bluuebunny/crossref_metadata_2025_split huggingface dataset:
Light‐Dependent Chloroplast Reorientation in Mougeotia and Mesotaenium: Riased by Pigment‐Regulated Plasmalemma Anchorage Sites to Actin Filaments?
Authors: Grolig F. , Wagner G. 
Published: February 2014

AbstractConjugatophycean green algae, such as Mougeotia and Mesotaenium, are presumably the most ancient organisms to show phytochrome‐mediated photomodulatory processes, i.e. chloroplast reorientational movements. Experiments have provided striking evidence for a dichroic mode of light absorption by the phytochrome molecules located at the periphery of the cylindrical cell; in addition, the transition moment of the chromophoric group of phytochrome has been shown to change by a fixed angle upon conversion of Pr to Pfr and vice versa. Consequently, a hypothesis has been put forward involving a tetrapolar phytochrome gradient at the plasmalemma. This presumed pigment pattern precisely controls chloroplast reorientation in the low‐irradiance response. Intriguingly, a blue‐light absorbing pigment is expressed in Mougeotia as well, which also mediates low‐irradiance response via a presumed tetrapolar gradient, apparently independent of the phytochrome.Two hypotheses for the controlling mechanism of chloroplast reorientation have been put forward:
Coupling of the influx of calcium through the plasmalemma to the tetrapolar gradient of the sensor pigment proper, resulting in a tetrapolar gradient of calcium in the cytoplasm. This is the “reorientation via calcium” hypothesis.
Coupling of actin anchorage sites on the plasmalemma to the tetrapolar gradient of the sensor pigment proper, resulting in a tetrapolar gradient of actin anchorage sites. Cytoplasmic calcium, released from internal stores or taken up through the plasmalemma, triggers actomyosin interaction. This is the “reorientation via anchorage sites” hypothesis.
Consistent with the latter hypothesis, photoregulation by two steps seems to be indicated, (i) cytoplasmic initiation of actomyosin interaction, (ii) the graded formation of plasmalemma anchorage sites for actin filaments.
General Mechanisms for Solute Transport Across the Tonoplast of Plant Vacuoles: a Patch‐Clamp Survey of Ion Channels and Proton Pumps
Authors: Hedrich R. , Barbier‐Brygoo H. , Felle H. , Flügge U. I. , Lüttge U. , Maathuis F. J. M. , Marx S. , Prins H. B. A. , Raschke K. , Schnabl H. , Schroeder J. I. , Struve I. , Taiz L. , Ziegler P. 
Published: February 2014

AbstractThe electrical properties of the tonoplast from a large variety of plant materials such as mesophyll cells, storage cells, tumor cells, suspension cultured cells, guard cells, coleoptile cells, and liverwort cells have been investigated using the patch‐clamp technique. Whole‐vacuole recordings were employed to study the dynamics of an ATP‐dependent proton pump by directly measuring the electrogenic currents. The addition of Mg‐ATP induced an inwardly directed current which depolarized the tonoplast (the vacuole becoming positive inside). Furthermore, voltage‐dependent passive ion fluxes were analyzed using whole vacuoles and isolated membrane patches. Whole‐vacuolar currents and single‐channel currents were induced at hyperpolarizing potentials, whereas currents decreased at positive trans‐tonoplast potentials. The electrical properties of the tonoplast of vacuoles from various plant tissues were similar and it was concluded that ion fluxes across the tonoplast follow the same general mechanisms.
Diurnal Changes in the Regulatory Properties of Phosphoenolpyruvate Carboxylase in CAM Plants: Are Alterations in the Quaternary Structure Involved?
Authors: Krüger I. , Kluge M. 
Published: February 2014

AbstractDay — and night‐forms of phosphoenolpyruvate carboxylase (EC 4.1.1.31) (PEP‐C) were extracted from leaves of the CAM plantKalanchoë daigremontiana. During storage after extraction, the day‐form spontaneously lost its sensitivity towards the allosteric inhibitorl‐malate. This effect was accelerated by inorganic phosphate, PEP, 3‐PGA and G‐6‐P.l‐Malate however stabilized the malate sensitivity of the day‐form of PEP‐C.Crude desalted extracts of the day‐form and of the night‐form of PEP‐C were subjected to ultracentrifugation on a continuous sucrose gradient in the presence of malate and of marker enzymes. Both forms of PEP‐C were found to have relative molecular masses of about 200,000. This suggests that both forms represent the dimers of the enzyme protein. The result also suggests that reversible dissociation and association of enzyme subunits is not the mechanism which brings about the interconversion of the two PEP‐C forms during the diurnal CAM cyclein vivo.
Superoxide Dismutase and Unribosylated Cytokinins Interact in the Control of NAD(P)H‐Peroxidation
Authors: Elstner E. F. , Galek Helena 
Published: February 2014

