bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cellulose and Callose Biosynthesis in Higher Plants (I. Solubilization and Separation of (1-&gt;3)- and (1-&gt;4)-β-Glucan Synthase Activities from Mung Bean)
Authors: Kudlicka K. , Brown Jr R. M. 
Published: July 2002

Abstract
(1-&gt;3)- and (1-&gt;4)-β-glucan synthase activities from higher plants have been physically separated by gel electrophoresis in nondenaturing conditions. The two glucan synthases show different mobilities in native polyacrylamide gels. Further separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a different polypeptide composition in these synthases. Three polypeptides (64, 54, and 32 kD) seem to be common to both synthase activities, whereas two polypeptides (78 and 38 kD) are associated only with callose synthase activity. Twelve polypeptides (170, 136, 108, 96, 83, 72, 66, 60, 52, 48, 42, and 34 kD) appear to be specifically associated with cellulose synthase activity. The successful separation of (1-&gt;3)- and (1-&gt;-4)-β-glucan synthase activities was based on the manipulation of digitonin concentrations used in the solubilization of membrane proteins. At low dipitomin concentrations (0.05 and 0.1%), the ratio of the cellulose to callose synthase activity was higher. At higher digitonin (0.5–1%) concentrations, the ratio of the callose to cellulose synthase activity was higher. Rosette-like particles with attached product were observed in samples taken from the top of the stacking gel, where only cellulose was synthesized. Smaller (nonrosette) particles were found in the running gel, where only callose was synthesized. These findings suggest that a higher level of subunit organization is required for in vitro cellulose synthesis in comparison with callose assembly.
The Intracellular Localization of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase in Chlamydomonas reinhardtii1
Authors: Borkhsenious Olga N. , Mason Catherine B. , Moroney James V. 
Published: July 2002

Abstract
The pyrenoid is a proteinaceous structure found in the chloroplast of most unicellular algae. Various studies indicate that ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is present in the pyrenoid, although the fraction of Rubisco localized there remains controversial. Estimates of the amount of Rubisco in the pyrenoid of Chlamydomonas reinhardtiirange from 5% to nearly 100%. Using immunolocalization, the amount of Rubisco localized to the pyrenoid or to the chloroplast stroma was estimated for C. reinhardtii cells grown under different conditions. It was observed that the amount of Rubisco in the pyrenoid varied with growth condition; about 40% was in the pyrenoid when the cells were grown under elevated CO2 and about 90% with ambient CO2. In addition, it is likely that pyrenoidal Rubisco is active in CO2 fixation because in vitro activity measurements showed that most of the Rubisco must be active to account for CO2-fixation rates observed in whole cells. These results are consistent with the idea that the pyrenoid is the site of CO2 fixation in C. reinhardtii and other unicellular algae containing CO2-concentrating mechanisms.
Multiple Genes Encoding the Conserved CCAAT-Box Transcription Factor Complex Are Expressed in Arabidopsis
Authors: Edwards David , Murray James A.H. , Smith Alison G. 
Published: July 2002

AbstractThe CCAAT motif is found in the promoters of many eukaryotic genes. In yeast a single complex of three proteins, termed HAP2, HAP3, and HAP5, binds to this sequence, and in mammals the three components of the equivalent complex (called variously NF-Y, CBF, or CP1) are also represented by single genes. Here we report the presence of multiple genes for each of the components of the CCAAT-binding complex, HAP2,3,5, from Arabidopsis. Three independent Arabidopsis HAP subunit 2 (AtHAP2) cDNAs were cloned by functional complementation of a yeast hap2 mutant, and two independent forms each of AtHAP3 and AtHAP5 cDNAs were detected in the expressed sequence tag database. Additional homologs (two of AtHAP3 and one of AtHAP5) have been identified from available Arabidopsis genomic sequences. Northern-blot analysis indicated ubiquitous expression for each AtHAP2 and AtHAP5 cDNA in a range of tissues, whereas expression of each AtHAP3 cDNA was under developmental and/or environmental regulation. The unexpected presence of multiple forms of each HAP homolog in Arabidopsis, compared with the single genes in yeast and vertebrates, suggests that the HAP2,3,5 complex may play diverse roles in gene transcription in higher plants.
Characterization of a Maize Tonoplast Aquaporin Expressed in Zones of Cell Division and Elongation1
Authors: Chaumont François , Barrieu François , Herman Eliot M. , Chrispeels Maarten J. 
Published: July 2002

