bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accumulation of Palmitate in Arabidopsis Mediated by the Acyl-Acyl Carrier Protein Thioesterase FATB1
Authors: Dörmann Peter , Voelker Toni A. , Ohlrogge John B. 
Published: July 2002

Abstract
The acyl-acyl carrier protein thioesterase B1 from Arabidopsis (AtFATB1) was previously shown to exhibit in vitro hydrolytic activity for long chain acyl-acyl carrier proteins (P. Dörmann, T.A. Voelker, J.B. Ohlrogge [1995] Arch Biochem Biophys 316: 612–618). In this study, we address the question of which role in fatty acid biosynthesis this enzyme plays within the plant. Over-expression of the AtFATB1 cDNA under a seed-specific promoter resulted in accumulation of high amounts of palmitate (16:0) in seeds. RNA and protein-blot analysis in Arabidopsis and rapeseed (Brassica napus) showed that the endogenous AtFATB1 expression was highest in flowers and lower in leaves. All floral tissues of wild-type plants contained elevated amounts of 16:0, and in the polar lipid fraction of flowers close to 50 mol % of the fatty acids were 16:0. Therefore, flowers contain polar lipids with an unusually high amount of saturated fatty acids as compared to all other plant tissues. Antisense expression of theAtFATB1 cDNA under the cauliflower mosaic virus 35S promoter resulted in a reduction of seed and flower 16:0 content, but no changes in leaf fatty acids. We conclude that the AtFATB1 thioesterase contributes to 16:0 production particularly in flowers, but that additional factors are involved in leaves.
Antisense Suppression of 2-Cysteine Peroxiredoxin in Arabidopsis Specifically Enhances the Activities and Expression of Enzymes Associated with Ascorbate Metabolism But Not Glutathione Metabolism
Authors: Baier Margarete , Noctor Graham , Foyer Christine H. , Dietz Karl-Josef 
Published: July 2002

Abstract
The aim of this study was to characterize the effect of decreased 2-cysteine peroxiredoxin (2-CP) on the leaf anti-oxidative system in Arabidopsis. At three stages of leaf development, two lines of transgenic Arabidopsis mutants with decreased contents of chloroplast 2-CP were compared with wild type and a control line transformed with an empty vector. Glutathione contents and redox state were similar in all plants, and no changes in transcript levels for enzymes involved in glutathione metabolism were observed. Transcript levels for chloroplastic glutathione peroxidase were much lower than those for 2-CP, and both cytosolic and chloroplastic glutathione peroxidase were not increased in the mutants. In contrast, the foliar ascorbate pool was more oxidized in the mutants, although the difference decreased with plant age. The activities of thylakoid and stromal ascorbate peroxidase and particularly monodehydroascorbate reductase were increased as were transcripts for these enzymes. No change in dehydroascorbate reductase activity was observed, and effects on transcript abundance for glutathione reductase, catalase, and superoxide dismutase were slight or absent. The results demonstrate that 2-CP forms an integral part of the anti-oxidant network of chloroplasts and is functionally interconnected with other defense systems. Suppression of 2-CP leads to increased expression of other anti-oxidative genes possibly mediated by increased oxidation state of the leaf ascorbate pool.
Production of Recombinant Proteins in Tobacco Guttation Fluid
Authors: Komarnytsky Slavko , Borisjuk Nikolai V. , Borisjuk Ljudmila G. , Alam Muhammad Z. , Raskin Ilya 
Published: July 2002

Abstract
Guttation, the loss of water and dissolved materials from uninjured plant organs, is a common phenomenon in higher plants. By using endoplasmic reticulum signal peptides fused to the recombinant protein sequences, we have generated transgenic tobacco (Nicotiana tabacum L. cv Wisconsin) plants that secrete three heterologous proteins of different genetic backgrounds (bacterial xylanase, green fluorescent protein of jellyfish [Aequorea victoria], and human placental alkaline phosphatase) through the leaf intercellular space into tobacco guttation fluid. Production rates of 1.1 μg/g of leaf dry weight per day were achieved for alkaline phosphatase with this protein comprising almost 3% of total soluble protein in the guttation fluid. Guttation fluid can be collected throughout a plant's life, thus providing a continuous and nondestructive system for recombinant protein production. Guttation fluid has the potential of increasing the efficiency of recombinant protein production technology by increasing yield, abolishing extraction, and simplifying its downstream processing.
Brassinosteroid Levels Increase Drastically Prior to Morphogenesis of Tracheary Elements
Authors: Yamamoto Ryo , Fujioka Shozo , Demura Taku , Takatsuto Suguru , Yoshida Shigeo , Fukuda Hiroo 
Published: July 2002

