed with dedicated spec-
troscopic instrumentation. Chen
et al. and Xomalis et al. report
optomechanical frequency
upconversion from the mid-
infrared to the visible domain
using molecular vibrations
coupled to a plasmonic nanocav-
ity at ambient conditions (see
the Perspective by Gordon).
Using different nanoantenna
designs, one with a nanoparticle-
on-resonator and the other with
nanoparticle-in-groove, both
approaches show the ability
to upconvert the mid-infrared
vibrations of the molecules in
the nanocavity to visible light
wavelengths. The effect could
be used to simplify infrared
spectroscopy, possibly with
single-molecule sensitivity. —ISO
Science, abk3106, abk2593, this issue
p. 1264, this issue p. 1268;
see also abm4252, p. 1201ORGANIC CHEMISTRY
Desaturating acids
Molecular motifs with neighbor-
ing C=C and C=O double bonds
are central to the synthesis of
fine chemicals, pharmaceuti-
cals, and polymers. Wang et al.
report a versatile palladium-
catalyzed reaction to produce
this motif from carboxylic acids
by oxidation of the adjacent
carbons, with molecular oxygen
as a viable terminal oxidant (see
the Perspective by Iwabuchi).
The method relies on fine-tuned
ligand geometry and comple-
ments approaches constrained
by their reliance on enolate
chemistry. Swapping in an alter-
nate ligand promotes extension
of the desaturation to coupling
with terminal alkynes. —JSY
Science, abl3939, this issue p. 1281;
see also abm4457, p. 1199Edited by Michael FunkALSO IN SCIENCE JOURNALS
RESEARCH