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Cellular and Molecular Requirements for Polar PIN Targeting and Transcytosis in Plants

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Molecular Plant 2008年第6期1卷 1056-1066页

作者： Jurgen Kleine-Vehn tukasz tangowski Justyna Wisniewska Pankaj Dhonukshe Philip B Brewer Jiri Friml department of Plant Systems Biology VIB and Department of Molecular Genetics Ghent University 9052 Gent Belgium Zentrum fur Molekularbiologie der Pflanzen (ZMBP) Universitat Tubingen 72076 Tubingen Germany present address: Institute of General and Molecular Biology Nicolas Copernicus University 87-100 Torun Poland present address: department of Biology Utrecht University 3508 TB Utrecht The Netherlands present address: Centre for Integrative Legume Research University of Queensland Brisbane Australia

The polar, sub-cellular localization of PIN auxin efflux carriers determines the direction of intercellular auxin flow, thus defining the spatial aspect of auxin signalling. Dynamic, transcytosis-like relocalizations of PIN proteins occur in response to external and internal signals, integrating these signals into changes in auxin distribution. Here, we examine the cellular and molecular mechanisms of polar PIN delivery and transcytosis. The mechanisms of the ARF-GEF-dependent polar targeting and transcytosis are well conserved and show little variations among diverse Arabidopsis ecotypes consistent with their fundamental importance in regulating plant development. At the cellular level, we refine previous findings on the role of the actin cytoskeleton in apical and basal PIN targeting, and identify a previously unknown role for microtubules, specifically in basal targeting. PIN protein delivery to different sides of the cell is mediated by ARFdependent trafficking with a previously unknown complex level of distinct ARF-GEF vesicle trafficking regulators. Our data suggest that alternative recruitment of PIN proteins by these distinct pathways can account for cell type- and cargo-specific aspects of polar targeting, as well as for polarity changes in response to different signals. The resulting dynamic PIN positioning to different sides of cells defines a three-dimensional pattern of auxin fluxes within plant tissues.

关键词： cytoskeleton polarity protein targeting.

SINGLE CRYSTAL HARDENING——MECHANISMS AND DESCRIPTION

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Acta Mechanica Sinica 1995年第2期11卷 162-167页

作者：孙守光黄克智 present address: department of Mechanical Engineering Northern Jiaotong UniversityBeijing China 100044 department of Engineering Mechanics Tsinghua University Beijing China 100084

Various work hardening mechanisms, on the basis of their characteristics, are classified into two categories: the pile-up hardening and the tangle hardening. Together with a discussion about the experimental investigations of work hardening, the descriptions for those two basic hardening mechanisms are suggested, respectively. Combining these descriptions, a new single crystal hardening law is proposed, which can be used to describe work hardening, particularly the cyclic hardening of a crystal grain in a polycrystalline material. Furthermore, some relevant discussion on the new single crystal hardening law is also made in this paper.

关键词： CRYSTAL PLASTICITY SINGLE CRYSTAL HARDENING CYCLIC HARDENING

In Situ TEM Observation of the Gasification and Growth of Carbon Nanotubes Using Iron Catalysts

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Nano Research 2011年第8期4卷 767-779页

作者： Xiaofeng Feng See Wee Chee Renu Sharma Kai Liu Xu Xie Qunqing Li Shoushan Fan Kaili Jiang department of Physics and Tsinghua-Foxconn Nanotechnology Research Center Tsinghua University Beijing 100084 China Leroy Eyring Center for Solid State Science Arizona State University Tempe AZ 85287 USA present address： department of Materials Science and Engineering University of California Berkeley CA 94720 USA present address： department of Materials Science and Engineerig Rensselaer Polytechnic Institute Troy NY 12180 USA present address： National Institute of Science and Technology Gaithersburg MD 20899 USA present address： department of Materials Science and Engineering University of Illinois at Urbana-Champaign Urbana IL 61801 USA

We report the in situ transmission electron microscope (TEM) observation of the catalytic gasification and growth of carbon nanotubes (CNTs). It was found that iron catalysts can consume the CNTs when pumping out the precursor gas, acetylene, at the growth temperature, and reinitiate the growth when acetylene is re-introduced. The switching between gasification and growth of CNTs can be repeated many times with the same catalyst. To understand the phenomenon, thermogravimetric analysis (TGA) coupled with mass spectroscopy was used to study the mechanism involved. It was shown that the residual water molecules in the growth chamber of the TEM react with and remove carbon atoms of CNTs as carbon monoxide vapor under the action of the catalyst, when the precursor gas is pumped out. This result contributes to a better understanding of the water-assisted and oxygen-assisted synthesis of CNT arrays, and provides useful clues on how to extend the lifetime and improve the activity of the catalysts.

