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  • 1
    Electronic Resource
    Electronic Resource
    Developmental changes in enzymes involved in the conversion of hexose phosphate and its subsequent metabolites during early tuberization of potato (1999)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A highly synchronized in vitro tuberization system, based on single-node cuttings containing an axillary bud, was used to investigate the activity patterns of enzymes involved in the conversion of hexose phosphates and related products during stolon-to-tuber transition of potato (Solanum tuberosum L.). At tuberization the activity of enzymes involved in glycolysis and the oxidative pentose phosphate pathway (OPPP) showed a small but clear increase. This increase reflects a higher capacity of respiratory(-related) metabolism, presumably due to the onset of rapid cell division in the apical part of the tuberizing stolon. During the phase of successive tuber growth these enzymes decreased in activity, suggesting that the concomitant massive starch accumulation is not accompanied by a large increase in respiration. A high degree of positive correlation between the activities of these enzymes could be observed, implying that the level of respiratory metabolism-related enzymes is co-ordinately regulated by the same mechanism of coarse control. The activity pattern of pyrophosphate:fructose-6-phosphate phosphotransferase (PFP) showed no developmental change and does not resemble the activity pattern of the enzymes participating in respiratory(-related) metabolism. Instead, its level of activity is very likely the result of metabolic regulation. The level of the content of the metabolites UDP-glucose (UDPGlc) and glucose-6-phosphate (Glc6P) decreased after the onset of tuberization. This decline indicates that tuber induction is not accompanied by an appreciable increase in the level of the cytosolic hexose phosphate (hexose-P) content but that it rather remains on a low level, which might be a prerequisite in order to maintain a high net rate of sucrose degradation during tuber development. In contrast to UDPGlc and Glc6P, the content of fructose-1,6-bisphosphate (Fru1,6bisP) showed an increase after tuber induction. The overall activities of ADP-glucose pyrophosphorylase (AGPase) and starch phosphorylase (STP) both showed a large increase after tuber initiation, which is consistent with their presumed role in the process of starch synthesis and accumulation during rapid tuber growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00473.x
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of different evaluation techniques on the results of interlaboratory comparisons Remarks on Linsinger TPJ, Kandler W, Krska R, Grasserbauer M (1998)
    Springer
    Accreditation and quality assurance 3 (1998), S. B497 
    Details
    ISSN: 1432-0517
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 3
    Electronic Resource
    Electronic Resource
    The Institute for Interlaboratory Studies (i.i.s.) now has formal accreditation for the organisation of proficiency tests (2000)
    Springer
    Accreditation and quality assurance 5 (2000), S. 215-215 
    Details
    ISSN: 1432-0517
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007690050448
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  • 4
    Electronic Resource
    Electronic Resource
    Phenylalanine and tyrosine accumulating cell lines of a dihaploid potato selected by resistance to 5-methyltryptophan (1985)
    Springer
    Plant cell reports 4 (1985), S. 151-154 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The selection and characterization of 5-methyltryptophan (5-MT) resistant cell lines is described in a dihaploid potato, clone H2578(007). The frequency of resistant calli was increased by treatment of a cell suspension with N-ethyl-N-nitroso-urea. Two lines, 5-MT-21 and 5-MT-26, accumulated tyrosine (160 nMol and 1546 nMol/g fresh callus), and the third, 5-MT-27, accumulated both tyrosine (841 nMol/g fresh callus) and phenylalanine (451 nMol/g fresh callus). In the wildtype tyrosine and phenylalanine content was 65 nMol and 42 nMol/g callus, respectively. The tryptophan content of line 5-MT-26 was significantly increased, from 20 nMol/g to 76 nMol/g fresh callus. The total free amino acid content of the three variant cell lines was higher than that of the wildtype. Variant cell lines 5-MT-21, -26 and -27 showed a low degree of resistance to 5-MT, when grown on a selective medium and were cross-resistant to parafluorophenylalanine and 3-fluorotyrosine, analogues of phenylalanine and tyrosine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571304
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  • 5
    Electronic Resource
    Electronic Resource
    Development of a plant regeneration system based on friable embryogenic callus in the ornamental Alstroemeria (2000)
    Springer
    Plant cell reports 19 (2000), S. 529-534 
    Details
    ISSN: 1432-203X