AbstractNAD(P)H is rapidly oxidized in the presence of peroxidase, a substituted monophenol such as p‐coumaric acid, and Mn2+ ions. As recently reported by Miller (1985), this NAD(P)H oxidation at the expense of molecular oxygen is inhibited by submicromolar concentrations of Cu2+ ions. This inhibition by cupric ions is counteracted by micromolar concentrations of cytokinins. We now show that NAD(P)H‐oxidation by the above system is under the control of superoxide dismutase, where in the absence of cytokinin‐copper, superoxide dismutase stimulates NAD(P)H‐oxidation. In the presence of unribosylated cytokinins and copper, however, superoxide dismutase acts as an inhibitor. Thus cytokinins and superoxide dismutase may interact in the control of the redox state of plant cells.
Biochemical and Immunological Properties of Solubilized Tonoplast ATPase of the Facultative CAM Plant Mesembryanthemum crystallinum in the C3 and CAM States
Authors: Struve I. , Lüttge U. 
Published: February 2014

AbstractA nitrate‐sensitive, azide‐insensitive ATPase isolated from M. crystallinum in the C3 and in the CAM state has been solubilized in active form using octylglucoside and Zwittergent 3–14. Like the membrane‐bound tonoplast ATPase, the solubilized ATPase showed an increase in ATP‐hydrolysis activity after transition from the C3 to the CAM mode of photosynthesis. The characteristics of the membrane‐bound and the solubilized tonoplast ATPase were comparable with respect to salt stimulation, inhibitor effects, and MgATP2–‐concentration dependence. Differing from the membrane‐bound ATPases, the solubilized ATPase from C3‐ and CAM‐M. crystallinum showed a pH optimum between pH 6.5 and 7.0.In order to compare the solubilized ATPases immunologically, antibodies were prepared against the tonoplast fraction of C3‐ and CAM‐M. crystallinum. A cross‐reaction was observed between antibodies against the tonoplast ATPase from C3‐ and CAM‐M. crystallinum and the solubilized ATPase from C3‐ and CAM‐M. crystallinum. A cross‐reaction was also observed between antibodies against the tonoplast ATPase from C3‐ and CAM‐M. crystallinum and the solubilized tonoplast ATPase from Kalanchoë daigremontiana. However, there was no cross‐reaction with the solubilized plasmalemma ATPase from Festuca rubra.
Isolation and Characterization of Mustard (Sinapis alba L.) Seed Storage Proteins
Authors: Fischer W. , Schopfer P. 
Published: February 2014

AbstractA total storage protein fraction was prepared from mustard (Sinapis alba L.) seeds via isolated protein bodies and characterized by sedimentation, immunological, and electrophoretic techniques. Mustard seed storage protein consists of three fractions (1) a “legumin‐like” 13‐S complex composed of two pairs of disulfide‐linked polypeptides (16.5 + 28.5 kDa and 19.5 + 34 kDa, respectively) and two single polypeptides (18 kDa and 26 kDa), (2) a “vicilin‐like” 9‐S complex composed of two glycoproteins (64 kDa and 77 kDa), and (3) two small polypeptides (10 kDa and 11 kDa) which probably represent the 1.7‐S complex found in other Cruciferae. In contrast to related species, no glycosylated polypeptide was found in the 13‐S complex. Immunological relationships were found between the paired polypeptides of the 13‐S complex but not between polypeptides of the 13‐S complex and polypeptides of the 9‐S complex. Pulse‐chase labeling and in vitro translation of polysomal RNA from young embryos demonstrated that the polypeptides of the 13‐S complex originate from high molecular mass precursors, except for the 18 kDa polypeptide which appears to be synthesized in its final size. The amino‐acid composition of the major polypeptides of the mustard storage protein is given.
Phototropism in Higher Plants — Controversies and Caveats1
Authors: Briggs W. R. , Baskin T. I. 
Published: February 2014

