bluuebunny/crossref_metadata_2025 huggingface dataset:
Phytochrome Regulates Gibberellin Biosynthesis during Germination of Photoblastic Lettuce Seeds
Authors: Toyomasu Tomonobu , Kawaide Hiroshi , Mitsuhashi Wataru , Inoue Yasunori , Kamiya Yuji
Published: July 2002

Germination of lettuce (Lactuca sativa L.) seed is regulated by phytochrome. The requirement for red light is circumvented by the application of gibberellin (GA). We have previously shown that the endogenous content of GA1, the main bioactive GA in lettuce seeds, increases after red-light treatment. To clarify which step of GA1synthesis is regulated by phytochrome, cDNAs encoding GA 20-oxidases (Ls20ox1 and Ls20ox2, for L. sativa GA20-oxidase) and 3β-hydroxylases (Ls3h1 and Ls3h2 for L. sativa GA3β-hydroxylase) were isolated from lettuce seeds by reverse-transcription polymerase chain reaction. Functional analysis of recombinant proteins expressed inEscherichia coli confirmed that the Ls20ox and Ls3h encode GA 20-oxidases and 3β-hydroxylases, respectively. Northern-blot analysis showed that Ls3h1 expression was dramatically induced by red-light treatment within 2 h, and that this effect was canceled by a subsequent far-red-light treatment. Ls3h2 mRNA was not detected in seeds that had been allowed to imbibe under any light conditions. Expression of the two Ls20ox genes was induced by initial imbibition alone in the dark. The level of Ls20ox2 mRNA decreased after the red-light treatment, whereas that of Ls20ox1 was unaffected by light. These results suggest that red light promotes GA1synthesis in lettuce seeds by inducing Ls3h1 expression via phytochrome action.
Root Xylem Embolisms and Refilling. Relation to Water Potentials of Soil, Roots, and Leaves, and Osmotic Potentials of Root Xylem Sap1
Authors: McCully Margaret E.
Published: July 2002

Embolism and refilling of vessels was monitored directly by cryomicroscopy of field-grown corn (Zea mays L.) roots. To test the reliability of an earlier study showing embolism refilling in roots at negative leaf water potentials, embolisms were counted, and root water potentials (Ψroot) and osmotic potentials of exuded xylem sap from the same roots were measured by isopiestic psychrometry. All vessels were full at dawn (Ψroot −0.1 MPa). Embolisms were first seen in late metaxylem vessels at 8 am. Embolized late metaxylem vessels peaked at 50% at 10 am (Ψroot −0.1 MPa), fell to 44% by 12 pm (Ψroot −0.23 MPa), then dropped steadily to zero by early evening (Ψroot−0.28 MPa). Transpiration was highest (8.5 μg cm−2s−1) between 12 and 2 pm when the percentage of vessels embolized was falling. Embolized vessels were refilled by liquid moving through their lateral walls. Xylem sap was very low in solutes. The mechanism of vessel refilling, when Ψroot is negative, requires further investigation. Daily embolism and refilling in roots of well-watered plants is a normal occurrence and may be a component of an important hydraulic signaling mechanism between roots and shoots.
Abscisic Acid Induction of Vacuolar H+-ATPase Activity in Mesembryanthemum crystallinum Is Developmentally Regulated1
Authors: Barkla Bronwyn J. , Vera-Estrella Rosario , Maldonado-Gama Minerva , Pantoja Omar
Published: July 2002

Abscisic acid (ABA) has been implicated as a key component in water-deficit-induced responses, including those triggered by drought, NaCl, and low- temperature stress. In this study a role for ABA in mediating the NaCl-stress-induced increases in tonoplast H+-translocating ATPase (V-ATPase) and Na+/H+ antiport activity in Mesembryanthemum crystallinum, leading to vacuolar Na+ sequestration, were investigated. NaCl or ABA treatment of adult M. crystallinum plants induced V-ATPase H+ transport activity, and when applied in combination, an additive effect on V-ATPase stimulation was observed. In contrast, treatment of juvenile plants with ABA did not induce V-ATPase activity, whereas NaCl treatment resulted in a similar response to that observed in adult plants. Na+/H+ antiport activity was induced in both juvenile and adult plants by NaCl, but ABA had no effect at either developmental stage. Results indicate that ABA-induced changes in V-ATPase activity are dependent on the plant reaching its adult phase, whereas NaCl-induced increases in V-ATPase and Na+/H+ antiport activity are independent of plant age. This suggests that ABA-induced V-ATPase activity may be linked to the stress-induced, developmentally programmed switch from C3 metabolism to Crassulacean acid metabolism in adult plants, whereas, vacuolar Na+ sequestration, mediated by the V-ATPase and Na+/H+ antiport, is regulated through ABA-independent pathways.
A Plastidial Lysophosphatidic Acid Acyltransferase from Oilseed Rape1
Authors: Bourgis Fabienne , Kader Jean-Claude , Barret Pierre , Renard Michel , Robinson David , Robinson Colin , Delseny Michel , Roscoe Thomas J.
Published: July 2002

