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Volume 452 Issue 7190, 24 April 2008

In the early 1990s an outbreak of papaya ringspot virus (PRSV) in the papaya groves in the Puna district of Hawaii caused severe damage to an important crop. Since then, the planting of two transgenic cultivars resistant to the virus - called 'SunUp' and 'Rainbow' ãƒâƒã‚âƒãƒâ‚ã‚âƒãƒâƒã‚â‚ãƒâ‚ã‚âƒãƒâƒã‚âƒãƒâ‚ã‚â‚ãƒâƒã‚â‚ãƒâ‚ã‚â‚ãƒâƒã‚âƒãƒâ‚ã‚âƒãƒâƒã‚â‚ãƒâ‚ã‚â‚ãƒâƒã‚âƒãƒâ‚ã‚â‚ãƒâƒã‚â‚ãƒâ‚ã‚â— has helped to maintain yields. SunUp is a transgenic red-fleshed fruit that expresses the coat protein gene of a mild mutant of PRSV, conferring resistance via post-transcriptional gene silencing. Rainbow is a yellow-fleshed (and therefore more popular) F1 hybrid bred from SunUp. Now the draft genome sequence of the SunUp strain of papaya has been determined - a first for a commercial virus-resistant transgenic fruit tree. Comparison of this plant genome to those of Arabidopsis and others sheds light on the evolution of qualities such as biosynthesis, starch deposition, control of photosynthesis and pathways for creating the volatile compounds that contribute to the characteristic flavour of papaya. On the cover, the disease free transgenic Rainbow and the severely infected and stunted non-transgenic Sunrise grow in adjoining plots.

Editorial

  • Within the next decade or so, it will become possible to derive sperm and eggs from skin cells. The ethical and technical hurdles need to be addressed with the scientific and therapeutic benefits in mind.

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  • It's time to make the case for proteins.

    Editorial
  • Yet another surprise has been uncovered in the complex oxides.

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News

  • Dora Akunyili is director-general of Nigeria's National Agency for Food and Drug Administration and Control (NAFDAC). Since her appointment in 2001, she has led a successful crusade against counterfeit pharmaceuticals, which are responsible for millions of deaths worldwide each year. Nature caught up with her last week in Washington DC.

    • Meredith Wadman
    News
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News in Brief

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News Feature

  • Lyle Palmer has plans for a 'ludicrously ambitious' gene - disease research project. Bijal Trivedi reports on the trials at Joondalup.

    • Bijal Trivedi
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  • Battling rumours of death beams and mind control, an ionosphere research facility in Alaska finally brings science to the fore. Sharon Weinberger reports.

    • Sharon Weinberger
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Correspondence

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Commentary

  • Science funding in the European Union needs to be revised to better serve economic, social and environmental goals, Luke Georghiou argues.

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Books & Arts

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  • The gut prevents nutrient overload during a meal by promoting satiety and enhancing insulin secretion. New findings show that nutrients in the gut also activate a neural circuit that increases insulin sensitivity.

    • Joshua P. Thaler
    • David E. Cummings
    News & Views
  • Light always travels at the same speed in a vacuum, no more, no less. But in materials, there's room for manoeuvre: tweak the right material in the right way, and exciting optoelectronic properties result.

    • Diederik Sybolt Wiersma
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  • Insects possess refined olfactory systems that use specific receptors on their antennae. It emerges that these receptors not only detect odour molecules but, unexpectedly, can also act as ion channels.

    • Alexander Chesler
    • Stuart Firestein
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  • What do you see if you peer into the exhaust of a jet engine larger than our Solar System? Only astronomers with the largest radio telescopes can see the full picture — and definitive observations are beginning to filter through.

    • David L. Meier
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  • Why would two distant genes — on separate chromosomes and from different nuclear locations — unite in response to signals for gene expression? They might be seeds for the formation of transcriptional hubs.

    • David M. Lonard
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Article

  • The beetle Tribolium castaneum is a commonly used laboratory model, combining the ease of systematic RNAi experiments like those in Caenorhabditis elegans, with biology that is more representative of most insects than Drosophila melanogaster. A large consortium has sequenced and analysed the genome of the red flour beetle, creating a resource for biologists everywhere.

    • Stephen Richards
    • Richard A. Gibbs
    • Gregor Bucher
    Article Open Access
  • A study that combines in vivo systems neuroscience with synaptic physiology and Drosophila genetics identifies a presynaptic form of lateral inhibition in the olfactory system. The mechanism allows for a flexible form of gain control, which promotes coding efficiency when stimuli are strong and unambiguous, but maximizes sensitivity when stimuli are weak and ambiguous.

    • Shawn R. Olsen
    • Rachel I. Wilson
    Article
  • Base lesions can be directly repaired by oxidative dealkylation catalysed by AlkB in bacteria and by ABH2/ABH3 in man. Several structures of AlkB and ABH2 bound to dsDNA are solved. These structures reveal why AlkB prefers ssDNA to dsDNA substrates, and how ABH2 differs structurally, to allow it to repair dsDNA.

    • Cai-Guang Yang
    • Chengqi Yi
    • Chuan He
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Letter

  • Sequences of high-resolution radio images and optical polarization measurements of the blazar BL Lacertae are reported. The data reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV γ-ray energies. It is concluded that the event starts in a region with a helical magnetic field as envisaged by the theories.