Abstract
We studied aquaporins in maize (Zea mays), an important crop in which numerous studies on plant water relations have been carried out. A maize cDNA,ZmTIP1, was isolated by reverse transcription-coupled PCR using conserved motifs from plant aquaporins. The derived amino acid sequence of ZmTIP1 shows 76% sequence identity with the tonoplast aquaporin γ-TIP (tonoplast intrinsic protein) from Arabidopsis. Expression of ZmTIP1 in Xenopus laevisoocytes showed that it increased the osmotic water permeability of oocytes 5-fold; this water transport was inhibited by mercuric chloride. A cross-reacting antiserum made against bean α-TIP was used for immunocytochemical localization of ZmTIP1. These results indicate that this and/or other aquaporins is abundantly present in the small vacuoles of meristematic cells. Northern analysis demonstrated thatZmTIP1 is expressed in all plant organs. In situ hybridization showed a high ZmTIP1 expression in meristems and zones of cell enlargement: tips of primary and lateral roots, leaf primordia, and male and female inflorescence meristems. The high ZmTIP1 expression in meristems and expanding cells suggests that ZmTIP1 is needed (a) for vacuole biogenesis and (b) to support the rapid influx of water into vacuoles during cell expansion.
Auxin-Growth Relationships in Maize Coleoptiles and Pea Internodes and Control by Auxin of the Tissue Sensitivity to Auxin
Authors: Haga Ken , Iino Moritoshi 
Published: July 2002

Abstract
Growth of a zone of maize (Zea mays L.) coleoptiles and pea (Pisum sativum L.) internodes was greatly suppressed when the organ was decapitated or ringed at an upper position with the auxin transport inhibitorN-1-naphthylphthalamic acid (NPA) mixed with lanolin. The transport of apically applied 3H-labeled indole-3-acetic acid (IAA) was similarly inhibited by NPA. The growth suppressed by NPA or decapitation was restored by the IAA mixed with lanolin and applied directly to the zone, and the maximal capacity to respond to IAA did not change after NPA treatment, although it declined slightly after decapitation. The growth rate at IAA saturation was greater than the rate in intact, nontreated plants. It was concluded that growth is limited and controlled by auxin supplied from the apical region. In maize coleoptiles the sensitivity to IAA increased more than 3 times when the auxin level was reduced over a few hours with NPA treatment. This result, together with our previous result that the maximal capacity to respond to IAA declines in pea internodes when the IAA level is enhanced for a few hours, indicates that the IAA concentration-response relationship is subject to relatively slow adaptive regulation by IAA itself. The spontaneous growth recovery observed in decapitated maize coleoptiles was prevented by an NPA ring placed at an upper position of the stump, supporting the view that recovery is due to regenerated auxin-producing activity. The sensitivity increase also appeared to participate in an early recovery phase, causing a growth rate greater than in intact plants.
Protein Phosphorylation during Coconut Zygotic Embryo Development1
Authors: Islas-Flores Ignacio , Oropeza Carlos , Hernández-Sotomayor S.M. Teresa 
Published: July 2002

Abstract
Evidence was obtained on the occurrence of protein threonine, serine, and tyrosine (Tyr) kinases in developing coconut (Cocos nucifera L.) zygotic embryos, based on in vitro phosphorylation of proteins in the presence of [γ-32P]ATP, alkaline treatment, and thin-layer chromatography analysis, which showed the presence of [32P]phosphoserine, [32P]phosphothreonine, and [32P]phosphotyrosine in [32P]-labeled protein hydrolyzates. Tyr kinase activity was further confirmed in extracts of embryos at different stages of development using antiphosphotyrosine monoclonal antibodies and the synthetic peptide derived from the amino acid sequence surrounding the phosphorylation site in pp60src (RR-SRC), which is specific for Tyr kinases. Anti-phosphotyrosine western blotting revealed a changing profile of Tyr-phosphorylated proteins during embryo development. Tyr kinase activity, as assayed using RR-SRC, also changed during embryo development, showing two peaks of activity, one during early and another during late embryo development. In addition, the use of genistein, a Tyr kinase inhibitor, diminished the ability of extracts to phosphorylate RR-SRC. Results presented here show the occurrence of threonine, serine, and Tyr kinases in developing coconut zygotic embryos, and suggest that protein phosphorylation, and the possible inference of Tyr phosphorylation in particular, may play a role in the coordination of the development of embryos in this species.
Distinct Biochemical and Topological Properties of the 31- and 27-Kilodalton Plasma Membrane Intrinsic Protein Subgroups from Red Beet1
Authors: Barone Lucille M. , He Mu Helen , Shih Connie J. , Kashlan Kenan B. , Wasserman Bruce P. 
Published: July 2002

