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Updated: 8 years 17 weeks ago

[Report] Transcriptional control of tissue formation throughout root development

Thu, 10/22/2015 - 23:00
Tissue patterns are dynamically maintained. Continuous formation of plant tissues during postembryonic growth requires asymmetric divisions and the specification of cell lineages. We show that the BIRDs and SCARECROW regulate lineage identity, positional signals, patterning, and formative divisions throughout Arabidopsis root growth. These transcription factors are postembryonic determinants of the ground tissue stem cells and their lineage. Upon further activation by the positional signal SHORT-ROOT (a mobile transcription factor), they direct asymmetric cell divisions and patterning of cell types. The BIRDs and SCARECROW with SHORT-ROOT organize tissue patterns at all formative steps during growth, ensuring developmental plasticity. Authors: Miguel A. Moreno-Risueno, Rosangela Sozzani, Galip Gürkan Yardımcı, Jalean J. Petricka, Teva Vernoux, Ikram Blilou, Jose Alonso, Cara M. Winter, Uwe Ohler, Ben Scheres, Philip N. Benfey
Categories: Journal Articles

[Report] Reduced grid-cell–like representations in adults at genetic risk for Alzheimer’s disease

Thu, 10/22/2015 - 23:00
Alzheimer’s disease (AD) manifests with memory loss and spatial disorientation. AD pathology starts in the entorhinal cortex, making it likely that local neural correlates of spatial navigation, particularly grid cells, are impaired. Grid-cell–like representations in humans can be measured using functional magnetic resonance imaging. We found that young adults at genetic risk for AD (APOE-ε4 carriers) exhibit reduced grid-cell–like representations and altered navigational behavior in a virtual arena. Both changes were associated with impaired spatial memory performance. Reduced grid-cell–like representations were also related to increased hippocampal activity, potentially reflecting compensatory mechanisms that prevent overt spatial memory impairment in APOE-ε4 carriers. Our results provide evidence of behaviorally relevant entorhinal dysfunction in humans at genetic risk for AD, decades before potential disease onset. Authors: Lukas Kunz, Tobias Navarro Schröder, Hweeling Lee, Christian Montag, Bernd Lachmann, Rayna Sariyska, Martin Reuter, Rüdiger Stirnberg, Tony Stöcker, Paul Christian Messing-Floeter, Juergen Fell, Christian F. Doeller, Nikolai Axmacher
Categories: Journal Articles

[Report] Methane metabolism in the archaeal phylum Bathyarchaeota revealed by genome-centric metagenomics

Thu, 10/22/2015 - 23:00
Methanogenic and methanotrophic archaea play important roles in the global flux of methane. Culture-independent approaches are providing deeper insight into the diversity and evolution of methane-metabolizing microorganisms, but, until now, no compelling evidence has existed for methane metabolism in archaea outside the phylum Euryarchaeota. We performed metagenomic sequencing of a deep aquifer, recovering two near-complete genomes belonging to the archaeal phylum Bathyarchaeota (formerly known as the Miscellaneous Crenarchaeotal Group). These genomes contain divergent homologs of the genes necessary for methane metabolism, including those that encode the methyl–coenzyme M reductase (MCR) complex. Additional non-euryarchaeotal MCR-encoding genes identified in a range of environments suggest that unrecognized archaeal lineages may also contribute to global methane cycling. These findings indicate that methane metabolism arose before the last common ancestor of the Euryarchaeota and Bathyarchaeota. Authors: Paul N. Evans, Donovan H. Parks, Grayson L. Chadwick, Steven J. Robbins, Victoria J. Orphan, Suzanne D. Golding, Gene W. Tyson
Categories: Journal Articles

[Report] Mechanosensitive channel MSL8 regulates osmotic forces during pollen hydration and germination

Thu, 10/22/2015 - 23:00
Pollen grains undergo dramatic changes in cellular water potential as they deliver the male germ line to female gametes, and it has been proposed that mechanosensitive ion channels may sense the resulting mechanical stress. Here, we identify and characterize MscS-like 8 (MSL8), a pollen-specific, membrane tension–gated ion channel required for pollen to survive the hypoosmotic shock of rehydration and for full male fertility. MSL8 negatively regulates pollen germination but is required for cellular integrity during germination and tube growth. MSL8 thus senses and responds to changes in membrane tension associated with pollen hydration and germination. These data further suggest that homologs of bacterial MscS have been repurposed in eukaryotes to function as mechanosensors in multiple developmental and environmental contexts. Authors: Eric S. Hamilton, Gregory S. Jensen, Grigory Maksaev, Andrew Katims, Ashley M. Sherp, Elizabeth S. Haswell
Categories: Journal Articles

