Volume 516 Number 7529

Editorials

Harsh reality p.7

Two reports highlight the plight of postdocs on both sides of the pond aiming for academia.

doi: 10.1038/516007b

The uncertain dash for gas p.7

The United States and other countries have made huge investments in fracking, but forecasts of production may be vastly overestimated.

doi: 10.1038/516007a

Look ahead p.8

Research into climate engineering must proceed — even if it turns out to be unnecessary.

doi: 10.1038/516008a

News

News Features

Quantum computer quest p.24

After a 30-year struggle to harness quantum weirdness for computing, physicists finally have their goal in reach.

doi: 10.1038/516024a

The fracking fallacy p.28

The United States is banking on decades of abundant natural gas to power its economic resurgence. That may be wishful thinking.

doi: 10.1038/516028a

News & Views

Autophagy transcribed p.40

Two studies find that an intracellular quality-control mechanism called autophagy is regulated by nuclear receptor proteins that govern the expression of autophagy genes. See Letters p.108 & p.112

doi: 10.1038/nature13939

Controls on isotopic gradients in rain p.41

Concentrations of heavy isotopes of hydrogen and oxygen decrease in rain as storms cross land. A model examines the transport of water vapour that causes this effect, and provides insight into past and present climates.

doi: 10.1038/516041a

A backup for bacteria p.42

The finding that intestinal viruses can substitute for intestinal bacteria to promote the health of their mammalian hosts raises the possibility that viruses in the gut may be beneficial in some circumstances. See Letter p.94

doi: 10.1038/nature13938

Stars fight back p.44

Galaxies contain fewer stars than predicted. The discovery of a massive galactic outflow of molecular gas in a compact galaxy, which forms stars 100 times faster than the Milky Way, may help to explain why. See Letter p.68

doi: 10.1038/516044a

A molecular knife to dice depression p.45

Chronic stress can cause depression in some individuals, but leaves others untouched. Engagement of a molecular pathway controlling the production of tiny RNA snippets might help to explain the difference. See Article p.51

doi: 10.1038/nature13942

Ultrafast imaging takes on a new design p.46

An imaging technique has been developed that can record non-repetitive ultrafast phenomena without strobe or flash illumination. The approach could find applications in biomedicine and security technologies. See Letter p.74

doi: 10.1038/516046a

Professional identity can increase dishonesty p.48

An experiment shows that although bank employees behave honestly on average, their dishonesty increases when they make decisions after having been primed to think about their professional identity. See Letter p.86

doi: 10.1038/nature14068

The good in fat p.49

A new class of fatty acid — found in food and synthesized by mammalian tissues — enhances glucose uptake from the blood and reduces inflammation, suggesting that these fats might be used to treat diabetes.

doi: 10.1038/nature14070

Articles

Deconstructing transcriptional heterogeneity in pluripotent stem cells p.56

This study uses single-cell expression profiling of pluripotent stem cells after various perturbations, and uncovers a high degree of variability that can be inherited through cell divisions—modulating microRNA or external signalling pathways induces a ground state with reduced gene expression heterogeneity and a distinct chromatin profile.

doi: 10.1038/nature13920

Structure of the V. cholerae Na+-pumping NADH:quinone oxidoreductase p.62

Here the structure of the membrane protein complex sodium-translocating NADH:quinone oxidoreductase (Na+-NQR) is described; as Na+-NQR is a component of the respiratory chain of various bacteria, including pathogenic ones, this structure may serve as the basis for the development of new antibiotics.

doi: 10.1038/nature14003

Letters

Nonlinear lattice dynamics as a basis for enhanced superconductivity in YBa2Cu3O6.5 p.71

