bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification and Characterization of an Inducible NAD(P)H Dehydrogenase from Red Beetroot Mitochondria
Authors: Menz R. I. , Day D. A. 
Published: October 2016

Abstract
Exogenous NADH oxidation of mitochondria isolated from red beetroots (Beta vulgaris L.) increased dramatically upon slicing and aging the tissue. Anion-exchange chromatography of soluble fractions derived by sonication from fresh and aged beetroot mitochondria yielded three NADH dehydrogenase activity peaks. The third peak from aged beetroot mitochondria was separated into two activities by blue-affinity chromatography. One of these (the unbound peak) readily oxidized dihydrolipoamide, whereas the other (the bound peak) did not. The latter was an NAD(P)H dehydrogenase with high quinone and ferricyanide reductase activity and was absent from fresh beet mitochondria. Further affinity chromatography of the NAD(P)H dehydrogenase indicated enrichment of a 58-kD polypeptide on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We propose that this 58-kD protein is the inducible, external NADH dehydrogenase.
Coarse and Fine Control and Annual Changes of Sucrose-Phosphate Synthase in Norway Spruce Needles
Authors: Loewe A. , Einig W. , Hampp R. 
Published: October 2016

Abstract
Annual changes of activity of sucrose-phosphate synthase (SPS) from spruce (Picea abies [L.] Karst.) needles were studied with respect to three regulatory levels: metabolic fine control, covalent modification (phosphorylation), and protein amount. Glucose-6-phosphate served as an allosteric activator of spruce SPS by shifting the Michaelis constant for the substrate fructose-6-phosphate from 4.2 to 0.59 mM, whereas inorganic phosphate competitively inhibited this activation. The affinity for the other substrate, UDP-glucose, was unaffected. Incubation of the crude extract with ATP resulted in a time- and concentration-dependent decrease of the maximal velocity of SPS. This inactivation was sensitive to staurosporine, a potent protein kinase inhibitor, indicating the participation of a protein kinase. Probing SPS protein with heterologous antibodies showed that the subunit of spruce SPS is an approximately 139-kD protein and that changes in the extractable activity during the course of a year were correlated with the amount of SPS protein. High SPS activities in winter were paralleled by increased levels of the activator glucose-6-phosphate and the substrate fructose-6-phosphate, indicating a high capacity for sucrose synthesis that may be necessary to maintain photosynthetic CO2 fixation in cold-hardened spruce needles.
Antioxidant Response to NaCl Stress in a Control and an NaCl-Tolerant Cotton Cell Line Grown in the Presence of Paraquat, Buthionine Sulfoximine, and Exogenous Glutathione
Authors: Gossett D. R. , Banks S. W. , Millhollon E. P. , Lucas M. C. 
Published: October 2016

Abstract
A cotton (Gossypium hirsutum L.) control and NaCl-tolerant cell line (cv Coker 312) were grown on media with or without NaCl in the presence or absence of paraquat, buthionine sulfoximine, and oxidized glutathione. On medium with 150 mM NaCl the NaCl-tolerant cell line exhibited no reduction in growth, whereas a 96% reduction was observed in the control line. The NaCl-tolerant cell line that was grown on 150 mM NaCl exhibited significantly greater catalase (341%), peroxidase (319%), glutathione reductase (287%), ascorbate peroxidase (450%), [gamma]-glutamylcysteine synthetase (224%), and glutathione S-transferase (500%) activities than the intolerant control. The NaCl-tolerant cell line had a significantly lower dehydroascorbic acid/ascorbic acid ratio. Paraquat reduced growth by 20 and 53.7%, respectively, in the NaCl-tolerant and control cell line. The NaCl-tolerant cell line also showed a slight tolerance to buthionine sulfoximine. In the buthionine sulfoximine experiments reduced glutathione restored growth in both cell lines, whereas oxidized glutathione restored growth only in the NaCl-tolerant cell line. These data indicate that the NaCl-tolerant cell line exhibited a cross-tolerance to a variety of stress variables and had a more active ascorbate-glutathione cycle.
Arginase, Arginine Decarboxylase, Ornithine Decarboxylase, and Polyamines in Tomato Ovaries (Changes in Unpollinated Ovaries and Parthenocarpic Fruits Induced by Auxin or Gibberellin)
Authors: Alabadi D. , Aguero M. S. , Perez-Amador M. A. , Carbonell J. 
Published: October 2016

