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  • 1
    ISSN: 1432-0789
    Keywords: Key words Arbuscular mycorrhizae ; Biological (organic) farming ; Conventional farming ; Glomus mosseae ; Winter wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Arbuscular mycorrhizal (AM) root colonization was studied in a long-term field trial in which four farming systems currently in use in Switzerland were continuously applied to a randomized set of plots at a single field site from 1978 till 1993. There were two low-input farming systems (organic and bio-dynamic) and two high-input (conventional) farming systems (according to Swiss guidelines of integrated plant production with and without farmyard manure). The systems had an identical 7-year crop rotation and tillage scheme and differed essentially only in the amount and type of fertilizer supplied and in plant protection management. The percentage of root colonization by AM fungi was determined in field samples 2–3 times over the growing season in crops in the rotation, namely in winter wheat (Triticum aestivum L. cv. Sardona), vetch-rye and grass-clover. We found the percentage of root length colonized by AM fungi to be 30–60% higher (P≤0.05) in the plants grown in soils from the low-input farming systems than in those grown in conventionally farmed soils. Approximately 50% of the variation of AM root colonization was explained by chemical properties of the soils (pH, soluble P and K, exchangeable Mg), the effect of soluble soil P being most pronounced. The potential of the field soils from the differently managed plots to cause symbiosis with AM fungi was tested in a glasshouse experiment, using wheat as a host plant. Soils from the low-input farming systems had a greatly enhanced capacity to initiate AM symbiosis. The relative differences in this capacity remained similar when propagules of the AM fungus Glomus mosseae were experimentally added to the soils, although overall root colonization by AM fungi was 2.8 times higher.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 109 (1976), S. 115-118 
    ISSN: 1432-072X
    Keywords: Yeast ; Protoplasts ; Vacuoles ; Concanavalin A ; Membrane asymmetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolated vacuoles of Saccharomyces cerevisiae did not bind Concanavalin A (labelled with tritium or with a fluorescent dye) unless the vacuoles were rendered permeable and their inner membrane surface made accessible. Yeast protoplasts, on the other hand, bound large amounts of Concanavalin A on their surface, and the number of binding sites was not increased after a gentle lysis expected to expose also the inner surface of the plasmalemma. It is concluded that both the plasmalemma and the vacuolar membrane carry Concanavalin A binding sites exclusively on the surface opposite to the cytoplasmic matrix.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 105 (1975), S. 319-327 
    ISSN: 1432-072X
    Keywords: Yeast ; Spheroplasts ; Vacuoles ; Isolation ; Basic macromolecules ; Poly-dl-lysine ; DEAE-dextran ; Transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The polybasic macromolecules DEAE-dextran (diethylaminoethyl-dextran, molecular weight 500 000) and poly-dl-lysine (molecular weight 30 000–70 000) were adsorbed with a high affinity by spheroplasts of Candida utilis and, subsequently, induced lysis. The extent of lysis of spheroplasts and of the liberated vacuoles was studied under various conditions using α-glucosidase activity and soluble arginine as cytoplasmic and vacuolar markers, respectively. Adsorption of polybases was rapidly completed even at 0°C; however, with small doses, lysis was poor at 0–12°C and extensive at temperatures above 12°C. This permitted the completion of adsorption before initiating lysis. The purified vacuoles were also sensitive to polybases though less so than the spheroplasts; however, after lysis of spheroplasts the liberated vacuoles were well protected against the action of polybases. A treatment with polybases which disrupted more than 99% of the spheroplasts left at least 70% of the vacuoles intact. Potassium chloride in high concentrations and calcium chloride in low concentrations inhibited polybase induced lysis of spheroplasts by preventing or even reversing the polybase adsorption. A polyacidic macromolecule, dextran sulfate, could prevent but not reverse the adsorption of polybase and subsequent lysis. Metabolic inhibitors reduced the susceptibility of spheroplasts to polybase induced lysis. Vacuoles isolated from polybase lysed spheroplasts still contained large pools of soluble amino acids, and their ability to transport arginine specifically is a further indication of their functional integrity.
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  • 4
    ISSN: 1432-072X
    Keywords: Ethylene ; Ethylene-forming enzyme ; Fusarium oxysporum ; Penicillium digitatum ; 2-Oxoglutarate ; Dioxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Liquid cultures of the deuteromycete, Fusarium oxysporum f. sp. tulipae, a tulip pathogen, produced high amounts of ethylene during stationary phase. 1-Aminocyclopropane-1-carboxylic acid, the direct precursor of ethylene in plants, was not present in the fungus. Radioactivity from [3,4-3H]glutamate as well as [U-14C]glutamate was incorporated into ethylene, indicating that it was derived from C3 and C4 of glutamate or 2-oxoglutarate. Ferrous ions markedly stimulated the rate of ethylene formation in vivo, whereas Fe3+, Cu2+ or Zn2+ had little or no effect. Ethylene biosynthesis was strongly inhibited by the heavy metal chelator α,α′-dipyridine. The effect of α,α′-dipyridine was fully reversed by Fe2+ ions and partially by Cu2+ and Zn2+ ions but not by the supply of glutamate or 2-oxoglutarate, suggesting that a step in the ethylene biosynthetic pathway downstream of 2-oxoglutarate is dependent on Fe2+. When stationary phase cultures were supplied with arginine, ornithine, or proline, ethylene production increased dramatically while addition of glutamate or 2-oxoglutarate had little effect. Tracer studies were performed to test the possibility that an intermediate in the catabolism of arginine to glutamate was the direct precursor of ethylene. In cultures supplied with [U-14C]arginine or [U-14C]glutamate, the specific radioactivity of ethylene was closely similar to the specific radioactivity of the endogenous glutamate pool, indicating that glutamate was on the pathway between arginine and ethylene. An enzyme system converting 2-oxoglutarate to ethylene in a reaction dependent on oxygen, ferrous ions and arginine has previously been described in extracts from Penicillium digitatum (Fukuda et al. 1986). The present results suggest that a similar enzyme system catalyzes the final step of ethylene biosynthesis in F. oxysporum.
