bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic Engineering of Plant Secondary Metabolism (Accumulation of 4-Hydroxybenzoate Glucosides as a Result of the Expression of the Bacterial ubiC Gene in Tobacco)
Authors: Siebert M. , Sommer S. , Li Sm. , Wang Zx. , Severin K. , Heide L. 
Published: July 2002

Abstract
The ubiC gene of Escherichia coli encodes chorismate pyruvatelyase, an enzyme that converts chorismate into 4-hydroxybenzoate (4HB) and is not normally present in plants. The ubiC gene was expressed in Nicotiana tabacum L. plants under control of a constitutive plant promoter. The gene product was targeted into the plastid by fusing it to the sequence for the chloroplast transit peptide of the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Transgenic plants showed high chorismate pyruvate-lyase activity and accumulated 4HB as β-glucosides, with the glucose attached to either the hydroxy or the carboxyl function of 4HB. The total content of 4HB glucosides was approximately 0.52% of dry weight, which exceeded the content of untransformed plants by at least a factor of 1000. Feeding experiments with [1,7-13C2]shikimic acid unequivocally proved that the 4HB that was formed in the transgenic plants was not derived from the conventional phenylpropanoid pathway but from the newly introduced chorismate pyruvate-lyase reaction.
Cytokinin, Acting through Ethylene, Restores Gravitropism to Arabidopsis Seedlings Grown under Red Light
Authors: Golan A. , Tepper M. , Soudry E. , Horwitz B. A. , Gepstein S. 
Published: July 2002

Abstract
Cytokinin replaces light in several aspects of the photomorphogenesis of dicot seedlings. Arabidopsis thaliana seedlings grown under red light have been shown to become disoriented, losing the negative hypocotyl gravitropism that has been observed in seedlings grown in darkness or white light. We report here that cytokinin at micromolar concentrations restores gravitropism to seedlings grown under red light. Cytokinin cancels the effect of red light on the gravity-sensing system and at the same time replaces light in the inhibition of hypocotyl elongation. Furthermore, application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid acts similarly to cytokinin. Cytokinin cannot restore gravitropism under red light to an ethylene-insensitive mutant that is defective at the EIN2 locus. Stimulation of ethylene production, therefore, can explain the action of cytokinin in restoring negative gravitropism to the hypocotyls of Arabidopsis seedlings grown under continuous red light.
Isolation and Characterization of Glutamine Synthetase Genes in Chlamydomonas reinhardtii
Authors: Chen Q. , Silflow C. D. 
Published: July 2002

Abstract
To elucidate the role of glutamine synthetase (GS) in nitrogen assimilation in the green alga Chlamydomonas reinhardtii we used maize GS1 (the cytosolic form) and GS2 (the chloroplastic form) cDNAs as hybridization probes to isolate C. reinhardtii cDNA clones. The amino acid sequences derived from the C. reinhardtii clones have extensive homology with GS enzymes from higher plants. A putative amino-terminal transit peptide encoded by the GS2 cDNA suggests that the protein localizes to the chloroplast. Genomic DNA blot analysis indicated that GS1 is encoded by a single gene, whereas two genomic fragments hybridized to the GS2 cDNA probe. All GS2 cDNA clones corresponded to only one of the two GS2 genomic sequences. We provide evidence that ammonium, nitrate, and light regulate GS transcript accumulation in green algae. Our results indicate that the level of GS1 transcripts is repressed by ammonium but induced by nitrate. The level of GS2 transcripts is not affected by ammonium or nitrate. Expression of both GS1 and GS2 genes is regulated by light, but perhaps through different mechanisms. Unlike in higher plants, no decreased level of GS2 transcripts was detected when cells were grown under conditions that repress photorespiration. Analysis of GS transcript levels in mutants with defects in the nitrate assimilation pathway show that nitrate assimilation and ammonium assimilation are regulated independently.
The Ferredoxin-Binding Site of Ferredoxin:Nitrite Oxidoreductase (Differential Chemical Modification of the Free Enzyme and Its Complex with Ferredoxin)
Authors: Dose M. M. , Hirasawa M. , Kleis-SanFrancisco S. , Lew E. L. , Knaff D. B. 
Published: July 2002