Abstract
Arginase (EC 3.5.3.1) activity has been found in the ovaries and Young fruits of tomato (Lycopersicon esculentum Mill. cv Rutgers).Changes in arginase, arginine decarboxylase (EC 4.1.1.19), and ornithine decarboxylase activity (EC 4.1.1.17) and levels of free and conjugated putrescine, spermidine, and spermine were determined in unpollinated ovaries and in parthenocarpic fruits during the early stages of development induced by 2,4-dichlorophenoxyacetic acid (2,4-D) or gibberellic acid (GA3). Levels of arginase, free spermine, and conjugates of the three polyamines were constant in unpollinated ovaries and characteristic of a presenescent step. A marked decrease in arginase activity, free spermine, and polyamine conjugates was associated with the initiation of fruit growth due to cell division, and when cell expansion was initiated, the absence of arginase indicated a redirection of nitrogen metabolism to the synthesis of arginine. A transient increase in arginine decarboxylase and ornithine decarboxylase was also observed in 2,4-D-induced fruits. In general, 2,4-D treatments produced faster changes than GA3, and without treatment, unpollinated ovaries developed only slightly and senescence was hardly visible. Sensitivity to 2,4-D and GA3 treatment remained for at least 2 weeks postanthesis.
3,7-Dichloroquinolinecarboxylic Acid Inhibits Cell-Wall Biosynthesis in Maize Roots
Authors: Koo S. J. , Neal J. C. , DiTomaso J. M. 
Published: October 2016

Abstract
The mode of action of the herbicide 3,7-dichloroquinolinecar-boxylic acid (quinclorac) was examined by measuring incorporation of [14C]glucose, [14C]acetate, [3H]thymidine, and [3H]uridine into maize (Zea mays) root cell walls, fatty acids, DNA, and RNA, respectively. Among the precursors examined, 10 [mu]M quinclorac inhibited [14C]glucose incorporation into the cell wall within 3 h. Fatty acid and DNA biosynthesis were subsequently inhibited, whereas RNA biosynthesis was unaffected. In contrast to the cellulose synthesis inhibitor 2,6-dichlorobenzonitrile, quinclorac strongly inhibited cellulose and a hemicellulose fraction presumed to be glucuronoarabinoxylan. However, the synthesis of (1–&gt;3),(1–&gt;4)-β-D-glucans was only slightly inhibited. The degree of inhibition was time- and dose-dependent. By 4 h after treatment, the concentration that inhibited [14C]glucose incorporation into the cell wall, cellulose, and the sensitive hemicellulose fraction by 50% was about 15, 5, and 20 [mu]M, respectively. Concomitant with an inhibition of [14C]glucose incorporation into the cell wall, quinclorac treatment led to a marked accumulation of radioactivity in the cytosol. The increased radioactivity was found mostly in glucose and fructose. However, total levels of glucose, fructose, and uridine diphosphate-glucose were not changed greatly by quinclorac. These data suggest that quinclorac acts primarily as a cell-wall biosynthesis inhibitor in a susceptible grass by a mechanism that is different from that of 2,6-dichlorobenzonitrile.
Stomatal Guard Cells Are Totipotent
Authors: Hall R. D. , Riksen-Bruinsma T. , Weyens G. , Lefebvre M. , Dunwell J. M. , Krens F. A. 
Published: October 2016

Abstract
It has been successfully demonstrated, using epidermis explants of sugar beet (Beta vulgaris L.), that stomatal guard cells retain full totipotent capacity. Despite having one of the highest degrees of morphological adaptation and a unique physiological specialization, it is possible to induce a re-expression of full (embryogenic) genetic potential in these cells in situ by reversing their highly differentiated nature to produce regenerated plants via a callus stage. The importance of these findings both to stomatal research and to our understanding of cytodifferentiation in plants is discussed.
Frequencies, Timing, and Spatial Patterns of Co-Suppression of Nitrate Reductase and Nitrite Reductase in Transgenic Tobacco Plants
Authors: Palauqui J. C. , Elmayan T. , de Borne F. D. , Crete P. , Charles C. , Vaucheret H. 
Published: October 2016

