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Zhenchuan Ma, Lin Zhu, Tianqiao Song, Yang Wang, Qi Zhang, Yeqiang Xia, Min Qiu, Yachun Lin, Haiyang Li, Liang Kong, Yufeng Fang, Wenwu Ye, Yan Wang, Suomeng Dong, Xiaobo Zheng, Brett M Tyler, Yuanchao Wang
The extracellular space (apoplast) of plant tissue represents a critical battleground between plants and attacking microbes. Here we show that a pathogen-secreted apoplastic Xyloglucan-specific EndoGlucanase PsXEG1 is a focus of this struggle in the Phytophthora sojae-soybean interaction. We show that soybean produces an apoplastic Glucanase Inhibitor Protein, (GmGIP1), that binds to PsXEG1 to block its contribution to virulence. P. sojae however, secretes a paralogous PsXEG1-Like Protein (PsXLP1) that has lost enzyme activity but binds to GmGIP1 more tightly than does PsXEG1, thus freeing PsXEG1 to support P...
January 12, 2017: Science
Yong Jin Choi, Chao-Po Lin, Davide Risso, Sean Chen, Thomas Aquinas Kim, Meng How Tan, Jin B Li, Yalei Wu, Caifu Chen, Zhenyu Xuan, Todd Macfarlan, Weiqun Peng, K C Kent Lloyd, Sang Yong Kim, Terence P Speed, Lin He
Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) efficiently generate all embryonic cell lineages, but rarely generate extra-embryonic cell types. We show that microRNA miR-34a deficiency expands the developmental potential of mouse pluripotent stem cells to yield both embryonic and extra-embryonic lineages and strongly induce MuERV-L (MERVL) endogenous retroviruses, similar to what is seen with totipotent 2-cell blastomeres. miR-34a restricts the acquisition of expanded cell fate potential in pluripotent stem cells, and represses MERVL expression through transcriptional regulation, at least in part, by targeting the transcription factor Gata2...
January 12, 2017: Science
Julia Su Zhou Li, Javier Miralles Fuste, Tatevik Simavorian, Cristina Bartocci, Jill Tsai, Jan Karlseder, Eros Lazzerini Denchi
Telomeres are found at the end of chromosomes and are important for chromosome stability. Here, we describe a specific telomere-associated protein: TZAP (Telomeric Zinc finger-Associated Protein). TZAP binds preferentially to long telomeres that have a low concentration of shelterin complex, competing with the telomeric repeat binding factors TRF1 and TRF2. When localized at telomeres, TZAP triggers "telomere trimming," a process that results in the rapid deletion of telomeric repeats. Based on these results, we propose a model for telomere length regulation in mammalian cells: The reduced concentration of the shelterin complex at long telomeres results in TZAP binding and initiation of telomere trimming...
January 12, 2017: Science
H B D Prasada Rao, Huanyu Qiao, Shubhang K Bhatt, Logan R J Bailey, Hung D Tran, Sarah L Bourne, Wendy Qiu, Anusha Deshpande, Ajay N Sharma, Connor J Beebout, Roberto J Pezza, Neil Hunter
Meiosis produces haploid gametes through a succession of chromosomal events including pairing, synapsis and recombination. Mechanisms that orchestrate these events remain poorly understood. We found that the SUMO-modification and ubiquitin-proteasome systems regulate the major events of meiotic prophase in mouse. Interdependent localization of SUMO, ubiquitin and proteasomes along chromosome axes was mediated largely by RNF212 and HEI10, two E3 ligases that are also essential for crossover recombination. RNF212-dependent SUMO conjugation effected a checkpoint-like process that stalls recombination by rendering the turnover of a subset of recombination factors dependent on HEI10-mediated ubiquitylation...
