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巴西研究指出过去十年大西洋森林出现大量非法砍伐 快报文章
资源环境快报,2025年第4期
作者:  裴惠娟
Microsoft Word(20Kb)  |  收藏  |  浏览/下载:412/0  |  提交时间:2025/02/28
Brazilian Atlantic Forest  Mature Forest  Deforestation  
成熟森林吸收大气额外二氧化碳的能力有限 快报文章
气候变化快报,2020年第9期
作者:  裴惠娟
Microsoft Word(15Kb)  |  收藏  |  浏览/下载:363/0  |  提交时间:2020/04/30
Mature Forest  Carbon Dioxide Enrichment  
Spectroscopic confirmation of a mature galaxy cluster at a redshift of 2 期刊论文
NATURE, 2020, 577 (7788) : 39-+
作者:  Willis, J. P.;  Canning, R. E. A.;  Noordeh, E. S.;  Allen, S. W.;  King, A. L.;  Mantz, A.;  Morris, R. G.;  Stanford, S. A.;  Brammer, G.
收藏  |  浏览/下载:37/0  |  提交时间:2020/07/03

Galaxy clusters are the most massive virialized structures in the Universe and are formed through the gravitational accretion of matter over cosmic time(1). The discovery(2) of an evolved galaxy cluster at redshift z = 2, corresponding to a look-back time of 10.4 billion years, provides an opportunity to study its properties. The galaxy cluster XLSSC 122 was originally detected as a faint, extended X-ray source in the XMM Large Scale Structure survey and was revealed to be coincident with a compact over-density of galaxies(2) with photometric redshifts of 1.9 +/- 0.2. Subsequent observations3 at millimetre wavelengths detected a Sunyaev-Zel'  dovich decrement along the line of sight to XLSSC 122, thus confirming the existence of hot intracluster gas, while deep imaging spectroscopy from the European Space Agency'  s X-ray Multi-Mirror Mission (XMM-Newton) revealed(4) an extended, X-ray-bright gaseous atmosphere with a virial temperature of 60 million Kelvin, enriched with metals to the same extent as are local clusters. Here we report optical spectroscopic observations of XLSSC 122 and identify 37 member galaxies at a mean redshift of 1.98, corresponding to a look-back time of 10.4 billion years. We use photometry to determine a mean, dust-free stellar age of 2.98 billion years, indicating that star formation commenced in these galaxies at a mean redshift of 12, when the Universe was only 370 million years old. The full range of inferred formation redshifts, including the effects of dust, covers the interval from 7 to 13. These observations confirm that XLSSC 122 is a remarkably mature galaxy cluster with both evolved stellar populations in the member galaxies and a hot, metal-rich gas composing the intracluster medium.


  
Injured adult neurons regress to an embryonic transcriptional growth state 期刊论文
NATURE, 2020, 581 (7806) : 77-+
作者:  Wang, Ruicong;  Li, Hongda;  Wu, Jianfeng;  Cai, Zhi-Yu;  Li, Baizhou;  Ni, Hengxiao;  Qiu, Xingfeng;  Chen, Hui;  Liu, Wei;  Yang, Zhang-Hua;  Liu, Min;  Hu, Jin;  Liang, Yaoji;  Lan, Ping;  Han, Jiahuai;  Mo, Wei
收藏  |  浏览/下载:54/0  |  提交时间:2020/07/03

Grafts of spinal-cord-derived neural progenitor cells (NPCs) enable the robust regeneration of corticospinal axons and restore forelimb function after spinal cord injury(1)  however, the molecular mechanisms that underlie this regeneration are unknown. Here we perform translational profiling specifically of corticospinal tract (CST) motor neurons in mice, to identify their '  regenerative transcriptome'  after spinal cord injury and NPC grafting. Notably, both injury alone and injury combined with NPC grafts elicit virtually identical early transcriptomic responses in host CST neurons. However, in mice with injury alone this regenerative transcriptome is downregulated after two weeks, whereas in NPC-grafted mice this transcriptome is sustained. The regenerative transcriptome represents a reversion to an embryonic transcriptional state of the CST neuron. The huntingtin gene (Htt) is a central hub in the regeneration transcriptome  deletion of Htt significantly attenuates regeneration, which shows that Htt has a key role in neural plasticity after injury.


