bluuebunny/crossref_metadata_2025 huggingface dataset:
Parallel Changes in H2O2 and Catalase during Thermotolerance Induced by Salicylic Acid or Heat Acclimation in Mustard Seedlings1
Authors: Dat James F. , Lopez-Delgado Humberto , Foyer Christine H. , Scott Ian M.
Published: July 2002

Spraying mustard (Sinapis alba L.) seedlings with salicylic acid (SA) solutions between 10 and 500 μm significantly improved their tolerance to a subsequent heat shock at 55°C for 1.5 h. The effects of SA were concentration dependent, with higher concentrations failing to induce thermotolerance. The time course of thermotolerance induced by 100 μm SA was similar to that obtained with seedlings acclimated at 45°C for 1 h. We examined the hypothesis that induced thermotolerance involved H2O2. Heat shock at 55°C caused a significant increase in endogenous H2O2 and reduced catalase activity. A peak in H2O2 content was observed within 5 min of either SA treatment or transfer to the 45°C acclimation temperature. Between 2 and 3 h after SA treatment or heat acclimation, both H2O2 and catalase activity significantly decreased below control levels. The lowered H2O2 content and catalase activity occurred in the period of maximum thermoprotection. It is suggested that thermoprotection obtained either by spraying SA or by heat acclimation may be achieved by a common signal transduction pathway involving an early increase in H2O2.
Galactosylononitol and Stachyose Synthesis in Seeds of Adzuki Bean1
Authors: Peterbauer Thomas , Richter Andreas
Published: July 2002

Stachyose synthase (STS) (EC 2.4.1.67) was purified to homogeneity from mature seeds of adzuki bean (Vigna angularis). Electrophoresis under denaturing conditions revealed a single polypeptide of 90 kD. Size-exclusion chromatography of the purified enzyme yielded two activity peaks with apparent molecular masses of 110 and 283 kD. By isoelectric focusing and chromatofocusing the protein was separated into several active forms with isoelectric point values between pH 4.7 and 5.0. Purified STS catalyzed the transfer of the galactosyl group from galactinol to raffinose andmyo-inositol. Additionally, the enzyme catalyzed the galactinol-dependent synthesis of galactosylononitol from d-ononitol. The synthesis of a galactosylcyclitol by STS is a new oberservation. Mutual competitive inhibition was observed when the enzyme was incubated with both substrates (raffinose and ononitol) simultaneously. Galactosylononitol could also substitute for galactinol in the synthesis of stachyose from raffinose. Although galactosylononitol was the less-efficient donor, the Michaelis constant value for raffinose was lower in the presence of galactosylononitol (13.2 mm) compared with that obtained in the presence of galactinol (38.6 mm). Our results indicate that STS catalyzes the biosynthesis of galactosylononitol, but may also mediate a redistribution of galactosyl residues from galactosylononitol to stachyose.
The Expression of Light-Regulated Genes in the High-Pigment-1 Mutant of Tomato1
Authors: Peters Janny L. , Széll Márta , Kendrick Richard E.
Published: July 2002

Three light-regulated genes, chlorophyll a/b-binding protein (CAB), ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit, and chalcone synthase (CHS), are demonstrated to be up-regulated in the high-pigment-1 (hp-1) mutant of tomato (Lycopersicon esculentum Mill.) compared with wild type (WT). However, the pattern of up-regulation of the three genes depends on the light conditions, stage of development, and tissue studied. Compared with WT, the hp-1 mutant showed higher CAB gene expression in the dark after a single red-light pulse and in the pericarp of immature fruits. However, in vegetative tissues of light-grown seedlings and adult plants, CAB mRNA accumulation did not differ between WT and the hp-1mutant. The ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit mRNA accumulated to a higher level in thehp-1 mutant than WT under all light conditions and tissues studied, whereas CHS gene expression was up-regulated in de-etiolated vegetative hp-1-mutant tissues only. The CAB and CHS genes were shown to be phytochrome regulated and both phytochrome A and B1 play a role in CAB gene expression. These observations support the hypothesis that the HP-1 protein plays a general repressive role in phytochrome signal transduction.
Purification and Characterization of NADP+-Linked Isocitrate Dehydrogenase from Scots Pine
Authors: Palomo Jesús , Gallardo Fernando , Suárez Maria F. , Cánovas Francisco M.
Published: July 2002

NADP+-isocitrate dehydrogenase (NADP+-IDH; EC 1.1.1.42) is involved in the supply of 2-oxoglutarate for ammonia assimilation and glutamate synthesis in higher plants through the glutamine synthetase/glutamate synthase (GS/GOGAT) cycle. Only one NADP+-IDH form of cytosolic localization was detected in green cotyledons of pine (Pinus spp.) seedlings. The pine enzyme was purified and exhibited molecular and kinetic properties similar to those described for NADP+-IDH from angiosperm, with a higher catalytic efficiency (105  m  −1s−1) than the deduced efficiencies for GS and GOGAT in higher plants. A polyclonal antiserum was raised against pine NADP+-IDH and used to assess protein expression in the seedlings. Steady-state levels of NADP+-IDH were coordinated with GS during seed germination and were associated with GS/GOGAT enzymes during chloroplast biogenesis, suggesting that NADP+-IDH is involved in the provision of carbon skeletons for the synthesis of nitrogen-containing molecules. However, a noncoordinated pattern of NADP+-IDH and GS/GOGAT was observed in advanced stages of cotyledon development and in the hypocotyl. A detailed analysis in hypocotyl sections revealed that NADP+-IDH abundance was inversely correlated with the presence of GS, GOGAT, and ribulose-1,5-bisphosphate carboxylase/oxygenase but was associated with the differentiation of the organ. These results cannot be explained by the accepted role of the enzyme in nitrogen assimilation and strongly suggest that NADP+-IDH may have other, as-yet-unknown, biological functions.
Comparative Analysis of the Regulation of Expression and Structures of Two Evolutionarily Divergent Genes for Δ1-Pyrroline-5-Carboxylate Synthetase from Tomato
Authors: Fujita Tomomichi , Maggio Albino , Garcia-Rios Mario , Bressan Ray A. , Csonka Laszlo N.
Published: July 2002