January 5, 2017: Science
Jasvinder S Ahuja, Rima Sandhu, Rana Mainpal, Crystal Lawson, Hanna Henley, Patricia A Hunt, Judith L Yanowitz, G Valentin Börner
During meiosis, paired homologous chromosomes (homologs) become linked via the synaptonemal complex (SC) and crossovers. Crossovers mediate homolog segregation and arise from self-inflicted double-strand breaks (DSBs). Here, we identified a role for the proteasome, the multi-subunit protease that degrades proteins in the nucleus and cytoplasm, in homolog juxtaposition and crossing over. Without proteasome function, homologs failed to pair and instead remained associated with non-homologous chromosomes. While dispensable for non-crossover formation, a functional proteasome was required for a coordinated transition that entails SC assembly between longitudinally organized chromosome axes and stable strand exchange of crossover-designated DSBs...
January 5, 2017: Science
Maksim V Plikus, Christian F Guerrero-Juarez, Mayumi Ito, Yun Rose Li, Priya H Dedhia, Ying Zheng, Mengle Shao, Denise L Gay, Raul Ramos, Tsai-Ching His, Ji Won Oh, Xiaojie Wang, Amanda Ramirez, Sara E Konopelski, Arijh Elzein, Anne Wang, Rarinthip June Supapannachart, Hye-Lim Lee, Chae Ho Lim, Arben Nace, Amy Guo, Elsa Treffeisen, Thomas Andl, Ricardo N Ramirez, Rabi Murad, Stefan Offermanns, Daniel Metzger, Pierre Chambon, Alan D Widgerow, Tai-Lan Tuan, Ali Mortazavi, Rana K Gupta, Bruce A Hamilton, Sarah E Millar, Patrick Seale, Warren S Pear, Mitchell A Lazar, George Cotsarelis
Although regeneration via the reprogramming of one cell lineage to another occurs in fish and amphibians, it is not observed in mammals. We discovered in mouse that during wound healing adipocytes regenerate from myofibroblasts, a cell type thought to be differentiated and non-adipogenic. Myofibroblast reprogramming required neogenic hair follicles, which triggered BMP signaling and then activation of adipocyte transcription factors expressed during development. Overexpression of the BMP antagonist, noggin, in hair follicles or deletion of the BMP receptor in myofibroblasts prevented adipocyte formation...
January 5, 2017: Science
Yoann Pertot, Cédric Schmidt, Mary Matthews, Adrien Chauvet, Martin Huppert, Vit Svoboda, Aaron von Conta, Andres Tehlar, Denitsa Baykusheva, Jean-Pierre Wolf, Hans Jakob Wörner
Time-resolved X-ray absorption spectroscopy (TR-XAS) has so far practically been limited to large-scale facilities, to sub-picosecond temporal resolution and to the condensed phase. Here, we report the realization of TR-XAS with a temporal resolution in the low femtosecond range by developing a table-top high-harmonic source reaching up to 350 eV, thus partially covering the spectral region of 280 to 530 eV, where water is transmissive. We use this source to follow previously unexamined light-induced chemical reactions in the lowest electronic states of isolated CF4(+) and SF6(+) molecules in the gas phase...
January 5, 2017: Science
Vy Nguyen, Christopher Wilson, Marc Hoemberger, John B Stiller, Roman V Agafonov, Steffen Kutter, Justin English, Douglas L Theobald, Dorothee Kern
With early life likely to have existed in a hot environment, enzymes had to cope with an inherent drop in catalytic speed caused by lowered temperature. Here we characterize the molecular mechanisms underlying thermoadaptation of enzyme catalysis in adenylate kinase using ancestral sequence reconstruction spanning 3 billion years of evolution. We show that evolution solved the enzyme's key kinetic obstacle-how to maintain catalytic speed on a cooler Earth-by exploiting transition-state heat capacity. Tracing the evolution of enzyme activity and stability from the hot-start toward modern hyperthermophilic, mesophilic, and psychrophilic organisms illustrates active pressure versus passive drift in evolution on a molecular level, refutes the debated activity/stability trade-off, and suggests that the catalytic speed of adenylate kinase is an evolutionary driver for organismal fitness...
