bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolic Bypass of the Tricarboxylic Acid Cycle during Lipid Mobilization in Germinating Oilseeds1
Authors: Falk Kimberly L. , Behal Robert H. , Xiang Chengbin , Oliver David J. 
Published: July 2002

Abstract
Biosynthesis of sucrose from triacylglycerol requires the bypass of the CO2-evolving reactions of the tricarboxylic acid (TCA) cycle. The regulation of the TCA cycle bypass during lipid mobilization was examined. Lipid mobilization in Brassica napus was initiated shortly after imbibition of the seed and proceeded until 2 d postimbibition, as measured by in vivo [1-14C]acetate feeding to whole seedlings. The activity of NAD+-isocitrate dehydrogenase (a decarboxylative enzyme) was not detected until 2 d postimbibition. RNA-blot analysis ofB. napus seedlings demonstrated that the mRNA for NAD+-isocitrate dehydrogenase was present in dry seeds and that its level increased through the 4 d of the experiment. This suggested that NAD+-isocitrate dehydrogenase activity was regulated by posttranscriptional mechanisms during early seedling development but was controlled by mRNA level after the 2nd or 3rd d. The activity of fumarase (a component of the nonbypassed section of the TCA cycle) was low but detectable in B. napus seedlings at 12 h postimbibition, coincident with germination, and increased for the next 4 d. RNA-blot analysis suggested that fumarase activity was regulated primarily by the level of its mRNA during germination and early seedling development. It is concluded that posttranscriptional regulation of NAD+-isocitrate dehydrogenase activity is one mechanism of restricting carbon flux through the decarboxylative section of the TCA cycle during lipid mobilization in germinating oilseeds.
The H+-Sucrose Cotransporter NtSUT1 Is Essential for Sugar Export from Tobacco Leaves1
Authors: Bürkle Lukas , Hibberd Julian M. , Quick W. Paul , Kühn Christina , Hirner Brigitte , Frommer Wolf B. 
Published: July 2002

Abstract
In many species translocation of sucrose from the mesophyll to the phloem is carrier mediated. A sucrose/H+-symporter cDNA,NtSUT1, was isolated from tobacco (Nicotiana tabacum) and shown to be highly expressed in mature leaves and at low levels in other tissues, including floral organs. To study the in vivo function of NtSUT1, tobacco plants were transformed with aSUT1 antisense construct under control of the cauliflower mosaic virus 35S promoter. Upon maturation, leaves of transformants expressing reduced amounts of SUT1 mRNA curled downward, and strongly affected plants developed chloroses and necroses that led to death. The leaves exhibited impaired ability to export recently fixed 14CO2 and were unable to export transient starch during extended periods of darkness. As a consequence, soluble carbohydrates accumulated and photosynthesis was reduced. Autoradiographs of leaves show a heterogenous pattern of CO2 fixation even after a 24-h chase. The 14C pattern does not change with time, suggesting that movement of photosynthate between mesophyll cells may also be impaired. The affected lines show a reduction in the development of the root system and delayed or impaired flowering. Taken together, the effects observed in a seed plant (tobacco) demonstrate the importance of SUT1 for sucrose loading into the phloem via an apoplastic route and possibly for intermesophyll transport as well.
Characterization of Transgenic Tobacco with an Increased α-Linolenic Acid Level
Authors: Hamada Tatsurou , Kodama Hiroaki , Takeshita Keizo , Utsumi Hideo , Iba Koh 
Published: July 2002

Abstract
Microsomal ω-3 fatty acid desaturase catalyzes the conversion of 18:2 (linoleic acid) to 18:3 (α-linolenic acid) in phospholipids, which are the main constituents of extrachloroplast membranes. Transgenic tobacco (Nicotiana tabacum) plants with increased 18:3 contents (designated SIIn plants) were produced through the introduction of a construct with the tobacco microsomal ω-3 fatty acid desaturase gene under the control of the highly efficient promoter containing the E12Ω sequence. 18:3 contents in the SIIn plants were increased by about 40% in roots and by about 10% in leaves compared with the control plants. With regard to growth at 15°C and 25°C and the ability to tolerate chilling at 1°C and 5°C, there were no discernible differences between the SIIn and the control plants. Freezing tolerance in leaves and roots, which was assessed by electrolyte leakage, was almost the same between the SIIn and the control plants. The fluidity of plasma membrane from the SIIn plants was almost the same as that of the control plants. These results indicate that an increase in the 18:3 level in phospholipids is not directly involved in compensation for the diminishment in growth or membrane properties observed under low temperatures.
Several Thaumatin-Like Proteins Bind to β-1,3-Glucans
Authors: Trudel Jean , Grenier Jean , Potvin Claude , Asselin Alain 
Published: July 2002