The biosynthesis of phosphatidic acid, a key intermediate in the biosynthesis of lipids, is controlled by lysophosphatidic acid (LPA, or 1-acyl-glycerol-3-P) acyltransferase (LPAAT, EC 2.3.1.51). We have isolated a cDNA encoding a novel LPAAT by functional complementation of the Escherichia coli mutant plsC with an immature embryo cDNA library of oilseed rape (Brassica napus). Transformation of the acyltransferase-deficientE. coli strain JC201 with the cDNA sequence BAT2 alleviated the temperature-sensitive phenotype of theplsC mutant and conferred a palmitoyl-coenzyme A-preferring acyltransferase activity to membrane fractions. The BAT2 cDNA encoded a protein of 351 amino acids with a predicted molecular mass of 38 kD and an isoelectric point of 9.7. Chloroplast-import experiments showed processing of a BAT2 precursor protein to a mature protein of approximately 32 kD, which was localized in the membrane fraction. BAT2 is encoded by a minimum of two genes that may be expressed ubiquitously. These data are consistent with the identity of BAT2 as the plastidial enzyme of the prokaryotic glycerol-3-P pathway that uses a palmitoyl-ACP to produce phosphatidic acid with a prokaryotic-type acyl composition. The homologies between the deduced protein sequence of BAT2 with prokaryotic and eukaryotic microsomal LAP acytransferases suggest that seed microsomal forms may have evolved from the plastidial enzyme.
Observations of Hydrogen and Oxygen Isotopes in Leaf Water Confirm the Craig-Gordon Model under Wide-Ranging Environmental Conditions1
Authors: Roden John S. , Ehleringer James R.
Published: July 2002

The Craig-Gordon evaporative enrichment model of the hydrogen (δD) and oxygen (δ18O) isotopes of water was tested in a controlled-environment gas exchange cuvette over a wide range (400‰ δD and 40‰ δ18O) of leaf waters. (Throughout this paper we use the term “leaf water” to describe the site of evaporation, which should not be confused with “bulk leaf water” a term used exclusively for uncorrected measurements obtained from whole leaf water extractions.) Regardless of how the isotopic composition of leaf water was achieved (i.e. by changes in source water, atmospheric vapor δD or δ18O, vapor pressure gradients, or combinations of all three), a modified version of the Craig-Gordon model was shown to be sound in its ability to predict the δD and δ18O values of water at the site of evaporation. The isotopic composition of atmospheric vapor was shown to have profound effects on the δD and δ18O of leaf water and its influence was dependent on vapor pressure gradients. These results have implications for conditions in which the isotopic composition of atmospheric vapor is not in equilibrium with source water, such as experimental systems that grow plants under isotopically enriched water regimes. The assumptions of steady state were also tested and found not to be a major limitation for the utilization of the leaf water model under relatively stable environmental conditions. After a major perturbation in the δD and δ18O of atmospheric vapor, the leaf reached steady state in approximately 2 h, depending on vapor pressure gradients. Following a step change in source water, the leaf achieved steady state in 24 h, with the vast majority of changes occurring in the first 3 h. Therefore, the Craig-Gordon model is a useful tool for understanding the environmental factors that influence the hydrogen and oxygen isotopic composition of leaf water as well as the organic matter derived from leaf water.
Roles of Sugar Alcohols in Osmotic Stress Adaptation. Replacement of Glycerol by Mannitol and Sorbitol in Yeast
Authors: Shen Bo , Hohmann Stefan , Jensen Richard G. , Bohnert and Hans J.
Published: July 2002

For many organisms there is a correlation between increases of metabolites and osmotic stress tolerance, but the mechanisms that cause this protection are not clear. To understand the role of polyols, genes for bacterial mannitol-1-P dehydrogenase and apple sorbitol-6-P dehydrogenase were introduced into a Saccharomyces cerevisiae mutant deficient in glycerol synthesis. Sorbitol and mannitol provided some protection, but less than that generated by a similar concentration of glycerol generated by glycerol-3-P dehydrogenase (GPD1). Reduced protection by polyols suggested that glycerol had specific functions for which mannitol and sorbitol could not substitute, and that the absolute amount of the accumulating osmoticum might not be crucial. The retention of glycerol and mannitol/sorbitol, respectively, was a major difference. During salt stress, cells retained more of the six-carbon polyols than glycerol. We suggest that the loss of >98% of the glycerol synthesized could provide a safety valve that dissipates reducing power, while a similar high intracellular concentration of retained polyols would be less protective. To understand the role of glycerol in salt tolerance, salt-tolerant suppressor mutants were isolated from the glycerol-deficient strain. One mutant, sr13, partially suppressed the salt-sensitive phenotype of the glycerol-deficient line, probably due to a doubling of [K+] accumulating during stress. We compare these results to the “osmotic adjustment” concept typically applied to accumulating metabolites in plants. The accumulation of polyols may have dual functions: facilitating osmotic adjustment and supporting redox control.
Stimulation of Border Cell Production in Response to Increased Carbon Dioxide Levels
Authors: Zhao Xiaowen , Misaghi Iraj J. , Hawes Martha C.
Published: July 2002

Field soil atmospheres have higher CO2 and lower O2 concentrations compared with ambient atmosphere, but little is known about the impact of such conditions on root exudation patterns. We used altered levels of CO2 and O2 relative to ambient conditions to examine the influence of the atmosphere on the production of root border cells by pea (Pisum sativum) root tips. During germination, atmospheres with high CO2 and low O2 inhibited root development and border cell separation in pea seedlings. Later in development, the same atmospheric composition stimulated border cell separation without significantly influencing root growth. Increased CO2, not low O2, was responsible for the observed stimulation of border cell number. High CO2 apparently can override endogenous signals that regulate the number of border cells released from pea roots into the rhizosphere. The same conditions that stimulated border cell production in pea had no such effect in alfalfa (Medicago sativa).
A Small Heat Shock Protein Cooperates with Heat Shock Protein 70 Systems to Reactivate a Heat-Denatured Protein
Authors: Lee Garrett J. , Vierling Elizabeth
Published: July 2002

