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Volume 471 Issue 7340, 31 March 2011

The early history of flowering plants (angiosperms) is contentious, but a steady stream of fossil discoveries from the Early Cretaceous of China is beginning to fill in some of the gaps in our knowledge. The latest of these, found in the Lower Cretaceous Yixian Formation, is a fossil that dates to between 124.4 million and 122.9 million years old. It is particularly informative because this angiosperm is a eudicot - the relatively derived group that dominates the flowering plants in the world today - and is also possibly a member of the Ranunculaceae. The fossil (pictured) confirms the presence of the eudicots at this time and documents an early burst of angiosperm evolution.

Editorial

World View

  • World View |

    Reassurances from 'experts' on the safety of nuclear power will not wash, says Colin Macilwain. The Fukushima crisis raises genuine questions.

    • Colin Macilwain

Research Highlights

Correction

Seven Days

News

News Feature

  • News Feature |

    Twenty-five years after the nuclear disaster, the clean-up grinds on and health studies are faltering. Are there lessons for Japan?

    • Mark Peplow
  • News Feature |

    Can computational social science help to prevent or win wars? The Pentagon is betting millions of dollars on the hope that it will.

    • Sharon Weinberger

Comment

  • Comment |

    A radical restructure is the only way to solve the systemic problems of the world's biggest funder of biomedical research, argues Michael M. Crow.

    • Michael M. Crow

Books & Arts

  • Books & Arts |

    From Roman reverence to dinosaur extinctions, Birger Schmitz is riveted by a history of the meteorite.

    • Birger Schmitz
  • Books & Arts |

    Nathan Myhrvold trained as a quantum cosmologist with Stephen Hawking and was chief technology officer of Microsoft before founding Intellectual Ventures, a US company that funds inventors and acquires patents. As he publishes a six-volume work on the science of cooking, Myhrvold explains why chemistry techniques could soon be seen in every restaurant.

  • Books & Arts |

    Thomas Schnalke calls on Germany to turn its historical scientific collections into centres for object research.

    • Thomas Schnalke

Correspondence

News & Views

  • News & Views |

    The natural pulse of a red-giant star provides crucial insight into what makes it shine. Observations of red giants by the Kepler space telescope shed light on a previously untested prediction of stellar evolution theory. See Letter p.608

    • Travis S. Metcalfe
  • News & Views |

    Memory T cells remember viruses from previous infections, providing immunity by facilitating the killing of infected cells. For this, they exploit cross-dressing, the transfer of antigens between antigen-presenting cells. See Letter p.629

    • Jonathan W. Yewdell
    • Brian P. Dolan
  • News & Views |

    There are various ways in which apparently 'silent' DNA mutations — those that don't result in a change in the encoded protein — have untoward consequences. A striking example has emerged in a study of Crohn's disease.

    • Laurence D. Hurst
  • News & Views |

    Twenty amino acids form the basis of all proteins, but another two genetically encoded amino acids have also been discovered. The biosynthesis of one of these, pyrrolysine, has now been elucidated. See Letter p.647

    • Stephen W. Ragsdale
  • News & Views |

    Winters are colder in northeastern North America and Asia than in other regions at the same latitude. Previous explanations may be incomplete, having overlooked the radiation of atmospheric wave energy. See Letter p.621

    • William R. Boos
  • News & Views |

    Signals from the external microenvironment or 'niche' determine the fate of stem cells. In the hair follicle, stem cells themselves seem to act as a niche for the adjoining muscle cells that cause goosebumps.