Abstract
Plasma membrane vesicles from red beet (Beta vulgaris L.) storage tissue contain two prominent major intrinsic protein species of 31 and 27 kD (X. Qi, C.Y Tai, B.P. Wasserman [1995] Plant Physiol 108: 387–392). In this study affinity-purified antibodies were used to investigate their localization and biochemical properties. Both plasma membrane intrinsic protein (PMIP) subgroups partitioned identically in sucrose gradients; however, each exhibited distinct properties when probed for multimer formation, and by limited proteolysis. The tendency of each PMIP species to form disulfide-linked aggregates was studied by inclusion of various sulfhydryl agents during tissue homogenization and vesicle isolation. In the absence of dithiothreitol and sulfhydryl reagents, PMIP27 yielded a mixture of monomeric and aggregated species. In contrast, generation of a monomeric species of PMIP31 required the addition of dithiothreitol, iodoacetic acid, orN-ethylmaleimide. Mixed disulfide-linked heterodimers between the PMIP31 and PMIP27 subgroups were not detected. Based on vectorial proteolysis of right-side-out vesicles with trypsin and hydropathy analysis of the predicted amino acid sequence derived from the gene encoding PMIP27, a topological model for a PMIP27 was established. Two exposed tryptic cleavage sites were identified from proteolysis of PMIP27, and each was distinct from the single exposed site previously identified in surface loop C of a PMIP31. Although the PMIP31 and PMIP27 species both contain integral proteins that appear to occur within a single vesicle population, these results demonstrate that each PMIP subgroup responds differently to perturbations of the membrane.
Characterization of a Low-Molecular-Weight Glutenin Subunit Gene from Bread Wheat and the Corresponding Protein That Represents a Major Subunit of the Glutenin Polymer
Authors: Masci Stefania , D'Ovidio Renato , Lafiandra Domenico , Kasarda Donald D. 
Published: July 2002

Abstract
Both high- and low-molecular-weight glutenin subunits (LMW-GS) play the major role in determining the viscoelastic properties of wheat (Triticum aestivum L.) flour. To date there has been no clear correspondence between the amino acid sequences of LMW-GS derived from DNA sequencing and those of actual LMW-GS present in the endosperm. We have characterized a particular LMW-GS from hexaploid bread wheat, a major component of the glutenin polymer, which we call the 42K LMW-GS, and have isolated and sequenced the putative corresponding gene. Extensive amino acid sequences obtained directly for this 42K LMW-GS indicate correspondence between this protein and the putative corresponding gene. This subunit did not show a cysteine (Cys) at position 5, in contrast to what has frequently been reported for nucleotide-based sequences of LMW-GS. This Cys has been replaced by one occurring in the repeated-sequence domain, leaving the total number of Cys residues in the molecule the same as in various other LMW-GS. On the basis of the deduced amino acid sequence and literature-based assignment of disulfide linkages, a computer-generated molecular model of the 42K subunit was constructed.
Abscisic Acid-Dependent and -Independent Expression of the Carrot Late-Embryogenesis-Abundant-Class Gene Dc3 in Transgenic Tobacco Seedlings
Authors: Siddiqui Najeeb U. , Chung Hwa-Jee , Thomas Terry L. , Drew Malcolm C. 
Published: July 2002

Abstract
We studied the expression of three promoter 5′ deletion constructs (−218, −599, and −1312) of the LEA (lateembryogenesis abundant)-class geneDc3 fused to β-glucuronidase (GUS), where each construct value refers to the number of base pairs upstream of the transcription start site at which the deletion occurred. TheDc3 gene is noted for its induction by abscisic acid (ABA), but its response to other plant hormones and various environmental stresses has not been reported previously for vegetative cells. Fourteen-day-old transgenic tobacco (Nicotiana tabacum L.) seedlings were exposed to dehydration, hypoxia, salinity, exogenous ethylene, or exogenous methyl jasmonate (MeJa). GUS activity was quantified fluorimetrically and expression was observed by histochemical staining of the seedlings. An increase in GUS activity was observed in plants with constructs −599 and −1312 in response to dehydration and salinity within 6 h of stress, and at 12 h in response to hypoxia. No increase in endogenous ABA was found in any of the three lines, even after 72 h of hypoxia. An ABA-independent increase in GUS activity was observed when endogenous ABA biosynthesis was blocked by fluridone and plants were exposed to 5 μL L−1 ethylene in air or 100 μm MeJa. Virtually no expression was observed in construct −218 in response to dehydration, salinity, or MeJa, but there was a moderate response to ethylene and hypoxia. This suggests that the region between −218 and −599 is necessary for ABA (dehydration and salinity)- and MeJa-dependent expression, whereas ethylene-mediated expression does not require this region of the promoter.
Evidence for Light-Stimulated Fatty Acid Synthesis in Soybean Fruit1
Authors: Willms Jennifer R. , Salon Christophe , Layzell David B. 
Published: July 2002

