bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purification and Characterization of a Low-Molecular-Weight Phospholipase A2 from Developing Seeds of Elm1
Authors: Ståhl Ulf , Ek Bo , Stymne Sten 
Published: July 2002

Abstract
Phospholipase A2(PLA2) was purified about 180,000 times compared with the starting soluble-protein extract from developing elm (Ulmus glabra) seeds. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified fraction showed a single protein band with a mobility that corresponded to 15 kD, from which activity could be recovered. When analyzed by matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry, the enzyme had a deduced mass of 13,900 D. A 53-amino acid-long N-terminal sequence was determined and aligned with other sequences, giving 62% identity to the deduced amino acid sequence of some rice (Oryza sativa) expressed sequence tag clones. The purified enzyme had an alkaline pH optimum and required Ca2+ for activity. It was unusually stable with regard to heat, acidity, and organic solvents but was sensitive to disulfide bond-reducing agents. The enzyme is a true PLA2, neither hydrolyzing the sn-1 position of phosphatidylcholine nor having any activity toward lysophosphatidylcholine or diacylglycerol. The biochemical data and amino acid sequence alignments indicate that the enzyme is related to the well-characterized family of animal secretory PLA2s and, to our knowledge, is the first plant enzyme of this type to be described.
The Superoxide Synthases of Rose Cells1
Authors: Murphy Terence M. , Vu Han , Nguyen Thuyhuong 
Published: July 2002

Abstract
In an effort to identify the enzymatic mechanism responsible for the synthesis of reactive oxygen species produced during the hypersensitive response, preparations of rose (Rosa damascena) cell plasma membranes, partially solubilized plasma membrane protein, and cytosol were assayed for the NADH- and NADPH-dependent synthesis of superoxide using assays for the reduction of cytochrome c (Cyt c), assays for the reduction of nitroblue tetrazolium, and assays for the chemiluminescence ofN,N′-dimethyl-9,9′-biacridium dinitrate (lucigenin). Each assay ascribed the highest activity to a different preparation: the Cyt c assay to cytosol, the nitroblue tetrazolium assay to plasma membrane, and the lucigenin assay to the partially solubilized plasma membrane protein (with NADH). This suggests that no two assays measure the same set of enzymes and that none of the assays is suitable for comparisons of superoxide synthesis among different cell fractions. With the plasma membrane preparation, the presence of large amounts of superoxide-dismutase-insensitive Cytc reductase confounded attempts to use Cytc to measure superoxide synthesis. With the partially solubilized membrane protein, direct reduction of lucigenin probably contributed to the chemiluminescence. Superoxide synthesis detected with lucigenin should be confirmed by superoxide-dismutase-sensitive Cyt c reduction.
In Vivo Ubiquinone Reduction Levels during Thermogenesis in Araceae1
Authors: Wagner Anneke M. , Wagner Marijke J. , Moore Anthony L. 
Published: July 2002

Abstract
In vivo ubiquinone (UQ) reduction levels were measured during the development of the inflorescences ofArum maculatum and Amorphophallus krausei. Thermogenesis in A. maculatum spadices appeared not to be confined to a single developmental stage, but occurred during various stages. The UQ pool in both A. maculatum and A. krausei appendices was approximately 90% reduced during thermogenesis. Respiratory characteristics of isolated appendix mitochondria did not change in the period around thermogenesis. Apparently, synthesis of the required enzyme capacity is regulated via a coarse control upon which a fine control of metabolism that regulates the onset of thermogenesis is imposed.
(+)-Abscisic Acid 8′-Hydroxylase Is a Cytochrome P450 Monooxygenase
Authors: Krochko Joan E. , Abrams Garth D. , Loewen Mary K. , Abrams Suzanne R. , Cutler Adrian J. 
Published: July 2002

Abstract
Abscisic acid (ABA) 8′-hydroxylase catalyzes the first step in the oxidative degradation of (+)-ABA. The development of a robust in vitro assay has now permitted detailed examination and characterization of this enzyme. Although several factors (buffer, cofactor, and source tissue) were critical in developing the assay, the most important of these was the identification of a tissue displaying high amounts of in vivo enzyme activity (A.J. Cutler, T.M. Squires, M.K. Loewen, J.J. Balsevich [1997] J Exp Bot 48: 1787–1795). (+)-ABA 8′-hydroxylase is an integral membrane protein that is localized to the microsomal fraction in suspension-cultured maize (Zea mays) cells. (+)-ABA metabolism requires both NADPH and molecular oxygen. NADH was not an effective cofactor, although there was substantial stimulation of activity (synergism) when it was included at rate-limiting NADPH concentrations. The metabolism of (+)-ABA was progressively inhibited at O2 concentrations less than 10% (v/v) and was very low (less than 5% of control) under N2. (+)-ABA 8′-hydroxylase activity was inhibited by tetcyclacis (50% inhibition at 10−6 m), cytochrome c (oxidized form), and CO. The CO inhibition was reversible by light from several regions of the visible spectrum, but most efficiently by blue and amber light. These data strongly support the contention that (+)-ABA 8′-hydroxylase is a cytochrome P450 monooxygenase.
12-Oxophytodienoate-10,11-Reductase: Occurrence of Two Isoenzymes of Different Specificity against Stereoisomers of 12-Oxophytodienoic Acid
Authors: Schaller Florian , Hennig Peter , Weiler Elmar W. 
Published: July 2002