Abstract
Pathogenesis-related proteins from intercellular fluid washings of stressed barley (Hordeum vulgare L.) leaves were analyzed to determine their binding to various water-insoluble polysaccharides. Three proteins (19, 16, and 15 kD) bound specifically to several water-insoluble β-1,3-glucans. Binding of the barley proteins to pachyman occurred quickly at 22°C at pH 5.0, even in the presence of 0.5 m NaCl, 0.2m urea, and 1% (v/v) Triton X-100. Bound barley proteins were released by acidic treatments or by boiling in sodium dodecyl sulfate. Acid-released barley proteins could bind again specifically and singly to pachyman. Water-soluble laminarin and carboxymethyl-pachyman competed for the binding of the barley proteins to pachyman. The N-terminal sequence of the 19-kD barley β-1,3-glucan-binding protein showed near identity to the barley seed protein BP-R and high homology to other thaumatin-like (TL) permatins. The 16-kD barley protein was also homologous to TL proteins, whereas the 15-kD barley protein N-terminal sequence was identical to the pathogenesis-related Hv-1 TL protein. Antifungal barley protein BP-R and corn (Zea mays) zeamatin were isolated by binding to pachyman. Two extracellular proteins from stressed pea (Pisum sativum L.) also bound to pachyman and were homologous to TL proteins.
Identification of a Calmodulin-Regulated Ca2+-ATPase in the Endoplasmic Reticulum1
Authors: Hong Bimei , Ichida Audrey , Wang Yuwen , Scott Gens J. , Pickard Barbara G. , Harper Jeffrey F. 
Published: July 2002

Abstract
A unique subfamily of calmodulin-dependent Ca2+-ATPases was recently identified in plants. In contrast to the most closely related pumps in animals, plasma membrane-type Ca2+-ATPases, members of this new subfamily are distinguished by a calmodulin-regulated autoinhibitor located at the N-terminal instead of a C-terminal end. In addition, at least some isoforms appear to reside in non-plasma membrane locations. To begin delineating their functions, we investigated the subcellular localization of isoform ACA2p (ArabidopsisCa2+-ATPase, isoform 2 protein) in Arabidopsis. Here we provide evidence that ACA2p resides in the endoplasmic reticulum (ER). In buoyant density sucrose gradients performed with and without Mg2+, ACA2p cofractionated with an ER membrane marker and a typical “ER-type” Ca2+-ATPase, ACA3p/ECA1p. To visualize its subcellular localization, ACA2p was tagged with a green fluorescence protein at its C terminus (ACA2-GFPp) and expressed in transgenic Arabidopsis. We collected fluorescence images from live root cells using confocal and computational optical-sectioning microscopy. ACA2-GFPp appeared as a fluorescent reticulum, consistent with an ER location. In addition, we observed strong fluorescence around the nuclei of mature epidermal cells, which is consistent with the hypothesis that ACA2p may also function in the nuclear envelope. An ER location makes ACA2p distinct from all other calmodulin-regulated pumps identified in plants or animals.
Iron-Superoxide Dismutase Expression in Transgenic Alfalfa Increases Winter Survival without a Detectable Increase in Photosynthetic Oxidative Stress Tolerance
Authors: McKersie Bryan D. , Murnaghan Julia , Jones Kim S. , Bowley Stephen R. 
Published: July 2002

Abstract
To determine whether overexpression of Fe-superoxide (SOD) dismutase would increase superoxide-scavenging capacity and thereby improve the winter survival of transgenic alfalfa (Medicago sativa L.) plants, two genotypes were transformed with the vector pEXSOD10, which contains a cDNA for Arabidopsis Fe-SOD with a chloroplast transit peptide and cauliflower mosaic virus 35S promoter. A novel Fe-SOD was detected by native PAGE in both greenhouse- and field-grown transgenic plants, but activity varied among independent transgenic plants. The increased Fe-SOD activity was associated with increased winter survival over 2 years in field trials, but not with oxidative stress tolerance as measured by resistance of leaves to methyl viologen, a superoxide generator. Total shoot dry matter production over 2 harvest years was not associated with Fe-SOD activity. There was no detectable difference in the pattern of primary freezing injury, as shown by vital staining, nor was there additional accumulation of carbohydrates in field-acclimated roots of the transgenic alfalfa plants. We did not detect any difference in growth of one transgenic plant with high Fe-SOD activity compared with a non-transgenic control. Therefore, the improvement in winter survival did not appear to be a consequence of improved oxidative stress tolerance associated with photosynthesis, nor was it a consequence of a change in primary freezing injury. We suggest that Fe-SOD overexpression reduced secondary injury symptoms and thereby enhanced recovery from stresses experienced during winter.
Cryo-Scanning Electron Microscopy Observations of Vessel Content during Transpiration in Walnut Petioles. Facts or Artifacts?
Authors: Cochard Hervé , Bodet Christian , Améglio Thierry , Cruiziat Pierre 
Published: July 2002