Abstract
Spinach (Spinacea oleracea) leaf ferredoxin (Fd)-dependent nitrite reductase was treated with either the arginine-modifying reagent phenyl-glyoxal or the lysine-modifying reagent pyridoxal-5[prime]-phosphate under conditions where only the Fd-binding affinity of the enzyme was affected and where complex formation between Fd and the enzyme prevented the inhibition by either reagent. Modification with [14C]phenylglyoxal allowed the identification of two nitrite reductase arginines, R375 and R556, that are protected by Fd against labeling. Modification of nitrite reductase with pyridoxal-5[prime]-phosphate, followed by reduction with NaBH4, allowed the identification of a lysine, K436, that is protected by Fd against labeling. Positive charges are present at these positions in all of the Fd-dependent nitrite reductases for which sequences are available, suggesting that these amino acids are directly involved in electrostatic binding of Fd to the enzyme.
Differential Expression of Chitinases in Vitis vinifera L. Responding to Systemic Acquired Resistance Activators or Fungal Challenge
Authors: Busam G. , Kassemeyer H. H. , Matern U. 
Published: July 2002

Abstract
The concept of systemic acquired resistance (SAR) enables a novel approach to crop protection, and particular pathogenesis-related proteins, i.e. an acidic chitinase, have been classified as markers of the SAR response. Basic class I (VCHIT1b) and a class III (VCH3) chitinase cDNAs were cloned from cultured Vitis vinifera L. cv Pinot Noir cells and used to probe the induction response of grapevine cells to salicylic acid or yeast elicitor. Furthermore, the cells were treated with the commercial SAR activators 2,6-dichloroiso-nicotinic acid or benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester. Elicitor or salicylic acid induced both VCHIT1b and VCH3 transcript abundances, whereas 2,6-dichloroiso-nicotinic acid or benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester enhanced exclusively the expression of VCH3. To assess the systemic sensation of chitinase expression, single leaves of Vitis vinifera L. cv Pinot Noir or Vitis rupestris plants were inoculated with Plasmopara viticola spore suspensions, and the VCH3 and VCHIT1b mRNA amounts in the infected versus the adjacent, healthy leaf were monitored. Two VCH3 mRNA maxima were observed 2 and 6 d postinoculation in the infected, susceptible V. vinifera tissue, whereas in the healthy leaf the transcript increased from low levels d 2 postinoculation to prominent levels d 6 to 8 postinoculation. The level of VCH3 mRNA increased also over 4 d in the inoculated, resistant V. rupestris tissue. However, necrotic spots rapidly limited the infection, and the VCH3 transcript was undetectable in the upper-stage, healthy leaf. The expression of VCHIT1b remained negligible under either experimental condition. Overall, the results suggest that the selective expression of VCH3 might be a reliable indicator of the SAR response in V. vinifera L.
Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Activase Deficiency Delays Senescence of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase but Progressively Impairs Its Catalysis during Tobacco Leaf Development
Authors: He Z. , von Caemmerer S. , Hudson G. S. , Price G. D. , Badger M. R. , Andrews T. J. 
Published: July 2002

Abstract
Transgenic tobacco (Nicotiana tabacum L. cv W38) plants with an antisense gene directed against the mRNA of ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) activase grew more slowly than wild-type plants in a CO2-enriched atmosphere, but eventually attained the same height and number of leaves. Compared with the wild type, the anti-activase plants had reduced CO2 assimilation rates, normal contents of chlorophyll and soluble leaf protein, and much higher Rubisco contents, particularly in older leaves. Activase deficiency greatly delayed the usual developmental decline in Rubisco content seen in wild-type leaves. This effect was much less obvious in another transgenic tobacco with an antisense gene directed against chloroplast-located glyceraldehyde-3-phosphate dehydrogenase, which also had reduced photosynthetic rates and delayed development. Although Rubisco carbamylation was reduced in the anti-activase plants, the reduction was not sufficient to explain the reduced photosynthetic rate of older anti-activase leaves. Instead, up to a 10-fold reduction in the catalytic turnover rate of carbamylated Rubisco in vivo appeared to be the main cause. Slower catalytic turnover by carbamylated Rubisco was particularly obvious in high-CO2-grown leaves but was also detectable in air-grown leaves. Rubisco activity measured immediately after rapid extraction of anti-activase leaves was not much less than that predicted from its degree of carbamylation, ruling out slow release of an inhibitor from carbamylated sites as a major cause of the phenomenon. Nor could substrate scarcity or product inhibition account for the impairment. We conclude that activase must have a role in vivo, direct or indirect, in promoting the activity of carbamylated Rubisco in addition to its role in promoting carbamylation.
The PsaD Subunit of Photosystem I (Mutations in the Basic Domain Reduce the Level of PsaD in the Membranes)
Authors: Chitnis V. P. , Ke A. , Chitnis P. R. 
Published: July 2002

