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More than 90% of the species that have populated Earth at some time during the past four billion years have vanished, many of them in mass extinctions. That puts the focus on those species that remain and their chances of survival. In a News Feature this week we try to take stock of what remains of life on Earth � not a simple matter it turns out � and ask what conservation measures would be needed to halt the attritional loss of biodiversity. Cover: Critically endangered black eyed tree frogs (Agalychnis moreletii) in the Pakaraima Mountains of Guyana ( Joe Riis/National Geographic Society/Corbis)
The European Commission’s plans to allow individual countries a veto on the farming of genetically modified crops, although a compromise, should enable the technology to move forward.
The week in science: NASA's Orion flight soars; James Watson's Nobel medal nabs US$4.1 million; and India becomes full partner in Thirty Meter Telescope
Disease is as much about the host as it is the infectious agent — the focus on microbes is hindering research into treatments, say Arturo Casadevall and Liise-anne Pirofski.
Pluripotent stem cells, which give rise to almost all cell types, can be engineered from mature cells. A thorough analysis of the process has led to the characterization of a new type of pluripotent cell. See Articles p.192 & p.198
The atomically thin material called graphene is impermeable to atoms as small as helium. The finding that protons can pass through it might enable new kinds of membrane to be developed and aid research into fuel cells. See Letter p.227
The protein FtsZ forms a ring structure that constricts to allow bacterial cells to divide. A second protein, MapZ, has now been found to guide FtsZ to the correct mid-cell position in the bacterium Streptococcus pneumoniae. See Letter p.259
The first crystal structures of bestrophin and lipid scramblase proteins cast light on how these protein families transport very different substrates across membranes, yet are both activated by calcium ions. See Articles p.207 & p.213
A cracked metal film on an elastic substrate has been shown to provide ultrahigh sensitivity in detecting mechanical vibrations. The result draws inspiration from principles of tiling that apply to many biological systems. See Letter p.222
A global analysis reveals growing societal dependence on the use of non-renewable freshwater resources that depletes groundwater reserves and undermines human resilience to water scarcity in a warming world.
Carbon atoms to which four distinct carbon substituents are attached — quaternary carbon stereocentres — are common features of molecules found in nature; in this Review, the authors discuss catalytic enantioselective reactions that have been developed during the past decade for synthesizing organic molecules containing such carbon atoms.
The forced expression of key transcription factors can induce somatic cells to acquire pluripotency characteristics; here high levels of reprogramming factors are used to induce mouse embryonic fibroblasts to a stable alternative pluripotent state with low intercellular adhesion.
This study presents an extensive molecular characterization of the reprograming process by analysis of transcriptomic, epigenomic and proteomic data sets describing the routes to pluripotency; it finds distinct routes towards two stable pluripotent states characterized by distinct epigenetic events.
The authors describe the structure of a Ca2+-activated lipid scramblase which catalyses the passive movement of lipids between the two leaflets of a lipid bilayer; the structure reveals the location of a regulatory calcium-binding site embedded within the membrane and the presence of a hydrophilic membrane-traversing cavity that is exposed to the lipid bilayer, where catalysis is likely to occur.
The X-ray crystal structure of a eukaryotic Ca2+-activated chloride channel, BEST1, and its function in liposomes are described; the structure shows that Ca2+ binds to the cytosolic region of this pentameric channel and reveals that the pore is approximately 95 Å long with at least 15 distinct anion-binding sites.
Observations of emission and absorption lines of the deuterated trihydrogen cation (H2D+) from a dense interstellar cloud core, combined with chemical modelling, reveal that the core needed at least one million years to form Sun-like stars.
A mechanical crack-based sensor inspired by the mechanism spiders use to sense minute variations in stress offers ultrahigh sensitivity to pressure and vibration and can easily be mounted on human skin for the purposes of speech recognition and the monitoring of physiological signals.
Measurements show that monolayers of graphene and hexagonal boron nitride are unexpectedly highly permeable to thermal protons and that their conductivity rapidly increases with temperature, but that no proton transport is detected for few-layer crystals.
Gas hydrates are ice-like solids that have guest species encaged within a crystalline water framework, making the empty hydrate a natural — though long assumed to be inaccessible — point of reference; it is now shown that several days of continuous vacuum pumping removes all guests from neon hydrate, and the physical properties of the empty hydrate have been determined.
Analysis of air trapped in Antarctic ice between 16,000 and 10,000 years before present yields nitrous oxide concentrations and isotopic data showing that the relative contributions from marine and terrestrial sources to nitrous oxide emission changes were equal during that period, but that terrestrial emissions dominated on centennial timescales.
Spheroidal microfossils from the Ediacaran Doushantuo phosphorites show clear signs of cell differentiation, programmed cell death, and separation between soma and germline, and seem to represent a hitherto unknown experiment in multicellular life like nothing on Earth today.
The authors show that two primate-specific genes encoding KRAB domain containing zinc finger proteins, ZNF91 and ZNF93, have evolved during the last 25 million years to repress retrotransposon families that emerged during this time period; according to the new data KZNF gene expansion limits the activity of newly emerged retrotransposons, which subsequently mutate to evade repression.
Pstpip2-mutant mice fed a high-fat diet are protected against inflammatory bone disease and bone erosion; this protection is associated with reductions in intestinal Prevotella levels and pro-IL-1β expression, and is dependent on the deletion of both caspases 1 and 8.
Inactivation of the S1PR2–Gα13–ARHGEF1 signalling pathway in mice allows Akt activation and promotes dissemination of germinal centre B cells, consistent with a role of function-disrupting mutations in the systemic dissemination of diffuse large B-cell lymphoma.
A new mechanism is identified for correct placement of the division machinery in Streptococcus pneumoniae that relies on the novel factor MapZ to form ring structures at the cell equator; these structures move apart as the cell elongates, acting as permanent markers of division sites.
In the presence of a short DNA oligonucleotide containing a protospacer adjacent motif, a guide-RNA-programmed Cas9 is able to specifically bind and/or cleave single-stranded RNA—this system can be used to isolate specific endogenous RNA transcripts from a cell lysate without any tag or modification.
A conserved tyrosine residue, Tyr 57, of histone H2A is phosphorylated by an unsuspected tyrosine kinase activity of casein kinase 2, influencing a series of histone marks associated with active transcription and regulating transcription elongation.
The interplay of histone acetylation and RNA polymerase II activity is investigated using fluorescence microscopy; acetylation of H3 at Lys 27 enhances the recruitment of a transcriptional activator and accelerates the transition of RNA polymerase II from initiation to elongation, thus indicating that histone acetylation has a causal effect on two distinct steps in transcription activation.