bluuebunny/crossref_metadata_2025 huggingface dataset:
The Regulation of Photosynthetic Electron Transport during Nutrient Deprivation inChlamydomonas reinhardtii1
Authors: Wykoff Dennis D. , Davies John P. , Melis Anastasios , Grossman Arthur R.
Published: July 2002

The light-saturated rate of photosynthetic O2 evolution in Chlamydomonas reinhardtii declined by approximately 75% on a per-cell basis after 4 d of P starvation or 1 d of S starvation. Quantitation of the partial reactions of photosynthetic electron transport demonstrated that the light-saturated rate of photosystem (PS) I activity was unaffected by P or S limitation, whereas light-saturated PSII activity was reduced by more than 50%. This decline in PSII activity correlated with a decline in both the maximal quantum efficiency of PSII and the accumulation of the secondary quinone electron acceptor of PSII nonreducing centers (PSII centers capable of performing a charge separation but unable to reduce the plastoquinone pool). In addition to a decline in the light-saturated rate of O2 evolution, there was reduced efficiency of excitation energy transfer to the reaction centers of PSII (because of dissipation of absorbed light energy as heat and because of a transition to state 2). These findings establish a common suite of alterations in photosynthetic electron transport that results in decreased linear electron flow when C. reinhardtii is limited for either P or S. It was interesting that the decline in the maximum quantum efficiency of PSII and the accumulation of the secondary quinone electron acceptor of PSII nonreducing centers were regulated specifically during S-limited growth by theSacI gene product, which was previously shown to be critical for the acclimation of C. reinhardtiito S limitation (J.P. Davies, F.H. Yildiz, and A.R. Grossman [1996] EMBO J 15: 2150–2159).
Temporal Sequence of Cell Wall Disassembly in Rapidly Ripening Melon Fruit1
Authors: Rose Jocelyn K.C. , Hadfield Kristen A. , Labavitch John M. , Bennett Alan B.
Published: July 2002

The Charentais variety of melon (Cucumis melo cv Reticulatus F1 Alpha) was observed to undergo very rapid ripening, with the transition from the preripe to overripe stage occurring within 24 to 48 h. During this time, the flesh first softened and then exhibited substantial disintegration, suggesting that Charentais may represent a useful model system to examine the temporal sequence of changes in cell wall composition that typically take place in softening fruit. The total amount of pectin in the cell wall showed little reduction during ripening but its solubility changed substantially. Initial changes in pectin solubility coincided with a loss of galactose from tightly bound pectins, but preceded the expression of polygalacturonase (PG) mRNAs, suggesting early, PG-independent modification of pectin structure. Depolymerization of polyuronides occurred predominantly in the later ripening stages, and after the appearance of PG mRNAs, suggesting the existence of PG-dependent pectin degradation in later stages. Depolymerization of hemicelluloses was observed throughout ripening, and degradation of a tightly bound xyloglucan fraction was detected at the early onset of softening. Thus, metabolism of xyloglucan that may be closely associated with cellulose microfibrils may contribute to the initial stages of fruit softening. A model is presented of the temporal sequence of cell wall changes during cell wall disassembly in ripening Charentais melon.
Auxin Deprivation Induces Synchronous Golgi Differentiation in Suspension-Cultured Tobacco BY-2 Cells1
Authors: Winicur Zev M. , Feng Zhang Guo , Andrew Staehelin L.
Published: July 2002

To date, the lack of a method for inducing plant cells and their Golgi stacks to differentiate in a synchronous manner has made it difficult to characterize the nature and extent of Golgi retailoring in biochemical terms. Here we report that auxin deprivation can be used to induce a uniform population of suspension-cultured tobacco (Nicotiana tabacum cv BY-2) cells to differentiate synchronously during a 4-d period. Upon removal of auxin, the cells stop dividing, undergo elongation, and differentiate in a manner that mimics the formation of slime-secreting epidermal and peripheral root-cap cells. The morphological changes to the Golgi apparatus include a proportional increase in the number oftrans-Golgi cisternae, a switch to larger-sized secretory vesicles that bud from the trans-Golgi cisternae, and an increase in osmium staining of the secretory products. Biochemical alterations include an increase in large, fucosylated, mucin-type glycoproteins, changes in the types of secreted arabinogalactan proteins, and an increase in the amounts and types of molecules containing the peripheral root-cap-cell-specific epitope JIM 13. Taken together, these findings support the hypothesis that auxin deprivation can be used to induce tobacco BY-2 cells to differentiate synchronously into mucilage-secreting cells.
Conditional Synergism between Cryptochrome 1 and Phytochrome B Is Shown by the Analysis of phyA, phyB, andhy4 Simple, Double, and Triple Mutants in Arabidopsis
Authors: Casal Jorge José , Mazzella Marı́a Agustina
Published: July 2002