Abstract
The reduction of 12-oxophytodienoic acid (OPDA) to 3-oxo-2(2′[Z]-pentenyl)-cyclopentane-1-octanoic acid is catalyzed by 12-oxophytodienoate-10,11-reductase (OPR). Analysis of the isomer preference of OPR has indicated that the activity is composed of two isoenzymes exhibiting different stereoselectivities. The two isoforms of OPR have been separated, using protein extracts of Rock Harlequin (Corydalis sempervirens) as the starting material. OPRI, the enzyme reported earlier from the same species and corresponding to the cloned OPR from Arabidopsis, utilized 9R,13R-OPDA &gt;&gt; 9S,13R-OPDA but not the 13S-configured isomers, whereas the new activity, OPRII, effectively reduced all four OPDA isomers, including the natural 9S,13S-OPDA (cis-[+]-OPDA). OPRII activity is characterized in detail. The enzyme's enzymatic, biochemical, and immunological properties prove that it is a close relative of OPRI. The roles of OPRI and OPRII in octadecanoid biology are discussed.
Heterologous Expression of Arabidopsis Phytochrome B in Transgenic Potato Influences Photosynthetic Performance and Tuber Development1
Authors: Thiele Alexandra , Herold Michael , Lenk Ingo , Quail Peter H. , Gatz Christiane 
Published: July 2002

Abstract
Transgenic potato (Solanum tuberosum) plants expressing Arabidopsis phytochrome B were characterized morphologically and physiologically under white light in a greenhouse to explore their potential for improved photosynthesis and higher tuber yields. As expected, overexpression of functional phytochrome B caused pleiotropic effects such as semidwarfism, decreased apical dominance, a higher number of smaller but thicker leaves, and increased pigmentation. Because of increased numbers of chloroplasts in elongated palisade cells, photosynthesis per leaf area and in each individual plant increased. In addition, photosynthesis was less sensitive to photoinactivation under prolonged light stress. The beginning of senescence was not delayed, but deceleration of chlorophyll degradation extended the lifetime of photosynthetically active plants. Both the higher photosynthetic performance and the longer lifespan of the transgenic plants allowed greater biomass production, resulting in extended underground organs with increased tuber yields.
Expression of a Gibberellin-Induced Leucine-Rich Repeat Receptor-Like Protein Kinase in Deepwater Rice and Its Interaction with Kinase-Associated Protein Phosphatase1
Authors: van der Knaap Esther , Song Wen-Yuan , Ruan De-Ling , Sauter Margret , Ronald Pamela C. , Kende Hans 
Published: July 2002

Abstract
We identified in deepwater rice (Oryza sativa L.) a gene encoding a leucine-rich repeat receptor-like transmembrane protein kinase, OsTMK(O.sativatransmembrane kinase). The transcript levels of OsTMK increased in the rice internode in response to gibberellin. Expression of OsTMKwas especially high in regions undergoing cell division and elongation. The kinase domain of OsTMK was enzymatically active, autophosphorylating on serine and threonine residues. A cDNA encoding a rice ortholog of a kinase-associated type 2C protein phosphatase (OsKAPP) was cloned. KAPPs are putative downstream components in kinase-mediated signal transduction pathways. The kinase interaction domain of OsKAPP was phosphorylated in vitro by the kinase domain of OsTMK. RNA gel-blot analysis indicated that the expression ofOsTMK and OsKAPP was similar in different tissues of the rice plant. In protein-binding assays, OsKAPP interacted with a receptor-like protein kinase, RLK5 of Arabidopsis, but not with the protein kinase domains of the rice and maize receptor-like protein kinases Xa21 and ZmPK1, respectively.
Biochemical Characterization of the Chlamydomonas reinhardtii α-1,4 Glucanotransferase Supports a Direct Function in Amylopectin Biosynthesis1
Authors: Colleoni Christophe , Dauvillée David , Mouille Gregory , Morell Matthew , Samuel Michael , Slomiany Marie-Christine , Liénard Luc , Wattebled Fabrice , d'Hulst Christophe , Ball Steven 
Published: July 2002