Abstract
Frequencies, timing, and spatial patterns of co-suppression of the nitrate (Nia) and nitrite (Nii) genes were analyzed in transgenic tobacco (Nicotiana tabacum) plants carrying either Nia or Nii cDNAs under the control of the 35S promoter, or a Nii gene with its own regulatory signals (promoter, introns, and terminator) cloned downstream of two copies of the enhancer of the 35S promoter. We show that (a) the frequencies of transgenic lines affected by co- suppression are similar for the three constructs, ranging from 19 to 25%; (b) Nia and Nii co-suppression are triggered stochastically during a phenocritical period of 2 weeks between germination and flowering; (c) the timing of co-suppression (i.e. the percentage of isogenic plants affected by co-suppression reported as a function of the number of days of culture) differs from one transgenic line to another; (d) the percentage of isogenic plants affected by co-suppression is increased by growing the plants in vitro prior to their transfer to the greenhouse and to the field; and (e) at the end of the culture period, plants are either unaffected, completely co-suppressed, or variegated. Suppressed and nonsuppressed parts of these variegated plants are separated by a vertical plane through the stem in Nia co-suppression, and separated by a horizontal plane in Nii co-suppression.
Accumulation of Al in Root Mucilage of an Al-Resistant and an Al-Sensitive Cultivar of Wheat
Authors: Archambault D. J. , Zhang G. , Taylor G. J. 
Published: October 2016

Abstract
To estimate rates of Al accumulation within the symplasm, all apoplastic pools of Al need to be eliminated or accounted for. We have developed a revised kinetic protocol that allows us to estimate the contribution of mucilage-bound Al to total, nonexchangeable Al, and to eliminate the mucilage as an apoplastic pool of Al. By comparing the Al content of excised root tips (2 cm) of wheat (Triticum aestivum L.) with and without the removal of the mucilage (using a 10-min wash in 1 M NH4Cl), we found that Al bound to the mucilage accounted for approximately 25 to 35% of Al remaining after desorption in citric acid. The kinetics of Al uptake into mucilage were biphasic, with a rapid phase occurring in the first 30 min of uptake, followed by a linear phase occurring in the remainder of the experimental period (180 min). By adopting a step for removal of mucilage into our existing kinetic protocol, we have been able to isolate a linear phase of uptake with only a slight deviation from linearity in the first 5 min. Although we cannot unambiguously identify this phase of uptake as uptake into the symplasm, we believe this new protocol provides us with the most accurate quantitative estimate of symplastic Al yet available.
Changes in Calcium-Dependent Protein Kinase Activity during in Vitro Tuberization in Potato
Authors: MacIntosh G. C. , Ulloa R. M. , Raices M. , Tellez-Inon M. T. 
Published: October 2016

Abstract
A soluble Ca2+-dependent protein kinase (CDPK) was purified to homogeneity in potato (Solanum tuberosum L.) plants. Potato CDPK was strictly dependent on Ca2+ (one-half maximal activation 0.6 [mu]M) and phosphorylated a wide diversity of substrates, in which Syntide 2 was the best phosphate acceptor (Michaelis constant = 30 [mu]M). The kinase was inhibited by Ca2+-chelating agents, phenotiazine derivatives, and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (one-half maximal inhibition = 0.25 mM). Polyclonal antibodies directed against the regulatory region of the soybean CDPK recognized a 53-kD polypeptide. In an autophosphorylation assay, this same band was strongly labeled with [[gamma]-32P]ATP in the presence of Ca2+. CDPK activity was high in nontuberized plants, but increased 2.5-fold at the onset of tuber development and was reduced to one-half of its original activity when the tuber had completed formation. In the early stages of tuberization, Ca2+-dependent phosphorylation of endogenous targets (specific bands of 68, 51, and 46 kD) was observed. These polypeptides were not labeled in nontuberizing plants or in completely formed tubers, indicating that this phosphorylation is a stage-specific event. In addition, dephosphorylation of specific polypeptides was detected in tuberizing plants, suggesting the involvement of a phosphatase. Preincubation of crude extracts with phosphatase inhibitors rendered a 100% increase in CDPK activity.
Characterization of Glutathione S-Transferase Isoforms in Three Maize Inbred Lines Exhibiting Differential Sensitivity to Alachlor
Authors: Rossini L. , Jepson I. , Greenland A. J. , Gorla M. S. 
Published: October 2016

Abstract
Glutathione S-transferases (GSTs) are a family of isozymes that catalyze the conjugation of glutathione to several xenobiotics, including a number of important herbicides. Several GST isoforms have been identified in maize (Zea mays L.). In this study we focused on three isoforms, GST I, II, and IV, derived from homo-or heterodimerization of two subunits GST-29 and GST-27, which have been shown to be responsible for reactivity to alachlor. The expression of these isoforms was examined in three inbred lines of maize that showed tolerance, susceptibility, and intermediate resistance to alachlor (2-Cl-N-[2,6-diethylphenyl]-N-[methoxymethyl]acetamide) treatment. The different isoforms were separated by anion-exchange chromatography and subunits were quantified by western blot analysis. GST assays were performed against both 1-Cl-2,4-dinitrobenzene and alachlor. This analysis showed that the susceptible and intermediate lines exhibit impaired function in the GST-27 and GST-29 subunits, respectively. In addition, this study suggests that GST IV is the principal, detoxifying enzyme for alachlor, although GST I and II are required to achieve tolerance to high rates of the herbicide.
Solubilization, Partial Purification, and Characterization of a Binding Site for a Glycopeptide Elicitor from Microsomal Membranes of Tomato Cells
Authors: Fath A. , Boller T. 
Published: October 2016