    • Bruce A. Morgan
  • News & Views |

    An exquisitely sensitive technique shows that a magnetic field only a few hundred times greater than Earth's can bring an exotic phase of matter known as a quantum spin liquid to an ordered magnetic state. See Letter p.612

    • Thomas F. Rosenbaum
  • News & Views |

    A newly discovered variation in the process by which bacteria resist invasion by foreign nucleic acids provides an intriguing parallel between the defence mechanisms of the different domains of life. See Article p.602

    • Susan Gottesman

Article

  • Article |

    In humans, vulnerability to tobacco addiction has been linked to variations in the gene encoding the α5 nicotinic acetylcholine receptor subunit, but the functional mechanisms linking gene to behaviour are unknown. Using a combination of knockout mice, lentiviral rescue, and RNAi knockdown in rats, this study shows that manipulating the levels of this subunit alters the drive to obtain nicotine, particularly at high doses that are aversive to wild-type animals. Furthermore, these subunits are implicated in the projection between medial habenula and interpeduncular nucleus in integrating negative side effects of high doses of nicotine and reward signals. It is proposed that this projection provides a negative motivational signal that limits nicotine consumption.

    • Christie D. Fowler
    • Qun Lu
    • Paul J. Kenny
  • Article |

    CRISPR is a microbial RNA-based immune system protecting against viral and plasmid invasions. The CRISPR system is thought to rely on cleavage of a precursor RNA transcript by Cas endonucleases, but not all species possessing CRISPR-type immunity encode Cas proteins. This study now describes an alternative pathway in Streptococcus pyogenes that employs trans-encoded small RNA that directs the processing of precursor RNA into crRNAs through endogenous RNase III and the CRISPR-associated Csn1 protein.

    • Elitza Deltcheva
    • Krzysztof Chylinski
    • Emmanuelle Charpentier

Letter

  • Letter |

    Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. However, it is difficult to distinguish between the two groups. Asteroseismology offers a way forward. This study reports observations of gravity-mode period spacings in red giants using high precision photometry obtained by the Kepler spacecraft. It is found that the stars fall into two clear groups, making it possible to distinguish unambiguously between hydrogen-shell-burning stars and those that are also burning helium.

    • Timothy R. Bedding
    • Benoit Mosser
    • Paolo Ventura
  • Letter |

    A quantum spin liquid is an intriguing exotic state of matter involving a magnetic system in which a magnetically ordered ground state at low temperatures is avoided despite strong interactions between magnetic units, due to quantum fluctuations. Experimental evidence for the existence of such a state has become available, but there are many fundamental questions about this novel state. This study uses an advanced magnetic probing technique, called muon spin rotation, to study a molecular layered system that is widely regarded as a prime candidate for quantum spin liquid. A complex magnetic phase diagram for this system is determined and characteristic critical properties of the spin liquid are measured, thereby providing important new insights into this exotic state of matter.

    • F. L. Pratt
    • P. J. Baker
    • G. Saito
  • Letter |

    Inelastic light scattering spectroscopy is a powerful tool in materials science to probe elementary excitations. In a quantum-mechanical picture, these excitations are generated by the incident photons via intermediate electronic transitions. It is now shown that it is possible to manipulate these intermediate 'quantum pathways' using electrostatically doped graphene. A surprising effect is revealed where blocking one pathway results in an increased intensity, unveiling a mechanism of destructive quantum interference between different Raman pathways. The study refines understanding of Raman scattering in graphene and indicates the possibility of controlling quantum pathways to produce unusual inelastic light scattering phenomena.

    • Chi-Fan Chen
    • Cheol-Hwan Park
    • Feng Wang
  • Letter |

    The presently accepted explanation for why the northeastern reaches of Asia and North America are far colder than western areas at similar latitudes relies on orographic controls of weather systems and the movement of prevailing atmospheric circulation over warm ocean currents. Here it is shown that oceans are indeed an important underlying cause, but via a different mechanism: the generation of strong atmospheric waves leading to anomalous cold over eastern continental boundaries.

    • Yohai Kaspi
    • Tapio Schneider
  • Letter |

    The early history of flowering plants (angiosperms) is contentious. However, many fossils attributable to flowering plants have been found in the Early Cretaceous of China. The plant reported in this study goes a step further: not only is it an angiosperm, but it is a member of a relatively derived group, the eudicots, and possibly a member of the Ranunculaceae, an extant family of plants. This indicates that angiosperm evolution probably got into its stride even earlier than the Early Cretaceous.