Abstract
The current controversy about the “cohesion-tension” of water ascent in plants arises from the recent cryo-scanning electron microscopy (cryo-SEM) observations of xylem vessels content by Canny and coworkers (1995). On the basis of these observations it has been claimed that vessels were emptying and refilling during active transpiration in direct contradiction to the previous theory. In this study we compared the cryo-SEM data with the standard hydraulic approach on walnut (Juglans regia) petioles. The results of the two techniques were in clear conflict and could not both be right. Cryo-SEM observations of walnut petioles frozen intact on the tree in a bath of liquid nitrogen (LN2) suggested that vessel cavitation was occurring and reversing itself on a diurnal basis. Up to 30% of the vessels were embolized at midday. In contrast, the percentage of loss of hydraulic conductance (PLC) of excised petiole segments remained close to 0% throughout the day. To find out which technique was erroneous we first analyzed the possibility that PLC values were rapidly returned to zero when the xylem pressures were released. We used the centrifugal force to measure the xylem conductance of petiole segments exposed to very negative pressures and established the relevance of this technique. We then analyzed the possibility that vessels were becoming partially air-filled when exposed to LN2. Cryo-SEM observations of petiole segments frozen shortly after their xylem pressure was returned to atmospheric values agreed entirely with the PLC values. We confirmed, with water-filled capillary tubes exposed to a large centrifugal force, that it was not possible to freeze intact their content with LN2. We concluded that partially air-filled conduits were artifacts of the cryo-SEM technique in our study. We believe that the cryo-SEM observations published recently should probably be reconsidered in the light of our results before they may be used as arguments against the cohesion-tension theory.
A Terminal Flower1-Like Gene from Perennial Ryegrass Involved in Floral Transition and Axillary Meristem Identity
Authors: Jensen Christian S. , Salchert Klaus , Nielsen Klaus K. 
Published: July 2002

Abstract
Control of flowering and the regulation of plant architecture have been thoroughly investigated in a number of well-studied dicot plants such as Arabidopsis, Antirrhinum, and tobacco. However, in many important monocot seed crops, molecular information on plant reproduction is still limited. To investigate the regulation of meristem identity and the control of floral transition in perennial ryegrass (Lolium perenne) we isolated a ryegrassTERMINAL FLOWER1-like gene, LpTFL1, and characterized it for its function in ryegrass flower development. Perennial ryegrass requires a cold treatment of at least 12 weeks to induce flowering. During this period a decrease inLpTFL1 message was detected in the ryegrass apex. However, upon subsequent induction with elevated temperatures and long-day photoperiods, LpTFL1 message levels increased and reached a maximum when the ryegrass apex has formed visible spikelets. Arabidopsis plants overexpressing LpTFL1 were significantly delayed in flowering and exhibited dramatic changes in architecture such as extensive lateral branching, increased growth of all vegetative organs, and a highly increased trichome production. Furthermore, overexpression of LpTFL1 was able to complement the phenotype of the severe tfl1-14 mutant of Arabidopsis. Analysis of the LpTFL1 promoter fused to the UidA gene in Arabidopsis revealed that the promoter is active in axillary meristems, but not the apical meristem. Therefore, we suggest that LpTFL1 is a repressor of flowering and a controller of axillary meristem identity in ryegrass.
Salt-Induced Expression of the Vacuolar H+-ATPase in the Common Ice Plant Is Developmentally Controlled and Tissue Specific
Authors: Golldack Dortje , Dietz Karl-Josef 
Published: July 2002