    • Alan P. Marscher
    • Svetlana G. Jorstad
    • Wesley T. Ryle
    Letter
  • In the conventional quantum Hall effect, a two-dimensional electronic system in the presence of a magnetic field forms metallic conduction paths at the edge of the sample. This paper experimentally demonstrates a sought-after three-dimensional and spontaneous version of this effect; the bulk of a Bi0.9Sb0.1 crystal is shown to be insulating, while two-dimensional metallic conduction paths exist at the surface, without any applied magnetic field.

    • D. Hsieh
    • D. Qian
    • M. Z. Hasan
    Letter
  • This paper reports first-principles calculations of the role of phonons in La2−xSrxCuO4 (LSCO). It is demonstrated that the phonon-induced renormalization of the electron energies and the Fermi velocity is almost one order of magnitude smaller than the effect observed in photoemission experiments. Therefore the present finding rules out electron–phonon interaction in bulk LSCO as the exclusive origin of the measured kink.

    • Feliciano Giustino
    • Marvin L. Cohen
    • Steven G. Louie
    Letter
  • A global biogeochemical box model is used to test competing hypotheses put forward to explain the Eocene/Oligocene transition. It is found that only shelf-to-deep-sea carbonate partitioning is capable of explaining the observed changes in both carbon isotope composition and calcium carbonate accumulation at the sea floor. This work sheds new light on the mechanisms linking glaciation and ocean acidity change across the climate transition of the Cenozoic.

    • Agostino Merico
    • Toby Tyrrell
    • Paul A. Wilson
    Letter
  • The results of first-principles molecular dynamics simulations of hydrous silicate melt is reported, showing that pressure has a profound influence on speciation of the water component. It is inferred that the speciation changes from being dominated by hydroxyls and water molecules at low pressure to extended structures at high pressure. This change in structure is linked to the finding that the water–silicate system becomes increasingly ideal at high pressure, indicating complete miscibility of water and silicate melt throughout almost the entire mantle pressure regime.

    • Mainak Mookherjee
    • Lars Stixrude
    • Bijaya Karki
    Letter
  • It is reported that the current severe outbreak of the mountain pine beetle (Dendroctonus ponderosae) in British Columbia is likely to convert the forest from a small net carbon sink to a large net carbon source, something, it is argued, should be taken into account when modelling the impact of climate change on carbon cycling.

    • W. A. Kurz
    • C. C. Dymond
    • L. Safranyik
    Letter
  • Researchers from Hawaii and an international consortium have produced a draft genome assembly for 'SunUp', the first commercial virus-resistant transgenic fruit tree. Comparison of this plant genome to those of Arabidopsis and others sheds light on evolution of characteristics such as biosynthesis, starch deposition, control of photosynthesis and pathways for creating volatile compounds.

    • Ray Ming
    • Shaobin Hou
    • Maqsudul Alam
    Letter Open Access
  • Across human populations, individual ability to deal with stress and anxiety spans a wide range. The causes of emotional resilience are complex; this paper shows the contribution of genetic variance in expression of neuropeptide Y (NPY), an anxiolytic peptide released in emotion-related neural circuitry. Genetic variants were predictive of not only NPY levels, but also fMRI and PET activation in response to emotional stimuli and pain-induced stress.

    • Zhifeng Zhou
    • Guanshan Zhu
    • David Goldman
    Letter
  • Olfactory cues are detected by large families of seven transmembrane-spanning receptors, which have until now been classified as G-protein-coupled receptors. In insects, these odorant receptors require a second protein (Or83b) for correct function. These heteromeric receptors form ligand-gated cation channels that are not dependent on G protein-coupled second messengers and it is speculated that seven other transmembrane-spanning proteins may show similar ion channel activity.

    • Koji Sato
    • Maurizio Pellegrino
    • Kazushige Touhara
    Letter
  • Olfactory cues are detected by large families of seven transmembrane-spanning receptors, which have until now been classified as G-protein-coupled receptors. In insects, these odorant receptors require a second protein (Or83b) for correct function. The second of two related papers shows that, in addition to direct channel activation, ligand binding to odorant receptors causes G-protein-coupled channel activation.

    • Dieter Wicher
    • Ronny Schäfer
    • Bill S. Hansson
    Letter
  • The presence of lipids in the intestine causes a reduction in nutrient intake, but it is now shown that lipids present in the intestine also regulate endogenous nutrient production. According to the data, putative intra-intestinal lipid sensors signal the presence of ingested lipids, via the brain, to the liver, which reduces the endogenous glucose production accordingly.

    • Penny Y. T. Wang
    • Liora Caspi
    • Tony K. T. Lam
    Letter
  • A genome-wide screen for mRNAs that were polyadenylated at meiotic transitions noted that many contained an ARE, a deadenylation element, as well as a cytoplasmic polyadenylation element (CPE). One such mRNA encodes C3H-4, a protein that promotes shortening of polyA tails. The data suggest a model in which the early extension of polyadenylation through the CPE element leads to expression of C3H-4, which then acts in a negative feedback loop to deadenylate, and deactivate, those mRNAs that also contain an ARE, thereby allowing exit from metaphase.

    • Eulàlia Belloc
    • Raúl Méndez
    Letter
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Prospects

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Special Report

  • Young researchers in China face stiff competition as they strive to establish labs or find other scientific careers. Wei Zeng explores what it takes to succeed as a Chinese scientist.

    • Wei Zeng
    Special Report
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Movers

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Mentors and Protégés

  • From a student's struggles, a new mentor programme for minority students blossoms.

    • Betty Mbom
    Mentors and Protégés
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Career View

  • I sacrifice an awful lot in the name of science.

    • Aliza le Roux
    Career View
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Futures

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Authors

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