A rapid rise in radiocarbon around AD 775 measured in tree rings is attributed to an increase of cosmic-ray intensity. The specific cause of this cosmic-ray event remains to be determined, but this study suggests that neither a solar flare nor a local supernova is likely to have been responsible.
This press release contains:
---Summaries of newsworthy papers:
Genetics: A crop of genetic variants in maize
Methods: Tracking every cell in a developing embryo
Chemical Biology: Network approach to activating tumor cell death
Geoscience: Unexpected carbon sinks
Medicine: SRC-1’s role in endometriosis progression
Neuroscience: The mind’s eye
Medicine: Genetic regulator controls autoimmune disease
Immunology: Dampening lung inflammation
And finally…Nature: Eighth-century cosmic rays preserved in trees
---Geographical listing of authors
,  &  Genetics: A crop of genetic variants in maize
Re-sequencing of diverse varieties of maize from around the world is reported by three studies published online this week in Nature Genetics. The studies identify millions of genetic variants that should be useful for maize geneticists and breeders to further improve crop yield.
Maize is an important cereal crop, but its genome is very large—about the size of the human genome—and substantially more diverse than the human genome. It has been technically challenging to comprehensively characterize the enormous wealth of genomic diversity present in this crop.
Doreen Ware and colleagues performed re-sequencing of 103 maize lines, including 60 improved maize lines, 23 maize landraces and 19 wild relatives of maize. They also generated sequence for a sister genus of maize, Tripsacum dactyloides (Eastern gamagrass). They identified 55 million single nucleotide polymorphisms, which is a large resource for the maize genetics and breeding community. Jeffrey Ross-Ibarra and colleagues analyzed this dataset to identify regions of the genome that were selected for during the initial phase of domestication, as well as subsequent improvement of maize landraces to modern maize. They identify a large number of genes that appear to have been selected for during the transformation of wild to modern maize.
Finally, Jinsheng Lai and colleagues performed re-sequencing of 278 maize lines. They performed comprehensive characterization of sequence variation present in these diverse maize lines, and identified a number of genetic regions that display evidence of selection during maize domestication.
Doreen Ware (Cold Spring Harbor Laboratory, NY, USA) Author paper 
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Jeffrey Ross-Ibarra (University of California, Davis, CA, USA) Author paper 
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Jinsheng Lai (China Agricultural University, Beijing, China) Author paper 
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 &  Methods: Tracking every cell in a developing embryo
Powerful microscopes capable of three-dimensional imaging and tracking of the cells in a developing fly embryo are described by two independent studies published online this week in Nature Methods.
Philipp Keller and colleagues and Lars Hufnagel and colleagues independently designed and built similar microscope systems that allow fast three-dimensional imaging of fluorescently labelled cells throughout an embryo—up to several millimeters in size—every 30 seconds or less. By illuminating the specimen with two independent and perpendicular sheets of light and imaging from two sides, they achieved sufficient speed and resolution to track fast-moving individual cells, as well as changes in their shape at a subcellular scale; the technique was able to image an entire fly embryo for up to 20 hours until the embryo hatched and the larvae crawled away.
These microscope systems acquire hundreds of megabytes of image data every second and should allow for the observation of small living organisms in their entirety at a previously inaccessible level of detail.
Philipp Keller (Howard Hughes Medical Institute, Ashburn, VA, USA)
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Lars Hufnagel (EMBL, Heidelberg, Germany)
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 Chemical Biology: Network approach to activating tumor cell death
New targets that when inhibited in combination with the activation of p53 can lead to cancer cell death are reported this week in Nature Chemical Biology.
p53 is a tumor suppressor that regulates cellular response to various stresses and it is known that the activation of p53 can promote cell death. The activation of p53 in cancer cells often results in reversible growth arrest rather than death of the cells. However, the pathways that govern cellular response—growth arrest versus death—in response to p53 activation are not well understood.
Joaquin Espinosa and colleagues perform a genome-wide screen to identify genes that modify response to the activation of p53 in cells that undergo growth arrest compared to those that die. They identify several pathways that were previously not known to impact a cell’s response to p53, and demonstrate that inhibition of the protein kinases ATM and MET in combination with activation of p53 promotes cell death. As inhibitors for both of these kinases are available but were set aside as they were not effective alone, the authors recommend that these drugs could be revisited and tested in combination with agents such as Nutlin-3 that activate p53.
Joaquin Espinosa (University of Colorado, Boulder, CO, USA)
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 Geoscience: Unexpected carbon sinks
Activity by organisms such as lichens, fungi and algae accounts for nearly half of the land-based conversion of atmospheric nitrogen into a chemical form that is useable by most plants, reports a study published online this week in Nature Geoscience. Because bio-available nitrogen often limits plant growth, this process could be crucial for carbon sequestration by plants.