Terahertz-frequency optical pulses can resonantly drive selected vibrational modes in solids and deform their crystal structures. In complex oxides, this method has been used to melt electronic order, drive insulator-to-metal transitions and induce superconductivity. Strikingly, coherent interlayer transport strongly reminiscent of superconductivity can be transiently induced up to room temperature (300 kelvin) in YBa2Cu3O6+x (refs 9, 10). Here we report the crystal structure of this exotic non-equilibrium state, determined by femtosecond X-ray diffraction and ab initio density functional theory calculations. We find that nonlinear lattice excitation in normal-state YBa2Cu3O6+x at above the transition temperature of 52 kelvin causes a simultaneous increase and decrease in the Cu–O2 intra-bilayer and, respectively, inter-bilayer distances, accompanied by anisotropic changes in the in-plane O–Cu–O bond buckling. Density functional theory calculations indicate that these motions cause drastic changes in the electronic structure. Among these, the enhancement in the character of the in-plane electronic structure is likely to favour superconductivity.

doi: 10.1038/nature13875

Business culture and dishonesty in the banking industry p.86

According to popular opinion, unethical business practices are common in the financial industry; here, the employees of a large, international bank are shown to behave, on average, honestly in a laboratory game to reveal dishonest behaviour, but when their professional identity as bank employees was rendered salient, the prevalence of dishonest behaviour increased.

doi: 10.1038/nature13977

Transcriptional regulation of autophagy by an FXR–CREB axis p.108

The FXR–CREB axis is identified as a key physiological switch that regulates autophagy during feeding/fasting cycles; in the fed state, the nuclear receptor FXR is shown to suppress autophagy in the liver by inhibiting autophagy-associated lipid breakdown triggered under fasting conditions by the transcriptional activator CREB.

doi: 10.1038/nature13949

Nutrient-sensing nuclear receptors coordinate autophagy p.112

The nuclear receptors FXR and PPARα are shown to regulate autophagy by competing for binding to shared sites in the promoters of autophagic genes; in the fed state FXR suppresses hepatic autophagy, whereas in the fasted state PPARα is activated and reverses the normal suppression of autophagy.

doi: 10.1038/nature13961

Piezo2 is the major transducer of mechanical forces for touch sensation in mice p.121

Mice lacking the mechanically activated ion channel Piezo2 in both sensory neurons and Merkel cells are almost totally incapable of light-touch sensation while other somatosensory functions, such as mechanical nociception, remain intact, implying that other mechanically activated ion channels must now be identified to account for painful touch sensation.

doi: 10.1038/nature13980

Physical mechanism for gating and mechanosensitivity of the human TRAAK K+ channel p.126

Activation of mechanosensitive ion channels by physical force underlies many physiological processes including the sensation of touch, hearing and pain. TRAAK (also known as KCNK4) ion channels are neuronally expressed members of the two-pore domain K+ (K2P) channel family and are mechanosensitive. They are involved in controlling mechanical and temperature nociception in mice. Mechanosensitivity of TRAAK is mediated directly through the lipid bilayer—it is a membrane-tension-gated channel. However, the molecular mechanism of TRAAK channel gating and mechanosensitivity is unknown. Here we present crystal structures of TRAAK in conductive and non-conductive conformations defined by the presence of permeant ions along the conduction pathway. In the non-conductive state, a lipid acyl chain accesses the channel cavity through a 5 Å-wide lateral opening in the membrane inner leaflet and physically blocks ion passage. In the conductive state, rotation of a transmembrane helix (TM4) about a central hinge seals the intramembrane opening, preventing lipid block of the cavity and permitting ion entry. Additional rotation of a membrane interacting TM2–TM3 segment, unique to mechanosensitive K2Ps, against TM4 may further stabilize the conductive conformation. Comparison of the structures reveals a biophysical explanation for TRAAK mechanosensitivity—an expansion in cross-sectional area up to 2.7 nm2 in the conductive state is expected to create a membrane-tension-dependent energy difference between conformations that promotes force activation. Our results show how tension of the lipid bilayer can be harnessed to control gating and mechanosensitivity of a eukaryotic ion channel.

doi: 10.1038/nature14013