In mouse models of central nervous system injury, Htt is shown to be a key component of the regulatory program associated with reversion of the neuronal transcriptome to a less-mature state.


  
The fate of carbon in a mature forest under carbon dioxide enrichment 期刊论文
NATURE, 2020, 580 (7802) : 227-+
作者:  Sun, P. Z.;  Yang, Q.;  Kuang, W. J.;  Stebunov, Y. V.;  Xiong, W. Q.;  Yu, J.;  Nair, R. R.;  Katsnelson, M. I.;  Yuan, S. J.;  Grigorieva, I. V.;  Lozada-Hidalgo, M.;  Wang, F. C.;  Geim, A. K.
收藏  |  浏览/下载:89/0  |  提交时间:2020/05/13

Carbon dioxide enrichment of a mature forest resulted in the emission of the excess carbon back into the atmosphere via enhanced ecosystem respiration, suggesting that mature forests may be limited in their capacity to mitigate climate change.


Atmospheric carbon dioxide enrichment (eCO(2)) can enhance plant carbon uptake and growth(1-5), thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration(6). Although evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth(3-5), it is unclear whether mature forests respond to eCO(2) in a similar way. In mature trees and forest stands(7-10), photosynthetic uptake has been found to increase under eCO(2) without any apparent accompanying growth response, leaving the fate of additional carbon fixed under eCO(2) unclear(4,5,7-11). Here using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responded to four years of eCO(2) exposure. We show that, although the eCO(2) treatment of +150 parts per million (+38 per cent) above ambient levels induced a 12 per cent (+247 grams of carbon per square metre per year) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone accounting for half of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO(2), and challenge the efficacy of climate mitigation strategies that rely on ubiquitous CO2 fertilization as a driver of increased carbon sinks in global forests.


  
The architecture of the Gram-positive bacterial cell wall 期刊论文
NATURE, 2020, 582 (7811) : 294-+
作者:  Farquharson, Jamie I.;  Amelung, Falk
收藏  |  浏览/下载:41/0  |  提交时间:2020/07/03

The primary structural component of the bacterial cell wall is peptidoglycan, which is essential for viability and the synthesis of which is the target for crucial antibiotics(1,2). Peptidoglycan is a single macromolecule made of glycan chains crosslinked by peptide side branches that surrounds the cell, acting as a constraint to internal turgor(1,3). In Gram-positive bacteria, peptidoglycan is tens of nanometres thick, generally portrayed as a homogeneous structure that provides mechanical strength(4-6). Here we applied atomic force microscopy(7-12) to interrogate the morphologically distinct Staphylococcus aureus and Bacillus subtilis species, using live cells and purified peptidoglycan. The mature surface of live cells is characterized by a landscape of large (up to 60 nm in diameter), deep (up to 23 nm) pores constituting a disordered gel of peptidoglycan. The inner peptidoglycan surface, consisting of more nascent material, is much denser, with glycan strand spacing typically less than 7 nm. The inner surface architecture is location dependent  the cylinder of B. subtilis has dense circumferential orientation, while in S. aureus and division septa for both species, peptidoglycan is dense but randomly oriented. Revealing the molecular architecture of the cell envelope frames our understanding of its mechanical properties and role as the environmental interface(13,14), providing information complementary to traditional structural biology approaches.


Using high-resolution atomic force microscopy of live cells, the authors present an updated view of the cell walls of both Staphylococcus aureus and Bacillus subtilis.