AbstractRecent literature on light‐induced changes in the distribution of growth and of endogenous growth regulators in the development of phototropic curvature is reviewed. It is concluded that in a great many cases the Cholodny‐Went hypothesis is sufficient to account for the growth changes bringing about curvature, though in certain dicotyledonous seedlings differential effects of light on the synthesis of growth inhibitors across the tissue from the lighted to the shaded side are implicated. The problems in the interpretation of results from experiments in which more than one photoresponse may be simultaneously induced are discussed and methods of circumventing them considered. Action spectroscopy suggests that dicotyledonous seedlings may have the same phototropic photoreceptor as monocotyledonous seedlings.
One Hundred and One Years of Chemotaxis. Pfeffer, Pheromones, and Fertilization
Authors: Jaenicke L. 
Published: February 2014

AbstractChemotaxis of flagellated unicellular gametes was discovered by Wilhelm Pfeffer. In most known systems the lure is a metabolic waste product ritualized for sexual attraction. A special case are the female gametes of brown algae. They secrete polyunsaturated C‐8 or C‐11 hydrocarbons mostly with straight chain or unsubstituted tri‐, penta‐ or heptacyclic structures. Their biogenetic origin stems from polyunsaturated fatty acids. The reactions leading to the different structures comprise lipoxygenase‐type radical formations and dehydrogenating decarboxylations. — Most gametes produce a variety of such hydrocarbons; however, only one of them is the active principle. Biological activity is highly stereospecific; but frequently the bouquets contain lures for other species. Although cross‐fertilization is excluded, they may be used to defend the habitat against overgrowth by other seaweeds. Besides chemoattractive action, some secretions also synchronize hatching of the spermatozoids. One of the compounds responsible is characterized by an epoxy substitution. — For most of the structures, stereospecific and versatile syntheses are available, which were used to investigate the binding site. This forms a template for the signal molecule with specifically situated polarizing groups that interact with the π‐electrons of the double bonds. The message is transformed into changes of flagellar beat patterns which ensure meeting of the partners followed by fertilization.
Salt‐Induced Hypodermal Transfer Cells in Roots of Prosopis farcta and Ion Distribution within Young Plants
Authors: Winter E. 
Published: February 2014

AbstractProsopis farcta was grown on hydroculture with additions of 0.5, 10, 50, and 100 mM NaCl and without salt treatment. In plants from a 0.5 mM NaCl treatment, Cl− was taken up into stems and leaves, but Na+ was withheld from the shoot. At 10 mM NaCl, shoot K+ concentration was below that of the control; Na+ and Cl− were taken up to stems and cotyledons in nearly equimolar amounts. However, in the leaves, Na+ concentrations were only half of those of Cl−. With increasing salt stress, Na+ and Cl− were transported to the shoot, but kept at relatively low levels in the roots. Na+/ K+ ratios in roots did not increase proportionally to those in the solution. At an external Na+/K+ of > 5 and a root Na+/K+ of >1 (10 mM NaCl treatment), K+ selectivity was induced which rose exponentially with increasing salt stress; and cell wall protuberances were discovered in the hypodermis at the zone of side root formation. These transfer cells were found neither in roots from the 0.5 mM NaCl treatment nor in the controls. Their possible role in the Na+/K+ selectivity of the roots of Prosopis farcta is discussed.
Cell Biology and Algal Taxonomy and Evolution Absolute Orientations of Basal Bodies in Green Algae Evaluated by Light Microscopy
Authors: Reize I. B. , Melkonian M. 
Published: February 2014

AbstractUsing high magnification Nomarski interference microscopy a series of optical sections has been obtained through flagellated cells of several green algae in an attempt to establish the absolute orientation of their basal bodies. Using this technique we have confirmed that inSpermatozopsis similisbasal bodies are displaced into the 1/7 o'clock position, whereas in gametes ofEnteromorpha linza, and zoospores ofTrebouxia ericibasal bodies are displaced into the 11/5 o'clock position. In addition we report for the first time that in zoospores ofMicrothamnion kuetzingianumbasal bodies are also displaced into the 11/5 o'clock position. Basal body absolute orientations can thus be determined by light microscopy and do not require serial section electron microscopy. The method should be useful for class‐level recognition of unknown green algae at the light microscope level.
Cryptophycean‐Like Double Membrane‐Bound Chloroplast in the Dinoflagellate, Dinophysis Ehrenb.: Evolutionary, Phylogenetic and Toxicological Implications
Authors: Schnepf E. , Elbrächter M. 
Published: February 2014