Abstract
In leaves, the light reactions of photosynthesis support fatty acid synthesis but disagreement exists as to whether this occurs in green oilseeds. To address this question, simultaneous measurements of the rates of CO2 and O2 exchange (CER and OER, respectively) were made in soybean (Glycine max L.) fruits. The imbalance between CER and OER was used to estimate the diverted reductant utilization rate (DRUR) in the equation: DRUR = 4 × (OER + CER). This yielded a quantitative measure of the rate of synthesis of biomass that is more reduced per unit carbon than glucose (in photosynthesizing tissues) or than the substrates of metabolism (in respiring tissues). The DRUR increased by about 2.2-fold when fruits were illuminated due to a greater increase in OER than decrease in CER. This characteristic was shown to be a property of the seed (not the pod wall), to be present in fruits at all developmental stages, and to reach a maximal response at relatively low light. When seeds were provided with 13CO2, light reduced12CO2 production but had little effect on13CO2 fixation. When they were provided with18O2, light stimulated16O2 production but had no effect on18O2 uptake. Together, these findings indicate that light stimulates fatty acid synthesis in photosynthetic oilseeds, probably by providing both ATP and carbon skeletons.
Overexpression of a Gene That Encodes the First Enzyme in the Biosynthesis of Asparagine-Linked Glycans Makes Plants Resistant to Tunicamycin and Obviates the Tunicamycin-Induced Unfolded Protein Response
Authors: Koizumi Nozomu , Ujino Tokuko , Sano Hiroshi , Chrispeels Maarten J. 
Published: July 2002

AbstractThe cytotoxic drug tunicamycin kills cells because it is a specific inhibitor of UDP-N-acetylglucosamine:dolichol phosphateN-acetylglucosamine-1-P transferase (GPT), an enzyme that catalyzes the initial step of the biosynthesis of dolichol-linked oligosaccharides. In the presence of tunicamycin, asparagine-linked glycoproteins made in the endoplasmic reticulum are not glycosylated with N-linked glycans, and therefore may not fold correctly. Such proteins may be targeted for breakdown. Cells that are treated with tunicamycin normally experience an unfolded protein response and induce genes that encode endoplasmic reticulum chaperones such as the binding protein (BiP). We isolated a cDNA clone for Arabidopsis GPT and overexpressed it in Arabidopsis. The transgenic plants have a 10-fold higher level of GPT activity and are resistant to 1 μg/mL tunicamycin, a concentration that kills control plants. Transgenic plants grown in the presence of tunicamycin haveN-glycosylated proteins and the drug does not induce BiP mRNA levels as it does in control plants. BiP mRNA levels are highly induced in both control and GPT-expressing plants by azetidine-2-carboxylate. These observations suggest that excess GPT activity obviates the normal unfolded protein response that cells experience when exposed to tunicamycin.
Direct Measurement of Xylem Pressure in Leaves of Intact Maize Plants. A Test of the Cohesion-Tension Theory Taking Hydraulic Architecture into Consideration
Authors: Wei Chunfang , Tyree Melvin T. , Steudle Ernst 
Published: July 2002

Abstract
The water relations of maize (Zea mays L. cv Helix) were documented in terms of hydraulic architecture and xylem pressure. A high-pressure flowmeter was used to characterize the hydraulic resistances of the root, stalk, and leaves. Xylem pressure measurements were made with a Scholander-Hammel pressure bomb and with a cell pressure probe. Evaporation rates were measured by gas exchange and by gravimetric measurements. Xylem pressure was altered by changing the light intensity, by controlling irrigation, or by gas pressure applied to the soil mass (using a root pressure bomb). Xylem pressure measured by the cell pressure probe and by the pressure bomb agreed over the entire measured range of 0 to −0.7 MPa. Experiments were consistent with the cohesion-tension theory. Xylem pressure changed rapidly and reversibly with changes in light intensity and root-bomb pressure. Increasing the root-bomb pressure increased the evaporation rate slightly when xylem pressure was negative and increased water flow rate through the shoots dramatically when xylem pressure was positive and guttation was observed. The hydraulic architecture model could predict all observed changes in water flow rate and xylem. We measured the cavitation threshold for oil- and water-filled pressure probes and provide some suggestions for improvement.
Gibberellins and Seed Development in Maize. II. Gibberellin Synthesis Inhibition Enhances Abscisic Acid Signaling in Cultured Embryos
Authors: White Constance N. , Rivin Carol J. 
Published: July 2002

