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Ice retreat in Wilkes Basin of East Antarctica during a warm interglacial 期刊论文
NATURE, 2020, 583 (7817) : 554-+
作者:  T. Blackburn;  G. H. Edwards;  S. Tulaczyk;  M. Scudder;  G. Piccione;  B. Hallet;  N. McLean;  J. C. Zachos;  B. Cheney;  J. T. Babbe
收藏  |  浏览/下载：58/0  |  提交时间：2020/08/09

Uranium isotopes in subglacial precipitates from the Wilkes Basin of the East Antarctic Ice Sheet reveal ice retreat during a warm Pleistocene interglacial period about 400,000 years ago.


Efforts to improve sea level forecasting on a warming planet have focused on determining the temperature, sea level and extent of polar ice sheets during Earth'  s past interglacial warm periods(1-3). About 400,000 years ago, during the interglacial period known as Marine Isotopic Stage 11 (MIS11), the global temperature was 1 to 2 degrees Celsius greater(2)and sea level was 6 to 13 metres higher(1,3). Sea level estimates in excess of about 10 metres, however, have been discounted because these require a contribution from the East Antarctic Ice Sheet(3), which has been argued to have remained stable for millions of years before and includes MIS11(4,5). Here we show how the evolution of(234)U enrichment within the subglacial waters of East Antarctica recorded the ice sheet'  s response to MIS11 warming. Within the Wilkes Basin, subglacial chemical precipitates of opal and calcite record accumulation of(234)U (the product of rock-water contact within an isolated subglacial reservoir) up to 20 times higher than that found in marine waters. The timescales of(234)U enrichment place the inception of this reservoir at MIS11. Informed by the(234)U cycling observed in the Laurentide Ice Sheet, where(234)U accumulated during periods of ice stability(6)and was flushed to global oceans in response to deglaciation(7), we interpret our East Antarctic dataset to represent ice loss within the Wilkes Basin at MIS11. The(234)U accumulation within the Wilkes Basin is also observed in the McMurdo Dry Valleys brines(8-10), indicating(11)that the brine originated beneath the adjacent East Antarctic Ice Sheet. The marine origin of brine salts(10)and bacteria(12)implies that MIS11 ice loss was coupled with marine flooding. Collectively, these data indicate that during one of the warmest Pleistocene interglacials, the ice sheet margin at the Wilkes Basin retreated to near the precipitate location, about 700 kilometres inland from the current position of the ice margin, which-assuming current ice volumes-would have contributed about 3 to 4 metres(13)to global sea levels.


  
A remnant planetary core in the hot-Neptune desert 期刊论文
NATURE, 2020, 583 (7814) : 39-+
作者:  David J. Armstrong;  Thé;  o A. Lopez;  Vardan Adibekyan;  Richard A. Booth;  Edward M. Bryant;  Karen A. Collins;  Magali Deleuil;  Alexandre Emsenhuber;  Chelsea X. Huang;  George W. King;  Jorge Lillo-Box;  Jack J. Lissauer;  Elisabeth Matthews;  Olivier Mousis;  Louise D. Nielsen;  Hugh Osborn;  Jon Otegi;  Nuno C. Santos;  Sé;  rgio G. Sousa;  Keivan G. Stassun;  Dimitri Veras;  Carl Ziegler;  Jack S. Acton;  Jose M. Almenara;  David R. Anderson;  David Barrado;  Susana C. C. Barros;  Daniel Bayliss;  Claudia Belardi;  Francois Bouchy;  Cé;  sar Briceñ;  o;  Matteo Brogi;  David J. A. Brown;  Matthew R. Burleigh;  Sarah L. Casewell;  Alexander Chaushev;  David R. Ciardi;  Kevin I. Collins;  Knicole D. Coló;  n;  Benjamin F. Cooke;  Ian J. M. Crossfield;  Rodrigo F. Dí;  az;  Elisa Delgado Mena;  Olivier D. S. Demangeon;  Caroline Dorn;  Xavier Dumusque;  Philipp Eigmü;  ller;  Michael Fausnaugh;  Pedro Figueira;  Tianjun Gan;  Siddharth Gandhi;  Samuel Gill;  Erica J. Gonzales;  Michael R. Goad;  Maximilian N. Gü;  nther;  Ravit Helled;  Saeed Hojjatpanah;  Steve B. Howell;  James Jackman;  James S. Jenkins;  Jon M. Jenkins;  Eric L. N. Jensen;  Grant M. Kennedy;  David W. Latham;  Nicholas Law;  Monika Lendl;  Michael Lozovsky;  Andrew W. Mann;  Maximiliano Moyano;  James McCormac;  Farzana Meru;  Christoph Mordasini;  Ares Osborn;  Don Pollacco;  Didier Queloz;  Liam Raynard;  George R. Ricker;  Pamela Rowden;  Alexandre Santerne;  Joshua E. Schlieder;  Sara Seager;  Lizhou Sha;  Thiam-Guan Tan;  Rosanna H. Tilbrook;  Eric Ting;  Sté;  phane Udry;  Roland Vanderspek;  Christopher A. Watson;  Richard G. West;  Paul A. Wilson;  Joshua N. Winn;  Peter Wheatley;  Jesus Noel Villasenor;  Jose I. Vines;  Zhuchang Zhan
收藏  |  浏览/下载：86/0  |  提交时间：2020/07/06