AbstractDinoflagellates of the genus Dinophysis are responsible for diarrhetic shellfish poisoning. Phototrophic species have an orange primary fluorescence indicating the presence of phycobilins. The chloroplasts greatly resemble cryptophycean chloroplasts having pairs of thylakoids and electron‐dense material in the thylakoid lumen. They are bound by only two membranes, in contrast to the blue‐green chloroplasts of Amphidinium wigrense Woloszynsk, which are enveloped by three membranes (Wilcox and Wedemayer, 1985). Possible ways of evolution of the Dinophysis chloroplasts, phylogenetical questions and implications for the monitoring of toxic dinoflagellates are discussed.
Quantification by ELISA of Cytokinins in Root‐Pressure Exudates of Urtica dioica Plants Grown under Different Nitrogen Levels
Authors: Fußeder A. , Wagner B. , Beck E. 
Published: February 2014

SummaryELISAs for [9R]iP, [9R]Z and (diH) [9R]Z have been worked out which, in combination with HPLC., allow the quantitative determination of cytokinins of the isopentenyladenin‐, zeatin‐ and dihydrozeatin‐type in samples of plant material. The three ELISAs are optimally applicable in the range from 0.5 to 20 pmoles of cytokinins per assay but reliable measurements can still be performed down to 0.05 pmoles. The assay has been applied to root pressure exudates obtained from Urtica dioica plants grown under controlled conditions and at different nitrogen (nitrate) levels. The predominant cytokinins of the xylem exudate were Z, Z‐nucleotide, iP, [9R]iP and iP‐nucleotide, while (diH)Z was present to a minor extent. The concentrations of these compounds were found to range between 0.2 and 3 pmoles per ml exudate.Interestingly, no effect of the different nitrogen nutrition on the pattern and concentration of cytokinins in the xylem exudate could be established.
Helicteres ovata (Sterculiaceae), Pollinated by Bats in Southeastern Brazil
Authors: Sazima M. 
Published: February 2014

AbstractThe interactions between Helicteres ovata flowers and the bat Glossophaga soricina were observed in south eastern Brazil. During bat visits, pollen is unselectively spread over small areas of the visitors' body (which is uncommon for a bat flower). Seemingly related to this limitation of pollen availability, the variable orientation of the stigma makes it able to pick up grains scattered on almost any part of the bat's body. Day visitors were two hummingbird species which do not pollinate the flowers. Most Brazilian Helicteres species have red flowers with a long androgynophore. The few modifications departing from the bird flower type within the genus suggest, together with the problem of pollen placing and collecting, that H. ovata is a recent derivate from the ornithophilous stock.
Analysis of cDNA Clones Encoding the Entire Ferredoxin I Precursor Polypeptide from Spinach
Authors: Wedel N. , Bartling D. , Herrmann R. G. 
Published: February 2014

AbstractWe report the isolation and characterization of a recombinant cDNA phage from a lambda gt11 expression library made from polyadenylated spinach RNA that encodes the entire precursor polypeptide of ferredoxin I. The deduced sequence predicts a molecular mass of 10.5 kDa (97 amino acid residues) for the mature protein and a transit peptide of 50 residues (5.2 kDa). In vitro synthesized ferredoxin precursor was used for import experiments with isolated unbroken spinach chloroplasts. The polypeptide was correctly directed to the organelle stroma and processed to the size of the mature protein. Northern analysis indicates a mRNA size of ca. 850 nucleotides which is close to the size of the cDNA insert (ca. 700 bp).
Quantum Requirement for Photoreactivation of Inactivated Nitrate Reductase of Neurospora crassa Strain al‐2, bd
Authors: Pottiez B. , Krippahl G. , Ninnemann H. 
Published: February 2014

AbstractChemically inactivated nitrate reductase of Neurospora crassa strain al‐2, bd can be photoreactivated by blue light. The quantum requirement for this reaction in the presence of exogenous FMN was determined with different light intensities. The results are discussed with the alternate assumptions that free FMN or photoactivated FAD bound to the nitrate reductase molecule is the reactivating species.
The Molecular Analysis of the Light Adaptation Reactions in the Yellow‐green AlgaPleurochloris meiringensis(Xanthophyceae)
Authors: Büchel C. , Wilhelm C. , Lenartz‐Weiler I. 
Published: February 2014