We isolated two tomato (Lycopersicon esculentum) cDNA clones, tomPRO1 and tomPRO2, specifying Δ1-pyrroline-5-carboxylate synthetase (P5CS), the first enzyme of proline (Pro) biosynthesis. tomPRO1 is unusual because it resembles prokaryotic polycistronic operons (M.G. Garcı́a-Rı́os, T. Fujita, P.C. LaRosa, R.D. Locy, J.M. Clithero, R.A. Bressan, L.N. Csonka [1997] Proc Natl Acad Sci USA 94: 8249–8254), whereas tomPRO2 encodes a full-length P5CS. We analyzed the accumulation of Pro and the tomPRO1and tomPRO2 messages in response to NaCl stress and developmental signals. Treatment with 200 mm NaCl resulted in a >60-fold increase in Pro levels in roots and leaves. However, there was a <3-fold increase in the accumulation of thetomPRO2 message and no detectable induction in the level of the tomPRO1 message in response to NaCl stress. Although pollen contained approximately 100-fold higher levels of Pro than other plant tissues, there was no detectable increase in the level of either message in pollen. We conclude that transcriptional regulation of these genes for P5CS is probably not important for the osmotic or pollen-specific regulation of Pro synthesis in tomato. Using restriction fragment-length polymorphism mapping, we determined the locations of tomPRO1 and tomPRO2 loci in the tomato nuclear genome. Sequence comparison suggested thattomPRO1 is similar to prokaryotic P5CS loci, whereastomPRO2 is closely related to other eukaryotic P5CS genes.
The First Step of Gibberellin Biosynthesis in Pumpkin Is Catalyzed by at Least Two Copalyl Diphosphate Synthases Encoded by Differentially Regulated Genes
Authors: Smith Maria W. , Yamaguchi Shinjiro , Ait-Ali Tahar , Kamiya Yuji
Published: July 2002

The first step in gibberellin biosynthesis is catalyzed by copalyl diphosphate synthase (CPS) and ent-kaurene synthase. We have cloned from pumpkin (Cucurbita maxima L.) two cDNAs, CmCPS1 and CmCPS2, that each encode a CPS. Both recombinant fusion CmCPS proteins were active in vitro. CPS are translocated into plastids and processed by cleavage of transit peptides. For CmCPS1 andCmCPS2, the putative transit peptides cannot exceed the first 99 and 107 amino acids, respectively, because longer N-terminal deletions abolished activity. Levels of both CmCPStranscripts were strictly regulated in an organ-specific and developmental manner. Both transcripts were almost undetectable in leaves and were abundant in petioles. CmCPS1 transcript levels were high in young cotyledons and low in roots. In contrast,CmCPS2 transcripts were undetectable in cotyledons but present at significant levels in roots. In hypocotyls, apices, and petioles, CmCPS1 transcript levels decreased with age much more rapidly than those of CmCPS2. We speculate that CmCPS1 expression is correlated with the early stages of organ development, whereasCmCPS2 expression is correlated with subsequent growth. In contrast, C. maxima ent-kaurene synthase transcripts were detected in every organ at almost constant levels. Thus,ent-kaurene biosynthesis may be regulated through control of CPS expression.
Arachidonic Acid Alters Tomato HMG Expression and Fruit Growth and Induces 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase-Independent Lycopene Accumulation1
Authors: Rodrı́guez-Concepción Manuel , Gruissem Wilhelm
Published: July 2002

Regulation of isoprenoid end-product synthesis required for normal growth and development in plants is not well understood. To investigate the extent to which specific genes for the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) are involved in end-product regulation, we manipulated expression of theHMG1 and HMG2 genes in tomato (Lycopersicon esculentum) fruit using arachidonic acid (AA). In developing young fruit AA blocked fruit growth, inhibitedHMG1, and activated HMG2 expression. These results are consistent with other reports indicating thatHMG1 expression is closely correlated with growth processes requiring phytosterol production. In mature-green fruit AA strongly induced the expression of HMG2,PSY1 (the gene for phytoene synthase), and lycopene accumulation before the normal onset of carotenoid synthesis and ripening. The induction of lycopene synthesis was not blocked by inhibition of HMGR activity using mevinolin, suggesting that cytoplasmic HMGR is not required for carotenoid synthesis. Our results are consistent with the function of an alternative plastid isoprenoid pathway (the Rohmer pathway) that appears to direct the production of carotenoids during tomato fruit ripening.
The Arabidopsis CBF Gene Family Is Composed of Three Genes Encoding AP2 Domain-Containing Proteins Whose Expression Is Regulated by Low Temperature but Not by Abscisic Acid or Dehydration1
Authors: Medina Joaquı́n , Bargues Mónica , Terol Javier , Pérez-Alonso Manuel , Salinas Julio
Published: July 2002