The interiors of giant planets remain poorly understood. Even for the planets in the Solar System, difficulties in observation lead to large uncertainties in the properties of planetary cores. Exoplanets that have undergone rare evolutionary processes provide a route to understanding planetary interiors. Planets found in and near the typically barren hot-Neptune '  desert'  (1,2)(a region in mass-radius space that contains few planets) have proved to be particularly valuable in this regard. These planets include HD149026b(3), which is thought to have an unusually massive core, and recent discoveries such as LTT9779b(4)and NGTS-4b(5), on which photoevaporation has removed a substantial part of their outer atmospheres. Here we report observations of the planet TOI-849b, which has a radius smaller than Neptune'  s but an anomalously large mass of39.1-2.6+2.7Earth masses and a density of5.2-0.8+0.7grams per cubic centimetre, similar to Earth'  s. Interior-structure models suggest that any gaseous envelope of pure hydrogen and helium consists of no more than3.9-0.9+0.8 per cent of the total planetary mass. The planet could have been a gas giant before undergoing extreme mass loss via thermal self-disruption or giant planet collisions, or it could have avoided substantial gas accretion, perhaps through gap opening or late formation(6). Although photoevaporation rates cannot account for the mass loss required to reduce a Jupiter-like gas giant, they can remove a small (a few Earth masses) hydrogen and helium envelope on timescales of several billion years, implying that any remaining atmosphere on TOI-849b is likely to be enriched by water or other volatiles from the planetary interior. We conclude that TOI-849b is the remnant core of a giant planet.


Observations of TOI-849b reveal a radius smaller than Neptune'  s but a large mass of about 40 Earth masses, indicating that the planet is the remnant core of a gas giant.


  
A giant soft-shelled egg from the Late Cretaceous of Antarctica 期刊论文
NATURE, 2020
作者:  Lewnard, Joseph A.;  Lo, Nathan C.;  Arinaminpathy, Nimalan;  Frost, Isabel;  Laxminarayan, Ramanan
收藏  |  浏览/下载：25/0  |  提交时间：2020/06/22

Egg size and structure reflect important constraints on the reproductive and life-history characteristics of vertebrates(1). More than two-thirds of all extant amniotes lay eggs(2). During the Mesozoic era (around 250 million to 65 million years ago), body sizes reached extremes  nevertheless, the largest known egg belongs to the only recently extinct elephant bird(3), which was roughly 66 million years younger than the last nonavian dinosaurs and giant marine reptiles. Here we report a new type of egg discovered in nearshore marine deposits from the Late Cretaceous period (roughly 68 million years ago) of Antarctica. It exceeds all nonavian dinosaur eggs in volume and differs from them in structure. Although the elephant bird egg is slightly larger, its eggshell is roughly five times thicker and shows a substantial prismatic layer and complex pore structure(4). By contrast, the new fossil, visibly collapsed and folded, presents a thin eggshell with a layered structure that lacks a prismatic layer and distinct pores, and is similar to that of most extant lizards and snakes (Lepidosauria)(5). The identity of the animal that laid the egg is unknown, but these preserved morphologies are consistent with the skeletal remains of mosasaurs (large marine lepidosaurs) found nearby. They are not consistent with described morphologies of dinosaur eggs of a similar size class. Phylogenetic analyses of traits for 259 lepidosaur species plus outgroups suggest that the egg belonged to an individual that was at least 7 metres long, hypothesized to be a giant marine reptile, all clades of which have previously been proposed to show live birth(6). Such a large egg with a relatively thin eggshell may reflect derived constraints associated with body shape, reproductive investment linked with gigantism, and lepidosaurian viviparity, in which a '  vestigial'  egg is laid and hatches immediately(7).


A fossil egg unearthed from Cretaceous deposits in Antarctica is more than 20 cm long, exceeds all known nonavian eggs in volume, is soft-shelled, and was perhaps laid by a giant marine lizard such as a mosasaur.