Small heat shock proteins (sHsps) are a diverse group of heat-induced proteins that are conserved in prokaryotes and eukaryotes and are especially abundant in plants. Recent in vitro data indicate that sHsps act as molecular chaperones to prevent thermal aggregation of proteins by binding non-native intermediates, which can then be refolded in an ATP-dependent fashion by other chaperones. We used heat-denatured firefly luciferase (Luc) bound to pea (Pisum sativum) Hsp18.1 as a model to define the minimum chaperone system required for refolding of a sHsp-bound substrate. Heat-denatured Luc bound to Hsp18.1 was effectively refolded either with Hsc/Hsp70 from diverse eukaryotes plus the DnaJ homologs Hdj1 and Ydj1 (maximum = 97% Luc reactivation with k  ob = 1.0 × 10−2/min), or with prokaryotic Escherichia coli DnaK plus DnaJ and GrpE (100% Luc reactivation,k  ob = 11.3 × 10−2/min). Furthermore, we show that Hsp18.1 is more effective in preventing Luc thermal aggregation than the Hsc70 or DnaK systems, and that Hsp18.1 enhances the yields of refolded Luc even when other chaperones are present during heat inactivation. These findings integrate the aggregation-preventive activity of sHsps with the protein-folding activity of the Hsp70 system and define an in vitro system for further investigation of the mechanism of sHsp action.
Response to Xanthomonas campestris pv.vesicatoria in Tomato Involves Regulation of Ethylene Receptor Gene Expression
Authors: Ciardi Joseph A. , Tieman Denise M. , Lund Steven T. , Jones Jeffrey B. , Stall Robert E. , Klee Harry J.
Published: July 2002

Although ethylene regulates a wide range of defense-related genes, its role in plant defense varies greatly among different plant-microbe interactions. We compared ethylene's role in plant response to virulent and avirulent strains of Xanthomonas campestrispv. vesicatoria in tomato (Lycopersicon esculentum Mill.). The ethylene-insensitive Never ripe (Nr) mutant displays increased tolerance to the virulent strain, while maintaining resistance to the avirulent strain. Expression of the ethylene receptor genes NR andLeETR4 was induced by infection with both virulent and avirulent strains; however, the induction of LeETR4expression by the avirulent strain was blocked in the Nrmutant. To determine whether ethylene receptor levels affect symptom development, transgenic plants overexpressing a wild-typeNR cDNA were infected with virulent X. campestris pv. vesicatoria. Like theNr mutant, the NR overexpressors displayed greatly reduced necrosis in response to this pathogen.NR overexpression also reduced ethylene sensitivity in seedlings and mature plants, indicating that, like LeETR4, this receptor is a negative regulator of ethylene response. Therefore, pathogen-induced increases in ethylene receptors may limit the spread of necrosis by reducing ethylene sensitivity.
The Role of the Arabidopsis ELD1 Gene in Cell Development and Photomorphogenesis in Darkness
Authors: Cheng Jin-Chen , Lertpiriyapong Kvin , Wang Susanna , Sung Zinmay Renee
Published: July 2002

Because cell growth and differentiation are regulated by complex interactions among different signaling pathways, a growth defect affects subsequent differentiation. We report on a growth-defective mutant of Arabidopsis, called eld1 (elongation defective 1). Cell elongation was impaired in every organ examined. Later characteristics of the eld1 phenotype include defective vascular tissue differentiation, the inability to grow in soil, ectopic deposition of suberin around twisted vascular bundles, the de-etiolation phenotype, and continuation of shoot development and flowering in the dark. The dwarf phenotype of eld1 could not be rescued by treatment with exogenous growth regulators. Because defective cell elongation is the earliest and most universal feature detected in eld1 mutants, control of or activity in cell elongation may be the primary function of the ELD1 gene. The impaired cell growth results in pleiotropic effects on cell proliferation and differentiation, and the retardation in hypocotyl elongation enables growth and development in darkness.
Auxin Inhibition of Decapitation-Induced Branching Is Dependent on Graft-Transmissible Signals Regulated by GenesRms1andRms2
Authors: Beveridge Christine A. , Symons Gregory M. , Turnbull Colin G.N.
Published: July 2002

Decapitation-induced axillary bud outgrowth is a vital mechanism whereby shoots are able to continue normal growth and development. In many plants, including wild-type garden pea (Pisum sativum L.), this process can be inhibited by exogenous auxin. Using the ramosus (rms) increased branching mutants of pea, we present evidence that this response to auxin is dependent on graft-transmissible substance(s) regulated by the genes Rms1 and Rms2. The response to exogenous auxin is massively diminished in decapitatedrms1 and rms2 mutant plants. However, basipetal auxin transport is not reduced in intact or decapitated mutants. Grafting rms1 or rms2 shoots onto wild-type rootstocks restored the auxin response, indicating thatRms1 and Rms2 gene action in the rootstock is sufficient to enable an auxin response in mutant shoots. We conclude that Rms1 and Rms2 act in the rootstock and shoot to control levels of mobile substance(s) that interact with exogenous auxin in the inhibition of bud outgrowth after decapitation. At least for rms1, the reduced auxin response is unlikely to be due to an inability of auxin to decrease xylem sap cytokinin content, as this is already low in intactrms1 plants. Consequently, we have genetic evidence that auxin action in decapitated plants depends on at least one novel long-distance signal.
Farnesol-Induced Cell Death and Stimulation of 3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase Activity in Tobacco cv Bright Yellow-2 Cells,
Authors: Hemmerlin Andréa , Bach Thomas J.
Published: July 2002