    • Ge Sun
    • David L. Dilcher
    • Zhiduan Chen
  • Letter |

    The ubiquitin conjugation system regulates the canonical NF-κB-activation pathway, which mediates immune responses. Linear polyubiquitin chains—in which the C-terminal glycine of ubiquitin is conjugated to the α-amino group of the amino-terminal methionine of another ubiquitin—are generated by a unique ubiquitin ligase complex called linear ubiquitin chain assembly complex (LUBAC) composed of two RING domain proteins called HOIL-1 and HOIP. This is one of three complementary studies identifying a novel component of the LUBAC complex called SHARPIN, which is recruited to receptor signalling complexes (RSCs) that form after TNF and CD40L stimulation. The LUBAC complex containing SHARPIN stimulates the formation of linear ubiquitin chains in vitro and in vivo and is required for the activation of NF-κB signalling.

    • Fuminori Tokunaga
    • Tomoko Nakagawa
    • Kazuhiro Iwai
  • Letter |

    The ubiquitin conjugation system regulates the canonical NF-κB activation pathway, which mediates immune responses. Linear polyubiquitin chains—in which the C terminal glycine of ubiquitin is conjugated to the α-amino group of the amino-terminal methionine of another ubiquitin—are generated by a unique ubiquitin ligase complex called linear ubiquitin chain assembly complex (LUBAC) composed of two RING domain proteins called HOIL-1 and HOIP. This is one of three complementary studies identifying a novel component of the LUBAC complex called SHARPIN, which is recruited to receptor signalling complexes (RSCs) that form after TNF and CD40L stimulation. The LUBAC complex containing SHARPIN stimulates the formation of linear ubiquitin chains in vitro and in vivo and is required for the activation of NF-κB signalling.

    • Fumiyo Ikeda
    • Yonathan Lissanu Deribe
    • Ivan Dikic
  • Letter |

    Exchange of sister chromatids to form four-stranded Holliday junctions occurs naturally during meiosis, to hold sister chromatids together, and during various repair events. In eukaryotes, double Holliday junctions that escape dissolution by a helicase/topoisomerase (BTR) complex are instead processed by one of several nucleases known as resolvases. This study defines the activities of the GEN1, MUS81-EME1 and SLX1-SLX4 resolvases in the absence of BLM, the helicase component of BTR that is mutated in Bloom's syndrome.

    • Thomas Wechsler
    • Scott Newman
    • Stephen C. West
  • Letter |

    Pyrrolysine is the twenty-second naturally occurring amino acid, and it is required for the formation of methane from methylamines. Pyrrolysine is the last remaining natural amino acid with a poorly characterized biosynthetic pathway. Here it is shown that the radical SAM protein PylB converts lysine to 3-methylornithine, which then undergoes a PylC-catalysed condensation with another lysine to generate a product that is oxidized by PylD to generate pyrrolysine.

    • Marsha A. Gaston
    • Liwen Zhang
    • Joseph A. Krzycki
  • Letter |

    Here the X-ray crystal structure of the metarhodopsin II intermediate of the photoreceptor rhodopsin is solved. Comparison of this structure with previously published structures enabled the proposal of how retinal translocation and rotation induce the conformational changes observed in this structure.

    • Hui-Woog Choe
    • Yong Ju Kim
    • Oliver P. Ernst
  • Letter |

    This study solves the X-ray crystal structure of a constitutively active mutant of rhodopsin, a G-protein-coupled receptor, bound to a peptide derived from the C-terminus of the G protein transducin. Comparison of this structure with the structure of ground-state rhodopsin suggests how translocation of the retinal β-ionone ring leads to a rotational tilt of transmembrane helix 6, the critical conformational change that occurs upon activation.

    • Jörg Standfuss
    • Patricia C. Edwards
    • Gebhard F. X. Schertler

Technology Feature

  • Technology Feature |

    For years, scientists have struggled to reconstruct tissues and organs by combining cells and nanotechnology. These devices are now edging from cool concept to practical application.

    • Monya Baker

Feature

Career Brief

Futures

  • Futures |

    What you don't know can help you.

    • Dan Erlanson

Brief Communications Arising

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