  
Revealing enigmatic mucus structures in the deep sea using DeepPIV 期刊论文
NATURE, 2020, 583 (7814) : 78-+
作者:  Nguyen, Ngoc Uyen Nhi;  Canseco, Diana C.;  Xiao, Feng;  Nakada, Yuji;  Li, Shujuan;  Lam, Nicholas T.;  Muralidhar, Shalini A.;  Savla, Jainy J.;  Hill, Joseph A.;  Le, Victor;  Zidan, Kareem A.;  El-Feky, Hamed W.;  Wang, Zhaoning;  Ahmed, Mahmoud Salama;  Hubbi, Maimon E.;  Menendez-Montes, Ivan
收藏  |  浏览/下载：49/0  |  提交时间：2020/06/09

Advanced deep-sea imaging tools yield insights into the structure and function of mucus filtration houses built by midwater giant larvaceans.


Many animals build complex structures to aid in their survival, but very few are built exclusively from materials that animals create (1,2). In the midwaters of the ocean, mucoid structures are readily secreted by numerous animals, and serve many vital functions(3,4). However, little is known about these mucoid structures owing to the challenges of observing them in the deep sea. Among these mucoid forms, the '  houses'  of larvaceans are marvels of nature(5), and in the ocean twilight zone giant larvaceans secrete and build mucus filtering structures that can reach diameters of more than 1 m(6). Here we describe in situ laser-imaging technology(7) that reconstructs three-dimensional models of mucus forms. The models provide high-resolution views of giant larvacean houses and elucidate the role that house structure has in food capture and predator avoidance. Now that tools exist to study mucus structures found throughout the ocean, we can shed light on some of nature'  s most complex forms.


  
Nearest neighbours reveal fast and slow components of motor learning 期刊论文
NATURE, 2020, 577 (7791) : 526-+
作者:  Kollmorgen, Sepp;  Hahnloser, Richard H. R.;  Mante, Valerio
收藏  |  浏览/下载：17/0  |  提交时间：2020/07/03

A new method for analysing change in high-dimensional data is based on nearest-neighbour statistics and is applied here to song dynamics during vocal learning in zebra finches, but could potentially be applied to other biological and artificial behaviours.


Changes in behaviour resulting from environmental influences, development and learning(1-5) are commonly quantified on the basis of a few hand-picked features(2-4,6,7) (for example, the average pitch of acoustic vocalizations(3)), assuming discrete classes of behaviours (such as distinct vocal syllables)(2,3,8-10). However, such methods generalize poorly across different behaviours and model systems and may miss important components of change. Here we present a more-general account of behavioural change that is based on nearest-neighbour statistics(11-13), and apply it to song development in a songbird, the zebra finch(3). First, we introduce the concept of '  repertoire dating'  , whereby each rendition of a behaviour (for example, each vocalization) is assigned a repertoire time, reflecting when similar renditions were typical in the behavioural repertoire. Repertoire time isolates the components of vocal variability that are congruent with long-term changes due to vocal learning and development, and stratifies the behavioural repertoire into '  regressions'  , '  anticipations'  and '  typical renditions'  . Second, we obtain a holistic, yet low-dimensional, description of vocal change in terms of a stratified '  behavioural trajectory'  , revealing numerous previously unrecognized components of behavioural change on fast and slow timescales, as well as distinct patterns of overnight consolidation(1,2,4,14,15) across the behavioral repertoire. We find that diurnal changes in regressions undergo only weak consolidation, whereas anticipations and typical renditions consolidate fully. Because of its generality, our nonparametric description of how behaviour evolves relative to itself-rather than to a potentially arbitrary, experimenter-defined goal(2,3,14,16)-appears well suited for comparing learning and change across behaviours and species(17,18), as well as biological and artificial systems(5).


  
Field-resolved infrared spectroscopy of biological systems 期刊论文
NATURE, 2020, 577 (7788) : 52-+
作者:  Pupeza, Ioachim;  Huber, Marinus;  Trubetskov, Michael;  Schweinberger, Wolfgang;  Hussain, Syed A.;  Hofer, Christina;  Fritsch, Kilian;  Poetzlberger, Markus;  Vamos, Lenard;  Fill, Ernst;  Amotchkina, Tatiana;  Kepesidis, Kosmas V.;  Apolonski, Alexander;  Karpowicz, Nicholas;  Pervak, Vladimir;  Pronin, Oleg;  Fleischmann, Frank;  Azzeer, Abdallah;  Zigman, Mihaela;  Krausz, Ferenc
收藏  |  浏览/下载：31/0  |  提交时间：2020/07/03