Growth inhibition of tobacco (Nicotiana tabacum L. cv Bright Yellow-2) cells by mevinolin, a specific inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) could be partially overcome by the addition of farnesol. However, farnesol alone inhibited cell division and growth as measured by determination of fresh weight increase. When 7-d-old tobacco cv Bright Yellow-2 cells were diluted 40-fold into fresh culture, the cells exhibited a dose-dependent sensitivity to farnesol, with 25 μmsufficient to cause 100% cell death, as measured by different staining techniques, cytometry, and monitoring of fragmentation of genomic DNA. Cells were less sensitive to the effects of farnesol when diluted only 4-fold. Farnesol was absorbed by the cells, as examined by [1-3H]farnesol uptake, with a greater relative enrichment by the more diluted cells. Both mevinolin and farnesol treatments stimulated apparent HMGR activity. The stimulation by farnesol was also reflected in corresponding changes in the steady-state levels of HMGR mRNA and enzyme protein with respect to HMGR gene expression and enzyme protein accumulation.
A Plastid Terminal Oxidase Associated with Carotenoid Desaturation during Chromoplast Differentiation
Authors: Josse Eve-Marie , Simkin Andrew J. , Gaffé Joël , Labouré Anne-Marie , Kuntz Marcel , Carol Pierre
Published: July 2002

The Arabidopsis IMMUTANS gene encodes a plastid homolog of the mitochondrial alternative oxidase, which is associated with phytoene desaturation. Upon expression in Escherichia coli, this protein confers a detectable cyanide-resistant electron transport to isolated membranes. In this assay this activity is sensitive to n-propyl-gallate, an inhibitor of the alternative oxidase. This protein appears to be a plastid terminal oxidase (PTOX) that is functionally equivalent to a quinol:oxygen oxidoreductase. This protein was immunodetected in achlorophyllous pepper (Capsicum annuum) chromoplast membranes, and a corresponding cDNA was cloned from pepper and tomato (Lycopersicum esculentum) fruits. Genomic analysis suggests the presence of a single gene in these organisms, the expression of which parallels phytoene desaturase and ζ-carotene desaturase gene expression during fruit ripening. Furthermore, thisPTOX gene is impaired in the tomato ghostmutant, which accumulates phytoene in leaves and fruits. These data show that PTOX also participates in carotenoid desaturation in chromoplasts in addition to its role during early chloroplast development.
Polyphenol Oxidase from Hybrid Poplar. Cloning and Expression in Response to Wounding and Herbivory
Authors: Constabel C. Peter , Yip Lynn , Patton Joseph J. , Christopher Mary E.
Published: July 2002

The inducible expression of polyphenol oxidase (PPO), a presumed antiherbivore enzyme, was examined in hybrid poplar (Populus trichocarpa × Populus deltoides). Following mechanical wounding simulating insect damage, PPO activity increased dramatically in wounded and unwounded leaves on wounded plants beginning at 24 and 48 h, respectively. A hybrid poplar PPO cDNA was isolated and its nucleotide sequence determined. On northern blots, PPO transcripts were detected within 8 h of wounding, and reached peak levels at 16 and 24 h in wounded and unwounded leaves, respectively. Methyl jasmonate spray and feeding by forest tent caterpillar also induced PPO expression. The induction of PPO was strongest in the youngest four leaves, which were generally avoided by caterpillars in free feeding experiments. This wound- and herbivore-induced expression of PPO in hybrid poplar supports the defensive role of this protein against insect pests.
Simultaneous Measurement of ΔpH and Electron Transport in Chloroplast Thylakoids by 9-Aminoacridine Fluorescence,
Authors: Evron Yoav , McCarty Richard E.
Published: July 2002

Electron transport and the electrochemical proton gradient across the thylakoid membrane are two fundamental parameters of photosynthesis. A combination of the electron acceptor, ferricyanide and the ΔpH indicator, 9-aminoacridine, was used to measure simultaneously electron transport rates and ΔpH solely by changes in the fluorescence of 9-aminoacridine. This method yields values for the rate of electron transport that are comparable with those obtained by established methods. Using this method a relationship between the rate of electron transport and ΔpH at various uncoupler concentrations or light intensities was obtained. In addition, the method was used to study the effect of reducing the disulfide bridge in the γ-subunit of the chloroplast ATP synthase on the relation of electron transport to ΔpH. When the ATP synthase is reduced and alkylated, the threshold ΔpH at which the ATP synthase becomes leaky to protons is lower compared with the oxidized enzyme. Proton flow through the enzyme at a lower ΔpH may be a key step in initiation of ATP synthesis in the reduced enzyme and may be the way by which reduction of the disulfide bridge in the γ-subunit enables high rates of ATP synthesis at low ΔpH values.
Clausa, a Tomato Mutant with a Wide Range of Phenotypic Perturbations, Displays a Cell Type-Dependent Expression of the Homeobox Gene LeT6/TKn2
Authors: Avivi Yigal , Lev-Yadun Simcha , Morozova Nadya , Libs Laurence , Williams Leor , Zhao Jing , Varghese George , Grafi Gideon
Published: July 2002