December 22, 2016: Science
Francisco Balzarotti, Yvan Eilers, Klaus C Gwosch, Arvid H Gynnå, Volker Westphal, Fernando D Stefani, Johan Elf, Stefan W Hell
We introduce MINFLUX, a concept for localizing photon emitters in space. By probing the emitter with a local intensity minimum of excitation light, MINFLUX minimizes the fluorescence photons needed for high localization precision. A 22-fold reduction of photon detections over that required in popular centroid-localization is demonstrated. In superresolution microscopy, MINFLUX attained ~1-nm precision, resolving molecules only 6 nm apart. Tracking single fluorescent proteins by MINFLUX increased the temporal resolution and the number of localizations per trace by 100-fold, as demonstrated with diffusing 30S ribosomal subunits in living Escherichia coli As conceptual limits have not been reached, we expect this localization modality to break new ground for observing the dynamics, distribution, and structure of macromolecules in living cells and beyond...
December 22, 2016: Science
X Mi, J V Cady, D M Zajac, P W Deelman, J R Petta
Silicon is vital to the computing industry due to the high quality of its native oxide and well-established doping technologies. Isotopic purification, and the resulting seconds-long quantum coherence times, have recently put Si at the forefront of efforts to create a solid state quantum processor. Here we demonstrate strong coupling of a single electron in a silicon double quantum dot to the photonic field of a microwave cavity, as shown by the observation of vacuum Rabi splitting. Strong coupling of a quantum dot electron to a cavity photon would allow for long-range qubit coupling, and the long-range entanglement of electrons in semiconductor quantum dots...
December 22, 2016: Science
Chuangye Yan, Ruixue Wan, Rui Bai, Gaoxingyu Huang, Yigong Shi
Each cycle of pre-mRNA splicing comprises two sequential reactions, first freeing the 5'-exon and generating an intron lariat-3'-exon, and then ligating the two exons and releasing the intron lariat. The second reaction is executed by the step II catalytically activated spliceosome (known as the C* complex). Here, we present the cryo-electron microscopy (cryo-EM) structure of a C* complex from Saccharomyces cerevisiae at an average resolution of 4.0 Å. Compared with the preceding spliceosomal complex (C complex), the lariat junction has been translocated by 15 to 20 Å to vacate space for the incoming 3'-exon sequences...
December 15, 2016: Science
Malik Chaker-Margot, Jonas Barandun, Mirjam Hunziker, Sebastian Klinge
The small subunit (SSU) processome, a large ribonucleoprotein particle, organizes the assembly of the eukaryotic small ribosomal subunit by coordinating the folding, cleavage and modification of nascent pre-rRNA. Here, we present the cryo-EM structure of the yeast SSU processome at 5.1 Å resolution. The structure reveals how large ribosome biogenesis complexes assist the 5' external transcribed spacer and U3 snoRNA in providing an intertwined RNA-protein assembly platform for the separate maturation of 18S rRNA domains...
December 15, 2016: Science
T H Prettyman, N Yamashita, M J Toplis, H Y McSween, N Schorghofer, S Marchi, W C Feldman, J Castillo-Rogez, O Forni, D J Lawrence, E Ammannito, B L Ehlmann, H G Sizemore, S P Joy, C A Polanskey, M D Rayman, C A Raymond, C T Russell
The surface elemental composition of dwarf planet Ceres constrains its regolith ice content, aqueous alteration processes, and interior evolution. Using nuclear spectroscopy data acquired by NASA's Dawn mission, we determined the concentrations of H, Fe, and K on Ceres. The data show that surface materials were processed by the action of water within the interior. The non-icy portion of Ceres' C-bearing regolith contains similar amounts of H to aqueously altered carbonaceous chondrites, but less Fe. This allows for the possibility that Ceres experienced modest ice-rock fractionation, resulting in differences between surface and bulk composition...
