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  • 1
    Digitale Medien
    Digitale Medien
    New Routes to Plant Secondary Products (1987)
    [s.l.] : Nature Publishing Company
    Nature biotechnology 5 (1987), S. 800-804 
    Details
    ISSN: 1546-1696
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: [Auszug] For some years, there has been great interest in the exploitation of plant cell cultures to produce fine chemicals. With a few exceptions, progress in commercialization has been slow, largely due to the low and/or unstable productivity of many undifferentiated cultures. Recent developments leading ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/nbt0887-800
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  • 2
    Digitale Medien
    Digitale Medien
    Abiotic factors elicit sesquiterpenoid phytoalexin production but not alkaloid production in transformed root cultures of Datura stramonium (1991)
    Springer
    Plant cell reports 10 (1991), S. 111-114 
    Details
    ISSN: 1432-203X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The treatment of root cultures of Datura stramonium with copper and cadmium salts at external concentrations of approximately 1mM has been found to induce the rapid accumulation of high levels of sesquiterpenoid defensive compounds, notably lubimin and 3-hydroxylubimin. These compounds were undetectable in unelicited cultures. No net change was seen in the alkaloid content of the system following treatment with Cu2+ or Cd2+, the tropane alkaloid titre apparently being insensitive to elicitation. However, a considerable rapid and, in some instances, reversible release of alkaloid was observed. This resulted in the appearance of up to 50–75% of the total alkaloid in the medium after 40–60 h. Subsequently, in cultures treated with Cu2+ ions, though not in cultures treated with Cd2+ ions, this alkaloid was re-absorbed. These observations show how, in a single system, different groups of secondary products can show distinct differences in their responses to potential elicitors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00232039
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  • 3
    Digitale Medien
    Digitale Medien
    Toxicity of quinoline alkaloids to cultured Cinchona ledgeriana cells (1987)
    Springer
    Plant cell reports 6 (1987), S. 118-121 
    Details
    ISSN: 1432-203X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The toxicity of Cinchona alkaloids to cell cultures of C. ledgeriana has been studied in relation to alkaloid uptake and possibilities for selecting high-yielding cell lines. The most toxic, quinine, was completely toxic at 5.5 mM. Both quinine and quinidine were more toxic than their unmethoxylated precursors, cinchonidine and cinchonine. The permanently-charged metho-chlorides of quinine and cinchonidine were less toxic than the parent alkaloids, despite showing similar accumulation ratios in 5-day uptake experiments at sub-toxic concentrations (ca 1.7mM). The toxicity of the natural quinoline alkaloids appears to be a non-specific effect which may be caused by intracellular alkalinisation following uptake of the uncharged bases. The use of precursors of quinine and quinidine as toxic agents for the selection of cell lines with enhanced quinine and quinidine production is ruled out by the lower toxicity of these precursors and by the correlation of an apparently non-specific toxicity with uptake.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00276667
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  • 4
    Digitale Medien
    Digitale Medien
    Apparent free space and cell volume estimation: A non-destructive method for assessing the growth and membrane integrity/viability of immobilised plant cells (1984)
    Springer
    Plant cell reports 3 (1984), S. 161-164 
    Details
    ISSN: 1432-203X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Pre-existing methods for measuring cell or organelle volume based on the selective permeability of biological membranes have been modified to make them suitable for determining the intracellular volume of immoblised cells. When a freely permeable substance (e.g. tritiated water) and an impermeable substance (14C labelled mannitol is often suitable) are mixed with an immobilised cell culture, the two substances are diluted to different degrees. The extent of the difference allows the total intracellular volume of intact cells to be calculated. This volume is shown to be a useful parameter for assessing cell growth. The application of the method to follow membrane integrity and cell viability is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00270214
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  • 5
    Digitale Medien
    Digitale Medien
    Permeabilization of Cinchona ledgeriana cells by dimethylsulphoxide. effects on alkaloid release and long-term membrane integrity (1984)
    Springer
    Plant cell reports 3 (1984), S. 262-265 
    Details
    ISSN: 1432-203X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Dimethyl sulphoxide (DMSO) has been used to permeabilize cells of Cinchona ledgeriana in suspension culture and promote the release of intracellular alkaloids. 5–6% v/v is required before any release is seen, and greater than 20% DMSO is required for full release. Even at these high levels of DMSO release is slow, taking in excess of seven hours to reach completion. Conditions which produce significant release of alkaloids have a deleterious effect on cells. Many of the membranes permeabilized did not recover their ability to selectively exclude compounds such as mannitol when the DMSO was removed. It is concluded that DMSO is not a suitable material for inducing alkaloid release in any biotechnological exploitation of alkaloid production by C. ledgeriana.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00269308
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  • 6
    Digitale Medien
    Digitale Medien
    Alternative metabolic fates of hygrine in transformed root cultures of Nicandra physaloides (1992)
    Springer
    Plant cell reports 11 (1992), S. 270-273 
    Details
    ISSN: 1432-203X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Alkaloid production by several Agrobacterium rhizogenes-transformed root lines of Nicandra physaloides was studied. Early in the culture cycle all lines contained predominantly hygrine, which has previously been reported to be the major alkaloid in roots of this plant. A number of other hygrine-derived alkaloids were identified, and these generally increased in importance as the cultures matured. Some lines were found to differ quite markedly in the relative importance of the different hygrine-derived alkaloids. The possibility is raised that alkaloid biosynthesis in N. physaloides root cultures may be a good model system in which to study metabolite partitioning in branched metabolic pathways.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00235080