The proper functioning of living systems and physiological phenotypes depends on molecular composition. Yet simultaneous quantitative detection of a wide variety of molecules remains a challenge(1-8). Here we show how broadband optical coherence opens up opportunities for fingerprinting complex molecular ensembles in their natural environment. Vibrationally excited molecules emit a coherent electric field following few-cycle infrared laser excitation(9-12), and this field is specific to the sample'  s molecular composition. Employing electro-optic sampling(10,12-15), we directly measure this global molecular fingerprint down to field strengths 10(7) times weaker than that of the excitation. This enables transillumination of intact living systems with thicknesses of the order of 0.1 millimetres, permitting broadband infrared spectroscopic probing of human cells and plant leaves. In a proof-of-concept analysis of human blood serum, temporal isolation of the infrared electric-field fingerprint from its excitation along with its sampling with attosecond timing precision results in detection sensitivity of submicrograms per millilitre of blood serum and a detectable dynamic range of molecular concentration exceeding 10(5). This technique promises improved molecular sensitivity and molecular coverage for probing complex, real-world biological and medical settings.


  
Structure of the human metapneumovirus polymerase phosphoprotein complex 期刊论文
NATURE, 2020, 577 (7789) : 275-+
作者:  Pan, Junhua;  Qian, Xinlei;  Lattmann, Simon;  El Sahili, Abbas;  Yeo, Tiong Han;  Jia, Huan;  Cressey, Tessa;  Ludeke, Barbara;  Noton, Sarah;  Kalocsay, Marian;  Fearns, Rachel;  Lescar, Julien
收藏  |  浏览/下载：35/0  |  提交时间：2020/07/03

Respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) cause severe respiratory diseases in infants and elderly adults(1). No vaccine or effective antiviral therapy currently exists to control RSV or HMPV infections. During viral genome replication and transcription, the tetrameric phosphoprotein P serves as a crucial adaptor between the ribonucleoprotein template and the L protein, which has RNA-dependent RNA polymerase (RdRp), GDP polyribonucleotidyltransferase and cap-specific methyltransferase activities(2,3). How P interacts with L and mediates the association with the free form of N and with the ribonucleoprotein is not clear for HMPV or other major human pathogens, including the viruses that cause measles, Ebola and rabies. Here we report a cryo-electron microscopy reconstruction that shows the ring-shaped structure of the polymerase and capping domains of HMPV-L bound to a tetramer of P. The connector and methyltransferase domains of L are mobile with respect to the core. The putative priming loop that is important for the initiation of RNA synthesis is fully retracted, which leaves space in the active-site cavity for RNA elongation. P interacts extensively with the N-terminal region of L, burying more than 4,016 angstrom(2) of the molecular surface area in the interface. Two of the four helices that form the coiled-coil tetramerization domain of P, and long C-terminal extensions projecting from these two helices, wrap around the L protein in a manner similar to tentacles. The structural versatility of the four P protomers-which are largely disordered in their free state-demonstrates an example of a '  folding-upon-partner-binding'  mechanism for carrying out P adaptor functions. The structure shows that P has the potential to modulate multiple functions of L and these results should accelerate the design of specific antiviral drugs.


  
Potential circadian effects on translational failure for neuroprotection 期刊论文
NATURE, 2020
作者:  Sakai, Akito;  Minami, Susumu;  Koretsune, Takashi;  Chen, Taishi;  Higo, Tomoya;  Wang, Yangming;  Nomoto, Takuya;  Hirayama, Motoaki;  Miwa, Shinji;  Nishio-Hamane, Daisuke;  Ishii, Fumiyuki;  Arita, Ryotaro;  Nakatsuji, Satoru
收藏  |  浏览/下载：28/0  |  提交时间：2020/07/03

Neuroprotectant strategies that have worked in rodent models of stroke have failed to provide protection in clinical trials. Here we show that the opposite circadian cycles in nocturnal rodents versus diurnal humans(1,2) may contribute to this failure in translation. We tested three independent neuroprotective approaches-normobaric hyperoxia, the free radical scavenger alpha-phenyl-butyl-tert-nitrone (alpha PBN), and the N-methyl-d-aspartic acid (NMDA) antagonist MK801-in mouse and rat models of focal cerebral ischaemia. All three treatments reduced infarction in day-time (inactive phase) rodent models of stroke, but not in night-time (active phase) rodent models of stroke, which match the phase (active, day-time) during which most strokes occur in clinical trials. Laser-speckle imaging showed that the penumbra of cerebral ischaemia was narrower in the active-phase mouse model than in the inactive-phase model. The smaller penumbra was associated with a lower density of terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)-positive dying cells and reduced infarct growth from 12 to 72 h. When we induced circadian-like cycles in primary mouse neurons, deprivation of oxygen and glucose triggered a smaller release of glutamate and reactive oxygen species, as well as lower activation of apoptotic and necroptotic mediators, in '  active-phase'  than in '  inactive-phase'  rodent neurons. alpha PBN and MK801 reduced neuronal death only in '  inactive-phase'  neurons. These findings suggest that the influence of circadian rhythm on neuroprotection must be considered for translational studies in stroke and central nervous system diseases.