Wild-type or phyA,phyB, or hy4 mutant Arabidopsis seedlings lacking phytochrome A (phyA), phytochrome B (phyB), or cryptochrome 1 (cry1), respectively, and the double and triple mutants were used in combination with blue-light treatments given simultaneously with red or far-red light. We investigated the interaction between phytochromes and cry1 in the control of hypocotyl growth and cotyledon unfolding. Under conditions deficient for cry1 (short exposures to blue light) or phyB (far-red background), these photoreceptors acted synergistically: Under short exposures to blue light (3 h/d) added to a red-light background, cry1 activity required phyB (e.g. the hy4 mutant was taller than the wild type but the phyBhy4 mutant was not taller than thephyB mutant). Under prolonged exposures to blue light (24 h/d) added to a far-red light background, phyB activity required cry1 (e.g. the phyAphyB mutant was taller than thephyA mutant but the phyAphyBhy4 mutant was not taller than the phyAhy4 mutant). Under more favorable light inputs, i.e. prolonged exposures to blue light added to a red-light background, the effects of cry1 and phyB were independent. Thus, the synergism between phyB and cry1 is conditional. The effect of cry1 was not reduced by the phyA mutation under any tested light condition. Under continuous blue light the triple mutantphyAphyBhy4 showed reduced hypocotyl growth inhibition and cotyledon unfolding compared with the phyAphyBmutant. The action of cry1 in the phyAphyB double mutant was higher under the red-light than the far-red-light background, indicating a synergistic interaction between cry1 and phytochromes C, D, or E; however, a residual action of cry1 independent of any phytochrome is likely to occur.
Metabolism of Indole-3-Acetic Acid in Arabidopsis1
Authors: Östin Anders , Kowalyczk Mariusz , Bhalerao Rishikesh P. , Sandberg Göran
Published: July 2002

The metabolism of indole-3-acetic acid (IAA) was investigated in 14-d-old Arabidopsis plants grown in liquid culture. After ruling out metabolites formed as an effect of nonsterile conditions, high-level feeding, and spontaneous interconversions, a simple metabolic pattern emerged. Oxindole-3-acetic acid (OxIAA), OxIAA conjugated to a hexose moiety via the carboxyl group, and the conjugates indole-3-acetyl aspartic acid (IAAsp) and indole-3-acetyl glutamate (IAGlu) were identified by mass spectrometry as primary products of IAA fed to the plants. Refeeding experiments demonstrated that none of these conjugates could be hydrolyzed back to IAA to any measurable extent at this developmental stage. IAAsp was further oxidized, especially when high levels of IAA were fed into the system, yielding OxIAAsp and OH-IAAsp. This contrasted with the metabolic fate of IAGlu, since that conjugate was not further metabolized. At IAA concentrations below 0.5 μm, most of the supplied IAA was metabolized via the OxIAA pathway, whereas only a minor portion was conjugated. However, increasing the IAA concentrations to 5 μm drastically altered the metabolic pattern, with marked induction of conjugation to IAAsp and IAGlu. This investigation used concentrations for feeding experiments that were near endogenous levels, showing that the metabolic pathways controlling the IAA pool size in Arabidopsis are limited and, therefore, make good targets for mutant screens provided that precautions are taken to avoid inducing artificial metabolism.
Overexpression of an Arabidopsis cDNA Encoding a Sterol-C241-Methyltransferase in Tobacco Modifies the Ratio of 24-Methyl Cholesterol to Sitosterol and Is Associated with Growth Reduction
Authors: Schaller Hubert , Bouvier-Navé Pierrette , Benveniste Pierre
Published: July 2002

Higher plants synthesize 24-methyl sterols and 24-ethyl sterols in defined proportions. As a first step in investigating the physiological function of this balance, an Arabidopsis cDNA encoding anS-adenosyl-l-methionine 24-methylene lophenol-C241-methyltransferase, the typical plant enzyme responsible for the production of 24-ethyl sterols, was expressed in tobacco (Nicotiana tabacum L.) under the control of a constitutive promoter. Transgenic plants displayed a novel 24-alkyl-Δ5-sterol profile: the ratio of 24-methyl cholesterol to sitosterol, which is close to 1 in the wild type, decreased dramatically to values ranging from 0.01 to 0.31. In succeeding generations of transgenic tobacco, a highS-adenosyl-l-methionine 24-methylene lophenol-C241-methyltransferase enzyme activity and, consequently, a low ratio of 24-methyl cholesterol to sitosterol, was associated with reduced growth compared with the wild type. However, this new morphological phenotype appeared only below the threshold ratio of 24-methyl cholesterol to sitosterol of approximately 0.1. Because the size of cells was unchanged in small, transgenic plants, we hypothesize that a radical decrease of 24-methyl cholesterol and/or a concomitant increase of sitosterol would be responsible for a change in cell division through as-yet unknown mechanisms.
Distribution of Sulfur within Oilseed Rape Leaves in Response to Sulfur Deficiency during Vegetative Growth
Authors: Blake-Kalff Mechteld M.A. , Harrison Kevin R. , Hawkesford Malcolm J. , Zhao Fangjie J. , McGrath Steve P.
Published: July 2002

The distribution of S to sulfate, glucosinolates, glutathione, and the insoluble fraction within oilseed rape (Brassica napus L.) leaves of different ages was investigated during vegetative growth. The concentrations of glutathione and glucosinolates increased from the oldest to the youngest leaves, whereas the opposite was observed for SO4  2−. The concentration of insoluble S was similar among all of the leaves. At sufficient S supply and in the youngest leaves, 2% of total S was allocated to glutathione, 6% to glucosinolates, 50% to the insoluble fraction, and the remainder accumulated as SO4  2−. In the middle and oldest leaves, 70% to 90% of total S accumulated as SO4  2−, whereas glutathione and glucosinolates together accounted for less than 1% of S. When the S supply was withdrawn (minus S), the concentrations of all S-containing compounds, particularly SO4  2−, decreased in the youngest and middle leaves. Neither glucosinolates nor glutathione were major sources of S during S deficiency. Plants grown on nutrient solution containing minus S and low N were less deficient than plants grown on solution containing minus S and high N. The effect of N was explained by differences in growth rate. The different responses of leaves of different ages to S deficiency have to be taken into account for the development of field diagnostic tests to determine whether plants are S deficient.
Rhizosphere Bacteria Enhance Selenium Accumulation and Volatilization by Indian Mustard1
Authors: de Souza Mark P. , Chu Dara , Zhao May , Zayed Adel M. , Ruzin Steven E. , Schichnes Denise , Terry Norman
Published: July 2002

