bluuebunny/crossref_metadata_2025 huggingface dataset:
Membrane Lipid Integrity Relies on a Threshold of ATP Production Rate in Potato Cell Cultures Submitted to Anoxia1
Authors: Rawyler André , Pavelic Danijela , Gianinazzi Christian , Oberson Jacques , Braendle Roland
Published: July 2002

In this paper we report on our study of the changes in biomass, lipid composition, and fermentation end products, as well as in the ATP level and synthesis rate in cultivated potato (Solanum tuberosum) cells submitted to anoxia stress. During the first phase of about 12 h, cells coped with the reduced energy supply brought about by fermentation and their membrane lipids remained intact. The second phase (12–24 h), during which the energy supply dropped down to 1% to 2% of its maximal theoretical normoxic value, was characterized by an extensive hydrolysis of membrane lipids to free fatty acids. This autolytic process was ascribed to the activation of a lipolytic acyl hydrolase. Cells were also treated under normoxia with inhibitors known to interfere with energy metabolism. Carbonyl-cyanide-4-trifluoromethoxyphenylhydrazone did not induce lipid hydrolysis, which was also the case when sodium azide or salicylhydroxamic acid were fed separately. However, the simultaneous use of sodium azide plus salicylhydroxamic acid or 2-deoxy-d-glucose plus iodoacetate with normoxic cells promoted a lipid hydrolysis pattern similar to that seen in anoxic cells. Therefore, a threshold exists in the rate of ATP synthesis (approximately 10 μmol g−1 fresh weight h−1), below which the integrity of the membranes in anoxic potato cells cannot be preserved.
The AG Dinucleotide Terminating Introns Is Important but Not Always Required for Pre-mRNA Splicing in the Maize Endosperm1
Authors: Lal Shailesh , Choi Jae-Hyuk , Hannah L. Curtis
Published: July 2002

Previous RNA analysis of lesions within the 15 intron-containingSh2(shrunken2) gene of maize (Zea mays) revealed that the majority of these mutants affect RNA splicing. Here we decipher further two of these mutants, sh2-i(shrunken2intermediate phenotype) andsh2-7460. Each harbors a G-to-A transition in the terminal nucleotide of an intron, hence destroying the invariant AG found at the terminus of virtually all nuclear introns. Consequences of the mutations, however, differ dramatically. In sh2-i the mutant site is recognized as an authentic splice site in approximately 10% of the primary transcripts processed in the maize endosperm. The other transcripts exhibited exon skipping and lacked exon 3. A G-to-A transition in the terminus of an intron was also found in the mutantsh2-7460, in this case intron 12. The lesion activates a cryptic acceptor site downstream 22 bp within exon 13. In addition, approximately 50% ofsh2-7460 transcripts contain intron 2 and 3 sequences.
Chlamydomonas reinhardtii Mutants Abnormal in Their Responses to Phosphorus Deprivation1
Authors: Shimogawara Kosuke , Wykoff Dennis D. , Usuda Hideaki , Grossman Arthur R.
Published: July 2002

P-starved plants scavenge inorganic phosphate (Pi) by developing elevated rates of Pi uptake, synthesizing extracellular phosphatases, and secreting organic acids. To elucidate mechanisms controlling these acclimation responses in photosynthetic organisms, we characterized the responses of the green algaChlamydomonas reinhardtii to P starvation and developed screens for isolating mutants (designated psr[phosphorus-stress response]) abnormal in their responses to environmental levels of Pi. Thepsr1-1 mutant was identified in a selection for cells that survived exposure to high concentrations of radioactive Pi. psr1-2 andpsr2 were isolated as strains with aberrant levels of extracellular phosphatase activity during P-deficient or nutrient-replete growth. The psr1-1 andpsr1-2 mutants were phenotypically similar, and the lesions in these strains were recessive and allelic. They exhibited no increase in extracellular phosphatase activity or Pi uptake upon starvation. Furthermore, when placed in medium devoid of P, the psr1 strains lost photosynthetic O2evolution and stopped growing more rapidly than wild-type cells; they may not be as efficient as wild-type cells at scavenging/accessing P stores. In contrast, psr2 showed elevated extracellular phosphatase activity during growth in nutrient-replete medium, and the mutation was dominant. The mutant phenotypes and the roles of Psr1 and Psr2 in P-limitation responses are discussed.
Biosynthesis of Ascorbic Acid in Kidney Bean.l-Galactono-γ-Lactone Dehydrogenase Is an Intrinsic Protein Located at the Mitochondrial Inner Membrane1
Authors: Siendones Emilio , González-Reyes José A. , Santos-Ocaña Carlos , Navas Plácido , Córdoba Francisco
Published: July 2002

Hypocotyls of kidney beans (Phaseolus vulgaris L.) accumulated ascorbate after preincubation with a number of possible precursors, mainlyl-galactono-γ-lactone (l-GL) andl-gulono-γ-lactone. The increase in the intracellular ascorbate concentration was parallel to the high stimulation of thel-GL dehydrogenase (l-GLD) activity measured in vitro using l-GL as a substrate and cytochromec as an electron acceptor. Cell fractionation using a continuous linear Percoll gradient demonstrated that l-GLD is associated with mitochondria; therefore, pure mitochondria were isolated and subjected to detergent treatment to separate soluble from membrane-linked proteins. l-GLD activity was mainly associated with the detergent phase, suggesting that a membrane-intrinsic protein is responsible for the ascorbic acid biosynthetic activity. Subfractionation of mitochondria demonstrated that l-GLD is located at the inner membrane.
Changes in Cell Wall Polysaccharides of Green Bean Pods during Development
Authors: Stolle-Smits Trinette , Beekhuizen Jan Gerard , Kok Matthieu T.C. , Pijnenburg Mary , Recourt Kees , Derksen Jan , Voragen Alphons G.J.
Published: July 2002