AbstractThe xanthophycean algaPleurochloris meiringensiswas homocontinuously cultured under high light (16 W/m2) and low light (2 W/m2) conditions. In low light cells, the chlorophyll a content and the dry weight on per cell basis is increased, the maximal photosynthetic capacity per chlorophyll is decreased. The content of chlorophyll c, vaucheriaxanthin‐ester and heteroxanthin is similar in both cultures, whereas the content of diadinoxanthin and ß‐carotene is twice as high in high light cultures. High light cells contain more photosystem I and cytochrome f per chlorophyll than low light cells, whereas the QBcontent is found to be unchanged. Therefore, the ratio reaction center II/reaction center I is twofold higher in low light cells than in high light ones. The regulation of energy distribution between the photosystems is examined by fluorescence emission spectra at 77 K scanned after different preillumination of the cells. No wavelength dependent state I/state II transition can be detected. However,P. meiringensisregulates the energy distribution in response to light intensity: The higher the irradiance of preillumination, the higher the energy transfer to photosystem I. The sensitivity of the regulation to light intensity is increased in low light cells.
Photosensory Adaptation in Plants
Authors: Galland Paul 
Published: February 2014

AbstractPhotosensory adaptation (range adjustment) is of great importance in plants (including fungi and various microorganisms) that operate in large intensity ranges. The adaptation mechanisms of plants have some features in common with those of vertebrates and invertebrates. As with those systems, plants have biphasic exponential dark‐adaptation kinetics, that are much slower than the corresponding light adaptation kinetics. One needs to distinguish between sensor adaptation, which regulates range adjustment, and effector adaptation (habituation), which regulates the motor apparatus of the organism (flagellar movement or cell wall growth). In Phycomyces, and perhaps Stentor, sensor adaptation is mediated by the photoreceptor system. In contrast to vertebrates and invertebrates, dark adaptation can be controlled in some plants by special photoreceptors. In Phycomyces, these can be either photo‐products of the actinic photoreceptor(s) or not yet identified receptor pigments. In higher plants phytochrome can alter the state of adaptation.
Sugar Transport and Sulfite Action in Etioprotoplasts, Semi‐Etioprotoplasts and Green Protoplasts of Avena sativa L.
Authors: Lorenc‐Plucińska Gabriela , Miszalski Z. , Ziegler H. 
Published: February 2014

AbstractThe mechanism of glucose and sucrose transport and the influence of various concentrations of sulfite on its activity was studied in mesophyll protoplasts (etioprotoplasts, semi‐etioprotoplasts and green protoplasts) isolated from oat (Avena sativa L.) seedlings.Kinetic analysis of [14C] glucose loading (in darkness) revealed in each kind of protoplasts the presence of two transport components. At low exogenous glucose concentrations a saturable system was the main mode of transport. At concentrations higher than 20 mM the loading of glucose in all types of protoplasts was dominated by a non‐saturable, linear diffusion‐like component. The rate of glucose uptake was greatest in etioprotoplasts and lowest in green protoplasts.In contrast to the above we have not found saturable components of sucrose transport in any kind of protoplasts. The rate of its uptake was greatest in semi‐etioprotoplasts.Sulfite, at a concentration of < 1.0 mM stimulated and at ≥ 1.0 mM inhibited the uptake of glucose to etioprotoplasts and semi‐etioprotoplasts and inhibited that to green protoplasts at any concentration. The transport of sucrose underwent a significant inhibition in the various types of protoplasts only under the influence of 10.0 mM of sulfite ions.Inhibition of glucose uptake by sulfite was of the non‐competitive type.Sulfite also affected the level of adenylic nucleotides and lowered the energy charge and ATP/ADP ratio.Intensity of sulfite uptake was significantly higher in green protoplasts than in etioprotoplasts.
The Regulation of Chlorophyll Biosynthesis by the Action of Protochlorophyllide on glut‐RNA‐Ligase
Authors: Dörnem D. , Kotzaba K. , Rich P. , Breu V. , Senger H. 
Published: February 2014

AbstractThe pigment mutant C‐2A' of the green alga Scenedesmus obliquus accumulates considerable amounts of protochlorophyllide (PChlide), when grown in darkness. In this paper it is demonstrated that the accumulated PChlide directly acts on glut‐RNA‐ligase and thereby blocks further biosynthesis of ALA and chlorophyll. By increasing the amount of ligase at constant concentrations of PChlide and glut‐RNA it could clearly be demonstrated that PChlide directly inhibits ligase activity and does not act on the t‐RNA. The inhibitory effect of other tetrapyrroles like chlorophyll a, pheophytin a and protoporphyrin IX was much less effective even at oversaturating concentrations.