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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)

A chromosome-scale genome assembly of Rauvolfia tetraphylla facilitates identification of the complete ajmaline biosynthetic pathway

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Plant Communications 2024年第4期5卷 129-132页

作者： Enzo Lezin Ines Carqueijeiro Clement Cuello Mickael Durand Hans JJansen Valentin Verges Caroline Birer Williams Audrey Oudin Thomas Duge de Bernonville Julien Petrignet Noemie Celton Benoit St-Pierre Nicolas Papon Chao Sun Ron P.Dirks Sarah Ellen O’Connor Michael Krogh Jensen Sebastien Besseau Vincent Courdavault Biomole´cules et Biotechnologies Vegetales EA2106Universite´de Tours37200 ToursFrance Future Genomics Technologies 2333 BE Leidenthe Netherlands Laboratoire Synthe se et Isolement de Molecules BioActives(SIMBA EA 7502)Universitede Tours37200 ToursFrance Laboratoire de Cytoge´netique Constitutionnelle CHRU de Tours-Hopital Bretonneau37044 ToursFrance University Angers University BrestIRFSFR ICAT49000 AngersFrance Institute of Medicinal Plant Development Chinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing 2800China Department of Natural Product Biosynthesis Max Planck Institute for Chemical Ecology07745 JenaGermany Novo Nordisk Foundation Center for Biosustainability Technical University of Denmark100193 Kgs LyngbyDenmark present address:Limagrain Center de RechercheRoute d’EnnezatChappesFrance These authors contributed equally to this article

Dear Editor,Rauvolfia tetraphylla(aka the Devil pepper)(Supplemental Figure 1)is a well-known medicinal plant that produces monoterpenoid indole alkaloids(MIAs).This MIA biosynthesis occurs in several organs,including leaves,stems,fruit,and roots,which accumulate the famous antiarrhythmic ajmaline(Kumar et al.2016a,2016b;Kumara et al.,2019).MIAs are natural products notably involved in plant adaptation to the environment and defense against *** mainly results from their high biological activities,which also explain their pharmacological properties.

关键词： properties. Figure roots

Inhibition of the Ubiquitin-Proteasome Pathway Alters Cellular Levels of Nitric Oxide in Tomato Seedlings

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Molecular Plant 2010年第5期3卷 854-869页

作者： Sangeeta Negi Parankusam Santisree Eros Vasil Kharshiing Rameshwar Sharma School of Life Sciences University of Hyderabad Hyderabad-500 046 India present address: Donald Danforth Plant Science Centre 975 N. Warson Rd St Louis MO 63132 USA present address: St Edmunds College Shillong Meghalaya India

Nitric oxide （NO） is involved in diverse plant growth processes; however, little is known about pathways regulating NO levels in plants. In this study, we isolated a NO-overproducing mutant of tomato （Solanum lycopersicurn） in which hyper-accumulation of NO, associated with increase in nitric oxide synthase （NOS）-Iike activity, caused diminished vegetative growth of plants and showed delayed flowering. The hyper-accumulation of NO caused drastic shortening of primary root （shr） in the seedlings, while the scavenging of NO restored root elongation in shr mutant. Inhibition of NOS- like activity reduced NO levels and stimulated root elongation in the shr mutant seedlings, while inhibition of nitrate reductase （NR） activity could not rescue shr phenotype. The stimulation of NO levels in shr mutant also conferred increased resistance to pathogen Pseudomonas syringae. Application of pharmacological inhibitors regulating ubiquitin-proteasome pathway reduced NO levels and NOS-like activity and stimulated shr root elongation. Our data indicate that a signaling pathway involving regulated protein degradation likely regulates NO synthesis in tomato.

关键词： Nitric oxide tomato nitric oxide synthase short root mutant plant development.

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

FAST W TRANSFORM——ALGORITHMS AND PROGRAMS

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Science China Mathematics 1989年第3期32卷 338-350页

作者：王中德 Beijing University of Posts & Telecommunications present address:Beijing University of Posts & Telecommunications.

The W transform is an approach to spectrum analysis in real domain. There are fourcommonly used types of the discrete W transform (DWT), all of which may be appliedto digital signal processing. In this paper, new fast algorithms for computing the fourtypes of the DWT are introduced. These algorithms are simple in structure and moreefficient than any other algorithms for the DWT. FORTRAN subroutines to realize thesealgorithms have been provided.

关键词： fast algorithm W transform spectral analysis.

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.

Identification of Early Nuclear Target Genes of Plastidial Redox Signals that Trigger the Long- Term Response of Arabidopsis to Light Quality Sh∽ts

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Molecular Plant 2015年第8期8卷 1237-1252页