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  • 7
    Digitale Medien
    Digitale Medien
    Isolation and characterisation of the acetyl-CoA carboxylase gene from Aspergillus nidulans (1998)
    Springer
    Current genetics 34 (1998), S. 379-385 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Key words Acetyl-CoA carboxylase ; Aspergillus nidulans ; Malonyl-CoA ; Fatty acid synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The putative gene encoding acetyl-CoA carboxylase, accA, has been isolated from Aspergillus nidulans. This single-copy gene has an open reading frame (ORF) of 6864 bp and contains two small introns near the 5′-end. A short ORF upstream of the ATG start codon has been identified in this gene by RT-PCR. Based on sequence homology to acetyl-CoA carboxylases from other organisms, putative biotin-, ATP-, HCO3 –- and acetyl-CoA- binding sites have been assigned. Northern data and ACC enzyme-activity measurements from A. nidulans suggested that expression of accA was higher in media containing nitrate than ammonia as a sole nitrogen source. Deletion of accA in A. nidulans was unsuccessful. The failure of A. nidulans to grow in the presence of the ACC-specific inhibitor, soraphen A, supplemented with C16–18 fatty acids suggested that ACC is an essential enzyme.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002940050410
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  • 8
    Digitale Medien
    Digitale Medien
    Over-expressing a yeast ornithine decarboxylase gene in transgenic roots of Nicotiana rustica can lead to enhanced nicotine accumulation (1990)
    Springer
    Plant molecular biology 15 (1990), S. 27-38 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Agrobacterium rhizogenes-transformed root cultures ; Nicotiana rustica ; nicotine ; ornithine decarboxylase ; putrescine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Transformed root cultures of Nicotiana rustica have been generated in which the gene from the yeast Saccharomyces cerevisiae coding for ornithine decarboxylase has been integrated. The gene, driven by the powerful CaMV35S promoter with an upstream duplicated enhancer sequence, shows constitutive expression throughout the growth cycle of some lines, as demonstrated by the analysis of mRNA and enzyme activity. The presence of the yeast gene and enhanced ornithine decarboxylase activity is associated with an enhanced capacity of cultures to accumulate both putrescine and the putrescine-derived alkaloid, nicotine. Even, however, with the very powerful promoter used in this work the magnitude of the changes seen is typically only in the order of 2-fold, suggesting that regulatory factors exist which limit the potential increase in metabolic flux caused by these manipulations. Nevertheless, it is demonstrated that flux through a pathway to a plant secondary product can be elevated by means of genetic manipulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00017721
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  • 9
    Digitale Medien
    Digitale Medien
    Factors regulating tropane-alkaloid production in a transformed root culture of a Datura candida × D. aurea hybrid (1990)
    Springer
    Planta 181 (1990), S. 414-422 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Datura (root, alkaloid) ; Root culture (alkaloid production) ; Scopolamine synthesis ; Tropane alkaloid synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Using in combination an analysis of (i) the levels of enzyme activities present, (ii) the pool sizes of metabolic intermediates and end products and (iii) the effects of feeding metabolic intermediates, the limitations ℴ flux into tropane alkaloids in a Datura root culture have been examined. This culture, produced by transforming a Datura candida × D. aurea hybrid with Agrobacterium rhizogenes, is found to be highly competent in the biosynthesis of both hyoscyamine and scopolamine as well as a wide range of other hygrine-derived alkaloids. It has been found that, of six enzymes which are involved in this pathway, the two initial activities, ornithine decarboxylase (EC 4.1.1.17) and arginine decarboxylase (EC 4.1.1.19), are present at potentially flux-limiting levels, in contrast to those other enzymes assayed which act further down the pathway. An additional limitation to flux, involving the supply of activated acids for condensation with tropine to form the identified tropoyl and tigloyl derivatives, is also indicated from the observed effect of feeding free acids. The relative contribution to flux limitation caused by these two interacting phenomena is inferred from an analysis of the changing relative levels of metabolic intermediates and end products as cultures mature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00195896
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  • 10
    Digitale Medien
    Digitale Medien
    Studies on the biosynthesis of tropane alkaloids in Datura stramonium L. transformed root cultures (1991)
    Springer
    Planta 183 (1991), S. 196-201 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Datura (root, alkaloid) ; Hyoscyamine ; Putrescine ; α-Difluoromethylarginine ; α-Difluoromethy-lornithine ; Arginine decarboxylase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The relative contributions made by the l-arginine/agmatine/N-carbamoylputrescine/putrescine and the l-ornithine/putrescine pathways to hyoscyamine formation have been investigated in a transformed root culture of Datura stramonium. The activity of either arginine decarboxylase (EC 4.1.1.19) or ornithine decarboxylase (EC 4.1.1.17) was suppressed in vivo by using the specific irreversible inhibitors of these activities, dl-α-difluoromethylarginine or dl-α-difluoromethylornithine, respectively. It was found that suppression of arginine decarboxylase resulted in a severe decrease in free and conjugated putrescine and in the putrescine-derived intermediates of hyoscyamine biosynthesis. In contrast, the suppression of ornithine decarboxylase activity stimulated an elevation of arginine decarboxylase and minimal loss of metabolites from the amine and alkaloid pools. The stimulation of arginine decarboxylase was not, however, sufficient to maintain the same potential rate of putrescine biosynthesis as in control tissue. It is concluded that (i) in Datura the two routes by which putrescine may be formed do not act in isolation from one another, (ii) arginine decarboxylase is the more important activity for hyoscyamine formation, and (iii) the formation of polyamines is favoured over the biosynthesis of tropane alkaloids. An interaction between putrescine metabolism and other amines is also indicated from a stimulation of tyramine accumulation seen at high levels of dl-α-difluoromethylornithine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00197788
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