Indian mustard (Brassica juncea L.) accumulates high tissue Se concentrations and volatilizes Se in relatively nontoxic forms, such as dimethylselenide. This study showed that the presence of bacteria in the rhizosphere of Indian mustard was necessary to achieve the best rates of plant Se accumulation and volatilization of selenate. Experiments with the antibiotic ampicillin showed that bacteria facilitated 35% of plant Se volatilization and 70% of plant tissue accumulation. These results were confirmed by inoculating axenic plants with rhizosphere bacteria. Compared with axenic controls, plants inoculated with rhizosphere bacteria had 5-fold higher Se concentrations in roots (the site of volatilization) and 4-fold higher rates of Se volatilization. Plants with bacteria contained a heat-labile compound in their root exudate; when this compound was added to the rhizosphere of axenic plants, Se accumulation in plant tissues increased. Plants with bacteria had an increased root surface area compared with axenic plants; the increased area was unlikely to have caused their increased tissue Se accumulation because they did not accumulate more Se when supplied with selenite or selenomethionine. Rhizosphere bacteria also possibly increased plant Se volatilization because they enabled plants to overcome a rate-limiting step in the Se volatilization pathway, i.e. Se accumulation in plant tissues.
Arabidopsis det2 Is Defective in the Conversion of (24R)-24-Methylcholest-4-En-3-One to (24R)-24-Methyl-5α-Cholestan-3-One in Brassinosteroid Biosynthesis1
Authors: Noguchi Takahiro , Fujioka Shozo , Takatsuto Suguru , Sakurai Akira , Yoshida Shigeo , Li Jianming , Chory Joanne
Published: July 2002

Previously, we have shown that the Arabidopsis det2(deetiolated2) mutant is defective in the biosynthesis of brassinosteroids (BR) and that DET2 (a steroid 5α-reductase) acts early in the proposed BR biosynthetic pathway. In this paper we present further biochemical characterization of det2. We have undertaken metabolic experiments with 2H-labeled substrates of intermediates involved in the formation of campestanol from campesterol, and quantitative analysis of intermediates in Arabidopsis wild type anddet2. The results of these studies indicate the early operating steps of BR biosynthesis as: campesterol → 4-en-3β-ol → 4-en-3-one → 3-one → campestanol in Arabidopsis, withdet2 deficient in the conversion of 4-en-3-one to 3-one. We have also detected these intermediates in the formation of campestanol from campesterol and their metabolic conversions using cultured cells of Catharanthus roseus. These studies confirmed the biosynthetic sequence of events from campesterol to campestanol as was found in Arabidopsis. As such, the originally proposed biosynthetic pathway should be modified.
Cadmium Tolerance and Accumulation in Indian Mustard Is Enhanced by Overexpressing γ-Glutamylcysteine Synthetase
Authors: Zhu Yong Liang , Pilon-Smits Elizabeth A.H. , Tarun Alice S. , Weber Stefan U. , Jouanin Lise , Terry Norman
Published: July 2002

To investigate rate-limiting factors for glutathione and phytochelatin (PC) production and the importance of these compounds for heavy metal tolerance, Indian mustard (Brassica juncea) was genetically engineered to overexpress the Escherichia coli gshI gene encoding γ-glutamylcysteine synthetase (γ-ECS), targeted to the plastids. The γ-ECS transgenic seedlings showed increased tolerance to Cd and had higher concentrations of PCs, γ-GluCys, glutathione, and total non-protein thiols compared with wild-type (WT) seedlings. When tested in a hydroponic system, γ-ECS mature plants accumulated more Cd than WT plants: shoot Cd concentrations were 40% to 90% higher. In spite of their higher tissue Cd concentration, the γ-ECS plants grew better in the presence of Cd than WT. We conclude that overexpression of γ-ECS increases biosynthesis of glutathione and PCs, which in turn enhances Cd tolerance and accumulation. Thus, overexpression of γ-ECS appears to be a promising strategy for the production of plants with superior heavy metal phytoremediation capacity.
Altering Expression of Cinnamic Acid 4-Hydroxylase in Transgenic Plants Provides Evidence for a Feedback Loop at the Entry Point into the Phenylpropanoid Pathway
Authors: Blount Jack W. , Korth Kenneth L. , Masoud Sameer A. , Rasmussen Susanne , Lamb Chris , Dixon Richard A.
Published: July 2002