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  • 5
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Trehalase was studied in Schizosaccharomyces pombe cells growing vegetatively on minimal medium and in sporulating cultures. Acid trehalase activity, measured at pH 4.2, was absent in vegetative cells and occurred only in asci, indicating that this activity represented the sporulation-specific trehalase reported previously. In contrast, neutral trehalase, measured at pH 6.0, was constitutively present in vegetative cells during the expotential and stationary growth phase as well as in asci. In vegetative cells, neutral trehalase did not sediment with cell walls, suggesting a cytoplasmic localization. Its activity increased ten-fold when growing cells were subjected to heat treatment of 2 h. Neutral trehalase from heat-treated cells had a pH optimum of 6.0 and was almost completely inhibited by 3 mM ZnCl2. Acid trehalase activity could be measured in intact asci, indicating that it is localized in the ascus cell walls, while neutral trehalase was not detectable in intact asci and appeared to be present primarily in the walls of ascospores and in the ascus epiplasm.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 69 (1990), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A bioassay is described for the study of inhibitory activity of plant proteins on fungal growth. Fungal spores were germinated in liquid growth medium and pipetted into wells of a microtitre plate. Fungal growth was followed spectrophotometrically. The bioassay was tested using crude protein extracts from plant tissues known to have high activities of chitinase and β-1,3-glucanase, and with purified enzymes. Crude protein preparations and combinations of the purified enzymes produced a temporary reduction of growth but no permanent growth inhibition.
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  • 7
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The fission yeast Schizosaccharomyces pombe was found to accumulate large amounts of polyphosphate, particularly when grown on arginine as the nitrogen source. Upon transfer to a medium without phosphate, polyphosphate was degraded and served as an endogenous phosphate reserve. When phosphate was added again after a prolonged period of phosphate starvation, fission yeast cells synthesized more polyphosphate than they had contained before starvation, a phenomenon known as over-compensation. Strains carrying mutated structural genes for three different phosphatases, pho1, pho2 or pho3, degraded polyphosphate at the same rate as the wild-type strain during phosphate starvation and showed the same type of over-compensation when phosphate was added again.
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  • 8
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Yeast cells show an adaptive response to a mild heat shock, resulting in thermotolerance acquisition. This is accompanied by induction of heat-shock protein (hsp) synthesis and rapid accumulation of trehalose. Genetic approaches to determine the specific role of trehalose in heat-induced thermotolerance in Saccharomyces cerevisiae have been hampered by the finding that deletion of TPS1, the gene encoding trehalose-6-phosphate synthase, causes a variety of pleiotropic effects, including inability to grow on glucose-containing media. Here, we have studied a tps1 mutant of the yeast Schizosaccharomyces pombe that reportedly has no such growth defects. We show that tps1 mutants have a serious defect in heat shock-induced acquisition of thermotolerance if conditioned at highly elevated temperatures (40–42.5°C), which, in wild-type cells, prevent hsp but not trehalose synthesis. In contrast, hsp synthesis appears to become particularly important under conditions in which trehalose synthesis is either absent (in tps1 mutant strains) or not fully induced (conditioning at moderately elevated temperatures, i.e. 35°C). In addition, pka1 mutants deficient in cAMP-dependent protein kinase were examined. Unconditioned pka1 cells had low levels of trehalose but a high basal level of thermotolerance. It was found that pka1 mutant cells, contrary to wild-type cells, accumulated large amounts of trehalose, even during a 50°C treatment. pka1 tps1 double mutants lacked this ability and showed reduced intrinsic thermotolerance, indicating a particularly important role for trehalose synthesis, which takes place during the challenging heat shock.
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  • 9
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Synthesis of trehalose in the yeast Saccharomyces cerevisiae is catalysed by the trehalose-6-phosphate (Tre6P) synthase/phosphatase complex, which is composed of at least three different subunits encoded by the genes TPS1, TPS2, and TSL1. Previous studies indicated that Tps1 and Tps2 carry the catalytic activities of trehalose synthesis, namely Tre6P synthase (Tps1) and Tre6P phosphatase (Tps2), while Tsl1 was suggested to have regulatory functions. In this study two different approaches have been used to clarify the molecular composition of the trehalose synthase complex as well as the functional role of its potential subunits. Two-hybrid analyses of the in vivo interactions of Tps1, Tps2, Tsl1, and Tps3, a protein with high homology to Tsl1, revealed that both Tsl1 and Tps3 can interact with Tps1 and Tps2; the latter two proteins also interact with each other. In addition, trehalose metabolism upon heat shock was analysed in a set of 16 isogenic yeast strains carrying deletions of TPS1, TPS2, TSL1, and TPS3 in all possible combinations. These results not only confirm the previously suggested roles for Tps1 and Tps2, but also provide, for the first time, evidence that Tsl1 and Tps3 may share a common function with respect to regulation and/or structural stabilization of the Tre6P synthase/phosphatase complex in exponentially growing, heat-shocked cells.
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  • 10
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Plants sense potential microbial invaders by using pattern-recognition receptors to recognize pathogen-associated molecular patterns (PAMPs). In Arabidopsis thaliana, the leucine-rich repeat receptor kinases flagellin-sensitive 2 (FLS2) (ref. 2) and elongation factor Tu receptor ...
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