The changes in cell wall polysaccharides and selected cell wall-modifying enzymes were studied during the development of green bean (Phaseolus vulgarisL.) pods. An overall increase of cell wall material on a dry-weight basis was observed during pod development. Major changes were detected in the pectic polymers. Young, exponentially growing cell walls contained large amounts of neutral, sugar-rich pectic polymers (rhamnogalacturonan), which were water insoluble and relatively tightly connected to the cell wall. During elongation, more galactose-rich pectic polymers were deposited into the cell wall. In addition, the level of branched rhamnogalacturonan remained constant, while the level of linear homogalacturonan steadily increased. During maturation of the pods, galactose-rich pectic polymers were degraded, while the accumulation of soluble homogalacturonan continued. During senescence there was an increase in the amount of ionically complexed pectins, mainly at the expense of freely soluble pectins. The most abundant of the enzymes tested for was pectin methylesterase. Peroxidase, β-galactosidase, and α-arabinosidase were also detected in appreciable amounts. Polygalacturonase was detected only in very small amounts throughout development. The relationship between endogenous enzyme levels and the properties of cell wall polymers is discussed with respect to cell wall synthesis and degradation.
Purification and Characterization ofS-Adenosyl-l-Methionine: Desoxyhemigossypol-6-O-Methyltransferase from Cotton Plants. An Enzyme Capable of Methylating the Defense Terpenoids of Cotton
Authors: Liu Jinggao , Benedict Chauncey R. , Stipanovic Robert D. , Bell Alois A.
Published: July 2002

Cotton contains a unique group of terpenoids including desoxyhemigossypol, hemigossypol, gossypol, hemigossypolone, and the heliocides that are part of the plant's defense system against pathogenic fungi and insects. Desoxyhemigossypol is a key intermediate in the biosynthesis of these compounds. We have isolated, purified, and characterized from cotton stele tissue infected with Verticillium dahliae a methyltransferase (S-adenosyl-l-Met: desoxyhemigossypol-6-O-methyltransferase) that specifically methylates the 6-position of desoxyhemigossypol to form desoxyhemigossypol-6-methyl ether with a K  mvalue of 4.5 μm for desoxyhemigossypol and aK  cat/K  m of 5.08 × 104 s−1 (mol/L)−1. The molecular mass of the native enzyme is 81.4 kD and is dissociated into two subunits of 41.2 kD on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels. The enzymatic reaction does not require Mg+2 and is inhibited 98% with 10 mm  p-chloromercuribenzoate. Desoxyhemigossypol-6-methyl ether leads to the biosynthesis of methylated hemigossypol, gossypol, hemigossypolone, and the heliocides, which lowers their effectiveness as phytoalexins and insecticides.
Expression of Water Channel Proteins in Mesembryanthemum crystallinum
Authors: Kirch Hans-Hubert , Vera-Estrella Rosario , Golldack Dortje , Quigley Francoise , Michalowski Christine B. , Barkla Bronwyn J. , Bohnert Hans J.
Published: July 2002

We have characterized transcripts for nine major intrinsic proteins (MIPs), some of which function as water channels (aquaporins), from the ice plant Mesembryanthemum crystallinum. To determine the cellular distribution and expression of these MIPs, oligopeptide-based antibodies were generated against MIP-A, MIP-B, MIP-C, or MIP-F, which, according to sequence and functional characteristics, are located in the plasma membrane (PM) and tonoplast, respectively. MIPs were most abundant in cells involved in bulk water flow and solute flux. The tonoplast MIP-F was found in all cells, while signature cell types identified different PM-MIPs: MIP-A predominantly in phloem-associated cells, MIP-B in xylem parenchyma, and MIP-C in the epidermis and endodermis of immature roots. Membrane protein analysis confirmed MIP-F as tonoplast located. MIP-A and MIP-B were found in tonoplast fractions and also in fractions distinct from either the tonoplast or PM. MIP-C was most abundant but not exclusive to PM fractions, where it is expected based on its sequence signature. We suggest that within the cell, MIPs are mobile, which is similar to aquaporins cycling through animal endosomes. MIP cycling and the differential regulation of these proteins observed under conditions of salt stress may be fundamental for the control of tissue water flux.
Pattern of Aluminum-Induced Secretion of Organic Acids Differs between Rye and Wheat
Authors: Li Xiao Feng , Ma Jian Feng , Matsumoto Hideaki
Published: July 2002