December 15, 2016: Science
Alexei Kiselev, Felix Bachmann, Philipp Pedevilla, Stephen J Cox, Angelos Michaelides, Dagmar Gerthsen, Thomas Leisner
Ice formation on aerosol particles is a process of crucial importance to Earth's climate and the environmental sciences but it is not understood at the molecular level. This is so partly because the nature of active sites, local surface features where ice growth commences, is still unclear. Here we report direct electron-microscopic observations of deposition growth of aligned ice crystals on feldspar, an atmospherically important component of mineral dust. Our molecular-scale computer simulations indicate that this alignment arises from the preferential nucleation of prismatic crystal planes of ice on high-energy (100) surface planes of feldspar...
December 8, 2016: Science
Kyle C Costa, Nathaniel R Glasser, Stuart J Conway, Dianne K Newman
The opportunistic pathogen Pseudomonas aeruginosa produces colorful redox-active metabolites called phenazines, which underpin biofilm development, virulence and clinical outcomes. Though phenazines exist in many forms, the best studied is pyocyanin. Here, we describe pyocyanin demethylase (PodA), a hitherto uncharacterized protein that oxidizes the pyocyanin methyl group to formaldehyde and reduces the pyrazine ring via an unusual tautomerizing demethylation reaction. Treatment with PodA disrupts P. aeruginosa biofilm formation similarly to DNase, suggesting interference with the pyocyanin-dependent release of extracellular DNA into the matrix...
December 8, 2016: Science
Om Prakash, Anil Kumar, A Thamizhavel, S Ramakrishnan
At ambient pressure, bulk rhombohedral bismuth (Bi) is a semimetal that remains in the normal state down to at least 10 mK. The superconductivity (SC) in bulk Bi is thought to be unlikely because of the extremely low carrier density. We observe bulk SC in pure Bi single crystals below 0.53 mK under ambient pressure with an estimated critical magnetic field of 5.2 μT at 0 K. SC in Bi cannot be explained by the conventional Bardeen-Cooper-Schrieffer theory because its adiabatic approximation does not hold true for Bi...
December 1, 2016: Science
Rush Holt
No abstract text is available yet for this article.
November 17, 2016: Science
Daniel Barredo, Sylvain de Léséleuc, Vincent Lienhard, Thierry Lahaye, Antoine Browaeys
Large arrays of individually controlled atoms trapped in optical tweezers are a very promising platform for quantum engineering applications. However, deterministic loading of the traps is experimentally challenging. Here, we demonstrate the preparation of fully loaded, two-dimensional arrays of up to ~50 microtraps each containing a single atom, and arranged in arbitrary geometries. Starting from initially larger, half-filled matrices of randomly loaded traps, we obtain user-defined target arrays at unit filling...
November 3, 2016: Science
Manuel Endres, Hannes Bernien, Alexander Keesling, Harry Levine, Eric R Anschuetz, Alexandre Krajenbrink, Crystal Senko, Vladan Vuletic, Markus Greiner, Mikhail D Lukin
The realization of large-scale fully controllable quantum systems is an exciting frontier in modern physical science. We use atom-by-atom assembly to implement a platform for the deterministic preparation of regular one-dimensional arrays of individually controlled cold atoms. In our approach, a measurement and feedback procedure eliminates the entropy associated with probabilistic trap occupation and results in defect-free arrays of over 50 atoms in less than 400 milliseconds. The technique is based on fast, real-time control of 100 optical tweezers, which we use to arrange atoms in desired geometric patterns and to maintain these configurations by replacing lost atoms with surplus atoms from a reservoir...
November 3, 2016: Science
Martina Legris, Cornelia Klose, E Sethe Burgie, Cecilia Costigliolo, Maximiliano Neme, Andreas Hiltbrunner, Philip A Wigge, Eberhard Schäfer, Richard D Vierstra, Jorge J Casal
Ambient temperature regulates many aspects of plant growth and development but its sensors are unknown. Here, we demonstrate that the phytochrome B (phyB) photoreceptor participates in temperature perception through its temperature-dependent reversion from the active Pfr state to the inactive Pr state. Increased rates of thermal reversion upon exposing Arabidopsis seedlings to warm environments reduce both the abundance of the biologically active Pfr-Pfr dimer pool of phyB and the size of the associated nuclear bodies, even in daylight...
October 27, 2016: Science
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