We have identified two genes from Arabidopsis that show high similarity withCBF1, a gene encoding an AP2 domain-containing transcriptional activator that binds to the low-temperature-responsive element CCGAC and induces the expression of some cold-regulated genes, increasing plant freezing tolerance. These two genes, which we have named CBF2 and CBF3, also encode proteins containing AP2 DNA-binding motifs. Furthermore, like CBF1, CBF2 and CBF3 proteins also include putative nuclear-localization signals and potential acidic activation domains. The CBF2 andCBF3 genes are linked to CBF1,constituting a cluster on the bottom arm of chromosome IV. The high level of similarity among the three CBF genes, their tandem organization, and the fact that they have the same transcriptional orientation all suggest a common origin.CBF1, CBF2, and CBF3 show identical expression patterns, being induced very rapidly by low-temperature treatment. However, in contrast to most of the cold-induced plant genes characterized, they are not responsive to abscisic acid or dehydration. Taken together, all of these data suggest that CBF2 and CBF3 may function as transcriptional activators, controlling the level of low-temperature gene expression and promoting freezing tolerance through an abscisic acid-independent pathway.
Glycerol Is a Suberin Monomer. New Experimental Evidence for an Old Hypothesis1
Authors: Moire Laurence , Schmutz Alain , Buchala Antony , Yan Bin , Stark Ruth E. , Ryser Ulrich
Published: July 2002

The monomer composition of the esterified part of suberin can be determined using gas chromatography-mass spectroscopy technology and is accordingly believed to be well known. However, evidence was presented recently indicating that the suberin of green cotton (Gossypium hirsutum cv Green Lint) fibers contains substantial amounts of esterified glycerol. This observation is confirmed in the present report by a sodium dodecyl sulfate extraction of membrane lipids and by a developmental study, demonstrating the correlated accumulation of glycerol and established suberin monomers. Corresponding amounts of glycerol also occur in the suberin of the periderm of cotton stems and potato (Solanum tuberosum) tubers. A periderm preparation of wound-healing potato tuber storage parenchyma was further purified by different treatments. As the purification proceeded, the concentration of glycerol increased at about the same rate as that of α,ω-alkanedioic acids, the most diagnostic suberin monomers. Therefore, it is proposed that glycerol is a monomer of suberins in general and can cross-link aliphatic and aromatic suberin domains, corresponding to the electron-translucent and electron-opaque suberin lamellae, respectively. This proposal is consistent with the reported dimensions of the electron-translucent suberin lamellae.
Posttranscriptional Gene Silencing in Transgenic Sugarcane. Dissection of Homology-Dependent Virus Resistance in a Monocot That Has a Complex Polyploid Genome1
Authors: Ingelbrecht Ivan L. , Irvine James E. , Mirkov T. Erik
Published: July 2002

RNA-mediated, posttranscriptional gene silencing has been determined as the molecular mechanism underlying transgenic virus resistance in many plant virus-dicot host plant systems. In this paper we show that transgenic virus resistance in sugarcane (Saccharum spp. hybrid) is based on posttranscriptional gene silencing. The resistance is derived from an untranslatable form of the sorghum mosaic potyvirus strain SCH coat protein (CP) gene. Transgenic sugarcane plants challenged with sorghum mosaic potyvirus strain SCH had phenotypes that ranged from fully susceptible to completely resistant, and a recovery phenotype was also observed. Clones derived from the same transformation event or obtained after vegetative propagation could display different levels of virus resistance, suggesting the involvement of a quantitative component in the resistance response. Most resistant plants displayed low or undetectable steady-state CP transgene mRNA levels, although nuclear transcription rates were high. Increased DNA methylation was observed in the transcribed region of the CP transgenes in most of these plants. Collectively, these characteristics indicate that an RNA-mediated, homology-dependent mechanism is at the base of the virus resistance. This work extends posttranscriptional gene silencing and homology-dependent virus resistance, so far observed only in dicots, to an agronomically important, polyploid monocot.
Expansins Are Conserved in Conifers and Expressed in Hypocotyls in Response to Exogenous Auxin1
Authors: Hutchison Keith W. , Singer Patricia B. , McInnis Stephanie , Diaz-Sala Carmen , Greenwood Michael S.
Published: July 2002

Differential display reverse transcription-polymerase chain reaction was used to detect the induction of gene expression during adventitious root formation in loblolly pine (Pinus taeda) after treatment with the exogenous auxin indole-3-butyric acid. A BLAST search of the GenBank database using one of the clones obtained revealed very strong similarity to the α-expansin gene family in angiosperms. A near-full-length loblolly pine α-expansin sequence was obtained using 5′- and 3′-rapid amplification of cDNA end cloning, and the deduced amino acid sequence was highly conserved relative to those of angiosperm expansins. Northern analysis indicates that α-expansin mRNA expression increases 50- to 100-fold in the base of hypocotyl stem cuttings from loblolly pine seedlings in response to indole-3-butyric acid, with peak expression occurring 24 to 48 h after induction.
Functional Characterization and Expression Analysis of the Amino Acid Permease RcAAP3 from Castor Bean1
Authors: Neelam Anil , Marvier Allison C. , Hall J.L. , Williams Lorraine E.
Published: July 2002

A polymerase chain reaction-based library screening procedure was used to isolate RcAAP3, an amino acid permease cDNA from castor bean (Ricinus communis). RcAAP3 is 1.7 kb in length, with an open reading frame that encodes a protein with a calculated molecular mass of 51 kD. Hydropathy analysis indicates that the RcAAP3 protein is highly hydrophobic in nature with nine to 11 putative transmembrane domains. RcAAP3-mediated uptake of citrulline in a yeast transport mutant showed saturable kinetics with aKm of 0.4 mm. Transport was higher at acidic pH and was inhibited by the protonophore carbonylcyanide-m-chlorophenylhydrazone, suggesting a proton-coupled transport mechanism. Citrulline uptake was strongly inhibited (72%) by the permeable sulfydryl reagentN-ethylmaleimide, but showed lower sensitivity (30% inhibition) to the nonpermeable reagentp-chloromercuribenzenesulfonic acid. Diethylpyrocarbonate, a histidine modifier, inhibited citrulline uptake by 80%. A range of amino acids inhibited citrulline uptake, suggesting that RcAAP3 may be a broad substrate permease that can transport neutral and basic amino acids with a lower affinity for acidic amino acids. Northern analysis indicated that RcAAP3 is widely expressed in source and sink tissues of castor bean, and that the pattern of expression is distinct from RcAAP1 andRcAAP2.
Gibberellin Biosynthesis in Maize. Metabolic Studies with GA15, GA24, GA25, GA7, and 2,3-Dehydro-GA9
Authors: Davis Gordon , Kobayashi Masatomo , Phinney Bernard O. , Lange Theo , Croker Steve J. , Gaskin Paul , MacMillan Jake
Published: July 2002