Al-Induced secretion of organic acids from the roots has been considered as a mechanism of Al tolerance, but the processes leading to the secretion of organic acids are still unknown. In this study, the secretion pattern and alteration in the metabolism of organic acids under Al stress were examined in rye (Secale cereale L. cv King) and wheat (Triticum aestivum L. cv Atlas 66). Al induced rapid secretion of malate in the wheat, but a lag (6 and 10 h for malic and citric acids, respectively) between the exposure to Al and the secretion of organic acids was observed in the rye. The activities of isocitrate dehydrogenase, phosphoenolpyruvate carboxylase, and malate dehydrogenase were not affected by Al in either plant. The activity of citrate synthase was increased by the exposure to Al in the rye, but not in the wheat. The secretion of malate was not suppressed at low temperature in the wheat, but that of citrate was stopped in the rye. The Al-induced secretion of citrate from roots of the rye was inhibited by the inhibitors of a citrate carrier, which transports citrate from the mitochondria to the cytoplasm. All of these results suggest that alteration in the metabolism of organic acids is involved in the Al-induced secretion of organic acids in rye, but only activation of an anion channel seems to be responsible for the rapid secretion of malate in the wheat.
Emission of Isoprene from Salt-Stressed Eucalyptus globulus Leaves
Authors: Loreto Francesco , Delfine Sebastiano
Published: July 2002

Eucalyptus spp. are among the highest isoprene emitting plants. In the Mediterranean area these plants are often cultivated along the seashore and cope with recurrent salt stress. Transient salinity may severely but reversibly reduce photosynthesis and stomatal conductance of Eucalyptus globulusleaves but the effect on isoprene emission is not significant. When the stress is relieved, a burst of isoprene emission occurs, simultaneously with the recovery of photosynthetic performance. Later on, photosynthesis, stomatal conductance, and isoprene emission decay, probably because of the onset of leaf senescence. Isoprene emission is not remarkably affected by the stress at different light intensities, CO2 concentrations, and leaf temperatures. When CO2 was removed and O2 was lowered to inhibit both photosynthesis and photorespiration, we found that the residual emission is actually higher in salt-stressed leaves than in controls. This stimulation is particularly evident at high-light intensities and high temperatures. The maximum emission occurs at 40°C in both salt-stressed and control leaves sampled in ambient air and in control leaves sampled in CO2-free and low-O2 air. However, the maximum emission occurs at 45°C in salt-stressed leaves sampled in CO2-free and low-O2 air. Our results suggest the activation of alternative non-photosynthetic pathways of isoprene synthesis in salt-stressed leaves and perhaps in general in leaves exposed to stress conditions. The temperature dependence indicates that this alternative synthesis is also under enzymatic control. If this alternative synthesis still occurs in the chloroplasts, it may involve a thylakoid-bound isoprene synthase.
Isolation of Medicago truncatula Mutants Defective in Calcium Oxalate Crystal Formation
Authors: Nakata Paul A. , McConn Michele M.
Published: July 2002

Plants accumulate crystals of calcium oxalate in a variety of shapes, sizes, amounts, and spatial locations. How and why many plants form crystals of calcium oxalate remain largely unknown. To gain insight into the regulatory mechanisms of crystal formation and function, we have initiated a mutant screen to identify the genetic determinants. Leaves from a chemically mutagenized Medicago truncatula population were visually screened for alterations in calcium oxalate crystal formation. Seven different classes of calcium oxalate defective mutants were identified that exhibited alterations in crystal nucleation, morphology, distribution and/or amount. Genetic analysis suggested that crystal formation is a complex process involving more than seven loci. Phenotypic analysis of a mutant that lacks crystals, cod 5, did not reveal any difference in plant growth and development compared with controls. This finding brings into question the hypothesized roles of calcium oxalate formation in supporting tissue structure and in regulating excess tissue calcium.
Cell Surface Expansion in Polarly Growing Root Hairs ofMedicago truncatula
Authors: Shaw Sidney L. , Dumais Jacques , Long Sharon R.
Published: July 2002

Fluorescent microspheres were used as material markers to investigate the relative rates of cell surface expansion at the growing tips of Medicago truncatula root hairs. From the analysis of tip shape and microsphere movements, we propose three characteristic zones of expansion in growing root hairs. The center of the apical dome is an area of 1- to 2-μm diameter with relatively constant curvature and high growth rate. Distal to the apex is a more rapidly expanding region 1 to 2 μm in width exhibiting constant surges of off-axis growth. This middle region forms an annulus of maximum growth rate and is visible as an area of accentuated curvature in the tip profile. The remainder of the apical dome is characterized by strong radial expansion anisotropy where the meridional rate of expansion falls below the radial expansion rate. Data also suggest possible meridional contraction at the juncture between the apical dome and the cell body. The cell cylinder distal to the tip expands slightly over time, but only around the circumference. These data for surface expansion in the legume root hair provide new insight into the mechanism of tip growth and the morphogenesis of the root hair.
STUNTED PLANT 1 Mediates Effects of Cytokinin, But Not of Auxin, on Cell Division and Expansion in the Root of Arabidopsis
Authors: Beemster Gerrit T.S. , Baskin Tobias I.
Published: July 2002