Class I knox genes play an important role in shoot meristem function and are thus involved in the ordered development of stems, leaves, and reproductive organs. To elucidate the mechanism underlying the expression pattern of these homeobox genes, we studied a spontaneous tomato (Lycopersicon esculentum) mutant that phenotypically resembles, though is more extreme than, transgenic plants misexpressing class I knox genes. This mutant was found to carry a recessive allele, denoted clausa:shootyleaf (clau:shl)—a newly identified allele of clausa. Mutant plants exhibited abnormal leaf and flower morphology, epiphyllus inflorescences, fusion of organs, calyx asymmetry, and navel-like fruits. Analysis by scanning electron microscopy revealed that such fruits carried ectopic ovules, various vegetative primordia, as well as “forests” of stalked glandular trichomes. In situ RNA hybridization showed a peculiar expression pattern of the class I knoxgene LeT6/TKn2; expression was restricted to the vascular system and palisade layer of mature leaves and to the inner part of ovules integuments. We conclude that CLAUSA regulates various aspects of tomato plant development, at least partly, by rendering theLeT6/TKn2 gene silent in specific tissues during development. Considering the expression pattern ofLeT6/TKn2 in the clausa mutant, we suggest that the control over a given homeobox gene is maintained by several different regulatory mechanisms, in a cell type-dependent manner.
Changes in Gibberellin A1 Levels and Response during De-Etiolation of Pea Seedlings
Authors: O'Neill Damian P. , Ross John J. , Reid James B.
Published: July 2002

The level of gibberellin A1 (GA1) in shoots of pea (Pisum sativum) dropped rapidly during the first 24 h of de-etiolation. The level then increased between 1 and 5 d after transfer to white light. Comparison of the metabolism of [13C3H] GA20 suggested that the initial drop in GA1 after transfer is mediated by a light-induced increase in the 2β-hydroxylation of GA1 to GA8. A comparison of the elongation response to GA1 at early and late stages of de-etiolation provided strong evidence for a change in GA1 response during de-etiolation, coinciding with the return of GA1 levels to the normal, homeostatic levels found in light- and dark-grown plants. The emerging picture of the control of shoot elongation by light involves an initial inhibition of elongation by a light-induced decrease in GA1 levels, with continued inhibition mediated by a light-induced change in the plant's response to the endogenous level of GA1. Hence the plant uses a change in hormone level to respond to a change in the environment, but over time, homeostasis returns the level of the hormone to normal once the ongoing change in environment is accommodated by a change in the response of the plant to the hormone.
Responses of Sugar Beet Roots to Iron Deficiency. Changes in Carbon Assimilation and Oxygen Use
Authors: López-Millán Ana Flor , Morales Fermı́n , Andaluz Sofı́a , Gogorcena Yolanda , Abadı́a Anunciación , Rivas Javier De Las , Abadı́a Javier
Published: July 2002

Different root parts with or without increased iron-reducing activities have been studied in iron-deficient and iron-sufficient control sugar beet (Beta vulgaris L. Monohil hybrid). The distal root parts of iron-deficient plants, 0 to 5 mm from the root apex, were capable to reduce Fe(III)-chelates and contained concentrations of flavins near 700 μm, two characteristics absent in the 5 to 10 mm sections of iron-deficient plants and the whole root of iron-sufficient plants. Flavin-containing root tips had large pools of carboxylic acids and high activities of enzymes involved in organic acid metabolism. In iron-deficient yellow root tips there was a large increase in carbon fixation associated to an increase in phosphoenolpyruvate carboxylase activity. Part of this carbon was used, through an increase in mitochondrial activity, to increase the capacity to produce reducing power, whereas another part was exported via xylem. Root respiration was increased by iron deficiency. In sugar beet iron-deficient roots flavins would provide a suitable link between the increased capacity to produce reduced nucleotides and the plasma membrane associated ferric chelate reductase enzyme(s). Iron-deficient roots had a large oxygen consumption rate in the presence of cyanide and hydroxisalycilic acid, suggesting that the ferric chelate reductase enzyme is able to reduce oxygen in the absence of Fe(III)-chelates.
Induced Plant Defense Responses against Chewing Insects. Ethylene Signaling Reduces Resistance of Arabidopsis against Egyptian Cotton Worm But Not Diamondback Moth
Authors: Stotz Henrik U. , Pittendrigh Barry R. , Kroymann Jürgen , Weniger Kerstin , Fritsche Jacqueline , Bauke Antje , Mitchell-Olds Thomas
Published: July 2002