关键词： Carbon nanotubes gasification growth iron catalyst environmental transmission electron microscopy (ETEM),thermogravimetric analysis (TGA)

Functional Analysis of Semi-conserved Transit Peptide Motifs and Mechanistic Implications in Precursor Targeting and Recognition

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Molecular Plant 2016年第9期9卷 1286-1301页

作者： Kristen Holbrook Chitra Subramanian Prakitchai Chotewutmontri L. Evan Reddick Sarah Wright Huixia Zhang Lily Moncrief Barry D. Bruce department of Biochemistry Cellular and Molecular Biology Graduate Program in Plant Physiology and Genetics Graduate School of Genome Science and Technology department of Botany department of BotanyUniversity of Tennessee Knoxville TN 37996 USA present address: department of Infectious Disease St. Jude Children's Research Hospital Memphis TN 38105 USA present address: Institute of Molecular Biology University of Oregon Eugene OR 97403 USA present address: department of Microbiology University of Texas Southwestern Medical Center 5323 Harry Hines Boulevard Dallas TX 75390 USA present address: Albert R. Mann Library Cornell University Ithaca NY 14850 USA present address: U.S. Food and Drug Administration 10903 New Hampshire Avenue Silver Spring MD 20993 USA

Over 95% of plastid proteins are nuclear-encoded as their precursors containing an N-terminal extension known as the transit peptide （TP）. Although highly variable, TPs direct the precursors through a conserved, posttranslational mechanism involving translocons in the outer （TOC） and inner envelope （TOC）. The organelle import specificity is mediated by one or more components of the Toc complex. However, the high TP diversity creates a paradox on how the sequences can be specifically recognized. An emerging model of TP design is that they contain multiple loosely conserved motifs that are recognized at different steps in the targeting and transport process. Bioinformatics has demonstrated that many TPs contain semiconserved physicochemical motifs, termed FGLK. In order to characterize FGLK motifs in TP recognition and import, we have analyzed two well-studied TPs from the precursor of RuBisCO small subunit （SStp） and ferredoxin （Fdtp）. Both SStp and Fdtp contain two FGLK motifs. Analysis of large set mutations （-85） in these two motifs using in vitro, in organello, and in vivo approaches support a model in which the FGLK domains mediate interaction with TOC34 and possibly other TOC components. In vivo import analysis suggests that multiple FGLK motifs are functionally redundant. Furthermore, we discuss how FGLK motifs are required for efficient precursor protein import and how these elements may permit a convergent function of this highly variable class of targeting sequences.

关键词： chloroplast biology protein translocation Toc34 transit peptide cell biology

SWI1 Is Required for Meiotic Chromosome Remodeling Events

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Molecular Plant 2008年第4期1卷 620-633页

作者： Kingsley A. Boateng Xiaohui Yang Fuqui Dong Heather A. Owen Christopher A. Makaroff department of Chemistry and Biochemistry Miami University Oxford OH 45056 USA present address: department of Biological Sciences University of Wisconsin-Milwaukee Milwaukee Wl 53211 USA

The Arabidopsis dsy10 mutant was previously identified as being defective in the synapsis of meiotic chromosomes resulting in male and female sterility. We report here the molecular analysis of the mutation and show that it represents a T-DNA insertion in the third exon of the SWll gene. Four mutations have now been identified in SWI1, several of which exhibit different phenotypes. For example, the swil- 1 and dyad mutations only affect meiosis in megasporocytes, while the swil-2 and dsy10 mutations block both male and female meiosis. Furthermore, as part of a detailed cytological characterization of dsy10 meiocytes, we identified several differences during male meiosis between the swil-2 and dys10 mutants, including variations in the formation of axial elements, the distribution of cohesin proteins and the timing of the premature loss of sister chromatid cohesion. We demonstrate that dsy10 represents a complete loss-of-function mutation, while a truncated form of SWll is expressed during meiosis in swil-2 plants. We further show that dys10 meiocytes exhibit alterations in modified histone patterns, including acetylated histone H3 and dimethylated histone H3-Lysine 4.

关键词： Arabidopsis meiosis sister chromatid cohesion chromatin remodeling histone.

Arabidopsis thaliana AtUTr7 Encodes a Golgi-Localized UDP-Glucose/UDP-Galactose Transporter that Affects Lateral Root Emergence

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Molecular Plant 2012年第6期5卷 1263-1280页

作者： Michael Handford Cecilia Rodriguez-Furlan Lorena Marchan Marcelo Segura Daniela Gomez Elena Alvarez-Buyllal Guang-Yan Xiong Markus Pauly Ariel Orellana department of Biology Faculty of Sciences University of Chile Santiago Chile present address: department of Biochemistry University of Cambridge Cambridge CB2 1QW UK Centro de Biotecnologia Vegetal Facultad de Ciencias Biologicas Universidad Andres Bello Republica 217 Santiago Chile present address: Facultad de Ciencias Biologicas Universidad AndrOs Bello Vina del Mar Chile present address: department of pathobiology School of Veterinary Medicine University of Pennsylvania Philadelphia PA USA Instituto de Ecologia UNAM Mexico City Mexico department of Plant and Microbial Biology University of California Berkeley CA 94720 USA FONDAP Center for Genome Regulation