Plants control organ growth rate by adjusting the rate and duration of cell division and expansion. Surprisingly, there have been few studies where both parameters have been measured in the same material, and thus we have little understanding of how division and expansion are regulated interdependently. We have investigated this regulation in the root meristem of the stunted plant 1(stp1) mutation of Arabidopsis, the roots of which elongate more slowly than those of the wild type and fail to accelerate. We used a kinematic method to quantify the spatial distribution of the rate and extent of cell division and expansion, and we compared stp1 with wild type and with wild type treated with exogenous cytokinin (1 μm zeatin) or auxin (30 nm 2,4-dichlorophenoxyacetic acid). All treatments reduced average cell division rates, which reduced cell production by the meristem. Auxin lowered root elongation by narrowing the elongation zone and reducing the time spent by a cell in this zone, but did not decrease maximal strain rate. In addition, auxin increased the length of the meristem. In contrast, cytokinin reduced root elongation by lowering maximal strain rate, but did not change the time spent by a cell within the elongation zone; also, cytokinin blocked the increase in length and cell number of the meristem and elongation zone. The cytokinin-treated wild type phenocopied stp1 in nearly every detail, supporting the hypothesis that cytokinin affects root growth via STP1. The opposite effects of auxin and cytokinin suggest that the balance of these hormones may control the size of the meristem.
Freezing of Barley Studied by Infrared Video Thermography
Authors: Pearce Roger S. , Fuller Michael P.
Published: July 2002

Freezing of barley (Hordeum vulgare), Hordeum murinum, and Holcus lanatus was studied using infrared video thermography. In the field, ice could enter H. lanatus leaves through hydathodes. In laboratory tests with barley, initially 0.4% of the leaf water froze, spreading in alternate strips of high and low freezing intensity longitudinally at 1 to 4 cm s−1, and simultaneously spreading laterally at 0.3 cm s−1. Similar results were obtained in the field withH. lanatus. A distinct second, more intense, freezing event spread slowly from the margins of the leaves toward the midrib. Organs of uprooted barley tested in the laboratory froze in this order: nucleated leaf, roots, older leaves, younger leaves, and secondary tillers. When ice spread from one leaf to the rest of the plant the crown delayed spread to the roots and other leaves. There was a longer delay above than below −2°C, helping to protect the crown from freezing during mild frosts. Initial spread of freezing was not damaging. However, the initial spread is a prerequisite for the second freezing event, which can cause damage. The route of the initial spread of ice may be extracellular, drawing water from more gel-like parts of the cell wall.
Disruption of Microtubular Cytoskeleton Induced by Cryptogein, an Elicitor of Hypersensitive Response in Tobacco Cells
Authors: Binet Marie-Noëlle , Humbert Claude , Lecourieux David , Vantard Marylin , Pugin Alain
Published: July 2002

The dynamics of microtubular cytoskeleton were studied in tobacco (Nicotiana tabacum cv Xanthi) cells in response to two different plant defense elicitors: cryptogein, a protein secreted byPhytophthora cryptogea and oligogalacturonides (OGs), derived from the plant cell wall. In tobacco plants cryptogein triggers a hypersensitive-like response and induces systemic resistance against a broad spectrum of pathogens, whereas OGs induce defense responses, but fail to trigger cell death. The comparison of the microtubule (MT) dynamics in response to cryptogein and OGs in tobacco cells indicates that MTs appear unaffected in OG-treated cells, whereas cryptogein treatment caused a rapid and severe disruption of microtubular network. When hyperstabilized by the MT depolymerization inhibitor, taxol, the MT network was still disrupted by cryptogein treatment. On the other hand, the MT-depolymerizing agent oryzalin and cryptogein had different and complementary effects. In addition to MT destabilization, cryptogein induced the death of tobacco cells, whereas OG-treated cells did not die. We demonstrated that MT destabilization and cell death induced by cryptogein depend on calcium influx and that MT destabilization occurs independently of active oxygen species production. The molecular basis of cryptogein-induced MT disruption and its potential significance with respect to cell death are discussed.
Molecular Characterization of Tomato 3-Dehydroquinate Dehydratase-Shikimate:NADP Oxidoreductase
Authors: Bischoff Markus , Schaller Andreas , Bieri Fabian , Kessler Felix , Amrhein Nikolaus , Schmid Jürg
Published: July 2002

Analysis of cDNAs encoding the bifunctional 3-dehydroquinate dehydratase-shikimate:NADP oxidoreductase (DHQase-SORase) from tomato (Lycopersicon esculentum) revealed two classes of cDNAs that differed by 57 bp within the coding regions, but were otherwise identical. Comparison of these cDNA sequences with the sequence of the corresponding single gene unequivocally proved that the primary transcript is differentially spliced, potentially giving rise to two polypeptides that differ by 19 amino acids. Quantitative real-time polymerase chain reaction revealed that the longer transcript constitutes at most 1% to 2% of DHQase-SORase transcripts. Expression of the respective polypeptides in Escherichia colimutants lacking the DHQase or the SORase activity gave functional complementation only in case of the shorter polypeptide, indicating that skipping of a potential exon is a prerequisite for the production of an enzymatically active protein. The deduced amino acid sequence revealed that the DHQase-SORase is most likely synthesized as a precursor with a very short (13-amino acid) plastid-specific transit peptide. Like other genes encoding enzymes of the prechorismate pathway in tomato, this gene is elicitor-inducible. Tissue-specific expression resembles the patterns obtained for 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase 2 and dehydroquinate synthase genes. This work completes our studies of the prechorismate pathway in that cDNAs for all seven enzymes (including isozymes) of the prechorismate pathway from tomato have now been characterized.
Dissecting the Superoxide Dismutase-Ascorbate-Glutathione-Pathway in Chloroplasts by Metabolic Modeling. Computer Simulations as a Step towards Flux Analysis
Authors: Polle Andrea
Published: July 2002