作者： Lars Dietzel Christine Glaeer Monique Liebers Stefan Hiekel Florence Courtois Olaf Czarneckit Hagen Schlicke Yan Zubo Thomas Borner Klaus Mayer Bernhard Grimm Thomas Pfannschmidt Department of Plant Physiology Institute of General Botany and Plant Physiology Friedrich-Schiller-University of Jena Domburger Strasse 159 07743 JenaGermany MIPS/IBI Helmholtz Zentrum MGnchen German Research Center for Environmental Health (GmbH) Ingolst~dter Landstrasse 1 85764 Neuherberg Germany Institute of Biology/Plant Physiology Humboldt-University Berlin Philippstrasse 13 Building 12 10115 Berlin Germany Institute of Biology Genetics Humboldt-University Berlin Chausseestrasse 117 10115 Berlin Germany present address: Institut fer Molekulare Biowissenschaften Pflanzliche Zellphysiologie Max-von-Laue-Strasse 9 Biozentrum Goethe-Universit~t Frankfurt 60438Frankfurt am Main Germany present address: Zentrum fur Molekulare Biologie an der Universitat zu Heidelberg (ZMBH) Im Neuenheimer Feld 282 69120 Heidelberg Germany present address: Universite Grenoble-Alpes F-38000 Grenoble France present address: CNRS UMR5168 F-38054 Grenoble France present address: CEA iRTSV Laboratoire de Physiologie Cellulaire & Vgetale F-38054 Grenoble France present address: INRA USC1359 F-38054 Grenoble France present address: Plant Reproductive Biology Group Department of Physiology and Ceil-Biology Leibniz Institute of Rant Genetics and Crop Plant Research (IPK)OT Gatersleben Corrensstrasse 3 D-06466 Stadt Seeland Germany present address: KWS Saat AG Grimsehlstrasse 31 37555 Einbeck Germany present address: Dartmouth College Department of Biological Sciences Ufe Sciences Center 78 College Street Hanover NH 03755 USA

Natural illumination conditions are highly variable and because of their sessile life style, plants are forced to acclimate to them at the cellular and molecular level. Changes in light intensity or quality induce changes in the reduction/oxidation （redox） state of the photosynthetic electron chain that acts as a trigger for compen- satory acclimation responses comprising functional and structural adjustments of photosynthesis and metabolism. Such responses include redox-controlled changes in plant gene expression in the nucleus and organelles. Here we describe a strategy for the identification of early redox-regulated genes （ERGs） in the nucleus of the model organism Arabidopsis thaliana that respond significantly 30 or 60 min after the generation of a reduction signal in the photosynthetic electron transport chain. By comparing the response of wild-type plants with that of the acclimation mutant stn7, we could specifically identify ERGs. The results reveal a significant impact of chloroplast redox signals on distinct nuclear gene groups including genes for the mitochondrial electron transport chain, tetrapyrrole biosynthesis, carbohydrate metabolism, and signaling lipid synthesis. These expression profiles are clearly different from those observed in response to the reduction of photosynthetic electron transport by high light treatments. Thus, the ERGs identified are unique to redox imbalances in photosynthetic electron transport and were then used for analyzing potential redox-responsive cis-elements, trans-factors, and chromosomal regulatory hot spots. The data identify a novel redox-responsive element and indicate extensive redox control at transcriptional and chromosomal levels that point to an unprecedented impact of redox signals on epigenetic processes.

关键词： plastidial redox signaling,early redox-regulated gene Arabidopsis thaliana Molecular Plant

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

Blocking the Metabolism of Starch Breakdown Products in Arabidopsis Leaves Triggers Chloroplast Degradation

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Molecular Plant 2009年第6期2卷 1233-1246页

作者： Michaela Stettler Simona Eicke Tabea Mettler Gaelle Messerli Stefan Hortensteiner Samuel C. Zeeman Department of Biology ETH Zurich CH-8092 Zurich Switzerland Institute of Plant Biology University of Zurich CH-8008 Zurich Switzerland present address: Max Planck Institute for Molecular Plant Physiology Potsdam-Golm 14476 Germany present address: Johnson & Johnson Medical CH-8957 Spreitenbach Switzerland

In most plants, a large fraction of photo-assimilated carbon is stored in the chloroplasts during the day as starch and remobilized during the subsequent night to support metabolism. Mutations blocking either starch synthesis or starch breakdown in Arabidopsis thaliana reduce plant growth. Maltose is the major product of starch breakdown exported from the chloroplast at night. The maltose excess 1 mutant （mex1）, which lacks the chloroplast envelope maltose transporter, accumulates high levels of maltose and starch in chloroplasts and develops a distinctive but previously unexplained chlorotic phenotype as leaves mature. The introduction of additional mutations that prevent starch synthesis, or that block maltose production from starch, also prevent chlorosis of mex1. In contrast, introduction of mutations in disproportionating enzyme （DPE1） results in the accumulation of maltotriose in addition to maltose, and greatly increases chlorosis. These data suggest a link between maltose accumulation and chloroplast homeostasis. Microscopic analyses show that the mesophyll cells in chlorotic mex1 leaves have fewer than half the number of chloroplasts than wild-type cells. Transmission electron microscopy reveals autophagy-like chloroplast degradation in both mex1 and the dpe1/mex1 double mutant. Microarray analyses reveal substantial reprogramming of metabolic and cellular processes, suggesting that organellar protein turnover is increased in mex1, though leaf senescence and senescence-related chlorophyll catabolism are not induced. We propose that the accumulation of maltose and malto-oligosaccharides causes chloroplast dysfunction, which may by signaled via a form of retrograde signaling and trigger chloroplast degradation.

关键词： Carbohydrate metabolism photosynthesis senescence chloroplast biology Arabidopsis autophagy.