  
Hummingbird-sized dinosaur from the Cretaceous period of Myanmar 期刊论文
NATURE, 2020, 579 (7798) : 245-+
作者:  McBrien, Julia Bergild;  Mavigner, Maud;  Franchitti, Lavinia;  Smith, S. Abigail;  White, Erick;  Tharp, Gregory K.;  Walum, Hasse;  Busman-Sahay, Kathleen;  Aguilera-Sandoval, Christian R.;  Thayer, William O.;  Spagnuolo, Rae Ann;  Kovarova, Martina;  Wahl, Angela;  Cervasi, Barbara;  Margolis, David M.
收藏  |  浏览/下载:39/0  |  提交时间:2020/05/13

Skeletal inclusions in approximately 99-million-year-old amber from northern Myanmar provide unprecedented insights into the soft tissue and skeletal anatomy of minute fauna, which are not typically preserved in other depositional environments(1-3). Among a diversity of vertebrates, seven specimens that preserve the skeletal remains of enantiornithine birds have previously been described(1,4-8), all of which (including at least one seemingly mature specimen) are smaller than specimens recovered from lithic materials. Here we describe an exceptionally well-preserved and diminutive bird-like skull that documents a new species, which we name Oculudentavis khaungraae gen. et sp. nov. The find appears to represent the smallest known dinosaur of the Mesozoic era, rivalling the bee hummingbird (Mellisuga helenae)-the smallest living bird-in size. The O. khaungraae specimen preserves features that hint at miniaturization constraints, including a unique pattern of cranial fusion and an autapomorphic ocular morphology(9) that resembles the eyes of lizards. The conically arranged scleral ossicles define a small pupil, indicative of diurnal activity. Miniaturization most commonly arises in isolated environments, and the diminutive size of Oculudentavis is therefore consistent with previous suggestions that this amber formed on an island within the Trans-Tethyan arc(10). The size and morphology of this species suggest a previously unknown bauplan, and a previously undetected ecology. This discovery highlights the potential of amber deposits to reveal the lowest limits of vertebrate body size.


  
A conserved dendritic-cell regulatory program limits antitumour immunity 期刊论文
NATURE, 2020, 580 (7802) : 257-+
作者:  Perry, Rachel J.;  Zhang, Dongyan;  Guerra, Mateus T.;  Brill, Allison L.;  Goedeke, Leigh;  Nasiri, Ali R.;  Rabin-Court, Aviva;  Wang, Yongliang;  Peng, Liang;  Dufour, Sylvie;  Zhang, Ye;  Zhang, Xian-Man;  Butrico, Gina M.;  Toussaint, Keshia;  Nozaki, Yuichi;  Cline, Gary W.;  Petersen, Kitt Falk;  Nathanson, Michael H.;  Ehrlich, Barbara E.;  Shulman, Gerald I.
收藏  |  浏览/下载:55/0  |  提交时间:2020/07/03

After taking up tumour-associated antigens, dendritic cells in mouse and human tumours upregulate a regulatory gene program that limits dendritic cell immunostimulatory function, and modulating this program can rescue antitumor immunity in mice.


Checkpoint blockade therapies have improved cancer treatment, but such immunotherapy regimens fail in a large subset of patients. Conventional type 1 dendritic cells (DC1s) control the response to checkpoint blockade in preclinical models and are associated with better overall survival in patients with cancer, reflecting the specialized ability of these cells to prime the responses of CD8(+) T cells(1-3). Paradoxically, however, DC1s can be found in tumours that resist checkpoint blockade, suggesting that the functions of these cells may be altered in some lesions. Here, using single-cell RNA sequencing in human and mouse non-small-cell lung cancers, we identify a cluster of dendritic cells (DCs) that we name '  mature DCs enriched in immunoregulatory molecules'  (mregDCs), owing to their coexpression of immunoregulatory genes (Cd274, Pdcd1lg2 and Cd200) and maturation genes (Cd40, Ccr7 and Il12b). We find that the mregDC program is expressed by canonical DC1s and DC2s upon uptake of tumour antigens. We further find that upregulation of the programmed death ligand 1 protein-a key checkpoint molecule-in mregDCs is induced by the receptor tyrosine kinase AXL, while upregulation of interleukin (IL)-12 depends strictly on interferon-gamma and is controlled negatively by IL-4 signalling. Blocking IL-4 enhances IL-12 production by tumour-antigen-bearing mregDC1s, expands the pool of tumour-infiltrating effector T cells and reduces tumour burden. We have therefore uncovered a regulatory module associated with tumour-antigen uptake that reduces DC1 functionality in human and mouse cancers.