The induction of plant defenses by insect feeding is regulated via multiple signaling cascades. One of them, ethylene signaling, increases susceptibility of Arabidopsis to the generalist herbivore Egyptian cotton worm (Spodoptera littoralis; Lepidoptera: Noctuidae). The hookless1 mutation, which affects a downstream component of ethylene signaling, conferred resistance to Egyptian cotton worm as compared with wild-type plants. Likewise,ein2, a mutant in a central component of the ethylene signaling pathway, caused enhanced resistance to Egyptian cotton worm that was similar in magnitude to hookless1. Moreover, pretreatment of plants with ethephon (2-chloroethanephosphonic acid), a chemical that releases ethylene, elevated plant susceptibility to Egyptian cotton worm. By contrast, these mutations in the ethylene-signaling pathway had no detectable effects on diamondback moth (Plutella xylostella) feeding. It is surprising that this is not due to nonactivation of defense signaling, because diamondback moth does induce genes that relate to wound-response pathways. Of these wound-related genes, jasmonic acid regulates a novel β-glucosidase 1 (BGL1), whereas ethylene controls a putative calcium-binding elongation factor hand protein. These results suggest that a specialist insect herbivore triggers general wound-response pathways in Arabidopsis but, unlike a generalist herbivore, does not react to ethylene-mediated physiological changes.
Characterization of the Response of the Arabidopsis Response Regulator Gene Family to Cytokinin
Authors: D'Agostino Ingrid B. , Deruère Jean , Kieber Joseph J.
Published: July 2002

We examined the expression of a family of Arabidopsis response regulators (ARR) and found that the steady-state levels of RNA for most are elevated very rapidly by cytokinin. Using nuclear run-on assays we demonstrated that this increase in ARR transcript levels in response to cytokinin is due, at least in part, to increased transcription. The start site of transcription for the ARR5 gene was identified using primer extension analysis. A DNA fragment comprised of 1.6 kb upstream of the ARR5 transcript start site conferred cytokinin-inducible gene expression when fused to a β-glucuronidase reporter, confirming that the transcription rate ofARR5 is elevated by cytokinin. This reporter construct was also used to examine the spatial pattern of ARR5expression. The highest levels of expression were observed in the root and shoot apical meristems, at the junction of the pedicle and the silique, and in the central portion of mature roots. The expression ofARR5 in the apical meristems was confirmed by whole mount in situ analysis of seedlings and is consistent with a role for cytokinin in regulating cell division in vivo.
Mitochondrial Biogenesis during Germination in Maize Embryos
Authors: Logan David C. , Millar A. Harvey , Sweetlove Lee J. , Hill Steven A. , Leaver Christopher J.
Published: July 2002

Mitochondrial biogenesis and metabolism were investigated during maize (Zea mays) seed germination. Mitochondria from dry and imbibed seed exhibited NADH-dependent O2 uptake that was completely inhibited by KCN and antimycin A. Mitochondria in the dry seed had a lower rate of succinate-dependent O2 uptake relative to that measured in imbibed and germinated seed. The activities of the tricarboxylic acid (TCA) cycle enzymes, pyruvate dehydrogenase complex, 2-oxoglutarate dehydrogenase complex, NAD-malic enzyme, and citrate synthase, are similarly low in mitochondria from dry seed and this correlates with a lower relative abundance of the mitochondrial matrix-located citrate synthase and pyruvate dehydrogenase complex E1α-subunit polypeptides. Electron microscopy revealed that mitochondria in the dry seed have a poorly developed internal membrane structure with few cristae; following 24 h of germination the mitochondria developed a more normal structure with more developed cristae. The mitochondria from maize embryos could be fractionated into two subpopulations by Suc density gradient centrifugation: one subpopulation of buoyant density equivalent to 22% to 28% (w/w) Suc; the other equivalent to 37% to 42% (w/w) Suc. These two subpopulations had different activities of specific mitochondrial enzymes and contained different amounts of specific mitochondrial proteins as revealed by western-blot analysis. Both subpopulations from the dry embryo were comprised of poorly developed mitochondria. However, during imbibition mitochondria in the heavy fraction (37%–42% [w/w] Suc) progressively acquired characteristics of fully functional mitochondria found in the germinated seedling in terms of structure, enzymic activity, and protein complement. In contrast, mitochondria in the light fraction (22% to 28% [w/w] Suc) show no significant structural change during imbibition and the amounts of specific mitochondrial proteins decreased significantly during germination.
Arabidopsis Genes Encoding Components of the Chloroplastic Protein Import Apparatus
Authors: Jackson-Constan Diane , Keegstra Kenneth
Published: July 2002

The process of protein import into plastids has been studied extensively using isolated pea (Pisum sativum) chloroplasts. As a consequence, virtually all of the known components of the proteinaceous apparatus that mediates import were originally cloned from pea. With the recent completion of the Arabidopsis genome sequencing project, it is now possible to identify putative homologs of the import components in this species. Our analysis has revealed that Arabidopsis homologs with high sequence similarity exist for all of the pea import complex subunits, making Arabidopsis a valid model for further study of this system. Multiple homologs can be identified for over one-half of the components. In all but one case it is known that more than one of the putative isoforms for a particular subunit are expressed. Thus, it is possible that multiple types of import complexes are present within the same cell, each having a unique affinity for different chloroplastic precursor proteins, depending upon the exact mix of isoforms it contains. Sequence analysis of the putative Arabidopsis homologs for the chloroplast protein import apparatus has revealed many questions concerning subunit function and evolution. It should now be possible to use the genetic tools available in Arabidopsis, including the generation of knockout mutants and antisense technology, to address these questions and learn more about the molecular functions of each of the components during the import process.
An Early Tobacco Mosaic Virus-Induced Oxidative Burst in Tobacco Indicates Extracellular Perception of the Virus Coat Protein
Authors: Allan Andrew C. , Lapidot Moshe , Culver James N. , Fluhr Robert
Published: July 2002