[17-14C]-Labeled GA15, GA24, GA25, GA7, and 2,3-dehydro-GA9 were separately injected into normal,dwarf-1 (d1), and dwarf-5 (d5) seedlings of maize (Zea mays L.). Purified radioactive metabolites from the plant tissues were identified by full-scan gas chromatography-mass spectrometry and Kovats retention index data. The metabolites from GA15 were GA44, GA19, GA20, GA113, and GA15-15,16-ene (artifact?). GA24 was metabolized to GA19, GA20, and GA17. The metabolites from GA25 were GA17, GA25 16α,17-H2-17-OH, and HO-GA25 (hydroxyl position not determined). GA7was metabolized to GA30, GA3, isoGA3 (artifact?), and trace amounts of GA7-diene-diacid (artifact?). 2,3-Dehydro-GA9was metabolized to GA5, GA7 (trace amounts), 2,3-dehydro-GA10 (artifact?), GA31, and GA62. Our results provide additional in vivo evidence of a metabolic grid in maize (i.e. pathway convergence). The grid connects members of a putative, non-early 3,13-hydroxylation branch pathway to the corresponding members of the previously documented early 13-hydroxylation branch pathway. The inability to detect the sequence GA12 → GA15 → GA24 → GA9 indicates that the non-early 3,13-hydroxylation pathway probably plays a minor role in the origin of bioactive gibberellins in maize.
Physiological Implications of the Kinetics of Maize Leaf Phosphoenolpyruvate Carboxylase
Authors: Tovar-Méndez Alejandro , Mújica-Jiménez Carlos , Muñoz-Clares Rosario A.
Published: July 2002

It has been a common practice to assay phosphoenolpyruvate carboxylase (PEPC) under high, nonphysiological concentrations of Mg2+ and bicarbonate. We have performed kinetic studies on the enzyme from maize (Zea mays) leaves at near physiological levels of free Mg2+ (0.4 mm) and bicarbonate (0.1 mm), and found that both the nonphosphorylated and phosphorylated enzymes exhibited a high degree of cooperativity in the binding of phosphoenolpyruvate, a much lower affinity for this substrate and for activators, and a greater affinity for malate than at high concentrations of these ions. Inhibition of the phosphorylated enzyme by malate was overcome by glycine or alanine but not by glucose-6-phosphate, either in the absence or presence of high concentrations of glycerol, a compatible solute. Alanine caused significant activation at physiological concentrations, suggesting a pivotal role for this amino acid in regulating maize leaf PEPC activity. Our results showed that the maximum enzyme activity attainable in vivo would be less than 50% of that attainable in vitro under optimum conditions. Therefore, the high levels of PEPC protein in the cytosol of C4 mesophyll cells might be an adaptation for sustaining the steady-state rate of flux through the photosynthetic CO2 assimilation pathway despite the limitations imposed by the PEPC kinetic properties and the conditions of its environment.
Internal Conductance to CO2 Diffusion and C18OO Discrimination in C3 Leaves
Authors: Gillon Jim S. , Yakir Dan
Published: July 2002

18O discrimination in CO2 stems from the oxygen exchange between 18O-enriched water and CO2 in the chloroplast, a process catalyzed by carbonic anhydrase (CA). A proportion of this 18O-labeled CO2 escapes back to the atmosphere, resulting in an effective discrimination against C18OO during photosynthesis (Δ18O). By constraining the δ18O of chloroplast water (δe) by analysis of transpired water and the extent of CO2-H2O isotopic equilibrium (θeq) by measurements of CA activity (θeq = 0.75–1.0 for tobacco, soybean, and oak), we could apply measured Δ18O in a leaf cuvette attached to a mass spectrometer to derive the CO2 concentration at the physical limit of CA activity, i.e. the chloroplast surface (c  cs). From the CO2 drawdown sequence between stomatal cavities from gas exchange (c  i), from Δ18O (c  cs), and at Rubisco sites from Δ13C (c  c), the internal CO2 conductance (g  i) was partitioned into cell wall (g  w) and chloroplast (g  ch) components. The results indicated that g  ch is variable (0.42–1.13 mol m−2 s−1) and proportional to CA activity. We suggest that the influence of CA activity on the CO2 assimilation rate should be important mainly in plants with low internal conductances.
Tissue-Preferential Expression of a Rice α-Tubulin Gene,OsTubA1, Mediated by the First Intron
Authors: Jeon Jong-Seong , Lee Sichul , Jung Ki-Hong , Jun Sung-Hoon , Kim Chanhong , An Gynheung
Published: July 2002