Ulrich Poeschl and colleagues re-analysed published data on the spatial coverage of organisms that synthesize their own food from inorganic substances with the help of sunlight, such as lichens, fungi and algae. Based on their analysis of data on fluxes of carbon and nitrogen in a range of ecosystems, they estimate that these organisms contribute about 7% of the net primary production of the terrestrial vegetation, in addition to their role in the nitrogen cycle.
Ulrich Poeschl (Max-Planck Institute for Chemistry, Mainz, Germany)
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 Medicine: SRC-1’s role in endometriosis progression
The role that a particular steroid receptor coactivator, SRC-1, plays in the progression of endometriosis is elucidated in a paper published online in Nature Medicine this week. The work suggests that this protein could be used as a molecular target for the therapy of this disease.
Endometriosis is considered to be an estrogen-dependent inflammatory disease of the uterus. Previously, Bert W O’Malley and colleagues found lowered amounts of the full length SRC-1 protein in endometriotic tissue but how it contributes to disease progression remains unknown.
The authors now find that a previously unidentified truncated form of the protein, 70-kDa SRC-1, is highly elevated both in the endometriotic tissue of mice with surgically induced endometriosis and in endometriotic cells of the microenvironment of tissue samples from individuals with the disease. This increase is caused in response to signalling from the inflammatory mediator TNF-alpha.
The authors therefore propose a new pathogenic pathway, involving a shorter form of SRC-1, for the progression of endometriosis. The finding also suggests that the TNF-alpha therapy, etanercept, may be useful to treat this disease.
Bert W O’Malley (Baylor College of Medicine, Houston, TX, USA)
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 Neuroscience: The mind’s eye
Activity in the temporoparietal junction (TPJ) of the human brain could be the signature of visual perception, according to a study published online this week in Nature Neuroscience. These results suggest that signals in the TPJ support conscious awareness.
Previous work suggested that the TPJ is critical for detecting salient or unexpected stimuli, and damage to this area can result in spatial neglect, a deficit in the control of attention.
Michael Beauchamp and colleagues worked with patients who had electrodes implanted into their brains for surgical treatment of epilepsy. They stimulated an area in the early visual system of each person’s brain with low intensity electrical pulses that sometimes evoked the perception of a flash of light and sometimes did not. They found that people only reported seeing a light on occasions when there was also a response in the TPJ. The authors found that disruption of signals in the TPJ decreased the detectability of a barely visible visual target, further linking this brain area to visual perception.
Michael Beauchamp (University of Texas Medical School, Houston, TX, USA)
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 Medicine: Genetic regulator controls autoimmune disease
A class of genetic regulators called microRNAs can directly influence the severity of inflammatory diseases reports a study published online this week in Nature Medicine. Moreover, an inflammatory response can be amplified by turning off microRNAs, pointing to novel ways to decrease damaging inflammatory responses by influencing genetic regulatory programs.
Increased amounts of the cytokine interleukin-17 (IL-17) are found in several autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis. This cytokine promotes inflammatory damage by influencing the development of circulating immune cells. Youcun Qian and colleagues found that IL-17 can also contribute to this damage by suppressing a specific microRNA called miR-23b in cells residing in tissues. IL-17 amounts were elevated in the kidney and joint of individuals with systemic lupus erythematosus and rheumatoid arthritis, respectively, whereas the expression of miR-23b was decreased. The authors found a direct relationship between these two molecules in three mouse models of autoimmune disease—lupus, rheumatoid arthritis and multiple sclerosis—with IL-17 reducing the expression of miR-23b. Its overexpression, in turn, blocked autoimmune disease development in these mouse models.
Youcun Qian (Shanghai Institutes for Biological Sciences, China)
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 Immunology: Dampening lung inflammation
The way in which the inflammatory activity of the cytokine IL-33 is controlled is explained in a paper in Nature Immunology this week. IL-33 plays an important role in inflammatory conditions of the lung, such as asthma and understanding how this pathway is regulated may provide a strategy to ease such inflammatory conditions.
IL-33 mediates its effects exclusively through its receptor ST2L which led Yutong Zhao and colleagues to look at ways in which this interaction could be regulated. They identified an intracellular molecule called FBXL19 which binds directly to ST2L causing it to be degraded, thereby blunting the inflammatory action of IL-33. Loss of FBXL19 exacerbated the symptoms of lung inflammation whereas an overabundance of this molecule dampened inflammation. Because of the widespread expression of ST2L, the authors conclude that FBXL19 likely plays a generalized role in controlling the pro-inflammatory effects of IL-33.
Yutong Zhao (University of Pittsburgh, PA, USA)
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 And finally…Nature: Eighth-century cosmic rays preserved in trees
A rapid rise in radiocarbon around AD 775 measured in tree rings is attributed to an increase of cosmic-ray intensity in a Nature paper this week. Cosmic rays are thought to originate from a variety of sources, and the specific cause of this cosmic-ray event remains to be determined, but this study suggests that neither a solar flare nor a local supernova is likely to have been responsible.