Abstract
Purified glycopeptides derived from yeast invertase act as highly potent elicitors in suspension-cultured tomato (Lycopersicon esculentum [L.] Mill) cells, inducing ethylene biosynthesis and phenylalanine ammonia lyase half-maximally at concentrations of 1 to 5 nM. We previously demonstrated the presence of a high-affinity binding site that specifically recognized these glycopeptides in cells and microsomal membranes of tomato (C.W. Basse, A. Fath, T. Boller [1993] J Biol Chem 268: 14724–14731). This elicitor-binding site was solubilized in an active form from the microsomal membranes using the neutral detergents n-dodecylmaltoside and n-dodecanoylsucrose and purified 67-fold in a single step by anion-exchange chromatography. Ligand saturation studies and competition experiments with unlabeled glycopeptides and glycans demonstrated that the detergent-solubilized elicitor-binding site retained the high affinity (Kd approximately 1–4 nM) and selectivity of the membrane-bound form. The binding site was found to have a high affinity for N-linked glycans with nine mannosyl residues from fungal glycoproteins, whereas it did not recognize the typical mammalian glycans with nine mannosyl residues, demonstrating further its high selectivity.
Physiological Characterization of Root Zn2+ Absorption and Translocation to Shoots in Zn Hyperaccumulator and Nonaccumulator Species of Thlaspi
Authors: Lasat M. M. , Baker AJM. , Kochian L. V. 
Published: October 2016

Abstract
Radiotracer techniques were employed to characterize 65Zn2+ influx into the root symplasm and translocation to the shoot in Thlaspi caerulescens, a Zn hyperaccumulator, and Thlaspi arvense, a nonaccumulator. A protocol was developed that allowed us to quantify unidirectional 65Zn2+ influx across the root-cell plasma membrane (20 min of radioactive uptake followed by 15 min of desorption in a 100 [mu]M ZnCl2 + 5 mM CaCl2 solution). Concentration-dependent Zn2+ influx in both Thlaspi species yielded nonsaturating kinetic curves that could be resolved into linear and saturable components. The linear kinetic component was shown to be cell-wall-bound Zn2+ remaining in the root after desorption, and the saturable component was due to Zn2+ influx across the root-cell plasma membrane. This saturable component followed Michaelis-Menten kinetics, with similar apparent Michaelis constant values for T. caerulescens and T. arvense (8 and 6 [mu]M, respectively). However, the maximum initial velocity for Zn2+ influx in T. caerulescens root cells was 4.5-fold higher than for T. arvense, indicating that enhanced absorption into the root is one of the mechanisms involved in Zn hyperaccumulation. After 96 h 10-fold more 65Zn was translocated to the shoot of T. caerulescens compared with T. arvense. This indicates that transport sites other than entry into the root symplasm are also stimulated in T. caerulescens. We suggest that although increased root Zn2+ influx is a significant component, transport across the plasma membrane and tonoplast of leaf cells must also be critical sites for Zn hyperaccumulation in T. caerulescens.
Endo-β-Mannanase Activity Present in Cell Wall Extracts of Lettuce Endosperm prior to Radicle Emergence
Authors: Dutta S. , Bradford K. J. , Nevins D. J. 
Published: October 2016