Abstract
For salinity stress tolerance in plants, the vacuolar type H+-ATPase (V-ATPase) is of prime importance in energizing sodium sequestration into the central vacuole and it is known to respond to salt stress with increased expression and enzyme activity. In this work we provide information that the expressional response to salinity of the V-ATPase is regulated tissue and cell specifically under developmental control in the facultative halophyte common ice plant (Mesembryanthemum crystallinum). By transcript analysis of subunit E of the V-ATPase, amounts did not change in response to salinity stress in juvenile plants that are not salt-tolerant. In a converse manner, in halotolerant mature plants the transcript levels increased in leaves, but not in roots when salt stressed for 72 h. By in situ hybridizations and immunocytological protein analysis, subunit E was shown to be synthesized in all cell types. During salt stress, signal intensity declined in root cortex cells and in the cells of the root vascular cylinder. In salt-stressed leaves of mature plants, the strongest signals were localized surrounding the vasculature. Within control cells and with highest abundance in mesophyll cells of salt-treated leaves, accumulation of subunit E protein was observed in the cytoplasm, indicating its presence not only in the tonoplast, but also in other endoplasmic compartments.
X-ray diffraction texture analysis of cylindrical samples
Authors: Guillén R. , Cossu C. , Jacquot T. , François M. , Bourniquel B. 
Published: July 2002

The effect of the curvature of the sample surface on X-ray diffraction has been studied. A theoretical model, based on a ray-tracing method, has been developed to take into account the geometric effects which modify the collected intensities. The model enables alignment corrections for the sample and the incident beam, in relation to the goniometer centre. This can be achieved by comparing experimental normalized intensities for a zero tilt angle (ψ = 0°) to the normalized intensities calculated by the model. The texture analysis of a zircaloy-4 tube (with a 9.5 mm diameter and an incident-beam spot size of 1.2 mm diameter) confirms the validity of the results.
Synthesis, structure and magnetic properties of tetrakis-μ-carboxylato-bis(dodecylnicotinato)dicopper(II) complexes; crystal and molecular structure of the decyl carboxylate derivative
Authors: Rusjan Marcia , Chaia Zulema , Piro Oscar E. , Guillon Daniel , Cukiernik Fabio D. 
Published: July 2002

Dodecylnicotinate bis-adducts of binuclear copper carboxylates, of the general formula Cu2(O2CC
n − 1H2n − 1)4(C5H4NCOOC12H25)2, were synthesized for n = 10, 12, 14, 16, 18 and 20, and their crystal structure, thermal behavior and magnetic properties studied. The molecular structure of the decyl derivative has been determined from single-crystal X-ray diffraction data. The dimer is centrosymmetric with the CuII ions in a square-pyramidal coordination with four O-alkyl O atoms [average d(Cu—O) 1.960 (6) Å] in the basal plane and the nicotine N atom at apical positions [d(Cu—N) 2.183 (3)  Å]. The copper ions, 2.615 (1) Å apart, are bridged by four O-alkyl carboxylate groups. Both the n = 20 and n = 18 homologues exhibit lamellar phases, which can be related to the supramolecular arrangement found in the n = 10 derivative. The magnetic behavior of the decyl and octadecyl dimers was studied in the 2–300 K temperature range. They exhibit a strong intramolecular antiferromagnetic interaction (Cu–Cu superexchange coupling constant J = −347 cm−1 for the decyl derivative), which can be attributed to a large overlap of the metal 3d orbitals and the oxygen lone pair orbitals of the linking carboxylate groups.
Migration of the proton in the strong O—H...O hydrogen bond in urea–phosphoric acid (1/1)
Authors: Wilson Chick C. 
Published: July 2002

The structure of urea–phosphoric acid is reported at a large number of temperatures in the range 150–335 K from neutron diffraction data collected using a novel multiple single-crystal data collection method. The work focuses on the behaviour of the H atom involved in the short strong O—H...O hydrogen bond in this material. The position of this atom is shown to vary significantly, by around 0.035  Å, as a function of temperature, becoming effectively centred at the highest temperatures studied. This result, only accessible due to the accurate determination of H-atom parameters by neutron diffraction, has implications for the potential governing the hydrogen bond.
Structure determination of rubredoxin from Desulfovibrio vulgaris Miyazaki F in two crystal forms
Authors: Misaki Shintaro , Morimoto Yukio , Ogata Mari , Yagi Tatsuhiko , Higuchi Yoshiki , Yasuoka Noritake 
Published: July 2002