Abstract
The PsaD subunit of photosystem I (PSI) is a peripheral protein that provides a docking site for ferredoxin and interacts with the PsaB, PsaC, and PsaL subunits of PSI. We used site-directed mutagenesis to determine the function of a basic region in PsaD of the cyanobacterium Synechocystis sp. PCC 6803. We generated five mutant strains in which one or more charged residues were altered. Western blotting showed that replacement of lysine (Lys)-74 with glutamine or glutamic acid led to a substantial decrease in the level of PsaD in the membranes. The mutant PSI complexes showed reduced NADP+ photoreduction activity mediated by ferredoxin; the decrease in activity correlated with the reduced level of PsaD. Using protein synthesis inhibitors we showed that the degradation rates of the mutant and wild-type PsaD were similar, indicating a defect in the assembly of the mutant protein. Treatment of the mutant PSI complexes with a different concentration of Nal showed that the mutations decreased affinity between PsaD and the transmembrane components of PSI. With glutaraldehyde, the mutant and wild-type PsaD proteins could be cross-linked with PsaC, but the PsaD-PsaL cross-linked product was reduced drastically when arginine-72, Lys-74, and Lys-76 were mutated simultaneously. These studies demonstrate that the basic residues in the central region of PsaD, especially Lys-74, are crucial in the assembly of PsaD into the PSI complex.
Uptake of HCO3− and CO2 in Cells and Chloroplasts from the Microalgae Chlamydomonas reinhardtii and Dunaliella tertiolecta1
Authors: Amoroso Gabi , Sültemeyer Dieter , Thyssen Christoph , Fock Heinrich P. 
Published: July 2002

Abstract
Mass-spectrometric disequilibrium analysis was applied to investigate CO2 uptake and HCO3− transport in cells and chloroplasts of the microalgae Dunaliella tertiolecta andChlamydomonas reinhardtii, which were grown in air enriched with 5% (v/v) CO2 (high-Ci cells) or in ambient air (low-Ci cells). High- and low-Ci cells of both species had the capacity to transport CO2 and HCO3−, with maximum rates being largely unaffected by the growth conditions. In high- and low-Ci cells ofD. tertiolecta, HCO3− was the dominant inorganic C species taken up, whereas HCO3− and CO2 were used at similar rates by C. reinhardtii. The apparent affinities of HCO3− transport and CO2 uptake increased 3- to 9-fold in both species upon acclimation to air. Photosynthetically active chloroplasts isolated from both species were able to transport CO2 and HCO3−. For chloroplasts from C. reinhardtii, the concentrations of HCO3− and CO2 required for half-maximal activity declined from 446 to 33 μm and 6.8 to 0.6 μm, respectively, after acclimation of the parent cells to air; the corresponding values for chloroplasts from D. tertiolecta decreased from 203 to 58 μm and 5.8 to 0.5 μm, respectively. These results indicate the presence of inducible high-affinity HCO3− and CO2 transporters at the chloroplast envelope membrane.
Identification of Inositol 1,3,4-Trisphosphate 5-Kinase and Inositol 1,3,4,5-Tetrakisphosphate 6-Kinase in Immature Soybean Seeds
Authors: Phillippy Brian Q. 
Published: July 2002

Abstract
In extracts of immature soybean (Glycine max [L.] Merr.) seeds inositol tetrakisphosphate was formed from [3H]inositol 1,3,4-trisphosphate but not from [3H]inositol 1,4,5-trisphosphate. Inositol 1,3,4-trisphosphate kinase was purified to a specific activity of 3.55 min−1 mg−1 by polyethylenimine clarification and anion-exchange chromatography. The partially purified enzyme converted [3H]inositol 1,3,4-trisphosphate to inositol 1,3,4,5-tetrakisphosphate as the major product and inositol 1,3,4,6- and/or 1,2,3,4-tetrakisphosphate as the minor product. Subsequent experiments revealed a separate inositol 1,3,4,5-tetrakisphosphate 6-kinase activity, which could link these enzymes to inositol hexakisphosphate synthesis via the previously reported inositol 1,3,4,5,6-pentakisphosphate 2-kinase. The apparent Km values for inositol 1,3,4-trisphosphate kinase were 200 ± 0 nm for inositol 1,3,4-trisphosphate and 171 ± 4 μm for ATP, and the reaction was not reversible. The kinetics were such that no activity could be detected using unlabeled inositol 1,3,4-trisphosphate and [γ-32P]ATP, which suggested that other kinases may have been observed when less purified fractions were incubated with radiolabeled ATP. Inositol 1,3,4-trisphosphate kinase was nonspecifically inhibited more than 80% by various inositol polyphosphates at a concentration of 100 μm.
Evidence for a Cytoskeleton-Associated Binding Site Involved in Prolamine mRNA Localization to the Protein Bodies in Rice Endosperm Tissue1
Authors: Muench Douglas G. , Wu Yujia , Coughlan Sean J. , Okita Thomas W. 
Published: July 2002