Abstract
Plant α-1,4 glucanotransferases (disproportionating enzymes, or D-enzymes) transfer glucan chains among oligosaccharides with the concomitant release of glucose (Glc). Analysis of Chlamydomonas reinhardtii sta11-1 mutants revealed a correlation between a D-enzyme deficiency and specific alterations in amylopectin structure and starch biosynthesis, thereby suggesting previously unknown biosynthetic functions. This study characterized the biochemical activities of the α-1,4 glucanotransferase that is deficient in sta11-1 mutants. The enzyme exhibited the glucan transfer and Glc production activities that define D-enzymes. D-enzyme also transferred glucans among the outer chains of amylopectin (using the polysaccharide chains as both donor and acceptor) and from malto-oligosaccharides into the outer chains of either amylopectin or glycogen. In contrast to transfer among oligosaccharides, which occurs readily with maltotriose, transfer into polysaccharide required longer donor molecules. All three enzymatic activities, evolution of Glc from oligosaccharides, glucan transfer from oligosaccharides into polysaccharides, and transfer among polysaccharide outer chains, were evident in a single 62-kD band. Absence of all three activities co-segregated with thesta11-1 mutation, which is known to cause abnormal accumulation of oligosaccharides at the expense of starch. To explain these data we propose that D-enzymes function directly in building the amylopectin structure.
Differential Induction of Plant Volatile Biosynthesis in the Lima Bean by Early and Late Intermediates of the Octadecanoid-Signaling Pathway
Authors: Koch Thomas , Krumm Thomas , Jung Verena , Engelberth Jürgen , Boland Wilhelm 
Published: July 2002

Abstract
Plants are able to respond to herbivore damage with de novo biosynthesis of an herbivore-characteristic blend of volatiles. The signal transduction initiating volatile biosynthesis may involve the activation of the octadecanoid pathway, as exemplified by the transient increase of endogenous jasmonic acid (JA) in leaves of lima bean (Phaseolus lunatus) after treatment with the macromolecular elicitor cellulysin. Within this pathway lima bean possesses at least two different biologically active signals that trigger different biosynthetic activities. Early intermediates of the pathway, especially 12-oxo-phytodienoic acid (PDA), are able to induce the biosynthesis of the diterpenoid-derived 4,8,12-trimethyltrideca-1,3,7,11-tetraene. High concentrations of PDA result in more complex patterns of additional volatiles. JA, the last compound in the sequence, lacks the ability to induce diterpenoid-derived compounds, but is highly effective at triggering the biosynthesis of other volatiles. The phytotoxin coronatine and amino acid conjugates of linolenic acid (e.g. linolenoyl-l-glutamine) mimic the action of PDA, but coronatine does not increase the level of endogenous JA. The structural analog of coronatine, the isoleucine conjugate of 1-oxo-indanoyl-4-carboxylic acid, effectively mimics the action of JA, but does not increase the level of endogenous JA. The differential induction of volatiles resembles previous findings on signal transduction in mechanically stimulated tendrils of Bryonia dioica.
The t-SNARE AtVAM3p Resides on the Prevacuolar Compartment in Arabidopsis Root Cells
Authors: Sanderfoot Anton A. , Kovaleva Valentina , Zheng Haiyan , Raikhel Natasha V. 
Published: July 2002

Abstract
Protein cargo is trafficked between the organelles of the endomembrane system inside transport vesicles, a process mediated by integral membrane proteins called SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptors) that reside on the surface of the vesicle (v-SNAREs) and target membrane (t-SNAREs). In examining transport of cargo between the trans-Golgi network and the vacuole in Arabidopsis, we have previously characterized AtPEP12p as a t-SNARE residing on the prevacuolar compartment and AtVTI1a as a v-SNARE that interacts with AtPEP12p. Recently, we have begun to characterize AtVAM3p, another Arabidopsis t-SNARE that shows high sequence homology to AtPEP12p. We have found that AtVTI1a also interacts with AtVAM3p, suggesting a role for this t-SNARE in post-Golgi trafficking. AtVAM3p has been suggested to localize to the vacuolar membrane in Arabidopsis cells; however, using specific antisera and expression of epitope-tagged versions of each t-SNARE, we have discovered that AtVAM3p is found on the same prevacuolar structure as AtPEP12p in Arabidopsis root cells.
Genetic Engineering of Glycinebetaine Production toward Enhancing Stress Tolerance in Plants: Metabolic Limitations
Authors: Huang Jun , Hirji Rozina , Adam Luc , Rozwadowski Kevin L. , Hammerlindl Joe K. , Keller Wilf A. , Selvaraj Gopalan 
Published: July 2002