Abstract
As the first step toward understanding the involvement of endogenous brassinosteroids (BRs) in cytodifferentiation, we analyzed biosynthetic activities of BRs in zinnia (Zinnia elegansL. cv Canary Bird) cells differentiating into tracheary elements. The results of feeding experiments suggested that both the early and late C6-oxidation pathways occur during tracheary element differentiation. Gas chromatography-mass spectrometry analysis revealed that five BRs, castasterone, typhasterol, 6-deoxocastasterone, 6-deoxotyphasterol, and 6-deoxoteasterone, actually existed in cultured zinnia cells and culture medium. Quantification of endogenous BRs in each stage of tracheary element differentiation by gas chromatography-mass spectrometry exhibited that they increased dramatically prior to the morphogenesis, which was consistent with the idea that BRs are necessary for the initiation of the final stage of tracheary element differentiation. Moreover, the proportion of each BR in culture medium was quite different from that in cells, suggesting that specific BRs are selectively secreted into medium and may function outside the cells.
Salinity-Induced Inhibition of Leaf Elongation in Maize Is Not Mediated by Changes in Cell Wall Acidification Capacity
Authors: Neves-Piestun Beatriz G. , Bernstein Nirit 
Published: July 2002

Abstract
The physiological mechanisms underlying leaf growth inhibition under salt stress are not fully understood. Apoplastic pH is considered to play an important role in cell wall loosening and tissue growth and was demonstrated to be altered by several growth-limiting environmental conditions. In this study we have evaluated the possibility that inhibition of maize (Zea mays) leaf elongation by salinity is mediated by changes in growing cell wall acidification capacity. The kinetics of extended apoplast pH changes by leaf tissue of known expansion rates and extent of growth reduction under stress was investigated (in vivo) and was found similar for non-stressed and salt-stressed tissues at all examined apoplast salinity levels (0.1, 5, 10, or 25 mm NaCl). A similar rate of spontaneous acidification for the salt and control treatments was demonstrated also in in situ experiments. Unlike growing cells that acidified the external medium, mature nongrowing cells caused medium alkalinization. The kinetics of pH changes by mature tissue was also unchanged by salt stress. Fusicoccin, an enhancer of plasmalemma H+-ATPase activity level, greatly stimulated elongation growth and acidification rate to a similar extent in the control and salt treatments. That the ability of the growing tissue to acidify the apoplast did not change under same salt stress conditions that induced inhibition of tissue elongation rate suggests that salinity does not inhibit cell growth by impairing the acidification process or reducing the inherent capacity for cell wall acidification.
Iron Stress-Induced Changes in Root Epidermal Cell Fate Are Regulated Independently from Physiological Responses to Low Iron Availability
Authors: Schikora Adam , Schmidt Wolfgang 
Published: July 2002

Abstract
Iron-overaccumulating mutants were investigated with respect to changes in epidermal cell patterning and root reductase activity in response to iron starvation. In all mutants under investigation, ferric chelate reductase activity was up-regulated both in the presence and absence of iron in the growth medium. The induction of transfer cells in the rhizodermis appeared to be iron regulated in the pea (Pisum sativum L. cv Dippes Gelbe Viktoria and cv Sparkle) mutants bronze and degenerated leaflets, but not in roots of the tomato (Lycopersicon esculentum Mill. cv Bonner Beste) mutantchloronerva, suggesting that inchloronerva iron cannot be recognized by putative sensor proteins. Experiments with split-root plants supports the hypothesis that Fe(III) chelate reductase is regulated by a shoot-borne signal molecule, communicating the iron status of the shoot to the roots. In contrast, the formation of transfer cells was dependent on the local concentration of iron, implying that this shoot signal does not affect their formation. Different repression curves of the two responses imply that the induction of transfer cells occurs after the enhancement of electron transfer across the plasma membrane rather than being causally linked. Similar to transfer cells, the formation of extra root hairs in the Arabidopsis mutant man1 was regulated by the iron concentration of the growth medium and was unaffected by interorgan signaling.
Analysis and Expression of the α-Expansin and β-Expansin Gene Families in Maize
Authors: Wu Yajun , Meeley Robert B. , Cosgrove Daniel J. 
Published: July 2002

Abstract
Expansins comprise a multigene family of proteins in maize (Zea mays). We isolated and characterized 13 different maize expansin cDNAs, five of which are α-expansins and eight of which are β-expansins. This paper presents an analysis of these 13 expansins, as well as an expression analysis by northern blotting with materials from young and mature maize plants. Some expansins were expressed in restricted regions, such as the β-expansins ExpB1 (specifically expressed in maize pollen) and ExpB4 (expressed principally in young husks). Other expansins such as α-expansin Exp1 and β-expansin ExpB2 were expressed in several organs. The expression of yet a third group was not detected in the selected organs and tissues. An analysis of expansin sequences from the maize expressed sequence tag collection is also presented. Our results indicate that expansin genes may have general, overlapping expression in some instances, whereas in other cases the expression may be highly specific and limited to a single organ or cell type. In contrast to the situation in Arabidopsis, β-expansins in maize seem to be more numerous and more highly expressed than are α-expansins. The results support the concept that β-expansins multiplied and evolved special functions in the grasses.
Aluminum Activates a Citrate-Permeable Anion Channel in the Aluminum-Sensitive Zone of the Maize Root Apex. A Comparison Between an Aluminum- Sensitive and an Aluminum-Resistant Cultivar
Authors: Kollmeier Malte , Dietrich Petra , Bauer Claudia S. , Horst Walter J. , Hedrich Rainer 
Published: July 2002

AbstractIn search for the cellular and molecular basis for differences in aluminum (Al) resistance between maize (Zea mays) cultivars we applied the patch-clamp technique to protoplasts isolated from the apical root cortex of two maize cultivars differing in Al resistance. Measurements were performed on protoplasts from two apical root zones: The 1- to 2-mm zone (DTZ), described as most Al-sensitive, and the main elongation zone (3–5 mm), the site of Al-induced inhibition of cell elongation. Al stimulated citrate and malate efflux from intact root apices, revealing cultivar differences. In the elongation zone, anion channels were not observed in the absence and presence of Al. Preincubation of intact roots with 90 μmAl for 1 h induced a citrate- and malate-permeable, large conductance anion channel in 80% of the DTZ protoplasts from the resistant cultivar, but only 30% from the sensitive cultivar. When Al was applied to the protoplasts in the whole-cell configuration, anion currents were elicited within 10 min in the resistant cultivar only. La3+ was not able to replace or counteract with Al3+ in the activation of this channel. In the presence of the anion-channel blockers, niflumic acid and 4, 4′-dinitrostilbene-2, 2′disulfonic acid, anion currents as well as exudation rates were strongly inhibited. Application of cycloheximide did not affect the Al response, suggesting that the channel is activated through post-translational modifications. We propose that the Al-activated large anion channel described here contributes to enhanced genotypical Al resistance by facilitating the exudation of organic acid anions from the DTZ of the maize root apex.
The Phenylalanine Ammonia-Lyase Gene Family in Raspberry. Structure, Expression, and Evolution
Authors: Kumar Amrita , Ellis Brian E. 
Published: July 2002

AbstractIn raspberry (Rubus idaeus), development of fruit color and flavor are critically dependent on products of the phenylpropanoid pathway. To determine how these metabolic functions are integrated with the fruit ripening program, we are examining the properties and expression of key genes in the pathway. Here, we report that l- phenylalanine ammonia-lyase (PAL) is encoded in raspberry by a family of two genes (RiPAL1 andRiPAL2). RiPAL1 shares 88% amino acid sequence similarity to RiPAL2, but phylogenetic analysis places RiPAL1 and RiPAL2 in different clusters within the plant PAL gene family. The spatial and temporal expression patterns of the two genes were investigated in various vegetative and floral tissues using the reverse transcriptase competitor polymerase chain reaction assay. Although expression of both genes was detected in all tissues examined, RiPAL1 was associated with early fruit ripening events, whereas expression ofRiPAL2 correlated more with later stages of flower and fruit development. Determination of the absolute levels of the two transcripts in various tissues showed that RiPAL1transcripts were 3- to 10-fold more abundant than those ofRiPAL2 in leaves, shoots, roots, young fruits, and ripe fruits. The two RiPAL genes therefore appear to be controlled by different regulatory mechanisms.
Three-Dimensional Analysis of Syncytial-Type Cell Plates during Endosperm Cellularization Visualized by High Resolution Electron Tomography[W]
Authors: Otegui Marisa S. , Mastronarde David N. , Kang Byung-Ho , Bednarek Sebastian Y. , Staehelin L. Andrew 
Published: July 2002

AbstractThe three-dimensional architecture of syncytial-type cell plates in the endosperm of Arabidopsis has been analyzed at ∼6-nm resolution by means of dual-axis high-voltage electron tomography of high-pressure frozen/freeze-substituted samples. Mini-phragmoplasts consisting of microtubule clusters assemble between sister and nonsister nuclei. Most Golgi-derived vesicles appear connected to these microtubules by two molecules that resemble kinesin-like motor proteins. These vesicles fuse with each other to form hourglass-shaped intermediates, which become wide (∼45 nm in diameter) tubules, the building blocks of wide tubular networks. New mini-phragmoplasts also are generated de novo around the margins of expanding wide tubular networks, giving rise to new foci of cell plate growth, which later become integrated into the main cell plate. Spiral-shaped rings of the dynamin-like protein ADL1A constrict but do not fission the wide tubules at irregular intervals. These rings appear to maintain the tubular geometry of the network. The wide tubular network matures into a convoluted fenestrated sheet in a process that involves increases of 45 and 130% in relative membrane surface area and volume, respectively. The proportionally larger increase in volume appears to reflect callose synthesis. Upon fusion with the parental plasma membrane, the convoluted fenestrated sheet is transformed into a planar fenestrated sheet. This transformation involves clathrin-coated vesicles that reduce the relative membrane surface area and volume by ∼70%. A ribosome-excluding matrix encompasses the cell plate membranes from the fusion of the first vesicles until the onset of the planar fenestrated sheet formation. We postulate that this matrix contains the molecules that mediate cell plate assembly.
Subunit organization in cytoplasmic dynein subcomplexes
Authors: King Stephen J. , Bonilla Myriam , Rodgers Michael E. , Schroer Trina A. 
Published: July 2002

AbstractBecause cytoplasmic dynein plays numerous critical roles in eukaryotic cells, determining the subunit composition and the organization and functions of the subunits within dynein are important goals. This has been difficult partly because of accessory polypeptide heterogeneity of dynein populations. The motor domain containing heavy chains of cytoplasmic dynein are associated with multiple intermediate, light intermediate, and light chain accessory polypeptides. We examined the organization of these subunits within cytoplasmic dynein by separating the molecule into two distinct subcomplexes. These subcomplexes were competent to reassemble into a molecule with dynein‐like properties. One subcomplex was composed of the dynein heavy and light intermediate chains whereas the other subcomplex was composed of the intermediate and light chains. The intermediate and light chain subcomplex could be further separated into two pools, only one of which contained dynein light chains. The two pools had distinct intermediate chain compositions, suggesting that intermediate chain isoforms have different light chain–binding properties. When the two intermediate chain pools were characterized by analytical velocity sedimentation, at least four molecular components were seen: intermediate chain monomers, intermediate chain dimers, intermediate chain monomers with bound light chains, and a mixture of intermediate chain dimers with assorted bound light chains. These data provide new insights into the compositional heterogeneity and assembly of the cytoplasmic dynein complex and suggest that individual dynein molecules have distinct molecular compositions in vivo.
Enantioselectivity in Candida antarctica lipase B: A molecular dynamics study
Authors: Raza Sami , Fransson Linda , Hult Karl 
Published: July 2002

AbstractA major problem in predicting the enantioselectivity of an enzyme toward substrate molecules is that even high selectivity toward one substrate enantiomer over the other corresponds to a very small difference in free energy. However, total free energies in enzyme‐substrate systems are very large and fluctuate significantly because of general protein motion. Candida antarctica lipase B (CALB), a serine hydrolase, displays enantioselectivity toward secondary alcohols. Here, we present a modeling study where the aim has been to develop a molecular dynamics‐based methodology for the prediction of enantioselectivity in CALB. The substrates modeled (seven in total) were 3‐methyl‐2‐butanol with various aliphatic carboxylic acids and also 2‐butanol, as well as 3,3‐dimethyl‐2‐butanol with octanoic acid. The tetrahedral reaction intermediate was used as a model of the transition state. Investigative analyses were performed on ensembles of nonminimized structures and focused on the potential energies of a number of subsets within the modeled systems to determine which specific regions are important for the prediction of enantioselectivity. One category of subset was based on atoms that make up the core structural elements of the transition state. We considered that a more favorable energetic conformation of such a subset should relate to a greater likelihood for catalysis to occur, thus reflecting higher selectivity. The results of this study conveyed that the use of this type of subset was viable for the analysis of structural ensembles and yielded good predictions of enantioselectivity.
From proteases to proteomics
Authors: Neurath Hans 
Published: July 2002

AbstractThis personal and professional autobiography covers the 50‐yr period of 1950–2000 and includes the following topics: History of the University of Washington School of Medicine and its Department of Biochemistry (Mount Rainier and the University of Washington, recruiting faculty, biology, research programs); scientific editing (publication, Biochemistry, Protein Science, electronic publication); Europe revisited (Heidelberg, approaching retirement, the German Research Center, reunion in Vienna); and 50 yr of research on proteolytic enzymes (trypsin, carboxypeptidases, mast cell proteases, future developments).
Self‐assembly of the hydrophobin SC3 proceeds via two structural intermediates
Authors: De Vocht Marcel L. , Reviakine Ilya , Ulrich Wolf‐Peter , Bergsma‐Schutter Wilma , Wösten Han A.B. , Vogel Horst , Brisson Alain , Wessels Joseph G.H. , Robillard George T. 
Published: July 2002

AbstractHydrophobins self assemble into amphipathic films at hydrophobic–hydrophilic interfaces. These proteins are involved in a broad range of processes in fungal development. We have studied the conformational changes that accompany the self‐assembly of the hydrophobin SC3 with polarization‐modulation infrared reflection absorption spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, and circular dichroism, and related them to changes in morphology as observed by electron microcopy. Three states of SC3 have been spectroscopically identified previously as follows: the monomeric state, the α‐helical state that is formed upon binding to a hydrophobic solid, and the β‐sheet state, which is formed at the air–water interface. Here, we show that the formation of the β‐sheet state of SC3 proceeds via two intermediates. The first intermediate has an infrared spectrum indistinguishable from that of the α‐helical state of SC3. The second intermediate is rich in β‐sheet structure and has a featureless appearance under the electron microscope. The end state has the same secondary structure, but is characterized by the familiar 10‐nm‐wide rodlets.
A 1998 Survey of Extended-Spectrum β-Lactamases in
Enterobacteriaceae
in France
Authors: De Champs C. , Sirot D. , Chanal C. , Bonnet R. , Sirot J. ,   the French Study Group
Published: July 2002

ABSTRACT

In a 3-month period in 1998, 79 consecutive isolates of
Enterobacteriaceae
producing an extended-spectrum β-lactamase (ESBL) were collected. ESBLs were predominantly TEM derivatives (74 of 79): TEM-24-like (40 isolates), TEM-3-like (29 isolates), TEM-21 (3 isolates), and TEM-4 and TEM-52 (1 isolate each). Four isolates produced SHV derivatives SHV-4 (three isolates) and SHV-5 (one isolate), and one strain produced a CTX-M-3 enzyme. The high proportion of TEM-24-like-producing
Enterobacter aerogenes
isolates (36 of 79) suggests the occurrence of an epidemic strain in France.
Updated Sequence Information and Proposed Nomenclature for
bla
TEM
Genes and Their Promoters
Authors: Leflon-Guibout V. , Heym B. , Nicolas-Chanoine M.-H. 
Published: July 2002

ABSTRACT

The nucleotide sequences of 59
bla
TEM
genes encoding inhibitor-resistant TEM enzymes showed great genetic variability and were associated with different types of promoters. These findings led us to suggest an updated
bla
TEM
gene nomenclature based on the origin of the
bla
TEM
gene (
bla
TEM-1A
,
bla
TEM-1B
,
bla
TEM-1C
,
bla
TEM-1D
,
bla
TEM-1E
, and
bla
TEM-1F
) and the promoter type.