The present study introduces metabolic modeling as a new tool to analyze the network of redox reactions composing the superoxide dismutase-ascorbate (Asc)-glutathione (GSH) cycle. Based on previously determined concentrations of antioxidants and defense enzymes in chloroplasts, kinetic properties of antioxidative enzymes, and nonenzymatic rate constants of antioxidants with reactive oxygen, models were constructed to simulate oxidative stress and calculate changes in concentrations and fluxes of oxidants and antioxidants. Simulated oxidative stress in chloroplasts did not result in a significant accumulation of O2  .− and H2O2 when the supply with reductant was sufficient. Model results suggest that the coupling between Asc- and GSH-related redox systems was weak because monodehydroascorbate radical reductase prevented dehydroascorbate (DHA) formation efficiently. DHA reductase activity was dispensable. Glutathione reductase was mainly required for the recycling of GSH oxidized in nonenzymatic reactions. In the absence of monodehydroascorbate radical reductase and DHA reductase, glutathione reductase and GSH were capable to maintain the Asc pool more than 99% reduced. This suggests that measured DHA/Asc ratios do not reflect a redox balance related to the Asc-GSH-cycle. Decreases in Asc peroxidase resulted in marked H2O2 accumulation without significant effects on the redox balance of Asc/DHA or GSH/GSSG. Simulated loss of SOD resulted in higher H2O2 production rates, thereby affecting all subsequent steps of the Asc-GSH-cycle. In conclusion, modeling approaches contribute to the theoretical understanding of the functioning of antioxidant systems by pointing out questions that need to be validated and provide additional information that is useful to develop breeding strategies for higher stress resistance in plants.
N-Acylphosphatidylethanolamine Accumulation in Potato Cells upon Energy Shortage Caused by Anoxia or Respiratory Inhibitors
Authors: Rawyler André J. , Braendle Roland A.
Published: July 2002

A minor phospholipid was isolated from potato (Solanum tuberosum L. cv Bintje) cells, chromatographically purified, and identified by electrospray ionization mass spectrometry asN-acylphosphatidylethanolamine (NAPE). The NAPE level was low in unstressed cells (13 ± 4 nmol g fresh weight−1). According to acyl chain length, only 16/18/18 species (group II) and 18/18/18 species (group III) were present. NAPE increased up to 13-fold in anoxia-stressed cells, but only when free fatty acids (FFAs) started being released, after about 10 h of treatment. The level of groups II and III was increased by unspecificN-acylation of phosphatidylethanolamine, and new 16/16/18 species (group I) appeared viaN-palmitoylation. NAPE also accumulated in aerated cells treated with NaN3 plus salicylhydroxamate.N-acyl patterns of NAPE were dominated by 18:1, 18:2, and 16:0, but never reflected the FFA composition. Moreover, they did not change greatly after the treatments, in contrast withO-acyl patterns. Anoxia-induced NAPE accumulation is rooted in the metabolic homeostasis failure due to energy deprivation, but not in the absence of O2, and is part of an oncotic death process. The acyl composition of basal and stress-induced NAPE suggests the existence of spatially distinct FFA and phosphatidylethanolamine pools. It reflects the specificity of NAPE synthase, the acyl composition, localization and availability of substrates, which are intrinsic cell properties, but has no predictive value as to the type of stress imposed. Whether NAPE has a physiological role depends on the cell being still alive and its compartmentation maintained during the stress period.
Effects of Sugar on Vegetative Development and Floral Transition in Arabidopsis
Authors: Ohto Masa-aki , Onai Kiyoshi , Furukawa Yasuko , Aoki Etsuko , Araki Takashi , Nakamura Kenzo
Published: July 2002

Although sugar has been suggested to promote floral transition in many plant species, growth on high concentrations (5% [w/v]) of sucrose (Suc) significantly delayed flowering time, causing an increase in the number of leaves at the time of flowering in Arabidopsis. The effect of high concentrations of Suc seemed to be metabolic rather than osmotic. The delay of floral transition was due to extension of the late vegetative phase, which resulted in a delayed activation of LFY expression. In addition, growth on low concentrations (1% [w/v]) of Suc slightly inhibited flowering in wild-type plants. This delay resulted from effects on the early vegetative phase. This inhibition was more pronounced intfl1, an early flowering mutant, than in the wild type. Although 1% (w/v) Suc was reported to promote floral transition of late-flowering mutants such as co,fca, and gi, floral transition in these mutants was delayed by a further increase in Suc concentration. These results suggest that sugar may affect floral transition by activating or inhibiting genes that act to control floral transition, depending on the concentration of sugars, the genetic background of the plants, and when the sugar is introduced. Growth on 1% (w/v) Suc did not restore the reduced expression levels of FT andSOC1/AGL20 in co or fcamutants. Rather, expression of FT andSOC1/AGL20 was repressed by 1% (w/v) Suc in wild-type background. The possible effects of sugar on gene expression to promote floral transition are discussed.
Srchi24, A Chitinase Homolog Lacking an Essential Glutamic Acid Residue for Hydrolytic Activity, Is Induced during Nodule Development onSesbania rostrata
Authors: Goormachtig Sofie , Van de Velde Willem , Lievens Sam , Verplancke Christa , Herman Sylvia , De Keyser Annick , Holsters Marcelle
Published: July 2002