Abstract
Glycinebetaine (betaine) affords osmoprotection in bacteria, plants and animals, and protects cell components against harsh conditions in vitro. This and a compelling body of other evidence have encouraged the engineering of betaine production in plants lacking it. We have installed the metabolic step for oxidation of choline, a ubiquitous substance, to betaine in three diverse species, Arabidopsis, Brassica napus, and tobacco (Nicotiana tabacum), by constitutive expression of a bacterial choline oxidase gene. The highest levels of betaine in independent transgenics were 18.6, 12.8, and 13 μmol g−1 dry weight, respectively, values 10- to 20-fold lower than the levels found in natural betaine producers. However, choline-fed transgenic plants synthesized substantially more betaine. Increasing the choline supplementation further enhanced betaine synthesis, up to 613 μmol g−1 dry weight in Arabidopsis, 250 μmol g−1 dry weight in B. napus, and 80 μmol g−1 dry weight in tobacco. These studies demonstrate the need to enhance the endogenous choline supply to support accumulation of physiologically relevant amounts of betaine. A moderate stress tolerance was noted in some but not all betaine-producing transgenic lines based on relative shoot growth. Furthermore, the responses to stresses such as salinity, drought, and freezing were variable among the three species.
Spatial Regulation of Pectic Polysaccharides in Relation to Pit Fields in Cell Walls of Tomato Fruit Pericarp
Authors: Orfila Caroline , Knox J. Paul 
Published: July 2002

Abstract
Scanning electron microscopic examination of intact tomato (Lycopersicon esculentum) pericarp and isolated pericarp cell walls revealed pit fields and associated radiating ridges on the inner face of cell walls. In regions of the cell wall away from pit fields, equivalent ridges occurred in parallel arrays. Treatment of isolated cell walls with a calcium chelator resulted in the loss of these ridges, indicating that they contain homogalacturonan-rich pectic polysaccharides. Immunolabeling procedures confirmed that pit fields and associated radiating ridges contained homogalacturonan. Epitopes of the side chains of pectic polysaccharides were not located in the same regions as homogalacturonan and were spatially regulated in relation to pit fields. A (1→4)-β-galactan epitope was absent from cell walls in regions of pit fields. A (1→5)-α-arabinan epitope occurred most abundantly at the inner face of cell walls in regions surrounding the pit fields.
Import of Lyso-Phosphatidylcholine into Chloroplasts Likely at the Origin of Eukaryotic Plastidial Lipids
Authors: Mongrand Sébastien , Cassagne Claude , Bessoule Jean-Jacques 
Published: July 2002

Abstract
Plastids rely on the import of extraplastidial precursor for the synthesis of their own lipids. This key phenomenon in the formation of plastidial phosphatidylcholine (PC) and of the most abundant lipids on earth, namely galactolipids, is poorly understood. Various suggestions have been made on the nature of the precursor molecule(s) transferred to plastids, but despite general agreement that PC or a close metabolite plays a central role, there is no clear-cut answer to this question because of a lack of conclusive experimental data. We therefore designed experiments to discriminate between a transfer of PC, 1-acylglycero phosphorylcholine (lyso-PC), or glycerophosphorylcholine. After pulse-chase experiments with glycerol and acetate, plastids of leek (Allium porrum L.) seedlings were purified. The labels of the glycerol moiety and the sn-1- andsn-2-bound fatty acids of plastidial lipids were determined and compared with those associated with the extraplastidial PC. After import, plastid lipids contained the glycerol moiety and the fatty acids esterified to the sn-1 position originating from the extraplastidial PC; no import of sn-2-bound fatty acid was detected. These results rule out a transfer of PC or glycerophosphorylcholine, and are totally explained by an import of lyso-PC molecules used subsequently as precursor for the synthesis of eukaryotic plastid lipids.
Expression of Spinach Ascorbate Peroxidase Isoenzymes in Response to Oxidative Stresses
Authors: Yoshimura Kazuya , Yabuta Yukinori , Ishikawa Takahiro , Shigeoka Shigeru 
Published: July 2002