Pharmacological evidence implicates trans-cinnamic acid as a feedback modulator of the expression and enzymatic activity of the first enzyme in the phenylpropanoid pathway, l-phenylalanine ammonia-lyase (PAL). To test this hypothesis independently of methods that utilize potentially non-specific inhibitors, we generated transgenic tobacco lines with altered activity levels of the second enzyme of the pathway, cinnamic acid 4-hydroxylase (C4H), by sense or antisense expression of an alfalfa C4H cDNA. PAL activity and levels of phenylpropanoid compounds were reduced in leaves and stems of plants in which C4H activity had been genetically down-regulated. However, C4H activity was not reduced in plants in which PAL activity had been down-regulated by gene silencing. In crosses between a tobacco line over-expressing PAL from a bean PAL transgene and a C4H antisense line, progeny populations harboring both the bean PAL sense and C4H antisense transgenes had significantly lower extractable PAL activity than progeny populations harboring the PAL transgene alone. Our data provide genetic evidence for a feedback loop at the entry point into the phenylpropanoid pathway that had previously been inferred from potentially artifactual pharmacological experiments.
Gibberellin Requirement for Arabidopsis Seed Germination Is Determined Both by Testa Characteristics and Embryonic Abscisic Acid
Authors: Debeaujon Isabelle , Koornneef Maarten
Published: July 2002

The mechanisms imposing a gibberellin (GA) requirement to promote the germination of dormant and non-dormant Arabidopsis seeds were analyzed using the GA-deficient mutant ga1, several seed coat pigmentation and structure mutants, and the abscisic acid (ABA)-deficient mutant aba1. Testa mutants, which exhibit reduced seed dormancy, were not resistant to GA biosynthesis inhibitors such as tetcyclacis and paclobutrazol, contrarily to what was found before for other non-dormant mutants in Arabidopsis. However, testa mutants were more sensitive to exogenous GAs than the wild-types in the presence of the inhibitors or when transferred to a GA-deficient background. The germination capacity of thega1-1 mutant could be integrally restored, without the help of exogenous GAs, by removing the envelopes or by transferring the mutation to a tt background (tt4 and ttg1). The double mutants still required light and chilling for dormancy breaking, which may indicate that both agents can have an effect independently of GA biosynthesis. The ABA biosynthesis inhibitor norflurazon was partially efficient in releasing the dormancy of wild-type and mutant seeds. These results suggest that GAs are required to overcome the germination constraints imposed both by the seed coat and ABA-related embryo dormancy.
Gibberellins and Seed Development in Maize. I. Evidence That Gibberellin/Abscisic Acid Balance Governs Germination versus Maturation Pathways
Authors: White Constance N. , Proebsting William M. , Hedden Peter , Rivin Carol J.
Published: July 2002

Abscisic acid (ABA) is required for the regulation of seed maturation in maize (Zea mays L.). Mutants blocked in ABA synthesis (such asviviparous-5) do not mature to quiescent, desiccation-tolerant seeds, but germinate on the ear midway through kernel development. Because gibberellins (GA) and ABA act antagonistically in many aspects of plant development, we hypothesized that ABA antagonizes a positive GA signal for precocious germination in maize. In these experiments, we show that a GA deficiency early in seed development, induced genetically or via biosynthesis inhibitors, suppresses vivipary in ABA-deficient developing kernels. The resulting seeds have both desiccation tolerance and storage longevity. Temporal analysis of GA accumulation in wild-type kernels revealed the accumulation of bioactive GA1 and GA3 prior to the peak in ABA content. We speculate that these GAs stimulate a developmental program leading to vivipary in the absence of normal amounts of ABA, and that a reduction of GA content re-establishes an ABA/GA ratio appropriate for suppression of germination and induction of maturation. In contrast, the induction of a GA deficiency did not suppress vivipary in viviparous-1 mutant kernels, suggesting that VP1 acts downstream of both GA and ABA in programming seed development.
The Expression of Small Heat Shock Proteins in Seeds Responds to Discrete Developmental Signals and Suggests a General Protective Role in Desiccation Tolerance
Authors: Wehmeyer Nadja , Vierling Elizabeth
Published: July 2002

To learn more about the function and regulation of small heat shock proteins (sHSPs) during seed development, we studied sHSP expression in wild-type and seed maturation mutants of Arabidopsis by western analysis and using an HSP17.4 promoter-driven β-glucuronidase (GUS) reporter gene in transgenic plants. In the absence of stress, GUS activity increases during development until the entire embryo is stained before desiccation. Heat-stressed embryos stained for GUS at all stages, including early stages that showed no detectable HSP17.4::GUS activity without heat. Examination of HSP17.4 expression in seeds of the transcriptional activator mutants abi3-6,fus3-3 (AIMS no. CS8014/N8014), andlec1-2 (AIMS no. CS2922/N2922) showed that protein and HSP17.4::GUS activity were highly reduced infus3-3 and lec1-2 and undetectable inabi3-6 seeds. In contrast, heat-stressedabi3-6, fus3-3, and lec1-2seeds stained for GUS activity throughout the embryo. These data indicate that there is distinct developmental and stress regulation of HSP17.4, and imply that ABI3 activates HSP17.4 transcription during development. Quantitation of sHSP protein in desiccation-intolerant seeds of abi3-6, fus3-3,lec1-2, and line24 showed that all had <2% of wild-type HSP17.4 levels. In contrast, the desiccation-tolerant but embryo-defective mutants emb266(AIMS no. CS3049/N3049) and lec2-1 (AIMS no. CS2728/N2728) had wild-type levels of HSP17.4. These data correlate a reduction in sHSPs with desiccation intolerance and suggest that sHSPs have a general protective role throughout the seed.
Octadecanoid-Derived Alteration of Gene Expression and the “Oxylipin Signature” in Stressed Barley Leaves. Implications for Different Signaling Pathways
Authors: Kramell Robert , Miersch Otto , Atzorn Rainer , Parthier Benno , Wasternack Claus
Published: July 2002

