Volume 511 Number 7507

Editorials

STAP retracted p.5

Two retractions highlight long-standing issues of trust and sloppiness that must be addressed.

doi: 10.1038/511005b

Academic freedom under threat p.5

The human rights of academics in Egypt are being eroded by the military regime that has taken control of the country. The Arab Spring is on hold.

doi: 10.1038/511005a

Science and war p.6

As the centenary of its outbreak approaches, Nature looks back on the First World War.

doi: 10.1038/511006a

News

GM maize splits Mexico p.16

Legal challenge to transgenic crops has created a rift in the country's scientific community.

doi: 10.1038/511016a

News Features

Hope on the line p.19

A decade ago, voters in California changed the biomedical research landscape by directly funding embryonic stem-cell research. Now the organization they created needs a hit to survive.

doi: 10.1038/511019a

Planets in chaos p.22

The discovery of thousands of star systems wildly different from our own has demolished ideas about how planets form. Astronomers are searching for a whole new theory.

doi: 10.1038/511022a

News & Views

Use it or lose it p.34

A comparison of the development of adapted limbs in mammals uncovers multiple avenues to digit loss and highlights that early patterning events are not untouchable by evolutionary tinkering. See Articles p.41 & p.46

doi: 10.1038/nature13509

A tight duo in a trio of black holes p.35

Tight pairs of supermassive black holes are expected to emit gravitational waves that could give astronomers a new way to explore the cosmos. One relatively tight pair has been discovered within a rare triple system. See Letter p.57

doi: 10.1038/nature13511

Lipopolysaccharide rolls out the barrel p.37

Two crystal structures of the LptD–LptE protein complex reveal how the cell-wall component lipopolysaccharide is delivered and inserted into the external leaflet of the bacterial outer membrane. See Article p.52 & Letter p.108

doi: 10.1038/nature13508

Expulsion from history p.38

Global warming is projected to force climatic variables in some places beyond the range of historical experience, perhaps permanently. A reassessment shows that this could begin sooner or much later than recently estimated.

doi: 10.1038/511038a

Fixing the odds against tuberculosis p.39

A study that defines the interactions between three immunity-regulating molecules — type 1 interferon, interleukin-1 and prostaglandin E2 — will help to explain the variable outcomes of tuberculosis infections. See Letter p.99

doi: 10.1038/nature13512

Articles

Attenuated sensing of SHH by Ptch1 underlies evolution of bovine limbs p.46

The basic five-digit limb of tetrapods has been altered many times during evolution, usually by the progressive loss of digits — this study tracks the molecular underpinnings of this change, showing that in comparison to mouse, the polarized gene expression in the bovine limb bud is progressively lost due to evolutionary alteration of the cis-regulatory sequences that control Ptch1 expression in response to SHH signalling in the digit-forming handplate.

doi: 10.1038/nature13289

Structural basis for outer membrane lipopolysaccharide insertion p.52

Lipopolysaccharide, an essential component of the outer membranes of Gram-negative bacteria, is inserted by LptD–LptE, a protein complex with a unique ‘barrel and plug’ architecture; the structure, molecular dynamics simulations and functional assays of the LptD–LptE complex of Salmonella typhimurium suggest that lipopolysaccharide may pass through the barrel and is then inserted into the outer leaflet of the outer membrane through a lateral opening between two β-strands of LptD.

doi: 10.1038/nature13464

Letters

Giant nonlinear response from plasmonic metasurfaces coupled to intersubband transitions p.65

Multiple-quantum-well semiconductors can provide one of the largest known nonlinear material responses, which is, however, geometrically limited to light beams polarized perpendicular to the semiconductor layers; by coupling a plasmonic metasurface to the semiconductor heterostructure, this limitation can be lifted, opening a new path towards ultrathin planarized components with large nonlinear response.

doi: 10.1038/nature13455

Abrupt pre-Bølling–Allerød warming and circulation changes in the deep ocean p.75

Analysis of radiocarbon and uranium-series dates and clumped isotope temperature estimates from water column profiles of fossil deep-sea corals in the North Atlantic shows that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling–Allerød warming and reinvigoration of the Atlantic meridional overturning circulation 14,700 years ago.

doi: 10.1038/nature13472

Genomic divergence in a ring species complex p.83

Two species may be fully reproductively isolated at the point they meet, but be connected by continuous gene flow by a longer route around the back of a geographical barrier; such a ring species complex exists for the greenish warbler, and genomics shows that there have been several historical breaks in gene flow along the continuum, as well as some introgression between the end forms.

doi: 10.1038/nature13285

RLIM is dispensable for X-chromosome inactivation in the mouse embryonic epiblast p.86

The ubiquitin ligase RLIM is known to activate the long non-coding RNA Xist, which is crucial for X-chromosome inactivation in female mice; however, unlike imprinted X-chromosome inactivation that requires RLIM for Xist expression, evidence is now provided that during random X-chromosome inactivation Xist expression is regulated by an RLIM-independent pathway in vivo.

doi: 10.1038/nature13286

Structural basis for lipopolysaccharide insertion in the bacterial outer membrane p.108

Lipopolysaccharide, an essential component of the Gram-negative bacteria outer membrane, is inserted by LptD–LptE, a protein complex with a unique ‘barrel and plug’ architecture; the structure of the LptD–LptE complex of Shigella flexneri determined here shows LptD forming a 26-stranded β-barrel with LptE located inside the barrel of LptD, the first two β-strands are distorted by two proline residues, creating a potential portal in the barrel wall that might allow lateral diffusion of lipopolysaccharide into the outer membrane.

doi: 10.1038/nature13484