[Report] Sperm calcineurin inhibition prevents mouse fertility with implications for male contraceptive

Thu, 10/22/2015 - 23:00
Calcineurin inhibitors, such as cyclosporine A and FK506, are used as immunosuppressant drugs, but their adverse effects on male reproductive function remain unclear. The testis expresses somatic calcineurin and a sperm-specific isoform that contains a catalytic subunit (PPP3CC) and a regulatory subunit (PPP3R2). We demonstrate herein that male mice lacking Ppp3cc or Ppp3r2 genes (knockout mice) are infertile, with reduced sperm motility owing to an inflexible midpiece. Treatment of mice with cyclosporine A or FK506 creates phenocopies of the sperm motility and morphological defects. These defects appear within 4 to 5 days of treatment, which indicates that sperm-specific calcineurin confers midpiece flexibility during epididymal transit. Male mouse fertility recovered a week after we discontinued treatment. Because human spermatozoa contain PPP3CC and PPP3R2 as a form of calcineurin, inhibition of this sperm-specific calcineurin may lead to the development of a reversible male contraceptive that would target spermatozoa in the epididymis. Authors: Haruhiko Miyata, Yuhkoh Satouh, Daisuke Mashiko, Masanaga Muto, Kaori Nozawa, Kogiku Shiba, Yoshitaka Fujihara, Ayako Isotani, Kazuo Inaba, Masahito Ikawa
Categories: Journal Articles

[Report] Direct observation of ultrafast collective motions in CO myoglobin upon ligand dissociation

Thu, 10/22/2015 - 23:00
The hemoprotein myoglobin is a model system for the study of protein dynamics. We used time-resolved serial femtosecond crystallography at an x-ray free-electron laser to resolve the ultrafast structural changes in the carbonmonoxy myoglobin complex upon photolysis of the Fe-CO bond. Structural changes appear throughout the protein within 500 femtoseconds, with the C, F, and H helices moving away from the heme cofactor and the E and A helices moving toward it. These collective movements are predicted by hybrid quantum mechanics/molecular mechanics simulations. Together with the observed oscillations of residues contacting the heme, our calculations support the prediction that an immediate collective response of the protein occurs upon ligand dissociation, as a result of heme vibrational modes coupling to global modes of the protein. Authors: Thomas R. M. Barends, Lutz Foucar, Albert Ardevol, Karol Nass, Andrew Aquila, Sabine Botha, R. Bruce Doak, Konstantin Falahati, Elisabeth Hartmann, Mario Hilpert, Marcel Heinz, Matthias C. Hoffmann, Jürgen Köfinger, Jason E. Koglin, Gabriela Kovacsova, Mengning Liang, Despina Milathianaki, Henrik T. Lemke, Jochen Reinstein, Christopher M. Roome, Robert L. Shoeman, Garth J. Williams, Irene Burghardt, Gerhard Hummer, Sébastien Boutet, Ilme Schlichting
Categories: Journal Articles

[Report] Ubiquitin facilitates a quality-control pathway that removes damaged chloroplasts

Thu, 10/22/2015 - 23:00
Energy production by chloroplasts and mitochondria causes constant oxidative damage. A functioning photosynthetic cell requires quality-control mechanisms to turn over and degrade chloroplasts damaged by reactive oxygen species (ROS). Here, we generated a conditionally lethal Arabidopsis mutant that accumulated excess protoporphyrin IX in the chloroplast and produced singlet oxygen. Damaged chloroplasts were subsequently ubiquitinated and selectively degraded. A genetic screen identified the plant U-box 4 (PUB4) E3 ubiquitin ligase as being necessary for this process. pub4-6 mutants had defects in stress adaptation and longevity. Thus, we have identified a signal that leads to the targeted removal of ROS-overproducing chloroplasts. Authors: Jesse D. Woodson, Matthew S. Joens, Andrew B. Sinson, Jonathan Gilkerson, Patrice A. Salomé, Detlef Weigel, James A. Fitzpatrick, Joanne Chory
Categories: Journal Articles