Stress-induced gene expression in barley (Hordeum vulgare cv Salome) leaves has been correlated with temporally changing levels of octadecanoids and jasmonates, quantified by means of gas chromatography/mass spectrometry-single ion monitoring. Application of sorbitol-induced stress led to a low and transient rise of jasmonic acid (JA), its precursor 12-oxophytodienoic acid (OPDA), and the methyl esters JAME and OPDAME, respectively, followed by a large increase in their levels. JA and JAME peaked between 12 and 16 h, about 4 h before OPDA and OPDAME. However, OPDA accumulated up to a 2.5-fold higher level than the other compounds. Dihomo-JA and 9,13-didehydro-OPDA were identified as minor components. Kinetic analyses revealed that a transient threshold of jasmonates or octadecanoids is necessary and sufficient to initiate JA-responsive gene expression. Although OPDA and OPDAME applied exogenously were metabolized to JA in considerable amounts, both of them can induce gene expression, as evidenced by those genes that did not respond to endogenously formed JA. Also, coronatine induces JA-responsive genes independently from endogenous JA. Application of deuterated JA showed that endogenous synthesis of JA is not induced by JA treatment. The data are discussed in terms of distinct signaling pathways.
Mutation of Arabidopsis Plastid Phosphoglucose Isomerase Affects Leaf Starch Synthesis and Floral Initiation
Authors: Yu Tien-Shin , Lue Wei-Ling , Wang Shue-Mei , Chen Jychian
Published: July 2002

We isolated pgi1-1, an Arabidopsis mutant with a decreased plastid phospho-glucose (Glc) isomerase activity. Whilepgi1-1 mutant has a deficiency in leaf starch synthesis, it accumulates starch in root cap cells. It has been shown that a plastid transporter for hexose phosphate transports cytosolic Glc-6-P into plastids and expresses restricted mainly to the heterotrophic tissues. The decreased starch content in leaves of thepgi1-1 mutant indicates that cytosolic Glc-6-P cannot be efficiently transported into chloroplasts to complement the mutant's deficiency in chloroplastic phospho-Glc isomerase activity for starch synthesis. We cloned the Arabidopsis PGI1 gene and showed that it encodes the plastid phospho-Glc isomerase. The pgi1-1allele was found to have a single nucleotide substitution, causing a Ser to Phe transition. While the flowering times of the Arabidopsis starch-deficient mutants pgi1, pgm1, andadg1 were similar to that of the wild type under long-day conditions, it was significantly delayed under short-day conditions. The pleiotropic phenotype of late flowering conferred by these starch metabolic mutations suggests that carbohydrate metabolism plays an important role in floral initiation.
AXR2 Encodes a Member of the Aux/IAA Protein Family
Authors: Nagpal Punita , Walker Loni M. , Young Jeff C. , Sonawala Ami , Timpte Candace , Estelle Mark , Reed Jason W.
Published: July 2002

The dominant gain-of-function axr2-1 mutation of Arabidopsis causes agravitropic root and shoot growth, a short hypocotyl and stem, and auxin-resistant root growth. We have cloned theAXR2 gene using a map-based approach, and find that it is the same as IAA7, a member of the IAA(indole-3-acetic acid) family of auxin-inducible genes. Theaxr2-1 mutation changes a single amino acid in conserved domain II of AXR2/IAA7. We isolated loss-of-function mutations inAXR2/IAA7 as intragenic suppressors ofaxr2-1 or in a screen for insertion mutations inIAA genes. A null mutant has a slightly longer hypocotyl than wild-type plants, indicating that AXR2/IAA7 controls development in light-grown seedlings, perhaps in concert with other gene products. Dark-grown axr2-1 mutant plants have short hypocotyls and make leaves, suggesting that activation of AXR2/IAA7 is sufficient to induce morphological responses normally elicited by light. Previously described semidominant mutations in two other Arabidopsis IAA genes cause some of the same phenotypes as axr2-1, but also cause distinct phenotypes. These results illustrate functional differences among members of the Arabidopsis IAA gene family.
AN9, a Petunia Glutathione S-Transferase Required for Anthocyanin Sequestration, Is a Flavonoid-Binding Protein
Authors: Mueller Lukas A. , Goodman Christopher D. , Silady Rebecca A. , Walbot Virginia
Published: July 2002

AN9 is a glutathione S-transferase from petunia (Petunia hybrida) required for efficient anthocyanin export from the site of synthesis in the cytoplasm into permanent storage in the vacuole. For many xenobiotics it is well established that a covalent glutathione (GSH) tag mediates recognition of molecules destined for vacuolar sequestration by a tonoplast-localized ATP-binding cassette pump. Here we inquired whether AN9 catalyzes the formation of GSH conjugates with flavonoid substrates. Using high-performance liquid chromatography analysis of reaction mixtures containing enzyme, GSH, and flavonoids, including anthocyanins, we could detect neither conjugates nor a decrease in the free thiol concentration. These results suggest that no conjugate is formed in vitro. However, AN9 was shown to bind flavonoids using three assays: inhibition of the glutathione S-transferase activity of AN9 toward the common substrate 1-chloro 2,4-dinitrobenzene, equilibrium dialysis, and tryptophan quenching. We conclude that AN9 is a flavonoid-binding protein, and propose that in vivo it serves as a cytoplasmic flavonoid carrier protein.
Linear β-1,3 Glucans Are Elicitors of Defense Responses in Tobacco
Authors: Klarzynski Olivier , Plesse Bertrand , Joubert Jean-Marie , Yvin Jean-Claude , Kopp Marguerite , Kloareg Bernard , Fritig Bernard
Published: July 2002