Abstract
Abscisic acid (ABA) is required for seed maturation in maize (Zea mays L.) and other plants. Gibberellins (GAs) are also present in developing maize embryos, and mutual antagonism of GAs and ABA appears to govern the choice between precocious germination or quiescence and maturation. Exogenous ABA can also induce quiescence and maturation in immature maize embryos in culture. To examine the role of GAs versus ABA in regulating maize embryo maturation, the effects of modulating GA levels were compared with those of ABA in embryos cultured at successive stages of development. The effects of GA synthesis inhibition or exogenous GA application differed markedly in embryos at different stages of development, indicating changes in both endogenous GA levels and in the capacity for GA synthesis as embryogenesis and maturation progress. In immature embryos, the inhibition of GA synthesis mimicked the effects of exogenous ABA, as shown by the suppression of germination, the acquisition of anthocyanin pigments, and the accumulation of a variety of maturation-phase mRNAs. We suggest that GA antagonizes ABA signaling in developing maize embryos, and that the changing hormone balance provides temporal control over the maturation phase.
Characterization of Sulfate Assimilation in Marine Algae Focusing on the Enzyme 5′-Adenylylsulfate Reductase
Authors: Gao Yu , Schofield Oscar M.E. , Leustek Thomas 
Published: July 2002

Abstract
5′-Adenylylsulfate (APS) reductase was characterized in diverse marine algae. A cDNA encoding APS reductase from Enteromorpha intestinalis (EAPR) was cloned by functional complementation of an Escherichia coli cysH mutant. The deduced amino acid sequence shows high homology with APS reductase (APR) from flowering plants. Based on the probable transit peptide cleavage site the mature protein is 45.7 kD. EAPR expressed as a His-tagged recombinant protein catalyzes reduced glutathione-dependent reduction of APS to sulfite, exhibiting a specific activity of approximately 40 μmol min−1 mg protein−1 and Michealis-Menten kinetic constants of approximately 1.4 mm for reduced glutathione and approximately 6.5 μm for APS. APR activity and expression were studied in relation to the production of 3-dimethylsulfoniopropionate (DMSP), a sulfonium compound produced by many marine algae. A diverse group of DMSP-producing species showed extremely high enzyme activity (up to 400 times that found in flowering plants). Antibodies raised against a conserved peptide of APR strongly cross-reacted with a protein of 45 kD in several chlorophytes but insignificantly with chromophytes. In the chlorophyteTetraselmis sp., APR activity varies significantly during the culture cycle and does not follow the changes in cellular DMSP content. However, a positive correlation was found between cell-based APR activity and specific growth rate.
Assembly, Secretion, and Vacuolar Delivery of a Hybrid Immunoglobulin in Plants
Authors: Frigerio Lorenzo , Vine Nicholas D. , Pedrazzini Emanuela , Hein Mich B. , Wang Fei , Ma Julian K.-C. , Vitale Alessandro 
Published: July 2002

AbstractSecretory immunoglobulin (Ig) A is a decameric Ig composed of four α-heavy chains, four light chains, a joining (J) chain, and a secretory component (SC). The heavy and light chains form two tetrameric Ig molecules that are joined by the J chain and associate with the SC. Expression of a secretory monoclonal antibody in tobacco (Nicotiana tabacum) has been described: this molecule (secretory IgA/G [SIgA/G]) was modified by having a hybrid heavy chain sequence consisting of IgG γ-chain domains linked to constant region domains of an IgA α-chain. In tobacco, about 70% of the protein assembles to its final, decameric structure. We show here that SIgA/G assembly and secretion are slow, with only approximately 10% of the newly synthesized molecules being secreted after 24 h and the bulk probably remaining in the endoplasmic reticulum. In addition, a proportion of SIgA/G is delivered to the vacuole as at least partially assembled molecules by a process that is blocked by the membrane traffic inhibitor brefeldin A. Neither the SC nor the J chain are responsible for vacuolar delivery, because IgA/G tetramers have the same fate. The parent IgG tetrameric molecule, containing wild-type γ-heavy chains, is instead secreted rapidly and efficiently. This strongly suggests that intracellular retention and vacuolar delivery of IgA/G is due to the α-domains present in the hybrid α/γ-heavy chains and indicates that the plant secretory system may partially deliver to the vacuole recombinant proteins expected to be secreted.