[Report] The Ro60 autoantigen binds endogenous retroelements and regulates inflammatory gene expression

Thu, 10/22/2015 - 23:00
Autoantibodies target the RNA binding protein Ro60 in systemic lupus erythematosus (SLE) and Sjögren’s syndrome. However, it is unclear whether Ro60 and its associated RNAs contribute to disease pathogenesis. We catalogued the Ro60-associated RNAs in human cell lines and found that among other RNAs, Ro60 bound an RNA motif derived from endogenous Alu retroelements. Alu transcripts were induced by type I interferon and stimulated proinflammatory cytokine secretion by human peripheral blood cells. Ro60 deletion resulted in enhanced expression of Alu RNAs and interferon-regulated genes. Anti-Ro60–positive SLE immune complexes contained Alu RNAs, and Alu transcripts were up-regulated in SLE whole blood samples relative to controls. These findings establish a link among the lupus autoantigen Ro60, Alu retroelements, and type I interferon. Authors: T. Hung, G. A. Pratt, B. Sundararaman, M. J. Townsend, C. Chaivorapol, T. Bhangale, R. R. Graham, W. Ortmann, L. A. Criswell, G. W. Yeo, T. W. Behrens
Categories: Journal Articles

[New Products] New Products

Thu, 10/22/2015 - 23:00
A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.
Categories: Journal Articles

[Podcast] Science Podcast: 23 October Show

Thu, 10/22/2015 - 23:00
On this week's show: What treating blindness in India can tell us about the brain and a roundup of daily news stories.
Categories: Journal Articles

[Association Affairs] AAAS 2016 Annual Meeting Program

Thu, 10/22/2015 - 23:00
This issue of Science includes the program of the 2016 AAAS Annual Meeting. The theme of the AAAS Annual Meeting in Washington, DC, 11 to 15 February 2016, is Global Science Engagement.A PDF of the program as it appears in this issue is available here; for more information on the meeting (including registration forms and information on accommodations), please visit www.aaas.org/meetings/.
Categories: Journal Articles

[Working Life] The power of mentoring

Thu, 10/22/2015 - 23:00
Author: Carol Lynn Curchoe
Categories: Journal Articles

[Editorial] Preimplantation genetic screens

Thu, 09/24/2015 - 23:00
Although our knowledge of genetic abnormalities that cause health disorders is expanding, the pace of discovering cures for genetic diseases is not nearly as fast. However, technologies applicable to preventing heritable genetic diseases have been developing, among them so-called “next-generation sequencing.” This efficient and inexpensive means to sequence DNA has revolutionized the study of genomics and could play a major role in future preimplantation genetic screening approaches. It may even improve screening during early pregnancy. Author: Arthur L. Beaudet
Categories: Journal Articles

[In Brief] This week's section

Thu, 09/24/2015 - 23:00
In science news around the world, the U.S. government decides against declaring the greater sage grouse an endangered species, a European Space Agency committee endorses the FLuorescence EXplorer as the agency's next mission, a U.K. researcher applies to edit the genes of human embryos, a U.S. National Academies panel wants Congress to create a new entity to oversee federal policies that affect academic research, the 2015 Ig Nobel Prizes are awarded, and more. Also, President Barack Obama nominates veteran heart researcher Robert Califf to be head of the U.S. Food and Drug Administration, Pope Francis selects Jesuit brother Guy Consolmagno to lead the Vatican Observatory, and lawyer Christopher Pyne is sworn in as Australia's science minister. And artist Kindra Crick, granddaughter of molecular biologist Francis Crick, talks with Science about the DNA sculpture she created for an upcoming auction to raise money for the London-based Francis Crick Institute.
Categories: Journal Articles