Laminarin, a linear β-1,3 glucan (mean degree of polymerization of 33) was extracted and purified from the brown alga Laminaria digitata. Its elicitor activity on tobacco (Nicotiana tabacum) was compared to that of oligogalacturonides with a mean degree of polymerization of 10. The two oligosaccharides were perceived by suspension-cultured cells as distinct chemical stimuli but triggered a similar and broad spectrum of defense responses. A dose of 200 μg mL−1 laminarin or oligogalacturonides induced within a few minutes a 1.9-pH-units alkalinization of the extracellular medium and a transient release of H2O2. After a few hours, a strong stimulation of Phe ammonia-lyase, caffeic acid O-methyltransferase, and lipoxygenase activities occurred, as well as accumulation of salicylic acid. Neither of the two oligosaccharides induced tissue damage or cell death nor did they induce accumulation of the typical tobacco phytoalexin capsidiol, in contrast with the effects of the proteinaceous elicitor β-megaspermin. Structure activity studies with laminarin, laminarin oligomers, high molecular weight β-1,3–1,6 glucans from fungal cell walls, and the β-1,6–1,3 heptaglucan showed that the elicitor effects observed in tobacco with β-glucans are specific to linear β-1,3 linkages, with laminaripentaose being the smallest elicitor-active structure. In accordance with its strong stimulating effect on defense responses in tobacco cells, infiltration of 200 μg mL−1 laminarin in tobacco leaves triggered accumulation within 48 h of the four families of antimicrobial pathogenesis-related proteins investigated. Challenge of the laminarin-infiltrated leaves 5 d after treatment with the soft rot pathogen Erwinia carotovora subsp.carotovora resulted in a strong reduction of the infection when compared with water-treated leaves.
Cellular Localization of Isoprenoid Biosynthetic Enzymes inMarchantia polymorpha. Uncovering a New Role of Oil Bodies
Authors: Suire Claude , Bouvier Florence , Backhaus Ralph A. , Bégu Dominique , Bonneu Marc , Camara Bilal
Published: July 2002

Like seed plants, liverworts synthesize and accumulate a myriad of isoprenoid compounds. Using antibodies raised against several isoprenoid biosynthetic enzymes, we investigated their intracellular compartmentation by in situ immunolocalization from Marchantia polymorpha. The enzymes examined were deoxy-xylulose phosphate synthase, geranyl diphosphate synthase, farnesyl diphosphate synthase, geranylgeranyl diphosphate synthase, monoterpene synthase, geranylgeranyl diphosphate reductase, phytoene synthase, and phytoene desaturase. Our results show that liverwort oil bodies, which are organelles bound by a single unit membrane, possess isoprenoid biosynthetic enzymes similar to those found in plastids and the cytosol. We postulate that oil bodies play a dynamic role in cell metabolism in addition to their role as sites of essential oil accumulation and sequestration. The occurrence of such enzymes in different cellular compartments might be due to multiple targeting of gene products to various organelles.
Non-Targeted and Targeted Protein Movement through Plasmodesmata in Leaves in Different Developmental and Physiological States
Authors: Crawford Katrina M. , Zambryski Patricia C.
Published: July 2002

Plant cells rely on plasmodesmata for intercellular transport of small signaling molecules as well as larger informational macromolecules such as proteins. A green fluorescent protein (GFP) reporter and low-pressure microprojectile bombardment were used to quantify the degree of symplastic continuity between cells of the leaf at different developmental stages and under different growth conditions. Plasmodesmata were observed to be closed to the transport of GFP or dilated to allow the traffic of GFP. In sink leaves, between 34% and 67% of the cells transport GFP (27 kD), and between 30% and 46% of the cells transport double GFP (54 kD). In leaves in transition transport was reduced; between 21% and 46% and between 2% and 9% of cells transport single and double GFP, respectively. Thus, leaf age dramatically affects the ability of cells to exchange proteins nonselectively. Further, the number of cells allowing GFP or double GFP movement was sensitive to growth conditions because greenhouse-grown plants exhibited higher diffusion rates than culture-grown plants. These studies reveal that leaf cell plasmodesmata are dynamic and do not have a set size exclusion limit. We also examined targeted movement of the movement protein of tobacco mosaic virus fused to GFP, P30::GFP. This 58-kD fusion protein localizes to plasmodesmata, consistently transits from up to 78% of transfected cells, and was not sensitive to developmental age or growth conditions. The relative number of cells containing dilated plasmodesmata varies between different species of tobacco, with Nicotiana clevelandii exhibiting greater diffusion of proteins thanNicotiana tabacum.
A Biophysical Analysis of Stem and Root Diameter Variations in Woody Plants
Authors: Génard Michel , Fishman Svetlana , Vercambre Gilles , Huguet Jean-Gérard , Bussi Claude , Besset Jacques , Habib Robert
Published: July 2002