The genomic clone encoding an α-tubulin,OsTubA1, has been isolated from rice (Oryza sativa L.). The gene consists of four exons and three introns. RNA-blot analysis showed that the gene is strongly expressed in actively dividing tissues, including root tips, young leaves, and young flowers. Analysis of chimeric fusions between OsTubA1and β-glucuronidase (GUS) revealed that the intron 1 was required for high-level GUS expression in actively dividing tissues, corresponding with normal expression pattern ofOsTubA1. Fusion constructs lacking the intron 1 showed more GUS staining in mature tissues rather than young tissues. When the intron 1 was placed at the distal region from 5′-upstream region or at the 3′-untranslated region, no enhancement of GUS expression was observed. Sequential deletions of the OsTubA1 intron 1 brought about a gradual reduction of GUS activity in calli. These results suggest that tissue-preferential expression of theOsTubA1 gene is mediated by the intron 1 and that it may be involved in a mechanism for an efficient RNA splicing that is position dependent.
Female Reproductive Tissues Are the Primary Target ofAgrobacterium-Mediated Transformation by the Arabidopsis Floral-Dip Method
Authors: Desfeux Christine , Clough Steven J. , Bent Andrew F.
Published: July 2002

The floral-dip method for Agrobacterium-mediated transformation of Arabidopsis allows efficient plant transformation without need for tissue culture. To facilitate use with other plant species, we investigated the mechanisms that underlie this method. In manual outcrossing experiments, application of Agrobacterium tumefaciens to pollen donor plants did not produce any transformed progeny, whereas application ofAgrobacterium to pollen recipient plants yielded transformants at a rate of 0.48%. Agrobacterium strains with T-DNA carrying gusA (encoding β-glucuronidase [GUS]) under the control of 35S, LAT52, or ACT11 promoters revealed delivery of GUS activity to developing ovules, whereas no GUS staining of pollen or pollen tubes was observed. Transformants derived from the same seed pod contained independent T-DNA integration events. In Arabidopsis flowers, the gynoecium develops as an open, vase-like structure that fuses to form closed locules roughly 3 d prior to anthesis. In correlation with this fact, we found that the timing ofAgrobacterium infection was critical. Transformants were obtained and GUS staining of ovules and embryo sacs was observed only if the Agrobacterium were applied 5 d or more prior to anthesis. A 6-fold higher rate of transformation was obtained with a CRABS-CLAW mutant that maintains an open gynoecium. Our results suggest that ovules are the site of productive transformation in the floral-dip method, and further suggest that Agrobacterium must be delivered to the interior of the developing gynoecium prior to locule closure if efficient transformation is to be achieved.
Involvement of Polyamines in the Chilling Tolerance of Cucumber Cultivars
Authors: Shen Wenyun , Nada Kazuyoshi , Tachibana Shoji
Published: July 2002

The possible involvement of polyamines (PAs) in the chilling tolerance of cucumber (Cucumis sativus L. cv Jinchun No. 3 and cv Suyo) was investigated. Plants with the first expanded leaves were exposed to 3°C or 15°C in the dark for 24 h (chilling), and then transferred to 28°C/22°C under a 12-h photoperiod for another 24 h (rewarming). Chilling-tolerant cv Jinchun No. 3 showed a marked increase of free spermidine (Spd) in leaves, once during chilling and again during rewarming. Putrescine increased significantly during rewarming, but the increase of spermine was slight. Any of these PAs did not increase in chilling-sensitive cv Suyo during either period. PA-biosynthetic enzyme activities appear to mediate these differences between cultivars. Pretreatment of Spd to cv Suyo prevented chill-induced increases in the contents of hydrogen peroxide in leaves and activities of NADPH oxidases and NADPH-dependent superoxide generation in microsomes and alleviated chilling injury. Pretreatment of methylglyoxal-bis-(guanylhydrazone), a PA biosynthesis inhibitor, to chilled cv Jinchun No. 3 prevented Spd increase and enhanced microsomal NADPH oxidase activity and chilling injury. The results suggest that Spd plays important roles in chilling tolerance of cucumber, probably through prevention of chill-induced activation of NADPH oxidases in microsomes.
Gene Induction of Stilbene Biosynthesis in Scots Pine in Response to Ozone Treatment, Wounding, and Fungal Infection
Authors: Chiron Hélène , Drouet Alain , Lieutier François , Payer Hans-Dieter , Ernst Dieter , Sandermann Heinrich
Published: July 2002

TheS-adenosyl-l-methionine:pinosylvin-O-methyltransferase (PMT)2 gene was sequenced from Scots pine (Pinus sylvestris). The open reading frame is arranged in two exons spaced by one 102-bp intron. Promoter regulatory elements such as two “CAAT” boxes and one “TATA” box were identified. Several cis-regulatory elements were recognized: stress-responsive elements (Myb-responsive elements) as well as G, H, and GC boxes. Moreover, elicitor-responsive elements (W boxes) and a sequence resembling the simian virus 40 enhancer core were found. In phloem and needles of control trees, the transcripts of stilbene synthase (STS) and PMT were hardly detectable. Increased ozone fumigation up to 0.3 μL L−1 enhanced the transcript level of STSand PMT in needles but not in healthy phloem. Wounding, e.g. mock inoculation, of stem-phloem was characterized by a transient increase in STS and PMT transcripts, which was more pronounced in the case of fungal inoculation. Combination of fungal-challenge or mock treatment with ozone resulted in a positive interaction at 0.3 μL L−1. Scots pine stilbene formation appeared to be induced via STS andPMT gene expression upon ozone and fungal stress as well as wounding. The broad stress-responsiveness is in agreement with the range of various cis-acting elements detected in the STSand PMT promoters.
Efficient Screening of Arabidopsis T-DNA Insertion Lines Using Degenerate Primers
Authors: Young Jeffery C. , Krysan Patrick J. , Sussman Michael R.
Published: July 2002