  
FERONIA controls pectin- and nitric oxide-mediated male-female interaction 期刊论文
NATURE, 2020, 579 (7800) : 561-+
作者:  Venkadesan, Madhusudhan;  Yawar, Ali;  Eng, Carolyn M.;  Dias, Marcelo A.;  Singh, Dhiraj K.;  Tommasini, Steven M.;  Haims, Andrew H.;  Bandi, Mahesh M.;  Mandre, Shreyas
收藏  |  浏览/下载:41/0  |  提交时间:2020/07/03

Species that propagate by sexual reproduction actively guard against the fertilization of an egg by multiple sperm (polyspermy). Flowering plants rely on pollen tubes to transport their immotile sperm to fertilize the female gametophytes inside ovules. In Arabidopsis, pollen tubes are guided by cysteine-rich chemoattractants to target the female gametophyte(1,2). The FERONIA receptor kinase has a dual role in ensuring sperm delivery and blocking polyspermy(3). It has previously been reported that FERONIA generates a female gametophyte environment that is required for sperm release(4). Here we show that FERONIA controls several functionally linked conditions to prevent the penetration of female gametophytes by multiple pollen tubes in Arabidopsis. We demonstrate that FERONIA is crucial for maintaining de-esterified pectin at the filiform apparatus, a region of the cell wall at the entrance to the female gametophyte. Pollen tube arrival at the ovule triggers the accumulation of nitric oxide at the filiform apparatus in a process that is dependent on FERONIA and mediated by de-esterified pectin. Nitric oxide nitrosates both precursor and mature forms of the chemoattractant LURE1(1), respectively blocking its secretion and interaction with its receptor, to suppress pollen tube attraction. Our results elucidate a mechanism controlled by FERONIA in which the arrival of the first pollen tube alters ovular conditions to disengage pollen tube attraction and prevent the approach and penetration of the female gametophyte by late-arriving pollen tubes, thus averting polyspermy.


FERONIA prevents polyspermy in Arabidopsis by enabling pectin-stimulated nitric oxide accumulation at the filiform apparatus after the first pollen tube arrives, which disengages LURE1 chemoattraction to prevent late-arriving pollen tubes from entering the ovule.


  
Selective loading and processing of prespacers for precise CRISPR adaptation 期刊论文
NATURE, 2020
作者:  Liu, Guoxia;  Papa, Arianne;  Katchman, Alexander N.;  Zakharov, Sergey I.;  Roybal, Daniel;  Hennessey, Jessica A.;  Kushner, Jared;  Yang, Lin;  Chen, Bi-Xing;  Kushnir, Alexander;  Dangas, Katerina;  Gygi, Steven P.;  Pitt, Geoffrey S.;  Colecraft, Henry M.;  Ben-Johny, Manu;  Kalocsay, Marian;  Marx, Steven O.
收藏  |  浏览/下载:22/0  |  提交时间:2020/07/03

CRISPR-Cas immunity protects prokaryotes against invading genetic elements(1). It uses the highly conserved Cas1-Cas2 complex to establish inheritable memory (spacers)(2-5). How Cas1-Cas2 acquires spacers from foreign DNA fragments (prespacers) and integrates them into the CRISPR locus in the correct orientation is unclear(6,7). Here, using the high spatiotemporal resolution of single-molecule fluorescence, we show that Cas1-Cas2 selects precursors of prespacers from DNA in various forms-including single-stranded DNA and partial duplexes-in a manner that depends on both the length of the DNA strand and the presence of a protospacer adjacent motif (PAM) sequence. We also identify DnaQ exonucleases as enzymes that process the Cas1-Cas2-loaded prespacer precursors into mature prespacers of a suitable size for integration. Cas1-Cas2 protects the PAM sequence from maturation, which results in the production of asymmetrically trimmed prespacers and the subsequent integration of spacers in the correct orientation. Our results demonstrate the kinetic coordination of prespacer precursor selection and PAM trimming, providing insight into the mechanisms that underlie the integration of functional spacers in the CRISPR loci.


Cas1-Cas2 selects precursor prespacers from DNA fragments in a length- and PAM-sequence-dependent manner, and these precursors are trimmed by DnaQ exonucleases to enable integration into the CRISPR locus in the correct orientation.