The interaction between the tropical legume Sesbania rostrata and the bacterium Azorhizobium caulinodans results in the formation of nodules on both stem and roots. Stem nodulation was used as a model system to isolate early markers by differential display. One of them, Srchi24 is a novel early nodulin whose transcript level increased already 4 h after inoculation. This enhancement depended on Nod factor-producing bacteria. Srchi24 transcript levels were induced also by exogenous cytokinins. In situ hybridization and immunolocalization experiments showed that Srchi24 transcripts and proteins were present in the outermost cortical cell layers of the developing nodules. Sequence analyses revealed that Srchi24 is similar to class III chitinases, but lacks an important catalytic glutamate residue. A fusion between a maltose-binding protein and Srchi24 had no detectable hydrolytic activity. A function in nodulation is proposed for the Srchi24 protein.
Deconvolution of the instrumental functions in powder X-ray diffractometry
Authors: Ida T. , Toraya H.
Published: July 2002

A novel method to deconvolute the instrumental aberration functions from the experimental powder X-ray data has been developed. The method is based on the combination of scale transformation, interpolation of data and fast Fourier transformation. The effects of axial divergence, flat specimen, sample transparency and spectroscopic profile of the source X-ray are eliminated from the entire observed diffraction pattern in three-step operations. The errors in the deconvoluted data propagated from the statistical uncertainty in the source data are approximated by the reciprocal of the square root of the correlation between the reciprocal of the variance in the source data and the squared instrumental function. The deconvolution of the instrumental aberration functions enables automatic correction of peak shift and line broadening, and supplies narrow and symmetric peak profiles for a well crystallized sample, which can be fitted by a simple model function. It will be useful in preparatory data processing for precise line profile analysis, accurate determination of lattice parameters and whole pattern fitting for crystal structure analysis.
Protein crystallography in a vapour stream: data collection, reaction initiation and intermediate trapping in naked hydrated protein crystals
Authors: Sjögren Tove , Carlsson Gunilla , Larsson Gisela , Hajdu Andras , Andersson Christer , Pettersson Hans , Hajdu Janos
Published: July 2002

A procedure is presented for experiments on naked unfrozen protein crystals with the crystal mounted in a conventional cryo-loop and surrounded by a stream of a wet gas. The composition and temperature of the vapour stream can be adjusted to keep the crystal without deterioration for many hours. The arrangement allows (i) for rapidly testing crystals for diffraction before freezing, (ii) for data collection between 268–303 K with greatly reduced background, (iii) for the controlled drying or wetting of crystals, (iv) for the anaerobic manipulation of protein crystals, and (v) for the introduction of gaseous or volatile ingredients and reactants into the crystal. The technique offers new experimental possibilities,e.g.in time-resolved structural studies. Reaction initiation in many protein crystals can be achieved by changing the composition of the vapour stream to create a new chemical environment around the crystal and to introduce substrates/reactants either in the gas phase or as microdroplets. Spectral changes during such reactions can be monitored by single-crystal microspectrophotometry, and, once an intermediate has been detected at high concentrations, the crystal can be frozen,e.g.by rapidly switching the warm vapour stream to a cryogenically cooled helium or nitrogen jet. Representative examples are presented in this paper.
Quantitative texture analysis by Rietveld refinement
Authors: Von Dreele R. B.
Published: July 2002

A generalized spherical-harmonic description of the texture for polycrystalline materials has been implemented in a multiple-phase/multiple-data-set Rietveld refinement code. It has been tested using two sets of neutron time-of-flight data taken from a standard calcite sample previously used for a round-robin study [Wenk (1991). J. Appl. Cryst.
24, 920–927] and has been shown to give similar texture results as those obtained from individual pole figures. Simultaneous refinement of the calcite crystal structure including anisotropic thermal parameters gives results essentially identical to a recent single-crystal X-ray study.
Molecular replacement – historical background
Authors: Rossmann Michael G.
Published: July 2002

A review is given of the mathematical procedures required for a molecular-replacement structure determination. These apply equally to the more frequently encountered situations where a known homologous structure can be used as a search model and to phase determination in the presence of non-crystallographic symmetry (NCS). In general, the former represents improper NCS between two different unit cells, whereas the latter occurs when there is proper NCS within one unit cell.
Molecular placement of experimental electron density: a case study on UDP-galactopyranose mutase
Authors: Sanders D. A. R. , McMahon S. A. , Leonard G. L. , Naismith J. H.
Published: July 2002

The structure of UDP-galactopyranose mutase, the enzyme responsible for the conversion of UDP-galactopyranose to UDP-galactofuranose, has been solved. The structure solution required the use of two crystal forms and a selenomethionine variant. Crystal form P21 was used to collect a complete MAD data set, a native data set and a single-wavelength non-isomorphous selenomethionine data set. A starting set of MAD phases was then improved by non-crystallographic averaging and cross-crystal averaging of all P21 data. The initial maps were of such low quality that transformation matrices between cells could not be determined. It was therefore assumed that although there were large changes in unit-cell parameters, the molecule occupied the same position in each cell. This starting assumption was allowed to refine during the averaging procedure and did so satisfactorily. Despite a visible increase in the quality of the map allowing some secondary-structural elements to be located, the overall structure could not be traced and refined. The rediscovery of the second crystal form, P212121, allowed the collection of a native data set to 2.4 Å. Molecular placement of electron density was used to determine the relationship between the two unit cells. In this study, only the already averaged P21 experimental density could be placed in the P212121 map. Less extensively density-modified maps did not give a clear solution. The study suggests even poor non-isomorphous data can be used to significantly improve map quality. The relationship between P21 and P212121 could then be used in a final round of cross-crystal averaging to generate phases. The resulting map was easily traced and the structure has been refined. The structure sheds important light on a novel mechanism and is also a therapeutic target in the treatment of tuberculosis.
Crystallization and preliminary X-ray crystallographic studies on apolipoprotein H (β2-glycoprotein-I) from human plasma
Authors: Saxena Ajay , Gries Anna , Schwarzenbacher Robert , Kostner Gerhard M. , Laggner Peter , Prassl Ruth
Published: July 2002

Apolipoprotein-H (Apo-H, Mw
≃ 50 kDa) is a carbohydrate-rich human-plasma protein which exists in blood serum in the free form as well as distributed between several classes of lipoproteins. Single crystals of apo-H have been obtained and crystallographic data sets have been collected. The crystals belong to the orthorhombic space group C2221, with cell dimensions a = 158.47, b = 169.25, c = 113.28 Å (at 100 K). The data indicate that the crystallographic asymmetric unit contains one tetramer of the protein.
High-Pressure Solution X-ray Scattering of Protein Using a Hydrostatic Cell with Diamond Windows
Authors: Kato Minoru , Fujisawa Tetsuro
Published: July 2002

A hydrostatic high-pressure cell (maximum pressure 700 MPa) with synthetic diamond windows is applied to measure small-angle X-ray scattering of a protein at high pressure. Use of the present cell allows an accurate solvent background correction, providing quantitative analyses. The performance of the present cell for X-ray scattering is shown by using lysozyme as a sample solution. From the Guinier plot, values of the radius of gyration of lysozyme are evaluated to be 15.31 ± 0.09 Å at 1 atm (0.10 MPa) and 14.80 ± 0.15 Å at 400 MPa.
Concrete corrosion and control practices ‐ an overview
Authors: Lata Pandey Jyoti , Banerjee M.K.
Published: July 2002

Concrete forms a major component of the national infrastructure. Corrosion of reinforced steels embedded in concrete has recently received wide attention in R&D programmes. Different cases have been reported showing failures of concrete structures which means huge loss. An attempt has been made to identify the different factors affecting the corrosion of embedded steel. Comparative evaluation of different protective schemes use of additives in concrete admixtures and the application of the cathodic protection technique has been discussed.
Comparative marketing strategies of Greek and overseas firms
Authors: Theodorakioglou Fotini , Tiu Wright Len
Published: July 2002

This paper reports on research into the Greek drinks market with the comparison of the marketing strategies of a sample of indigenous Greek and foreign companies, the latter with subsidiaries operating in Greece. The methodology employed was a qualitative one reflected in the design of the research from the purposive sampling of the largest drinks companies in Greece, and the application of the in‐depth interview technique with senior managers to the results of the research. The findings revealed several positive differences in the marketing strategies of competing organisations, with greater willingness by Western companies, compared to their Greek competitors, to implement resource commitments towards enhancing the competitiveness of their marketing strategies. The findings also suggested that the weaknesses in marketing found in the Greek alcoholic and soft drinks companies undermined their marketing performances in comparison with Western multinationals. Consequently, the competitive positions of Greek firms in both the domestic and international markets were weakened.
Mapping access to food at a local level
Authors: Donkin Angela J.M. , Dowler Elizabeth A. , Stevenson Simon J. , Turner Sheila A.
Published: July 2002

Access to food is currently on the political agenda. This paper presents a quantitative method for local level use to help identify the geographic location of areas with inadequate access to food. A census of retail outlets selling food of any kind was carried out in a deprived area within a 2km radius from a central point between two estates. Information on the price and availability of “healthy” food lists, acceptable to each of the four major ethnic groups in the area, was collected. The food lists were not mutually exclusive. Food shops were mapped in terms of food availability and price indices using Geographical Information System (GIS) software. Maps show, progressively: roads within/outside 500m of a postcode with any outlet selling food; any outlet selling more than 50 per cent of the food list, below the area mean price, acceptable to a Gujarati Hindu; the latter in relation to population density. Within the area analysed there appears to be reasonable walking access to the more reasonably priced shops within the area, however the cost of a healthy diet would still require more than 50 per cent of the income of someone in receipt of income support.
Complexity theory: the changing role of leadership
Authors: Keene Angelique
Published: July 2002

The study of complex adaptive systems which explains the constant flux of living systems is arousing much interest as a paradigm and model for studying organisational behaviour and associated disciplines. A new order of reality emerges as a result of the constant interaction and coevolution of the elements of the system as well as their interaction with the system itself. The space of complexity is that state which the system occupies and which lies between order and chaos. One major impact on organisations in applying the concepts of complexity theory is the way in which leadership is seen and the need for change.
Changing skill needs: what makes people employable?
Authors: Dench Sally
Published: July 2002

Many of the skills needed to make people employable are specific to particular occupations. However, increasingly employers are defining a set of “generic”, usually personal, skills which they seek when recruiting new employees. These “generic skills” include, for example, communication skills, the ability to apply basic literacy and numeracy in a work situation, being a “team player”, the ability to relate to customers and clients, taking initiative (for one’s own work and personal and career development), taking responsibility and making decisions. Occupational skills may be seen as necessary but not enough, or as “easily trained in”. Although these “generic skills” are not new needs in many workplaces, they do appear to be receiving greater emphasis as organizations change and adjust to meet new competitive pressures and develop new working practices. There is some debate about the extent to which these types of skill can be developed in people, or whether certain characteristics or predisposition are necessary for their development. Many organizations are adapting their recruitment processes and internal appraisal systems to explore more fully the abilities of potential recruits in these areas. Discusses the nature of these “skills” and their relevance in different workplaces and jobs, and in relation to occupation‐specific skills. Also looks at why they are currently receiving emphasis and likely current trends. Finally, explores how these “skills” are examined in the recruitment process. Draws on the findings from a series of projects conducted by the Institute for Employment Studies on employers’ skill needs in different occupations and how and why these are changing.
An organizational culture compatible with employability
Authors: Estiénne Marion
Published: July 2002

Discusses the organizational culture appropriate to new forms of “employability” as being characterized by its success in challenging and empowering its staff, motivating them, and even satisfying their needs for belongingness in today’s downsizing environment. These characteristics strongly reflect Roger Harrison’s descriptions of person and task cultures in organizations. Reflecting elements of both and, at the same time, increasingly incorporating “Generation X‐ers”, an organization which develops an employability culture is more likely a fifth alternative to Harrison’s classification scheme. Discusses the changing nature of work and why an employability culture is inevitable. However, such a culture presents dilemmas to the organization. One of the most predominant dilemmas is how the organization reconciles individual needs for career ownership with its own, which is to align its members’ efforts towards organizational goals. A solution is put forward by way of suggesting that employers and employees engage in adult‐adult interactions around a framework of negotiation.
Anatomy of a merger: behavior of organizational factors and processes throughout the pre‐ during‐ post‐ stages (part 2)
Authors: Appelbaum Steven H. , Gandell Joy , Shapiro Barbara T. , Belisle Pierre , Hoeven Eugene
Published: July 2002

The multiple organizational factors impacting upon a merger as well as those processes being impacted upon throughout the merger process will be examined. Part 1 of this article examined corporate culture and its affects on employees when two companies merge and considered the importance of lucid communication throughout the process. Part 2 of the article addresses the critical issue of stress, which is an outcome within the new and uncertain environment. Finally, the article concludes with the process of managing and strategy throughout the phases, giving guidelines that managers and CEOs should follow in the event of an M&A. Furthermore, the five major sections (communications, corporate culture, change, stress, and managing/strategy) are sub‐divided into three sub‐sections: pre‐merger; during the merger; post‐merger. This is intended to further assist managers and CEOs distinguish the important issues facing employees at each of the three junctures of the M&A process.
Trends in US prime‐time television food advertising across three decades
Authors: Byrd‐Bredbenner Carol , Grasso Darlene
Published: July 2002

The purpose of this study was to describe the content of food advertisements broadcast during prime‐time network programs and determine what changes have occurred over the last 30 years. The sample comprised foods advertisements (N = 38, N = 31, N = 91, N = 105, N = 108) from 1971, 1977, 1988, 1992 and 1998, respectively. Of the commercials shown in 1977, 1988, 1992 and 1998, 31, 35, 20, and 15 per cent, respectively, were for food advertisements (data were unavailable for 1971). Using simple linear regression, the hourly rate for total commercials is increasing significantly (p = 0.04) by 1.4 commercials per hour each year. However, the hourly rate for food advertisements is not changing over time in a statistically significant fashion. There is very strong evidence of an association between the type of food advertised and year (chi‐square = 62.691, p < 0.001). The top four categories contributing to the chi‐square are: restaurants, low‐nutrient beverages, protein‐rich foods, and breads and cereals which, together, account for 75 per cent of the chi‐square value. For the past three decades, the “prime‐time diet” has comprised mostly low nutrient density foods that are promoted by slender, healthy actors.
The education and training of future information systems professionals: an undergraduate programme in Hong Kong
Authors: Yee Wah Wong Eva
Published: July 2002

In Hong Kong, the application of information technology (IT) in both the public and private sectors is essential to maintaining Hong Kong’s position as one of the world’s leading financial and commercial centres. IT or IS (information systems) professionals working in the IT industry, with technical know‐how and business acumen, are key elements to the success of most IT projects. A major concern is that there are not enough of these IS professionals to cope with the growing demand. The Bachelor of Arts (Honours) in Information Systems (BAIS) was implemented at City University of Hong Kong (CityU) to meet this shortfall. The programme aims to produce a new breed of IS people who are experts in areas of IT and IS; those who realize the importance of business functions and understand how to fit IT and IS into a business, helping it to gain strategic advantages over its competitors. Looks at IS professional requirements in Hong Kong, and presents an introduction and an initial report on the BAIS programme currently being offered at CityU.