Induction of reactive oxygen species (ROS) was observed within seconds of the addition of exogenous tobacco mosaic virus (TMV) to the outside of tobacco (Nicotiana tabacum cv Samsun NN, EN, or nn) epidermal cells. Cell death was correlated with ROS production. Infectivity of the TMV virus was not a prerequisite for this elicitation and isolated coat protein (CP) subunits could also elicit the fast oxidative burst. The rapid induction of ROS was prevented by both inhibitors of plant signal transduction and inhibitors of NAD(P)H oxidases, suggesting activation of a multi-step signal transduction pathway. Induction of intracellular ROS by TMV was detected in TMV-resistant and -susceptible tobacco cultivars isogenic for theN allele. The burst was also detected with strains of virus that either elicit (ToMV) or fail to elicit (TMV U1)N′ gene-mediated responses. Hence, early ROS generation is independent or upstream of known genetic systems in tobacco that can mediate hypersensitive responses. Analysis of other viruses and TMV CP mutants showed marked differences in their ability to induce ROS showing specificity of the response. Thus, initial TMV-plant cell interactions that lead to early ROS induction occur outside the plasma membrane in an event requiring specific CP epitopes.
Anti‐corrosion protection of chimneys and flue gas ducts
Authors: Bordzilowski J. , Darowicki K.
Published: July 2002

Industrial chimneys are a great part of environmental protection in industrial countries. In recent years many of them have been used to carrying away very aggressive gases from boilers and flue gas desulphurisation (FGD) units below acid dew‐point temperature. It is opf very important to modernize the old stacks and protect them against corrosion. The proper anti‐corrosion protection of modern high stacks is also an important technical and economical problem. In this paper the mechanism of acid dew‐point corrosion, as well as construction of industrial chimneys, methods of their anti‐corrosion protection and modernisation are described.
Improving the numbers and performance of women‐owned businesses: some implications for training and advisory services
Authors: Carter Sara
Published: July 2002

The importance of women as a largely untapped pool of entrepreneurs has been widely recognised by economic development agencies. However, despite a number of initiatives designed to stimulate female self‐employment, relatively few women are starting in business. Research has shown that the experience of business ownership for women is very different than for men. While early studies of female entrepreneurship suggested that the start up period posed particular constraints for women, it was assumed that these barriers were resolved once trading commenced. The use of more sophisticated methodologies and sampling strategies has revealed profound gender differences in both women’s experiences of business ownership and the performance of women owned firms. Some of the key research findings which have emerged from gender based studies of business ownership are outlined, and the implications of these findings for training and advisory services dealing with the small business sector are examined.
Management NVQs in higher education: reflections on experience
Authors: Swailes Stephen
Published: July 2002

Reviews the experience gained from delivering National Vocational Qualifications in Management in higher education. Identifies factors affecting achievement of management NVQs and notes these cluster around three elements; the candidate, the institution and the employer. Discusses the implications for each of these with particular reference to the institution’s management of vocational qualifications. Central to the student experience is the development of an institutional vision that positions NVQs within other management development programmes and which articulates the portfolio process. Suggests that the findings should interest institutions involved with the delivery and assessment of high level vocational qualifications.
Modern apprenticeships: a regional overview
Authors: Churchill Sue
Published: July 2002

Provides an overview of modern apprenticeships, setting it within the context of the “skills gap”, particularly in relation to intermediate skills. Includes an outline of how the frameworks are produced and clarifies the distinction between modern apprenticeships and training credits, commonly known as YT. Focuses mainly on the take‐up of the programme in Devon and Cornwall. Discusses four sectoral areas ‐ engineering manufacture, the hospitality sector, construction and agriculture ‐ all major sectors in the region. Presents the responses of young people, employers and training providers and examines the viability of modern apprenticeships as a vocational alternative to full‐time education and its effectiveness in meeting the skills needs of employers.
Remedying Sexual Harassment via Industrial Tribunal Claims
Authors: Earnshaw Jill , Davidson Marilyn J.
Published: July 2002

Though surveys of sexual harassment at work have consistently shown it
to be a widespread and under‐reported problem, there has been little
research directed at investigating the appropriateness of seeking a
solution to it via claims to industrial tribunals under the Sex
Discrimination Act. Based on research which aimed to explore, through
interviews and questionnaires, the motives of those who had brought such
legal proceedings and their experiences before, during and subsequent to
the tribunal hearing, the findings cast doubt on the suitability of
tribunal remedies and highlight the devastating long‐term psychological
effects of sexual harassment on the victims. Overall the research
suggests that remedying sexual harassment via tribunal claims can never
be more than a second‐best solution. Concludes that prevention is better
than cure and places the onus on management to take effective action
against harassment.
What has been happening in organization theory and does it matter?
Authors: Willmott Hugh
Published: July 2002

Examines recent developments in organization theory and considers
their relevance for personnel practitioners. Suggests that an important
contribution of these developments has been their challenge to the
authority of established analyses in which there has been a tendency to
overlook the constructed and fundamentally political nature of this
knowledge. More specifically, provides a critical appraisal of the work
of Stewart Clegg and, in particular, his Modern Organizations.
Argues that the commitment in earlier work to extend and enrich the
analysis of organizations has been displaced and diluted in his
examination of “things postmodern”. In Modern
Organizations, the critical thrust of earlier books is blunted by an
objectivism which dilutes or suspends their concerns in favour of an
attempt to provide seemingly more refined or accurate maps of
organizational reality. It is difficult to see how this move is
compatible with a commitment to develop theory which by challenging
established ways of thinking about organizing, may contribute to the
fostering of less divisive and destructive organizational practices.
Instabilities induced by coarse meshes for a nonlinear shell problem
Authors: Crisfield M.A. , Peng X.
Published: July 2002