    Keywords: Key words Friable embryogenic callus ; Regeneration ; Rhizome ; Alstroemeria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Stem segments of seedlings from two Alstroemeria breeding lines, cultured on media supplemented with 4 mg/l 2,4-dichlorophenoxyacetic acid and 0.5–1.0 mg/l 6-benzylaminopurine (BA), initiated soft callus, which became compact after subculture on a medium with only 0.5 mg/l BA. Friable embryogenic calli were initiated from compact callus on a medium supplemented with 10 mg/l picloram. Proembryos developed from friable embryogenic calli via embryos into plants after subculture on medium supplemented with 0.1 mg/l BA. The proembryos formed friable embryogenic calli again after culture on medium supplemented with 10 mg/l picloram. The total time needed to regenerate a complete plantlet from friable callus was approximately 6 months. This system for the production of embryogenic material is considered to have valuable applications for genetic transformation in Alstroemeria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050768
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  • 6
    Electronic Resource
    Electronic Resource
    Improvements of cyclic somatic embryogenesis of cassava (Manihot esculenta Crantz) (1993)
    Springer
    Plant cell reports 12 (1993), S. 226-229 
    Details
    ISSN: 1432-203X
    Keywords: direct somatic embryogenesis ; primary and higher cycles ; liquid culture ; shoot development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In cassava a cyclic system of somatic embryogenesis was developed. Primary (torpedo shaped or germinated) embryos, originating from leaf lobes, could only be obtained after culture on solid medium. Cyclic embryos, originating from embryos, could be obtained in both liquid and on solid medium. The production of embryos in liquid medium was distinctly higher, faster and more synchronized than on solid medium. Lower densities and fragmentation of starting embryos improved the production significantly. The highest production found was 32.1 embryos per initial embryo. In all treatments the explants initiated multiple embryos. The production of single embryos was achieved by pressing starting embryos through a fine meshed sieve, indicating that embryos can be produced from a piece of tissue with a restricted number of cells. The shoot conversion rate of embryos from liquid medium was comparable with that of embryos from solid medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237059
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  • 7
    Electronic Resource
    Electronic Resource
    Cloning, partial sequencing and expression of a cDNA coding for branching enzyme in cassava (1992)
    Springer
    Plant molecular biology 20 (1992), S. 809-819 
    Details
    ISSN: 1573-5028
    Keywords: Branching enzyme ; cassava ; cDNA ; expression pattern ; Manihot esculenta Crantz ; sequence homology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Branching enzyme is involved in the synthesis of amylopectin in plant reserve starch. A cDNA coding for cassava (Manihot esculenta Crantz) branching enzyme was cloned from a λgt11 cDNA library using a potato cDNA probe. The cloned cDNA was partially sequenced. The sequence data confirmed the identity of the clone when compared to that of potato, the homology being ca. 80% at the nucleotide level and 85% at the amino acid level. Furthermore, the cloned cassava cDNA was able to restore branching enzyme activity in a branching enzyme deficient Escherichia coli mutant. Results of the Southern analysis suggested that there is a single gene for this particular branching enzyme in the cassava genome. Study of expression patterns by northern hybridization showed that the gene is highly expressed in tubers. The transcript is detectable in stem and petiole, but not in leaves. In roots, the mRNA is hardly present. The expression levels at different stages of tuber growth are similar with exception of very young tubers in which it is relatively low. It is also shown that there is a difference in the level of branching enzyme expression between different cassava genotypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027152
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  • 8
    Electronic Resource
    Electronic Resource
    Isolation and characterization of a cDNA encoding granule-bound starch synthase in cassava (Manihot esculenta Crantz) and its antisense expression in potato (1993)
    Springer
    Plant molecular biology 23 (1993), S. 947-962 
    Details
    ISSN: 1573-5028
    Keywords: antisense effect ; granule-bound starch synthase ; cassava ; cDNA ; heterologous gene ; potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A tuber-specific cDNA library of cassava (Manihot esculenta Crantz) was constructed and a full-length cDNA for granule-bound starch synthase (GBSS, also known as waxy protein), the enzyme responsible for the synthesis of amylose in reserve starch, was cloned. Sequencing of the cloned cDNA showed that it has 74% identity with potato GBSS and 60–72% identity with GBSS from other plant species. The cDNA encodes a 608 amino acid protein of which 78 amino acids form a chloroplast/amyloplast transit peptide of 8.37 kDa. The mature protein has a predicted molecular mass of 58.61 kDa (530 amino acids). Comparison of the GBSS proteins of various plant species and glycogen synthase of bacteria showed extensive identity among the mature form of plant GBSS proteins, in which the monocots and dicots form two separate branches in the evolutionary tree. From analysis of the genomic DNA of allotetraploid cassava, it is shown that GBSS is a low-copy-number gene. GBSS transcript is synthesized in a number of different organs, but most abundantly in tubers. