bluuebunny/crossref_metadata_2025_split huggingface dataset:
(+)-Abscisic Acid Metabolism, 3-Ketoacyl-Coenzyme A Synthase Gene Expression, and Very-Long-Chain Monounsaturated Fatty Acid Biosynthesis inBrassica napus Embryos1
Authors: Qi Qungang , Rose Patricia A. , Abrams Garth D. , Taylor David C. , Abrams Suzanne R. , Cutler Adrian J. 
Published: July 2002

Abstract
Microspore-derived embryos ofBrassica napus cv Reston were used to examine the effects of exogenous (+)-abscisic acid (ABA) and related compounds on the accumulation of very-long-chain monounsaturated fatty acids (VLCMFAs), VLCMFA elongase complex activity, and induction of the 3-ketoacyl-coenzyme A synthase (KCS) gene encoding the condensing enzyme of the VLCMFA elongation system. Of the concentrations tested, (+)-ABA at 10 μm showed the strongest effect. Maximum activity of the elongase complex, observed 6 h after 10 μm (+)-ABA treatment, was 60% higher than that of the untreated embryos at 24 h. The transcript of the KCS gene was induced by 10 μm (+)-ABA within 1 h and further increased up to 6 h. The VLCMFAs eicosenoic acid (20:1) and erucoic acid (22:1) increased by 1.5- to 2-fold in embryos treated with (+)-ABA for 72 h. Also, (+)-8′-methylene ABA, which is metabolized more slowly than ABA, had a stronger ABA-like effect on the KCS gene transcription, elongase complex activity (28% higher), and level of VLCMFAs (25–30% higher) than ABA. After 24 h approximately 60% of the added (+)-[3H]ABA (10 μm) was metabolized, yielding labeled phaseic and dihydrophaseic acid. This study demonstrates that (+)-ABA promotes VLCMFA biosynthesis via increased expression of the KCS gene and that reducing ABA catabolism would increase VLCMFAs in microspore-derived embryos.
Overexpression of 20-Oxidase Confers a Gibberellin-Overproduction Phenotype in Arabidopsis
Authors: Huang Shihshieh , Raman Anuradha S. , Ream Joel E. , Fujiwara Hideji , Cerny R. Eric , Brown Sherri M. 
Published: July 2002

Abstract
In the gibberellin (GA) biosynthesis pathway, 20-oxidase catalyzes the oxidation and elimination of carbon-20 to give rise to C19-GAs. All bioactive GAs are C19-GAs. We have overexpressed a cDNA encoding 20-oxidase isolated from Arabidopsis seedlings in transgenic Arabidopsis plants. These transgenic plants display a phenotype that may be attributed to the overproduction of GA. The phenotype includes a longer hypocotyl, lighter-green leaves, increased stem elongation, earlier flowering, and decreased seed dormancy. However, the fertility of the transgenic plants is not affected. Increased levels of endogenous GA1, GA9, and GA20 were detected in seedlings of the transgenic line examined. GA4, which is thought to be the predominantly active GA in Arabidopsis, was not present at increased levels in this line. These results suggest that the overexpression of this 20-oxidase increases the levels of some endogenous GAs in transgenic seedlings, which causes the GA-overproduction phenotype.
Cellular Compartmentation of Zinc in Leaves of the Hyperaccumulator Thlaspi caerulescens1
Authors: Küpper Hendrik , Jie Zhao Fang , McGrath Steve P. 
Published: July 2002

Abstract
Cellular compartmentation of Zn in the leaves of the hyperaccumulator Thlaspi caerulescens was investigated using energy-dispersive x-ray microanalysis and single-cell sap extraction. Energy-dispersive x-ray microanalysis of frozen, hydrated leaf tissues showed greatly enhanced Zn accumulation in the epidermis compared with the mesophyll cells. The relative Zn concentration in the epidermal cells correlated linearly with cell length in both young and mature leaves, suggesting that vacuolation of epidermal cells may promote the preferential Zn accumulation. The results from single-cell sap sampling showed that the Zn concentrations in the epidermal vacuolar sap were 5 to 6.5 times higher than those in the mesophyll sap and reached an average of 385 mm in plants with 20,000 μg Zn g−1 dry weight of shoots. Even when the growth medium contained no elevated Zn, preferential Zn accumulation in the epidermal vacuoles was still evident. The concentrations of K, Cl, P, and Ca in the epidermal sap generally decreased with increasing Zn. There was no evidence of association of Zn with either P or S. The present study demonstrates that Zn is sequestered in a soluble form predominantly in the epidermal vacuoles in T. caerulescens leaves and that mesophyll cells are able to tolerate up to at least 60 mm Zn in their sap.
Evidence for a Slow-Turnover Form of the Ca2+-Independent Phosphoenolpyruvate Carboxylase Kinase in the Aleurone-Endosperm Tissue of Germinating Barley Seeds1
Authors: Osuna Lidia , Pierre Jean-Nöel , González Marı́a-Cruz , Alvarez Rosario , Cejudo Francisco J. , Echevarrı́a Cristina , Vidal Jean 
Published: July 2002

Abstract
Phosphoenolpyruvate carboxylase (PEPC) activity was detected in aleurone-endosperm extracts of barley (Hordeum vulgare) seeds during germination, and specific anti-sorghum (Sorghum bicolor) C4 PEPC polyclonal antibodies immunodecorated constitutive 103-kD and inducible 108-kD PEPC polypeptides in western analysis. The 103- and 108-kD polypeptides were radiolabeled in situ after imbibition for up to 1.5 d in 32P-labeled inorganic phosphate. In vitro phosphorylation by a Ca2+-independent PEPC protein kinase (PK) in crude extracts enhanced the enzyme's velocity and decreased its sensitivity to l-malate at suboptimal pH and [PEP]. Isolated aleurone cell protoplasts contained both phosphorylated PEPC and a Ca2+-independent PEPC-PK that was partially purified by affinity chromatography on blue dextran-agarose. This PK activity was present in dry seeds, and PEPC phosphorylation in situ during imbibition was not affected by the cytosolic protein-synthesis inhibitor cycloheximide, by weak acids, or by various pharmacological reagents that had proven to be effective blockers of the light signal transduction chain and PEPC phosphorylation in C4 mesophyll protoplasts. These collective data support the hypothesis that this Ca2+-independent PEPC-PK was formed during maturation of barley seeds and that its presumed underlying signaling elements were no longer operative during germination.
Refilling of Embolized Vessels in Young Stems of Laurel. Do We Need a New Paradigm?1
Authors: Tyree Melvin Thomas , Salleo Sebastiano , Nardini Andrea , Assunta Lo Gullo Maria , Mosca Roberto 
Published: July 2002

AbstractRecovery of hydraulic conductivity after the induction of embolisms was studied in woody stems of laurel (Laurus nobilis). Previous experiments confirming the recovery of hydraulic conductivity when xylem pressure potential was less than −1 MPa were repeated, and new experiments were done to investigate the changes in solute composition in xylem vessels during refilling. Xylem sap collected by perfusion of excised stem segments showed elevated levels of several ions during refilling. Stem segments were frozen in liquid N2 to view refilling vessels using cryoscanning electron microscopy. Vessels could be found in all three states of presumed refilling: (a) mostly water with a little air, (b) mostly air with a little water, or (c) water droplets extruding from vessel pits adjacent to living cells. Radiographic probe microanalysis of refilling vessels revealed nondetectable levels of dissolved solutes. Results are discussed in terms of proposed mechanisms of refilling in vessels while surrounding vessels were at a xylem pressure potential of less than −1 MPa. We have concluded that none of the existing paradigms explains the results.
Histidine-41 of the Cytochrome b
5Domain of the Borage Δ6 Fatty Acid Desaturase Is Essential for Enzyme Activity
Authors: Sayanova Olga , Shewry Peter R. , Napier Johnathan A. 
Published: July 2002

Abstract
Unlike most other plant microsomal desaturases, the Δ6-fatty acid desaturase from borage (Borago officinalis) contains an N-terminal extension that shows homology to the small hemoprotein cytochrome (Cyt)b 5. To determine if this domain serves as a functional electron donor for the Δ6-fatty acid desaturase, mutagenesis and functional analysis by expression in transgenic Arabidopsis was carried out. Although expression of the wild-type borage Δ6-fatty acid desaturase resulted in the synthesis and accumulation of Δ6-unsaturated fatty acids, this was not observed in plants transformed with N-terminally deleted forms of the desaturase. Site-directed mutagenesis was used to disrupt one of the axial heme-binding residues (histidine-41) of the Cytb 5 domain; expression of this mutant form of the Δ6-desaturase in transgenic plants failed to produce Δ6-unsaturated fatty acids. These data indicate that the Cyt b 5 domain of the borage Δ6-fatty acid desaturase is essential for enzymatic activity.
Bordered Pit Structure and Vessel Wall Surface Properties. Implications for Embolism Repair
Authors: Zwieniecki Maciej Andrzej , Holbrook Noel Michele 
Published: July 2002

Abstract
The idea that embolized xylem vessels can be refilled while adjacent vessels remain under tension is difficult to accept if the cavitated vessels remain hydraulically connected to vessels under tension. A mechanism by which embolized conduits could be hydraulically isolated from adjacent conduits requires the existence of a non-zero contact angle and a flared opening into the bordered pit chamber such that a convex air-water interface forms at the entrance into the pit chamber. We measured the contact angle and pit chamber geometry for six species. The contact angle measured in the vessel lumen ranged between 42° to 55°, whereas the opening into the pit chamber ranged between 144° and 157°. If the surface properties within the pit chamber are similar to those in the lumen, a convex meniscus will form at the flared opening into the pit chamber. The maximum pressure difference between water in the lumen and gas in the pit chamber that could be stabilized by this interface was calculated to be within the range of 0.07 to 0.30 MPa.
Ethylene Induces Epidermal Cell Death at the Site of Adventitious Root Emergence in Rice
Authors: Mergemann Heidi , Sauter Margret 
Published: July 2002

Abstract
In deepwater rice (Oryza sativa), adventitious root primordia initiate at the nodes as part of normal development. Emergence of the roots is dependent on flooding of the plant and is mediated by ethylene action. Root growth was preceded by the induced death of epidermal cells of the node external to the tip of the root primordium. Cell death proceeded until the epidermis split open. Through this crack the root eventually emerged. Induced death was confined to nodal epidermal cells covering the tip of the primordia. Our results suggest that this process facilitates adventitious root emergence and prevents injury to the growing root. Cell death was inducible not only by submergence but also by application of 1-aminocyclopropane-1-carboxylic acid, the natural precursor of ethylene and it was suppressed in the presence of 2,5-norbornadiene (bicyclo[2.2.1]hepta-2,5-diene), an inhibitor of ethylene action. Adventitious root growth and epidermal cell death are therefore linked to the ethylene signaling pathway, which is activated in response to low oxygen stress.
Hydroxylated Phytosiderophore Species Possess an Enhanced Chelate Stability and Affinity for Iron(III)
Authors: von Wirén Nicolaus , Khodr Hicham , Hider Robert C. 
Published: July 2002

Abstract
Graminaceous plant species acquire soil iron by the release of phytosiderophores and subsequent uptake of iron(III)-phytosiderophore complexes. As plant species differ in their ability for phytosiderophore hydroxylation prior to release, an electrophoretic method was set up to determine whether hydroxylation affects the net charge of iron(III)-phytosiderophore complexes, and thus chelate stability. At pH 7.0, non-hydroxylated (deoxymugineic acid) and hydroxylated (mugineic acid; epi-hydroxymugineic acid) phytosiderophores form single negatively charged iron(III) complexes, in contrast to iron(III)-nicotianamine. As the degree of phytosiderophore hydroxylation increases, the corresponding iron(III) complex was found to be less readily protonated. Measured pKa values of the amino groups and calculated free iron(III) concentrations in presence of a 10-fold chelator excess were also found to decrease with increasing degree of hydroxylation, confirming that phytosiderophore hydroxylation protects against acid-induced protonation of the iron(III)-phytosiderophore complex. These effects are almost certainly associated with intramolecular hydrogen bonding between the hydroxyl and amino functions. We conclude that introduction of hydroxyl groups into the phytosiderophore skeleton increases iron(III)-chelate stability in acid environments such as those found in the rhizosphere or the root apoplasm and may contribute to an enhanced iron acquisition.
Isoprene Increases Thermotolerance of Fosmidomycin-Fed Leaves
Authors: Sharkey Thomas D. , Chen Xiuyin , Yeh Sansun 
Published: July 2002

Abstract
Isoprene is synthesized and emitted in large amounts by a number of plant species, especially oak (Quercus sp.) and aspen (Populussp.) trees. It has been suggested that isoprene improves thermotolerance by helping photosynthesis cope with high temperature. However, the evidence for the thermotolerance hypothesis is indirect and one of three methods used to support this hypothesis has recently been called into question. More direct evidence required new methods of controlling endogenous isoprene. An inhibitor of the deoxyxylulose 5-phosphate pathway, the alternative pathway to the mevalonic acid pathway and the pathway by which isoprene is made, is now available. Fosmidomycin eliminates isoprene emission without affecting photosynthesis for several hours after feeding to detached leaves. Photosynthesis of fosmidomycin-fed leaves recovered less following a 2-min high-temperature treatment at 46°C than did photosynthesis of leaves fed water or fosmidomycin-fed leaves in air supplemented with isoprene. Photosynthesis of Phaseolus vulgaris leaves, which do not make isoprene, exhibited increased thermotolerance when isoprene was supplied in the airstream flowing over the leaf. Other short-chain alkenes also improved thermotolerance, whereas alkanes reduced thermotolerance. It is concluded that thermotolerance of photosynthesis is a substantial benefit to plants that make isoprene and that this benefit explains why plants make isoprene. The effect may be a general hydrocarbon effect and related to the double bonds in the isoprene molecule.
Crystallization and preliminary X-ray analysis of a complex between the Bowman–Birk trypsin inhibitor from barley and porcine pancreatic trypsin
Authors: Kim Young Sil , Song Hyun Kyu , Suh Se Won 
Published: July 2002

A 1:2 complex between the Bowman–Birk trypsin inhibitor from barley seeds and porcine pancreatic trypsin has been crystallized at 291 K using polyethylene glycol as precipitant. The crystals belong to the orthorhombic space group P212121, with unit-cell parameters a = 67.10, b = 88.38 and c = 203.65 Å. The asymmetric unit contains two monomers of the complex, with a corresponding Vm
of 2.41 Å3 Da−1 and a solvent content of 49%. Native data to 2.2 Å resolution have been collected at 100 K using synchrotron X-rays.
Crystallization and preliminary X-ray diffraction analysis of the homodimeric form α2 of the HU protein from Escherichia coli
Authors: Coste Franck , Hervouet Nadège , Oberto Jacques , Zelwer Charles , Castaing Bertrand 
Published: July 2002

The homodimeric form α2 of the Escherichia coli DNA-binding protein HU was crystallized by the hanging-drop vapour-diffusion method using PEG 4000 as a precipitant. The crystals belong to space group I222, with unit-cell parameters a = 31.09, b = 55.34, c = 117.63 Å, and contain one monomer per asymmetric unit. A full diffraction data set was collected to 2.3 Å resolution on a conventional X-ray source. The molecular-replacement method, using the HU crystallographic model from Bacillus stearothermophilus as a starting point, gave a reliable solution for the rotation and translation functions.
Environmentally induced reversible conformational switching in the yeast cell adhesion protein α‐agglutinin
Authors: Zhao Hui , Chen Min‐Hao , Shen Zheng‐Ming , Kahn Peter C. , Lipke Peter N. 
Published: July 2002

AbstractThe yeast cell adhesion protein α‐agglutinin is expressed on the surface of a free‐living organism and is subjected to a variety of environmental conditions. Circular dichroism (CD) spectroscopy shows that the binding region of α‐agglutinin has a β‐sheet‐rich structure, with only ∼2% α‐helix under native conditions (15–40°C at pH 5.5). This region is predicted to fold into three immunoglobulin‐like domains, and models are consistent with the CD spectra as well as with peptide mapping and site‐specific mutagenesis. However, secondary structure prediction algorithms show that segments comprising ∼17% of the residues have high α‐helical and low β‐sheet potential. Two model peptides of such segments had helical tendencies, and one of these peptides showed pH‐dependent conformational switching. Similarly, CD spectroscopy of the binding region of α‐agglutinin showed reversible conversion from β‐rich to mixed α/β structure at elevated temperatures or when the pH was changed. The reversibility of these changes implied that there is a small energy difference between the all‐β and the α/β states. Similar changes followed cleavage of peptide or disulfide bonds. Together, these observations imply that short sequences of high helical propensity are constrained to a β‐rich state by covalent and local charge interactions under native conditions, but form helices under non‐native conditions.
Multiphase Mechanics of Capsule Formation in Tumors
Authors: Lubkin S. R. , Jackson T. 
Published: July 2002

AbstractThe presence of a capsule around a tumor is known to be correlated with benign status, and the absence of a capsule often has negative implications for patient prognosis. A mechanical description is presented of the growth of a tumor and the resulting deformations of surrounding normal tissue. A mathematical model of the mechanics is analyzed using physical parameters measured in vivo and in vitro. The model has only three dimensionless parameters, and its results are very robust with respect to parameter variation. We show that the presence of contractility in the surrounding tissue, corresponding to a host defense, can make an existing capsule denser and constrain the tumor better, but cannot be responsible for the observed pressure gradients in encapsulated tumors. Some implications for treatment are discussed.
Evaluation of Multiaxial Fatigue Life Prediction Methodologies for Ti-6Al-4V
Authors: Kallmeyer Alan R. , Krgo Ahmo , Kurath Peter 
Published: July 2002

AbstractMany critical engineering components are routinely subjected to cyclic multiaxial stress states, which may include non-proportional loading and multidimensional mean stresses. Existing multiaxial fatigue models are examined to determine their suitability at estimating fatigue damage in Ti-6Al-4V under complex, multiaxial loading, with an emphasis on long-life conditions. Both proportional and non-proportional strain-controlled tension/torsion experiments were conducted on solid specimens. Several multiaxial fatigue damage parameters are evaluated based on their ability to correlate the biaxial fatigue data and uniaxial fatigue data with tensile mean stresses (R&gt;−1) to a fully-reversed (R=−1) uniaxial baseline. Both equivalent stress-based models and critical plane approaches are evaluated. Only one equivalent stress model and two critical plane models showed promise for the range of loadings and material considered.
Thermal Charge Conditioning for Optimal HCCI Engine Operation
Authors: Martinez-Frias Joel , Aceves Salvador M. , Flowers Daniel , Smith J. Ray , Dibble Robert 
Published: July 2002

Abstract
This work investigates a purely thermal control system for HCCI engines, where thermal energy from exhaust gas recirculation (EGR) and compression work in the supercharger are either recycled or rejected as needed. HCCI engine operation is analyzed with a detailed chemical kinetics code, HCT (Hydrodynamics, Chemistry and Transport), which has been extensively modified for application to engines. HCT is linked to an optimizer that determines the operating conditions that result in maximum brake thermal efficiency, while meeting the restrictions of low NOx and peak cylinder pressure. The results show the values of the operating conditions that yield optimum efficiency as a function of torque for a constant engine speed (1800 rpm). For zero torque (idle), the optimizer determines operating conditions that result in minimum fuel consumption. The optimizer is also used for determining the maximum torque that can be obtained within the operating restrictions of NOx and peak cylinder pressure. The results show that a thermally controlled HCCI engine can successfully operate over a wide range of conditions at high efficiency and low emissions.
Computational and Mathematical Modeling of Turbine Rim Seal Ingestion
Authors: Hills Nicholas J. , Chew John W. , Turner Alan B. 
Published: July 2002

Abstract
Understanding and modeling of main annulus gas ingestion through turbine rim seals is considered and advanced in this paper. Unsteady three-dimensional computational fluid dynamics (CFD) calculations and results from a more elementary model are presented and compared with experimental data previously published by Hills et al. (1997). The most complete CFD model presented includes both stator and rotor in the main annulus and the interdisk cavity. The k-ε model of turbulence with standard wall function approximations is assumed in the model which was constructed in a commercial CFD code employing a pressure correction solution algorithm. It is shown that considerable care is needed to ensure convergence of the CFD model to a periodic solution. Compared to previous models, results from the CFD model show encouraging agreement with pressure and gas concentration measurements. The annulus gas ingestion is shown to result from a combination of the stationary and rotating circumferential pressure asymmetries in the annulus. Inertial effects associated with the circumferential velocity component of the flow have an important effect on the degree of ingestion. The elementary model used is an extension of earlier models based on orifice theory applied locally around the rim seal circumference. The new model includes a term accounting for inertial effects. Some good qualitative and fair quantitative agreement with data is shown.
Autoregressive Model-Based Gear Fault Diagnosis
Authors: Wang Wenyi , Wong Albert K. 
Published: July 2002

Abstract
This paper presents a model-based technique for the detection and diagnosis of gear faults. Based on the signal averaging technique, the proposed technique first establishes an autoregressive (AR) model on the vibration signal of the gear of interest in its healthy-state. The model is then used as a linear prediction error filter to process the future-state signal from the same gear. The health condition of the gear is diagnosed by characterizing the error signal between the filtered and unfiltered signals. The technique is validated using both numerical simulation and experimental data. The results show that the AR model technique is an effective tool in the detection and diagnosis of gear faults and it may lead to an effective solution for in-flight diagnosis of helicopter transmissions.