Presents a range of numerical results obtained from the geometrically nonlinear analysis of a cantilevered cylindrical shell. Shows that, while the fine‐mesh solution involves no limit points, as the mesh is coarsened, an increasing series of “false limit points” is encountered.
A comparison of managerial skills of middle managers with MBAs, with other masters’ and undergraduate degrees ten years after the Porter and McKibbin report
Authors: Shipper Frank
Published: July 2002

Multiple initiatives have been taken to address the lack of managerial skills of MBA graduates since the Porter and McKibbin report. How effective or widespread these initiatives have been has been questioned. Before proceeding, 11 managerial skills were identified and tested for their relevance to performance. Support was found that nine of the 11 skills were associated with managerial performance. Why these two skills were not associated with performance was explored. To test for the effectiveness of the initiatives to teach managerial skills in MBA programs, multiple comparisons of the managerial skills of recent and past MBA graduates and other graduates were made. In general, the comparisons failed to find that MBAs have a significant advantage in managerial skills. Reasons for these findings are explored in the paper. In addition, the challenge this represents to MBA programs is also discussed.
An exploration of the relationships between the adoption of managerial competencies, organisational characteristics, human resource sophistication and performance in Irish organisations
Authors: Heffernan Margaret M. , Flood Patrick C.
Published: July 2002

This paper is developed from research conducted with the Irish Management Institute. A model is presented to illustrate the relationships between the adoption of competency‐based human resource management and a range of other variables. These include HRM sophistication and several organisational characteristics. The linkages to business performance are also explored. The empirical evidence to validate this model was derived from a 114‐company respondent survey. Key findings are that organisational characteristics impact on the adoption of competencies, particularly company size and length of time in operation. Another finding is the effect of HR sophistication on the incidence of competency frameworks at company level. Organisations which already have sophisticated and well resourced HR processes in place are more likely to use competencies. The final finding relates to organisational performance. Organisations which are performing well are more likely to adopt competencies. This might also be interpreted as meaning that organisations which adopt competencies are more superior performers, although the cross‐sectional evidence presented here does not allow us to make this assertion with full confidence.
Company‐based lifelong learning: what’s the pay‐off for employers?
Authors: Pate Judy , Martin Graeme , Beaumont Phil , McGoldrick Jim
Published: July 2002

Addresses the question: will investment in HRD through company‐based programmes of lifelong learning pay dividends to companies in terms of knowledge transfer from courses and more positive psychological contracts? Develops a model of the relationship between HRD investment, the content of psychological contracts and key consequences such as satisfaction, continuance commitment and knowledge transfer. This model is tested empirically using data from a survey of a cohort of participants in a major Scottish electronics company. The results show that the programme paid off in terms of more positive psychological contracts and knowledge transfer. However, contrary to other research, the nature of the transfer climate (e.g. manager support, career and salary advancement, etc.) was not seen to be important in affecting knowledge transfer. This latter finding has important implications for HR policies in knowledge creating companies.
Workforce training:
Authors: Joyce Paul , McNulty Tony , Woods Adrian
Published: July 2002

The British CBI introduced national educational and training
targets in 1991. Small firms might be regarded as unlikely to respond to
them because of, for example, lack of time, cost constraints and fears
of other firms poaching their employees. Is this true? Surveys of South
London employers in November 1992 and February 1993, which were carried
out for South London Training and Enterprise Council (SOLOTEC), provide
some interesting insights on the relative standards of training in small
businesses. Reports findings which show that size does matter and goes
on to argue that there could be a different set of training dynamics in
many small firms. Poses a culture of rational and incremental change in
training activity in large firms against a more visionary approach in
small firms to explain some curious evidence on the uptake of National
Vocational Qualifications (NVQs).
Management development and training in the police
Authors: Gaston Kevin C. , King Lillian
Published: July 2002

Little is known generally about the content and process of
promotion in the police forces in the UK. Surveys 128 officers from a
large police force who have been promoted recently from constable to
sergeant. Reports their views on the timing, content and effectiveness
of both on‐the‐job pre‐promotion training (known as acting duties) and
formal training courses for newly promoted officers. Identifies
shortcomings and makes suggestions for improvements. Of particular
interest is the desire for management training of a general rather than
police‐specific nature and for more exposure to knowledge and experience
of management theory and practice in non‐police organizations. The
findings suggest greater collaboration between police career development
and training departments and non‐police management trainers.
Fear as a strategy: effects and impact within the organization
Authors: Appelbaum Steven H. , Bregman Michael , Moroz Peter
Published: July 2002

The use of reinforcement and punishment have been studied extensively in laboratory and organizational settings. It has been found that positive reinforcement is the most effective way to achieve the required behavior. Many theories and models have been developed in order to explain the relationship between punishment and fear and it has been found that these are correlated. The use of punishment and fear in the organizational setting has proved to be ineffective and undesirable. Managers must try to create an environment and climate where employees can express their full potential and respond to difficult challenges by letting go of fear of failure, fear of change, or fear of risk taking. Human resource management offers some alternatives and programs to assist in executing this task.