Abstract
Previous studies have demonstrated that the mRNAs encoding the prolamine and glutelin storage proteins are localized to morphologically distinct membranes of the endoplasmic reticulum (ER) complex in developing rice (Oryza sativa L.) endosperm cells. To gain insight about this mRNA localization process, we investigated the association of prolamine polysomes on the ER that delimit the prolamine protein bodies (PBs). The bulk of the prolamine polysomes were resistant to extraction by 1% Triton X-100 either alone or together with puromycin, which suggests that these translation complexes are anchored to the PB surface through a second binding site in addition to the well-characterized ribosome-binding site of the ER-localized protein translocation complex. Suppression of translation initiation shows that these polysomes are bound through the mRNA, as shown by the simultaneous increase in the amounts of ribosome-free prolamine mRNAs and decrease in prolamine polysome content associated with the membrane-stripped PB fraction. The prolamine polysome-binding activity is likely to be associated with the cytoskeleton, based on the association of actin and tubulin with the prolamine polysomes and PBs after sucrose-density centrifugation.
Differential Expression of a Novel Gene in Response to Coronatine, Methyl Jasmonate, and Wounding in the Coi1Mutant of Arabidopsis1
Authors: Benedetti Celso E. , Costa Cinthia L. , Turcinelli Silvia R. , Arruda Paulo 
Published: July 2002

Abstract
Coronatine is a phytotoxin produced by some plant-pathogenic bacteria. It has been shown that coronatine mimics the action of methyl jasmonate (MeJA) in plants. MeJA is a plant-signaling molecule involved in stress responses such as wounding and pathogen attack. In Arabidopsis thaliana, MeJA is essential for pollen grain development. The coi1 (forcoronatine-insensitive) mutant of Arabidopsis, which is insensitive to coronatine and MeJA, produces sterile male flowers and shows an altered response to wounding. When the differential display technique was used, a message that was rapidly induced by coronatine in wild-type plants but not incoi1 was identified and the corresponding cDNA was cloned. The coronatine-induced gene ATHCOR1 (forA.thalianacoronatine-induced) is expressed in seedlings, mature leaves, flowers, and siliques but was not detected in roots. The expression of this gene was dramatically reduced in coi1plants, indicating that COI1 affects its expression.ATHCOR1 was rapidly induced by MeJA and wounding in wild-type plants. The sequence of ATHCOR1 shows no strong homology to known proteins. However, the predicted polypeptide contains a conserved amino acid sequence present in several bacterial, animal, and plant hydrolases and includes a potential ATP/GTP-binding-site motif (P-loop).
Contribution of Malic Enzyme, Pyruvate Kinase, Phosphoenolpyruvate Carboxylase, and the Krebs Cycle to Respiration and Biosynthesis and to Intracellular pH Regulation during Hypoxia in Maize Root Tips Observed by Nuclear Magnetic Resonance Imaging and Gas Chromatography-Mass Spectrometry1
Authors: Edwards Shaune , Nguyen Bich-Ty , Do Binh , Roberts Justin K.M. 
Published: July 2002

Abstract
In vivo pyruvate synthesis by malic enzyme (ME) and pyruvate kinase and in vivo malate synthesis by phosphoenolpyruvate carboxylase and the Krebs cycle were measured by 13C incorporation from [1-13C]glucose into glucose-6-phosphate, alanine, glutamate, aspartate, and malate. These metabolites were isolated from maize (Zea mays L.) root tips under aerobic and hypoxic conditions. 13C-Nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry were used to discern the positional isotopic distribution within each metabolite. This information was applied to a simple precursor-product model that enabled calculation of specific metabolic fluxes. In respiring root tips, ME was found to contribute only approximately 3% of the pyruvate synthesized, whereas pyruvate kinase contributed the balance. The activity of ME increased greater than 6-fold early in hypoxia, and then declined coincident with depletion of cytosolic malate and aspartate. We found that in respiring root tips, anaplerotic phosphoenolpyruvate carboxylase activity was high relative to ME, and therefore did not limit synthesis of pyruvate by ME. The significance of in vivo pyruvate synthesis by ME is discussed with respect to malate and pyruvate utilization by isolated mitochondria and intracellular pH regulation under hypoxia.
Strontium-Induced Repetitive Calcium Spikes in a Unicellular Green Alga1
Authors: Bauer Claudia S. , Plieth Christoph , Bethmann Birgit , Popescu Ondina , Hansen Ulf-Peter , Simonis Wilhelm , Schönknecht Gerald 
Published: July 2002