The structures of two crystal forms (form I, P3221, a = b = 43.7, c = 50.7 Å; form II, P21, a = 27.3, b = 44.9, c = 51.2 Å and β = 90.6°) of the rubredoxin from Desulfovibrio vulgaris Miyazaki F have been solved by the molecular-replacement method. Form I has been refined at a resolution of 2.0 Å to an R value of 20.8% and includes 32 water molecules. Form II includes 86 water molecules and has been refined at 1.9 Å resolution to an R value of 17.5%. In form II, there are three molecules in the asymmetric unit with the molecules related by a non-crystallographic 32 symmetry axis. In both crystal forms, it was found that only a few residues effectively participate in the formation of intermolecular contacts along both the crystallographic (form I) and the non-crystallographic (form II) 32 axes. The crystal structure of the form II crystal is compared with those of other rubredoxin molecules from anaerobic bacteria. From this comparison, a similarity in the core region, which is composed of aromatic residues and includes the active centre, has been revealed.
Energy landscape of a peptide consisting of α‐helix, 310‐helix, β‐turn, β‐hairpin, and other disordered conformations
Authors: Higo Junichi , Ito Nobutoshi , Kuroda Masataka , Ono Satoshi , Nakajima Nobuyuki , Nakamura Haruki 
Published: July 2002

AbstractThe energy landscape of a peptide [Ace‐Lys‐Gln‐Cys‐Arg‐Glu‐Arg‐Ala‐Nme] in explicit water was studied with a multicanonical molecular dynamics simulation, and the AMBER parm96 force field was used for the energy calculation. The peptide was taken from the recognition helix of the DNA‐binding protein, c‐Myb. A rugged energy landscape was obtained, in which the random‐coil conformations were dominant at room temperature. The CD spectra of the synthesized peptide revealed that it is in the random state at room temperature. However, the 300 K canonical ensemble, Q(300K), contained α‐helix, 310‐helix, β‐turn, and β‐hairpin structures with small but notable probabilities of existence. The complete α‐helix, imperfect α‐helix, and random‐coil conformations were separated from one another in the conformational space. This means that the peptide must overcome energy barriers to form the α‐helix. The overcoming process may correspond to the hydrogen‐bond rearrangements from peptide–water to peptide–peptide interactions. The β‐turn, imperfect 310‐helix, and β‐hairpin structures, among which there are no energy barriers at 300 K, were embedded in the ensemble of the random‐coil conformations. Two types of β‐hairpin with different β‐turn regions were observed in Q(300K). The two β‐hairpin structures may have different mechanisms for the β‐hairpin formation. The current study proposes a scheme that the random state of this peptide consists of both ordered and disordered conformations. In contrast, the energy landscape obtained from the parm94 force field was funnel like, in which the peptide formed the helical conformation at room temperature and random coil at high temperature.
Self-Preserving Properties of Unsteady Round Nonbuoyant Turbulent
Starting Jets and Puffs in Still Fluids
Authors: Sangras R. , Kwon O. C. , Faeth G. M. 
Published: July 2002

Abstract
The self-preserving properties of round nonbuoyant turbulent starting jets, puffs, and interrupted jets were investigated both experimentally and theoretically for flows in still and unstratified environments. The experiments involved dye-containing fresh water sources injected into still fresh water within a large windowed tank. Time-resolved video images of the flows were obtained using a CCD camera. Experimental conditions were as follows: jet exit diameters of 3.2 and 6.4 mm, jet exit Reynolds numbers of 3000–12,000, jet passage lengths in excess of 50 injector passage diameters, volume of injected fluid for puffs and interrupted jets up to 191 source diameters, and streamwise penetration lengths up to 140 source diameters. Near-source behavior varied significantly with source properties but the flows generally became turbulent within 5 source diameters from the source and self-preserving behavior was generally observed at distances greater than 20–30 source diameters from the source. Within the self-preserving region, both the normalized streamwise penetration distance and the normalized maximum flow radius varied as functions of time in agreement with estimates for self-preserving turbulent flows to the following powers: 1/2 for starting nonbuoyant jets and 1/4 for nonbuoyant puffs and interrupted jets. Effects of injected fluid quantity for self-preserving puffs and interrupted jets could be handled by correlating the location of the virtual origin as a function of the volume of the injected fluid represented by the number of passage lengths of injected fluid. In particular, the virtual origin for puffs was independent of injected fluid volume for injected passage lengths less than 120 but became proportional to the injected fluid volume thereafter, defining a boundary between puff and interrupted-jet behavior.