Abstract
We studied the response of each ascorbate peroxidase (APX) isoenzyme in spinach leaves under stress conditions imposed by high light intensity, drought, salinity, and applications of methyl viologen and abscisic acid. The steady-state transcript level of cytosolic APX remarkably increased in response to high-light stress and methyl viologen treatment, but not in response to the other stress treatments. The transcript levels of the chloroplastic (stromal and thylakoid-bound) and microbody-bound APX isoenzymes were not changed in response to any of the stress treatments. To explore the responses of the APX isoenzymes to photooxidative stress, the levels of transcript and protein and activities of each isoenzyme were studied during high-light stress and following its recovery. The cytosolic APX activity increased in parallel with transcript abundance during high-light stress, while the protein level was not altered. The other isoenzymes showed no significant changes in transcript and protein levels and activities, except for the gradual decrease in chloroplastic isoenzyme activities.
The Mechanic State of “Inner Tissue” in the Growing Zone of Sunflower Hypocotyls and the Regulation of Its Growth Rate Following Excision
Authors: Peters Winfried S. , Tomos A. Deri 
Published: July 2002

Abstract
Spontaneous growth of isolated inner tissue from the etiolated sunflower (Helianthus annuus L.) hypocotyl growing zone was investigated. A new preparation technique allowed measurements starting 3 s after excision. Elongation with respect to the turgescent and plasmolized state was quantified in terms of relative growth rates, facilitating comparison to growth in situ. Turgor and turgor-induced strain were determined. Overall longitudinal strain in inner tissues in situ was positive, indicating that compressive forces exerted by peripheral tissues are outweighed by turgor-dependent tensile stress. Inner tissue expansion following isolation depended on water uptake. Extreme plastic extension rates occurred immediately after excision, suggesting that mechanical parameters of inner tissue in situ cannot be extrapolated from the mechanics of excised sections. In the long term, excised inner tissue autonomously established values of turgor, turgor-induced strain, and relative growth rates similar to values in the living plant. These results support historic models of tissue cooperation during organ growth, in which inner tissues actively participate in the control of growth rates.
Cell-Specific and Conditional Expression of Caffeoyl-Coenzyme A-3-O-Methyltransferase in Poplar
Authors: Chen Cuiying , Meyermans Hugo , Burggraeve Bart , De Rycke Riet M. , Inoue Kentaro , De Vleesschauwer Vera , Steenackers Marijke , Van Montagu Marc C. , Engler Gilbert J. , Boerjan Wout A. 
Published: July 2002

Abstract
Caffeoyl coenzyme A-3-O-methyltransferase (CCoAOMT) plays an important role in lignin biosynthesis and is encoded by two genes in poplar (Populus trichocarpa). Here, we describe the expression pattern conferred by the two CCoAOMTpromoters when fused to the gus-coding sequence in transgenic poplar (Populus tremula × Populus alba). Both genes were expressed similarly in xylem and differentially in phloem. In xylem, expression was preferentially observed in vessels and contact rays, whereas expression was barely detectable in storage rays and fibers, suggesting different routes to monolignol biosynthesis in the different xylem types. Furthermore, after wounding, fungal infection, and bending, the expression of both genes was induced concomitantly with de novo lignin deposition. Importantly, upon bending and leaning of the stem, the cell-specific expression pattern was lost, and both genes were expressed in all cell types of the xylem. CCoAOMT promoter activity correlated well with the presence of the CCoAOMT protein, as shown by immunolocalization. These expression data may explain, at least in part, the heterogeneity in lignin composition that is observed between cell types and upon different environmental conditions.
Analysis of the N Gene Hypersensitive Response Induced by a Fluorescently Tagged Tobacco Mosaic Virus
Authors: Wright Kathryn M. , Duncan George H. , Pradel Katja S. , Carr Fiona , Wood Susannah , Oparka Karl J. , Cruz Simon Santa 
Published: July 2002

Abstract
The hypersensitive response (HR) triggered on Nicotiana edwardsonii by tobacco mosaic virus was studied using a modified viral genome that directed expression of the green fluorescent protein. Inoculated plants were initially incubated at 32°C to inhibit the N gene-mediated HR. Transfer to 20°C initiated the HR, and fluorescent infection foci were monitored for early HR-associated events. Membrane damage, which preceded visible cell collapse by more than 3 h, was accompanied by a transient restriction of the xylem within infection sites. Following cell collapse and the rapid desiccation of tissue undergoing the HR, isolated, infected cells were detected at the margin of necrotic lesions. These virus-infected cells were able to reinitiate infection on transfer to 32°C, however, if maintained at 20°C they eventually died. The results indicate that the tobacco mosaic virus-induced HR is a two-phase process with an early stage culminating in rapid cell collapse and tissue desiccation followed by a more extended period during which the remaining infected cells are eliminated.