The sequencing of the Arabidopsis plant genome is providing a fuller understanding of the number and types of plant genes. However, in most cases we do not know which genes are responsible for specific metabolic and signal transduction pathways. Analysis of gene function is also often confounded by the presence of multiple isoforms of the gene of interest. Recent advances in PCR-based reverse genetic techniques have allowed the search for plants carrying T-DNA insertions in any gene of interest. Here we report preliminary screening results from an ordered population of nearly 60,470 independently derived T-DNA lines. Degenerate PCR primers were used on large DNA pools (n = 2,025 T-DNA lines) to screen for more than one gene family member at a time. Methods are presented that facilitated the identification and isolation of isoform-specific mutants in almost all members of the Arabidopsis H+-proton ATPase gene family. Multiple mutant alleles were found for several isoforms.
The Arabidopsis ISR1 Locus Controlling Rhizobacteria-Mediated Induced Systemic Resistance Is Involved in Ethylene Signaling
Authors: Ton Jurriaan , Davison Sylke , Van Wees Saskia C.M. , Van Loon L.C. , Pieterse Corné M.J.
Published: July 2002

In Arabidopsis, the rhizobacterial strain Pseudomonas fluorescens WCS417r triggers an induced systemic resistance (ISR) response that is effective against different types of pathogens. The ISR signaling pathway functions independent of salicylic acid, but requires responsiveness to jasmonate (JA) and ethylene. Using the genetic variability of ISR inducibility between Arabidopsis accessions, we recently identified a locus (ISR1) on chromosome III that is involved in ISR signaling. Accessions RLD and Wassilewskija (Ws) are recessive at the ISR1 locus and are, therefore, unable to develop ISR. Here we investigated whether theISR1 locus is involved in JA or ethylene signaling. Compared with the ISR-inducible accession Columbia (Col), accessions RLD and Ws were not affected in JA-induced inhibition of root growth and expression of the JA-responsive gene Atvsp, suggesting that the ISR1 locus is not involved in JA signaling. However, RLD and Ws showed an affected expression of the triple response and a reduced expression of the ethylene responsive genes Hel and Pdf1.2 after exogenous application of the ethylene precursor 1-aminocyclopropane-1-carboxylate. Moreover, in contrast to Col, RLD and Ws did not develop resistance against P. syringaepv. tomato DC3000 after treatment of the leaves with 1-aminocyclopropane-1-carboxylate. Analysis of the F2 and F3 progeny of a cross between Col (ISR1/ISR1) and RLD (isr1/isr1) revealed that reduced sensitivity to ethylene cosegregates with the recessive alleles of theISR1 locus. These results suggest that theISR1 locus encodes a component of the ethylene response, which is required for the expression of rhizobacteria-mediated ISR.
Cabbage Cryoprotectin Is a Member of the Nonspecific Plant Lipid Transfer Protein Gene Family
Authors: Hincha Dirk K. , Neukamm Birgit , Sror Hany A.M. , Sieg Frank , Weckwarth Wolfgang , Rückels Markus , Lullien-Pellerin Valérie , Schröder Werner , Schmitt Jürgen M.
Published: July 2002

We have recently purified a protein (cryoprotectin) from the leaves of cold-acclimated cabbage (Brassica oleracea) to electrophoretic homogeneity, which protects thylakoids isolated from the leaves of nonacclimated spinach (Spinacia oleracea) from freeze-thaw damage. Sequencing of cryoprotectin showed the presence of at least three isoforms of WAX9 proteins, which belong to the class of nonspecific lipid transfer proteins. Antibodies raised against two synthetic peptides derived from the WAX9 proteins recognized a band of approximately 10 kD in western blots of crude cryoprotectin preparations. This protein and the cryoprotective activity could be precipitated from solution by the antiserum. We show further that cryoprotectin is structurally and functionally different from WAX9 isolated from the surface wax of cabbage leaves. WAX9 has lipid transfer activity for phosphatidylcholine, but no cryoprotective activity. Cryoprotectin, on the other hand, has cryoprotective, but no lipid transfer activity. The cryoprotective activity of cryoprotectin was strictly dependent on Ca2+ and Mn2+ and could be inhibited by chelating agents, whereas the lipid transfer activity of WAX9 was higher in the presence of ethylenediaminetetraacetate than in the presence of Ca2+and Mn2+.
Amyloplasts That Sediment in Protonemata of the MossCeratodon purpureus Are Nonrandomly Distributed in Microgravity
Authors: Kern Volker D. , Smith Jeffrey D. , Schwuchow Jochen M. , Sack Fred D.
Published: July 2002

Little is known about whether or how plant cells regulate the position of heavy organelles that sediment toward gravity. Dark-grown protonemata of the moss Ceratodon purpureus displays a complex plastid zonation in that only some amyloplasts sediment along the length of the tip cell. If gravity is the major force determining the position of amyloplasts that sediment, then these plastids should be randomly distributed in space. Instead, amyloplasts were clustered in the subapical region in microgravity. Cells rotated on a clinostat on earth had a roughly similar non-random plastid distribution. Subapical clusters were also found in ground controls that were inverted and kept stationary, but the distribution profile differed considerably due to amyloplast sedimentation. These findings indicate the existence of as yet unknown endogenous forces and mechanisms that influence amyloplast position and that are normally masked in stationary cells grown on earth. It is hypothesized that a microtubule-based mechanism normally compensates forg-induced drag while still allowing for regulated amyloplast sedimentation.
Enzymes That Scavenge Reactive Oxygen Species Are Down-Regulated Prior to Gibberellic Acid-Induced Programmed Cell Death in Barley Aleurone
Authors: Fath Angelika , Bethke Paul C. , Jones Russell L.
Published: July 2002