A comprehensive model of stem and root diameter variation was developed. The stem (or root) was represented using two coaxial cylinders corresponding with the mature xylem and the extensible tissues. The extensible tissues were assumed to behave as a single cell separated from the mature xylem by a virtual membrane. The mature xylem and the extensible tissues are able to dilate with temperature and grow. Moreover, the extensible tissues are able to shrink and swell according to water flow intensity. The model is mainly based on the calculation of water volume flows in the “single cell” that are described using the principles of irreversible thermodynamics. The elastic response to storage volume and plastic extension accompanying growth are described. The model simulates diameter variation due to temperature, solute accumulation, and xylem, water potential. The model was applied to the peach (Prunus persica) stem and to the plum (Prunus domestica × Prunus spinosa) root. The simulation outputs corresponded well with the diameter variation observed. The model predicts that variations of turgor pressure and osmotic potential are smaller than the variations of xylem water potential. It also demonstrates correlations between the xylem water potential, the turgor pressure, the elastic modulus, and the osmotic potential. The relationship between the diameter and the xylem water potential exhibits a subtential hysteresis, as observed in field data. A sensitivity analysis using the model parameters showed that growth and shrinkage were highly sensitive to the initial values of the turgor pressure and to the reflection coefficient of solutes. Shrinkage and growth were sensitive to elastic modulus and wall-yielding threshold pressure, respectively. The model was not sensitive to changes in temperature.
Novel Patterns of Ectopic Cell Plate Growth and Lipid Body Distribution in the Arabidopsis gemini pollen1Mutant
Authors: Park Soon Ki , Twell David
Published: July 2002

The nature of aberrant gametophytic cell divisions and altered pollen cell fate in the gemini pollen1(gem1) mutant was investigated through ultrastructural analysis. The earliest noticeable defect in gem1 was the appearance of extended membrane profiles at the early bicellular stage. These were replaced by ectopic internal walls, which divided the cytoplasm into twin or multiple cell compartments. Complete or partial internal walls were callosic with highly complex profiles, indicating failed guidance or deregulated cell plate growth. Extended membrane profiles and delayed callose synthesis at division sites further suggested a novel pattern of cell plate assembly ingem1. Multiple cell compartments in gem1adopted vegetative cell fate with regard to lipid body distribution. In the wild type, lipid bodies appear specifically in the vegetative cell, whereas in gem1, lipid bodies accumulated in all cytoplasmic compartments. Our results support the hypothesis that altered pollen cell fate in gem1 results from abnormal inheritance of cell fate determinants as a result of disturbed cytokinesis.
BIN2, a New Brassinosteroid-Insensitive Locus in Arabidopsis
Authors: Li Jianming , Nam Kyoung Hee , Vafeados Dionne , Chory Joanne
Published: July 2002

Brassinosteroids (BRs) play important roles throughout plant development. Although many genes have been identified that are involved in BR biosynthesis, genetic approaches in Arabidopsis have led to the identification of only one gene, BRI1, that encodes a membrane receptor for BRs. To expand our knowledge of the molecular mechanism(s) of plant steroid signaling, we analyzed many dwarf and semidwarf mutants collected from our previous genetic screens and identified a semidwarf mutant that showed little response to exogenous BR treatments. Genetic analysis of the bin2(BR-INSENSITIVE 2) mutant indicated that the BR-insensitive dwarf phenotype was due to a semidominant mutation in the BIN2 gene that mapped to the middle of chromosome IV between the markers CH42 and AG. A direct screening for similar semidwarf mutants resulted in the identification of a second allele of the BIN2 gene. Despite some novel phenotypes observed with the bin2/+ mutants, the homozygousbin2 mutants were almost identical to the well-characterized bri1 mutants that are defective in BR perception. In addition to the BR-insensitive dwarf phenotype,bin2 mutants exhibited BR insensitivity when assayed for root growth inhibition and feedback inhibition of CPDgene expression. Furthermore, bin2 mutants displayed an abscisic acid-hypersensitive phenotype that is shared by thebri1 and BR-deficient mutants. A gene dosage experiment using triploid plants suggested that the bin2 phenotypes were likely caused by either neomorphic or hypermorphic gain-of-function mutations in the BIN2 gene. Thus, the two bin2 mutations define a novel genetic locus whose gene product might play a role in BR signaling.
The Chinese learner – a question of style
Authors: Chan Sally
Published: July 2002

This paper challenges any misconceptions that Westerners may have about Chinese learning styles by highlighting how the Chinese mind operates and why certain styles of learning are preferred by Chinese students. The author discusses some of the reasons for the over‐emphasis on education for the Chinese overseas, how cultural values and beliefs have helped to shape Chinese thinking and how typical classroom behaviour has been developed over centuries of rote/repetitive learning. The problems that Western educators may face when teaching Chinese students is also considered, such as the lack of abstract thinking, constraints on behaviour caused by face, the over‐emphasis on concrete examples, lack of creativity, and the need to compromise in group situations. The author suggests that further understanding is needed to unravel the mystery of the Chinese learner before Western educators can fully appreciate the different approaches to learning and design better educational programmes for Chinese students on management courses.
HRM in practice
Authors: Gall Gregor
Published: July 2002

Returns to a case study of a newspaper company introducing HRM
presented five years earlier in this journal. Looks at all the editorial
offices of the company and examines the extent to which the company has
succeeded in implementing HRM and what this has meant for a key section
of its employees, the journalists. Discusses the consequences of HRM for
journalists′ union rights, wages and conditions. Shows that the extent
to which HRM has been implemented has been dependent on force and
conditions not created by the company and that the journalists′ union
rights have been curbed and their wages and conditions diminished. The
material was derived from extensive face‐to‐face interviews with lay and
full‐time union officials and company managers.
Muddle in the middle: organizational restructuring and middle management careers
Authors: Newell Helen , Dopson Sue
Published: July 2002