Nucleotide sugar transporters （NSTs） are antiporters comprising a gene family that plays a fundamental role in the biosynthesis of complex cell wall polysaccharides and glycoproteins in plants. However, due to the limited number of related mutants that have observable phenotypes, the biological function（s） of most NSTs in cell wall biosynthesis and assembly have remained elusive. Here, we report the characterization of AtUTr7 from Arabidopsis （Arabidopsis thaliana （L.） Heynh.）, which is homologous to multi-specific UDP-sugar transporters from Drosophila melanogaster, humans, and Caenorhabditis elegans. We show that AtUTr7 possesses the common structural characteristics conserved among NSTs. Using a green fluorescent protein （GFP） tagged version, we demonstrate that AtUTr7 is localized in the Golgi apparatus. We also show that AtUTr7 is widely expressed, especially in the roots and in specific floral organs. Additionally, the results of an in vitro nucleotide sugar transport assay carried out with a tobacco and a yeast expression system suggest that AtUTr7 is capable of transferring UDP-Gal and UDP-GIc, but not a range of other UDP- and GDP-sugars, into the Golgi lumen. Mutants lacking expression of AtUTr7 exhibited an early proliferation of lateral roots as well as distorted root hairs when cultivated at high sucrose concentrations. Furthermore, the distribution of homogalacturonan with a low degree of methyl esterification differed in lateral root tips of the mutant compared to wild-type plants, although additional analytical procedures revealed no further differences in the composition of the root cell walls. This evidence suggests that the transport of UDP-Gal and UDP-GIc into the Golgi under conditions of high root biomass production plays a role in lateral root and root hair development.

关键词： nucleotide sugars nucleotide sugar transporters Golgi apparatus cell wall.

THE DELAY OF TRANSITION OF A LAMINAR BOUNDARY LAYER OVER COMPLIANT WALL

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Acta Mechanica Sinica 1990年第1期6卷 15-21页

作者： Li Wanping Zhou Heng Tianjin University present address:department of Mechanics Huazhong University of Science and TechnologyWuhan 430074

In a previous paper, a method has been developed to study the stability characteristics of laminar boundary layers over compliant walls. In this paper, the effect of double layered compliant wall and Kramer type compliant wall on delaying the transition is investigated, and it is shown that there does exist the possibility to de- lay the transition by applying such compliant walls.

关键词： transition compliant wall stability

Autoionizing Process of the Double Rydberg State

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Chinese Physics Letters 1995年第12期12卷 713-716页

作者： XU Chengbin XU Xiangyuan HUANG Wen XUE Ping ZHAO Runchuan ZHU Cheng CHEN Dieyan department of Modern Applied Physics Tsinghua UniversityBeijing 100084 present address:Institute of Physics Academia SinicaBeijing 100080

Using five-laser resonance excitation and double time-of-flight spectroscopy,the double Rydberg states NLnl(N≤66;n≤85;L,1<4)of Ca have been *** distribution of Ca^(+)Rydberg states,which is from the autoionization o... 详细信息

关键词： Rydberg double excitation

A Peroxidase Contributes to ROS Production during Arabidopsis Root Response to Potassium Deficiency

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Molecular Plant 2010年第2期3卷 420-427页

作者： Min Jung Kim Silvano Ciani Daniel P. Schachtman Donald Danforth Plant Science Center 975 North Warson Road St Louis MO 63132 USA present address: department of Biology Washington University in St Louis St Louis MO 63130 USA present address: Monsanto Company St Louis MO 63017 USA

Reactive oxygen species （ROS） play an important role in root responses to potassium deprivation by regulating the expression of the high-affinity K＋ transporter gene AtHAK5 and other genes. Activation-tagged lines of Arabidopsis plants containing the AtHAK5 promoter driving luciferase were screened for bioluminescence under potassium- sufficient conditions. A member of the type Ill peroxidase family, RCI3, was isolated and when it was overexpressed by the activation tag, this led to the enhanced expression of luciferase and the endogenous AtHAKS. RCI3 was found to be up- regulated upon potassium deprivation. Plants overexpressing RCI3 （RCI3-ox） showed more ROS production and AtHAK5 expression whereas the ROS production and AtHAK5 expression were reduced in rci3-1 under K＋-deprived conditions. These results suggested that RCI3 is involved in the production of ROS under potassium deprivation and that RCI3- mediated ROS production affects the regulation of AtHAK5 expression. This peroxidase appears to be another component of the low-potassium signal transduction pathway in Arabidopsis roots.

关键词： Abiotic/environmental stress nutrition signal transduction Arabidopsis ROS production peroxidase.