[In Depth] Sleuthing sheds light on STAP cell fiasco

Thu, 09/24/2015 - 23:00
Stressed-out cells sometimes glow under fluorescent light. That phenomenon, a common problem for researchers using fluorescent microscopy, may be at the root of last year's sensational claims surrounding STAP cells, the supposedly powerful stem cells derived using a remarkably simple recipe. The STAP claims have been shown to be false, and the two Nature papers describing the cells have both been retracted. Now, researchers from seven labs have described what they saw when they tried to replicate the experiments in the weeks and months following the original publications. All report observations that may have misled the researchers who made the original claims, including cells that glow, faintly, under fluorescent light. The STAP team took this for evidence that key stem cell genes had been turned on, but more cautious researchers would have realized the glow was an artifact, the authors of the new paper say. To avoid a repeat of the STAP fiasco, leading stem cell scientists lay out criteria in another paper for future claims about new ways to derive stem cells. They suggest a range of tests that should help protect against both misleading assays and cell line contamination; before they publish, researchers should also demonstrate that the technique can be replicated in independent laboratories. Author: Gretchen Vogel
Categories: Journal Articles

[In Depth] How teeth got tough: enamel's evolutionary journey

Thu, 09/24/2015 - 23:00
The hardest bit of your body is the enamel coating your teeth. But new analyses of fish fossils, as well as genetic analyses of a living fish species, suggest that this specialized material once served a very different function: to toughen some bones and scales of ancient fish. Well-preserved fossils of an ancient fish called Psarolepis romeri reveal that this 20-centimeter-long mini-predator, which prowled the seas between 410 million and 415 million years ago, had enamel in its scales and its skull--but not its teeth. The findings bolster earlier suggestions that ancient fish had armored scales, and they point to a new scenario for exactly how enamel ended up on teeth. Previously, researchers had suggested that over millions of years of evolution, hardened structures such as external scales gradually migrated into the mouth and changed shape to become teeth. But the patchy distribution of enamel in Psarolepis may suggest a different scenario, in which the pattern of enamel production, rather than the shape and location of already-enameled structures, shifted over time. Author: Sid Perkins
Categories: Journal Articles

[In Depth] The Martian's ode to science

Thu, 09/24/2015 - 23:00
The director, author, and a NASA expert on how they balanced realism and movie magic Author: Meghna Sachdev
Categories: Journal Articles

[In Depth] NIH opens precision medicine study to nation

Thu, 09/24/2015 - 23:00
Next year, the National Institutes of Health (NIH) expects to begin recruiting at least 1 million people for what may become the world's largest study of how genes influence disease risks and drug responses. Plans for the study came into focus last week with the release of a blueprint from a panel of human geneticists, medical researchers, and other experts. It urged that NIH recruit participants not only through academic medical centers and health care organizations, but also by issuing an open invitation to anyone living in the United States. For NIH Director Francis Collins, the project, known as the Precision Medicine Initiative (PMI) Cohort Program, brings to fruition an idea he first proposed 11 years ago. But whether NIH can design and effectively manage such a massive endeavor remains an open question. Author: Jocelyn Kaiser
Categories: Journal Articles

[In Depth] China's island building is destroying reefs

Thu, 09/24/2015 - 23:00
The geopolitical maneuvering in the South China Sea (SCS) is taking a heavy toll on the marine environment, scientists believe. The Spratly or Nansha Islands, a cluster of coral reefs and atolls, has become the focus of a territorial dispute between China and its neighbors. To the dismay of other countries bordering the SCS, China claims most of the sea, and it is bolstering its claims with a massive landfilling effort to transform some of the atolls into full-fledged islands. The scale and speed of the effort emerged earlier this month, when the Center for Strategic and International Studies in Washington, D.C., released high-resolution satellite photos showing that over the past 2 to 3 years, China has created 13 square kilometers of island area—abxzxout a quarter the size of Manhattan. In doing so, China has destroyed large areas of biodiverse reef that served as nurseries for fisheries throughout much of the SCS. Author: Christina Larson
Categories: Journal Articles

[In Depth] Scripps hooks prominent pair to lead it to health

Thu, 09/24/2015 - 23:00
The Scripps Research Institute has named two eminent scientists to lead one of the world's largest private biomedical research institutions. Scripps chemist Peter Schultz will serve as CEO, while Steve Kay, formerly a dean at the University of Southern California (USC), will serve as president. The announcement ends a contentious period between Scripps leadership and its faculty, who revolted a year ago when Scripps leaders attempted to merge the institute with USC. Schultz and Kay say they intend to marry the institute's historic strength in basic research with a new emphasis on translational research that aims to turn discoveries into medicines. If they succeed, the duo say, that should stabilize the institute's long-term finances. Author: Robert F. Service
Categories: Journal Articles