Considers the extent to which one organization through rationalization and redundancy programmes has violated its psychological contracts with its middle manager employees by removing the prospect of a traditional career. Offers a review of the issues raised in the literature on careers and the psychological contract and a case study of the impact of change on individual middle managers. Describes the empirical work carried out in British Telecom on which the article is based. Concludes that both the nature of middle management jobs and the career opportunities available have changed considerably, resulting in breaches of the psychological contract. However, individual managers have reacted differently to the changes, depending on their ability and willingness to pursue informal networks and personal contacts.
Perceptions of the older employee: is anything really changing?
Authors: Lyon Phil , Pollard David
Published: July 2002

Investigates whether the recent emphasis on persuading employers to abandon ageist attitudes and appoint or promote on merit, irrespective of the applicant’s age, has been justified by comparing the results of the 1992 Institute of Personnel Management survey with those from 221 post‐experience management students from a survey carried out in 1995. In this preliminary analysis of the data, major points of similarity and divergence are examined to see if a “new generation” of managers are thinking in substantially different ways on this long‐standing labour market issue.
Preservation and Library Management
Authors: Eden Paul , Feather John , Matthews Graham
Published: July 2002

Discusses the results of a questionnaire survey into preservation
policies and practice in British libraries, focusing on responsibility
for preservation, preservation policies, disaster control planning,
staff training and user education, co‐operative initiatives, factors
inhibiting preservation activity and spending on preservation. Findings
indicate that preservation is considered most applicable to special
collections and to rare or valuable items, and that funding is a major
problem even in libraries with a strong commitment to preservation.
Increased activity in areas such as disaster control planning indicate a
greater awareness of preservation issues than in the past. Highlights
the advantages of written preservation policies and the success of
co‐operative initiatives such as Newsplan, suggesting that a national
preservation policy would enable libraries to take a more rational
approach to problems such as what to preserve and funding allocation,
while helping to clarify their national heritage responsibilities.
The effects of cross‐cultural training on the acculturation process of the global workforce
Authors: Zakaria Norhayati
Published: July 2002

Cross‐cultural training is fast becoming a recognizably important component in the world of international business. This paper discusses the effectiveness of cross‐cultural training in facilitating the process of acculturation, and in developing the culture‐specific and culture‐general skills needed to increase the sociocultural and psychological adjustments of sojourners and expatriates when they encounter a foreign culture. A new cross‐cultural training model is created by integrating acculturation and training effectiveness models. This new model suggests that providing two different types of training program prior to cultural contact will help recipients to effectively modify existing culture‐general and culture‐specific skills. As a consequence, they will achieve a higher degree of sociocultural and psychological adjustment. Experiential training should trigger affective and behavioral responses, which are the basis of intercultural effectiveness skills, and thus enhance psychological adjustment. By contrast, cognitive training should trigger cognitive responses, especially cultural awareness and interpersonal skills, and enhance sociocultural adjustment.
Design and implementation of an aided fruit‐harvesting robot (Agribot)
Authors: Ceres R. , Pons J.L. , Jiménez A.R. , Martín J.M. , Calderón L.
Published: July 2002

This work presents a robot prototype designed and built for a new aided fruit‐harvesting strategy in highly unstructured environments, involving human‐machine task distribution. The operator drives the robotic harvester and performs the detection of fruits by means of a laser range‐finder, the computer performs the precise location of the fruits, computes adequate picking sequences and controls the motion of all the mechanical components (picking arm and gripper‐cutter). Throughout this work, the specific design of every module of the robotized fruit harvester is presented. The harvester has been built and laboratory tests with artificial trees were conducted to check range‐finder’s localization accuracy and dependence on external conditions, harvesting arm’s velocity, positioning accuracy and repeatability; and gripper‐cutter performance. Results show excellent range‐finder and harvesting arm operation, while a bottleneck is detected in gripper‐cutter performance. Some figures showing overall performance are given.
Polychronicity and the Inventory of Polychronic Values (IPV)
Authors: Bluedorn Allen C. , Kalliath Thomas J. , Strube Michael J , Martin Gregg D.
Published: July 2002

The ten‐item Inventory of Polychronic Values (IPV), a psychometric measure of polychronicity (the extent to which people in a culture prefer to be engaged in two or more tasks or events simultaneously and believe their preference is the best way to do things), was developed using data from 11 samples (N = 2,190) collected from bank employees, undergraduate students, hospital personnel, dentists and their staffs, and state agency managers. Principal components, alpha, correlation, and confirmatory factor analyses supported the IPV in its internal consistency, test‐retest reliability, content adequacy, construct validity (both discriminant and convergent), and nomological validity.
The resource‐based view of the firm: some stumbling‐blocks on the road to understanding sustainable competitive advantage
Authors: Fahy John
Published: July 2002

The resource‐based view of the firm (RBV) is an important, emerging theory of firm heterogeneity. It is well grounded in industrial economics and has benefited in its development from a multiplicity of contributions by management writers. But like any developing body of knowledge, it is not short of confusion, ambiguity and conceptual and empirical difficulties. This paper provides an integrated review of the resource‐based view of the firm in an effort to eliminate much of the ambiguity caused by weak taxonomies and the inconsistent and conflicting use of terminology. It provides a detailed insight into the logic of the RBV and illuminates its contributions to the debate on the nature of competitive advantage. The paper then evaluates the status of some ongoing debates that are germane to our understanding of competitive advantage and outlines prospective directions for the development of the resource‐based view.