Studies in rats and mice at different times of day suggest that the failure of neuroprotective strategies for stroke in translational studies might be related to the difference in circadian cycles between humans and rodents.


  
Hidden neural states underlie canary song syntax 期刊论文
NATURE, 2020
作者:  Bao, Han;  Duan, Junlei;  Jin, Shenchao;  Lu, Xingda;  Li, Pengxiong;  Qu, Weizhi;  Wang, Mingfeng;  Novikova, Irina;  Mikhailov, Eugeniy E.;  Zhao, Kai-Feng;  Molmer, Klaus;  Shen, Heng;  Xiao, Yanhong
收藏  |  浏览/下载：33/0  |  提交时间：2020/07/03

Neurons in the canary premotor cortex homologue encode past song phrases and transitions, carrying information relevant to future choice of phrases as '  hidden states'  during song.


Coordinated skills such as speech or dance involve sequences of actions that follow syntactic rules in which transitions between elements depend on the identities and order of past actions. Canary songs consist of repeated syllables called phrases, and the ordering of these phrases follows long-range rules(1)in which the choice of what to sing depends on the song structure many seconds prior. The neural substrates that support these long-range correlations are unknown. Here, using miniature head-mounted microscopes and cell-type-specific genetic tools, we observed neural activity in the premotor nucleus HVC(2-4)as canaries explored various phrase sequences in their repertoire. We identified neurons that encode past transitions, extending over four phrases and spanning up to four seconds and forty syllables. These neurons preferentially encode past actions rather than future actions, can reflect more than one song history, and are active mostly during the rare phrases that involve history-dependent transitions in song. These findings demonstrate that the dynamics of HVC include '  hidden states'  that are not reflected in ongoing behaviour but rather carry information about prior actions. These states provide a possible substrate for the control of syntax transitions governed by long-range rules.


  
poly(UG)-tailed RNAs in genome protection and epigenetic inheritance 期刊论文
NATURE, 2020, 582 (7811) : 283-+
作者:  Raj, Dipak K.;  Das Mohapatra, Alok;  Jnawali, Anup;  Zuromski, Jenna;  Jha, Ambrish;  Cham-Kpu, Gerald;  Sherman, Brett;  Rudlaff, Rachel M.;  Nixon, Christina E.;  Hilton, Nicholas;  Oleinikov, Andrew V.;  Chesnokov, Olga;  Merritt, Jordan;  Pond-Tor, Sunthorn
收藏  |  浏览/下载：27/0  |  提交时间：2020/07/03

Mobile genetic elements threaten genome integrity in all organisms. RDE-3 (also known as MUT-2) is a ribonucleotidyltransferase that is required for transposon silencing and RNA interference in Caenorhabditis elegans(1-4). When tethered to RNAs in heterologous expression systems, RDE-3 can add long stretches of alternating non-templated uridine (U) and guanosine (G) ribonucleotides to the 3 '  termini of these RNAs (designated poly(UG) or pUG tails)(5). Here we show that, in its natural context in C. elegans, RDE-3 adds pUG tails to targets of RNA interference, as well as to transposon RNAs. RNA fragments attached to pUG tails with more than 16 perfectly alternating 3 '  U and G nucleotides become gene-silencing agents. pUG tails promote gene silencing by recruiting RNA-dependent RNA polymerases, which use pUG-tailed RNAs (pUG RNAs) as templates to synthesize small interfering RNAs (siRNAs). Our results show that cycles of pUG RNA-templated siRNA synthesis and siRNA-directed pUG RNA biogenesis underlie double-stranded-RNA-directed transgenerational epigenetic inheritance in the C. elegans germline. We speculate that this pUG RNA-siRNA silencing loop enables parents to inoculate progeny against the expression of unwanted or parasitic genetic elements.


In Caenorhabditis elegans, the ribonucleotidyltransferase RDE-3 adds alternating uridine and guanosine ribonucleotides to the 3 '  termini of RNAs, a key step in RNA interference and thus epigenetic inheritance in the C. elegans germline.