Rises in the carbon-14 (14C) content of trees in the past 3,000 years have been detected in previous studies, but none have shown increases on the timescale of around one year. Achieving this resolution, Fusa Miyake and colleagues report radiocarbon measurements in annual rings of Japanese cedar trees that demonstrate a rapid increase in 14C content, around 12‰ (1.2%), from AD 774 to AD 775. These findings are consistent with data from North American and European trees and from Antarctic ice cores, indicating that elevated 14C resulted from an increase in cosmic-ray intensity.
The authors rule out solar flares as the cause because the 14C spike is around 20 times larger than expected from this solar activity. Likewise, the rapid increase in 14C is not consistent with a supernova explosion, and no such events have been recorded for this time.
Fusa Miyake (Nagoya University, Japan)
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 Neural population dynamics during reaching
 Structure of the immature retroviral capsid at 8Å resolution by cryo-electron microscopy
DOI: 10.1038/nature 11169
 Programmable single-cell mammalian biocomputers
DOI: 10.1038/nature 11149
 PGC7 binds histone H3K9me2 to protect against conversion of 5mC to 5hmC in early embryos
DOI: 10.1038/nature 11093
 Autoregulation of microRNA biogenesis by let-7 and Argonaute
DOI: 10.1038/nature 11134
 A map of nucleosome positions in yeast at base-pair resolution
DOI: 10.1038/nature 11142
NATURE CELL BIOLOGY
 Syndecan–syntenin–ALIX regulates the biogenesis of exosomes
 Genome-wide RNAi screening identifies human proteins with a regulatory function in the early secretory pathway
 MPS1/Mph1 phosphorylates the kinetochore protein KNL1/Spc7 to recruit SAC components
NATURE CHEMICAL BIOLOGY
 KlenTaq polymerase replicates unnatural base pairs by inducing a Watson-Crick geometry
 Mechanically induced chemiluminescence from polymers incorporating a 1,2-dioxetane unit in the main chain
 An ultrasensitive universal detector based on neutralizer displacement
 Closed-shell and open-shell square-planar iridium nitrido complexes
 Single solvent molecules can affect the dynamics of substitution reactions
NATURE CLIMATE CHANGE
 Vulnerability of US and European electricity supply to climate change
 Transfer payments in global climate policy
 Eurasian Arctic greening reveals teleconnections and the potential for structurally novel ecosystems
 The beet R locus encodes a new cytochrome P450 required for red betalain production
 Photocrosslinkable pMHC monomers stain T cells specifically and cause ligand-bound TCRs to be ‘preferentially’ transported to the cSMAC
 A partially interpenetrated metal–organic framework for selective hysteretic sorption of carbon dioxide
 Viral delivery of miR-196a ameliorates the spinal and bulbar muscular atrophy phenotype via the silencing of CUGBP, Elav-like family member 2
 Single cell systems biology by super-resolution imaging and combinatorial labeling
 Molecularly self-assembled nucleic acid nanoparticles for targeted in vivo siRNA delivery
 Protein–inorganic hybrid nanoflowers
 Flexible molecular-scale electronic devices
 Dual-gated bilayer graphene hot-electron bolometer
 Rational regulation of learning dynamics by pupil-linked arousal systems
 State- and location-dependence of action potential metabolic cost in cortical pyramidal neurons
 Structure and functional interaction of the extracellular domain of human GABAB receptor GBR2
 Quantum interference and phonon-mediated back-action in lateral quantum-dot circuits
 Highly efficient spin transport in epitaxial graphene on SiC
 Multiscale photosynthetic and biomimetic excitation energy transfer
 Emergent rank-5 nematic order in URu2Si2
NATURE STRUCTURAL & MOLECULAR BIOLOGY
 AMP-activated protein kinase undergoes nucleotide-dependent conformational changes
 Duplex interrogation by a direct DNA repair protein in search of base damage
 Intronic RNAs mediate EZH2 regulation of epigenetic targets
GEOGRAPHICAL LISTING OF AUTHORS
The following list of places refers to the whereabouts of authors on the papers numbered in this release. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.
St Lucia: 44
Beijing: 1, 2, 3, 36, 46, 47
Shanghai: 10, 19, 46, 47
Shenzen: 1, 3
Grenoble: 43, 46
Goettingen: 25, 40
Heidelberg: 5, 14, 20
Mulheim an der Ruhr: 25
Kyoto: 16, 45
Nagoya: 12, 33
Tokyo: 21, 45
Amsterdam: 25, 40
UNITED STATES OF AMERICA
Davis: 1, 3
La Jolla: 17, 22, 26
Los Angeles: 37
Palo Alto: 13
San Diego: 22
San Francisco: 31
Stanford: 13, 31, 36
College Park: 38
East Lansing: 30
St Paul: 3
Columbia: 1, 3
Cold Spring Harbor: 1, 3
Ithaca: 1, 3
New York: 13, 41
Houston: 8, 9, 37
Madison: 1, 3, 30
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