Abstract
Lettuce (Lactuca sativa L.) endosperm cell walls isolated prior to radicle emergence underwent autohydrolysis, the rate of which was correlated with whether radicle emergence would subsequently occur. Extraction of endosperm cell walls with 6 M LiCl suppressed autohydrolysis, and the desalted extract possessed activity that was capable of hydrolyzing purified locust bean galactomannan but not arabinogalactan, carboxymethylcellulose, glucomannan, polygalacturonic acid, tomato galactomannan, or native lettuce endosperm cell walls. Some hydrolytic activity was detected on endosperm cell walls if they were modified by partial trifluoroacetic acid hydrolysis or pretreatment with guanidinium thiocyanate. In extended incubations the cell wall enzyme extract released only large molecular mass fragments from locust bean galactomannan, indicating primarily endo-activity. Galactomannan-hydrolyzing activity in the cell wall extract increased as a function of imbibition time and was greatest just prior to radicle emergence. Thermoinhibition (imbibition at 32[deg]C) or treatment with abscisic acid at a temperature optimal for germination (25[deg]C) suppressed both germination and endosperm cell wall mannanase activity, whereas alleviation of thermoinhibition with gibberellic acid was accompanied by significant enhancement of mannanase activity. We conclude that a cell wall-bound endo-β-mannanase is expressed in lettuce endosperm prior to radicle emergence and is regulated by the same conditions that govern germination.
Influence of Gene Dosage on Carbohydrate Synthesis and Enzymatic Activities in Endosperm of Starch-Deficient Mutants of Maize
Authors: Singletary G. W. , Banisadr R. , Keeling P. L. 
Published: October 2016

Abstract
In cereals, starch is synthesized in endosperm cells, which have a ploidy level of three. By studying the allelic dosage of mutants affecting starch formation in maize (Zea mays L.) kernels, we determined the effect of down-regulated enzyme activity on starch accumulation and the activity of associated enzymes of carbohydrate metabolism. We found a direct relationship between the amount of starch produced in the endosperm and the gene dosage of amylose extender-1, brittle-2, shrunken1, and sugary-1 mutant alleles. Changes in starch content were found to be caused by changes in the duration as well as the rate of starch synthesis, depending on the mutant. Branching enzyme, ADP-glucose pyrophosphorylase, and sucrose synthase activities were linearly reduced in endosperm containing increasing dosages of amylose extender-1, brittle-2, and shrunken-1 alleles, respectively. De-branching enzyme activity declined only in the presence of two or three copies of sugary-1. No enzyme-dosage relationship occurred with the dull1 mutant allele. All mutants except sugary-1 displayed large increases (approximately 2- to 5-fold) in activity among various enzymes unrelated to the structural gene. This occurred in homozygous recessive genotypes, as did elevated concentrations of soluble sugars, and differed in magnitude and distribution among enzymes according to the particular mutation.
Ultraviolet B-Sensitive Rice Cultivar Deficient in Cyclobutyl Pyrimidine Dimer Repair
Authors: Hidema J. , Kumagai T. , Sutherland J. C. , Sutherland B. M. 
Published: October 2016

Abstract
Repair of cyclobutyl pyrimidine dimers (CPDs) in DNA is essential in most organisms to prevent biological damage by ultraviolet (UV) light. In higher plants tested thus far, UV-sensitive strains had higher initial damage levels or deficient repair of nondimer DNA lesions but normal CPD repair. This suggested that CPDs might not be important for biological lesions. The photosynthetic apparatus has also been proposed as a critical target. We have analyzed CPD induction and repair in the UV-sensitive rice (Oryza sativa L.) cultivar Norin 1 and its close relative UV-resistant Sasanishiki using alkaline agarose gel electrophoresis. Norin 1 is deficient in cyclobutyl pyrimidine dimer photoreactivation and excision; thus, UV sensitivity correlates with deficient dimer repair.
Observations of Ice Nucleation and Propagation in Plants Using Infrared Video Thermography
Authors: Wisniewski M. , Lindow S. E. , Ashworth E. N. 
Published: October 2016

Abstract
We evaluated the use of infrared (IR) video thermography to observe directly ice nucleation and propagation in plants. An imaging radiometer with an HgCdTe long-wave (8–12 [mu]m) detector was utilized to image the thermal response of plants during freezing. IR images were analyzed in real time and recorded on videotape. Information on the videotape was subsequently accessed and analyzed utilizing IR image analysis software. Freezing of water droplets as small as 0.5 [mu]L was clearly detectable with the radiometer. Additionally, a comparison of temperature tracking data collected by the radiometer with data collected with thermocouples showed close correspondence. Monitoring of an array of plant species under different freezing conditions revealed that ice nucleation and propagation are readily observable by thermal imaging. In many instances, the ice nucleation-active bacterium Pseudomonas syringae placed on test plants could be seen to initiate freezing of the whole plant. Apparent ice nucleation by intrinsic nucleators, despite the presence of ice nucleation-active bacteria, was also evident in some species. Floral bud tissues of peach (Prunus persica) could be seen to supercool below the temperature of stem tissues, and ice nucleation at the site of insertion of the thermocouple was frequently observed. Rates of propagation of ice in different tissues were also easily measured by thermal imaging. This study demonstrates that IR thermography is an excellent method for studying ice nucleation and propagation in plants.