Gibberellins (GAs) initiate a series of events that culminate in programmed cell death, whereas abscisic acid (ABA) prevents this process. Reactive oxygen species (ROS) are key elements in aleurone programmed cell death. Incubation of barley (Hordeum vulgare) aleurone layers in H2O2 causes rapid death of all cells in GA- but not ABA-treated layers. Sensitivity to H2O2 in GA-treated aleurone cells results from a decreased ability to metabolize ROS. The amounts and activities of ROS scavenging enzymes, including catalase (CAT), ascorbate peroxidase, and superoxide dismutase are strongly down-regulated in aleurone layers treated with GA. CAT activity, protein, andCat2 mRNA decline rapidly following exposure of aleurone layers to GA. In ABA-treated layers, on the other hand, the amount and activity of CAT and Cat2 mRNA increases. Incubation in ABA maintains high amounts of ascorbate peroxidase and superoxide dismutase, whereas GA brings about a rapid reduction in the amounts of these enzymes. These data imply that GA-treated cells loose their ability to scavenge ROS and that this loss ultimately results in oxidative damage and cell death. ABA-treated cells, on the other hand, maintain their ability to scavenge ROS and remain viable.
Genetic Control of Natural Variation in Arabidopsis Glucosinolate Accumulation
Authors: Kliebenstein Daniel J. , Kroymann Juergen , Brown Paul , Figuth Antje , Pedersen Deana , Gershenzon Jonathan , Mitchell-Olds Thomas
Published: July 2002

Glucosinolates are biologically active secondary metabolites of the Brassicaceae and related plant families that influence plant/insect interactions. Specific glucosinolates can act as feeding deterrents or stimulants, depending upon the insect species. Hence, natural selection might favor the presence of diverse glucosinolate profiles within a given species. We determined quantitative and qualitative variation in glucosinolates in the leaves and seeds of 39 Arabidopsis ecotypes. We identified 34 different glucosinolates, of which the majority are chain-elongated compounds derived from methionine. Polymorphism at only five loci was sufficient to generate 14 qualitatitvely different leaf glucosinolate profiles. Thus, there appears to be a modular genetic system regulating glucosinolate profiles in Arabidopsis. This system allows the rapid generation of new glucosinolate combinations in response to changing herbivory or other selective pressures. In addition to the qualitative variation in glucosinolate profiles, we found a nearly 20-fold difference in the quantity of total aliphatic glucosinolates and were able to identify a single locus that controls nearly three-quarters of this variation.
Class I β-1,3-Glucanase and Chitinase Are Expressed in the Micropylar Endosperm of Tomato Seeds Prior to Radicle Emergence
Authors: Wu Chun-Ta , Leubner-Metzger Gerhard , Meins Frederick , Bradford Kent J.
Published: July 2002

β-1,3-Glucanase (EC 3.2.1.39) and chitinase (EC 3.2.1.14) mRNAs, proteins, and enzyme activities were expressed specifically in the micropylar tissues of imbibed tomato (Lycopersicon esculentum Mill.) seeds prior to radicle emergence. RNA hybridization and immunoblotting demonstrated that both enzymes were class I basic isoforms. β-1,3-Glucanase was expressed exclusively in the endosperm cap tissue, whereas chitinase localized to both endosperm cap and radicle tip tissues. β-1,3-Glucanase and chitinase appeared in the micropylar tissues of gibberellin-deficient gib-1tomato seeds only when supplied with gibberellin. Accumulation of β-1,3-glucanase mRNA, protein and enzyme activity was reduced by 100 μM abscisic acid, which delayed or prevented radicle emergence but not endosperm cap weakening. In contrast, expression of chitinase mRNA, protein, and enzyme activity was not affected by abscisic acid. Neither of these enzymes significantly hydrolyzed isolated tomato endosperm cap cell walls. Although both β-1,3-glucanase and chitinase were expressed in tomato endosperm cap tissue prior to radicle emergence, we found no evidence that they were directly involved in cell wall modification or tissue weakening. Possible functions of these hydrolases during tomato seed germination are discussed.
Ozone Quenching Properties of Isoprene and Its Antioxidant Role in Leaves
Authors: Loreto Francesco , Mannozzi Michela , Maris Christophe , Nascetti Pamela , Ferranti Francesco , Pasqualini Stefania
Published: July 2002

Isoprene is formed in and emitted by plants and the reason for this apparent carbon waste is still unclear. It has been proposed that isoprene stabilizes cell and particularly chloroplast thylakoid membranes. We tested if membrane stabilization or isoprene reactivity with ozone induces protection against acute ozone exposures. The reduction of visible, physiological, anatomical, and ultrastructural (chloroplast) damage shows that clones of plants sensitive to ozone and unable to emit isoprene become resistant to acute and short exposure to ozone if they are fumigated with exogenous isoprene, and that isoprene-emitting plants that are sensitive to ozone do not suffer damage when exposed to ozone. Isoprene-induced ozone resistance is associated with the maintenance of photochemical efficiency and with a low energy dissipation, as indicated by fluorescence quenching. This suggests that isoprene effectively stabilizes thylakoid membranes. However, when isoprene reacts with ozone within the leaves or in a humid atmosphere, it quenches the ozone concentration to levels that are less or non-toxic for plants. Thus, protection from ozone in plants fumigated with isoprene may be due to a direct ozone quenching rather than to an induced resistance at membrane level. Irrespective of the mechanism, isoprene is one of the most effective antioxidants in plants.
Functional Conservation of Plant Secondary Metabolic Enzymes Revealed by Complementation of Arabidopsis Flavonoid Mutants with Maize Genes
Authors: Dong Xiaoyun , Braun Edward L. , Grotewold Erich
Published: July 2002