AbstractThe divalent cation Sr2+ induced repetitive transient spikes of the cytosolic Ca2+ activity [Ca2+]cy and parallel repetitive transient hyperpolarizations of the plasma membrane in the unicellular green algaEremosphaera viridis. [Ca2+]cymeasurements, membrane potential measurements, and cation analysis of the cells were used to elucidate the mechanism of Sr2+-induced [Ca2+]cyoscillations. Sr2+ was effectively and rapidly compartmentalized within the cell, probably into the vacuole. The [Ca2+]cy oscillations cause membrane potential oscillations, and not the reverse. The endoplasmic reticulum (ER) Ca2+-ATPase blockers 2,5-di-tert-butylhydroquinone and cyclopiazonic acid inhibited Sr2+-induced repetitive [Ca2+]cy spikes, whereas the compartmentalization of Sr2+ was not influenced. A repetitive Ca2+ release and Ca2+ re-uptake by the ER probably generated repetitive [Ca2+]cyspikes in E. viridis in the presence of Sr2+. The inhibitory effect of ruthenium red and ryanodine indicated that the Sr2+-induced Ca2+ release from the ER was mediated by a ryanodine/cyclic ADP-ribose type of Ca2+ channel. The blockage of Sr2+-induced repetitive [Ca2+]cy spikes by La3+ or Gd3+ indicated the necessity of a certain influx of divalent cations for sustained [Ca2+]cy oscillations. Based on these data we present a mathematical model that describes the baseline spiking [Ca2+]cy oscillations in E. viridis.
Implications of a Developmental-Stage-Dependent Thylakoid-Bound Protease in the Stabilization of the Light-Harvesting Pigment-Protein Complex Serving Photosystem II during Thylakoid Biogenesis in Red Kidney Bean1
Authors: Tziveleka Leto-Aikaterini , Argyroudi-Akoyunoglou Joan H. 
Published: July 2002

Abstract
Intact etioplasts of bean (Phaseolus vulgaris) plants exhibit proteolytic activity against the exogenously added apoprotein of the light-harvesting pigment-protein complex serving photosystem II (LHCII) that increases as etiolation is prolonged. The activity increases in the membrane fraction but not in the stroma, where it remains low and constant and is mainly directed against LHCII and protochlorophyllide oxidoreductase. The thylakoid proteolytic activity, which is low in etioplasts of 6-d-old etiolated plants, increases in plants pretreated with a pulse of light or exposed to intermittent-light (ImL) cycles, but decreases during prolonged exposure to continuous light, coincident with chlorophyll (Chl) accumulation. To distinguish between the control of Chl and/or development on proteolytic activity, we used plants exposed to ImL cycles of varying dark-phase durations. In ImL plants exposed to an equal number of ImL cycles with short or long dark intervals (i.e. equal Chl accumulation but different developmental stage) proteolytic activity increased with the duration of the dark phase. In plants exposed to ImL for equal durations to such light-dark cycles (i.e. different Chl accumulation but same developmental stage) the proteolytic activity was similar. These results suggest that the protease, which is free to act under limited Chl accumulation, is dependent on the developmental stage of the chloroplast, and give a clue as to why plants in ImL with short dark intervals contain LHCII, whereas those with long dark intervals possess only photosystem-unit cores and lack LHCII.
Phosphorylated Nitrate Reductase and 14-3-3 Proteins
Authors: Athwal Gurdeep S. , Huber Joan L. , Huber Steven C. 
Published: July 2002

Abstract
The inactivation of phosphorylated nitrate reductase (NR) by the binding of 14-3-3 proteins is one of a very few unambiguous biological functions for 14-3-3 proteins. We report here that serine and threonine residues at the +6 to +8 positions, relative to the known regulatory binding site involving serine-543, are important in the interaction with GF14ω, a recombinant plant 14-3-3. Also shown is that an increase in ionic strength with KCl or inorganic phosphate, known physical effectors of NR activity, directly disrupts the binding of protein and peptide ligands to 14-3-3 proteins. Increased ionic strength attributable to KCl caused a change in conformation of GF14ω, resulting in reduced surface hydrophobicity, as visualized with a fluorescent probe. Similarly, it is shown that the 5′ isomer of AMP was specifically able to disrupt the inactive phosphorylated NR:14-3-3 complex. Using the 5′-AMP fluorescent analog trinitrophenyl-AMP, we show that there is a probable AMP-binding site on GF14ω.