Mutations in the transparent testa(tt) loci abolish pigment production in Arabidopsis seed coats. The TT4, TT5, andTT3 loci encode chalcone synthase, chalcone isomerase, and dihydroflavonol 4-reductase, respectively, which are essential for anthocyanin accumulation and may form a macromolecular complex. Here, we show that the products of the maize (Zea mays)C2, CHI1, and A1 genes complement Arabidopsis tt4, tt5, andtt3 mutants, restoring the ability of these mutants to accumulate pigments in seed coats and seedlings. Overexpression of the maize genes in wild-type Arabidopsis seedlings does not result in increased anthocyanin accumulation, suggesting that the steps catalyzed by these enzymes are not rate limiting in the conditions assayed. The expression of the maize A1 gene in the flavonoid 3′ hydroxylase Arabidopsis tt7 mutant resulted in an increased accumulation of pelargonidin. We conclude that enzymes involved in secondary metabolism can be functionally exchangeable between plants separated by large evolutionary distances. This is in sharp contrast to the notion that the more relaxed selective constrains to which secondary metabolic pathways are subjected is responsible for the rapid divergence of the corresponding enzymes.
Mainshafts for the Trent
Authors: Ford Terry
Published: July 2002

Reports on the development of the Super CMV mainshaft for the Trent class jet engine from Rolls‐Royce. Describes in depth how the new mainshaft was designed to outperform the earlier generations. In comparison with the previous generation, the new mainshaft, through the use of improved materials, is able to cope with approximately twice the amount of torque transmitted to the fan, has a shaft weight per unit of transmitted torque ratio of 25 per cent less, a diameter that is similar in size, and yet was still able to be manufactured at a similar cost. Also reports on the increase in fatigue lives for the shaft oil holes and splines that was achieved through design improvements.
How corrosion affects industry and life
Authors: Javaherdashti Reza
Published: July 2002

Corrosion management principles, along with conventional technical solutions to corrosion problems in industry, can be utilized to mitigate corrosion and its resulting problems.
Meat consumption and vegetarianism among young adults in the UK
Authors: Beardsworth Alan , Bryman Alan
Published: July 2002

This article is based on a six‐year survey of first year undergraduates and their meat consumption. The main focus is vegetarianism and the declining consumption of red meat over the past two decades. The levels of meat consumption and avoidance were analysed by gender, father’s occupation, voting intention and the reasons given for reduction/avoidance. The results found that the majority of vegetarians were women, although they were also the majority of the sample. Age, political inclination and social class appear to have had little bearing on meat consumption. There is also the suggestion that vegetarianism has reached a plateau. A wide range of further studies is suggested.
Functional foods: some relevant considerations?
Authors: Ovesen Lars
Published: July 2002

An unambiguous and agreed definition of what a functional food is does not exist. However, broadly speaking, a food is said to be functional if it contains a food component which affects one or more targeted functions of the body in a positive way. Functional foods often fall into the grey area between foods and medicine, but from a regulatory standpoint they are foods and consequently subject to food regulations. According to the food labelling directive, it is not permitted to label a food in such a way that, first, it will attribute the property of preventing, treating and curing human disease, or refer to such properties, and second, that it can mislead the consumer. The first aspect refers to the claims a food product may carry and specifically prohibits health claims – even if scientifically valid. It is argued that a claim on a food is a health claim if the consumer perceives it as such. The second aspect states that a given claim must be validated by sufficient scientific evidence, and far too often associations between food intake and disease risk have been misinterpreted as causal relations.
Management training and development at Aeroquip‐Vickers, Inc.: a process model – part 2
Authors: LaHote David , Simonetti Jack L. , Longenecker Clinton O.
Published: July 2002

The second part of the article aims to show how the principles established during the evolution of the management development program at Aeroquip‐Vickers can be applied to other organizations. In particular, the design of each manager’s individual development program is a responsibility shared between the organization and the manager themselves. It was also found that most managers remember and learnt most from real, challenging situations they had to deal with and development programs need to recognise this by incorporating challenging assignments and opportunities as well as training and education.
Developing core skills – lessons from Germany and Sweden
Authors: Gibbons‐Wood David , Lange Thomas
Published: July 2002

Examines the experiences of Germany and Sweden in their attempts to develop core skills and key competencies among trainees and young employees. Particular attention is devoted to vocational training as a promising school‐to‐work transition process, which stimulates and supports the development of core skills. Some case study material (Germany) and relevant policy responses (Sweden) have also been used to go beyond mere theoretical considerations and to provide some practical help and guidance when it comes to defining, implementing, assessing and administering the concepts of core skills and key competencies. In particular, the paper highlights the importance of employer enthusiasm in the development and delivery of core skills.
Workplace learning: its potential and limitations
Authors: Billett Stephen
Published: July 2002

The workplace is now commonly used as a setting for acquiring vocational knowledge. This situated approach to learning offers access to authentic vocational activities and the guidance of more expert others. However, questions about the effectiveness of workplace learning processes need to be addressed. These questions are central to the evaluation and improvement of learning arrangements which aim to develop vocational skills. Draws on the findings of three recent studies of workplace learning conducted in Queensland, Australia, in order to address questions about the efficacy of workplace learning. Uses these studies to understand further potential and limitations of these learning arrangements.
Information architecture
Authors: Carter Hayley
Published: July 2002

Most organisations, in spite of the attention and investment focused on ERP software, have a number of discrete computer systems that operate independently of one another. In addition to the problems of unmanageability, this results in an inability to fully exploit the information resources available. The concept of an information architecture, which draws on the architectural profession, is an attempt to focus discipline on the design and building of information systems, to facilitate prioritisation and decision making, in support of business strategy.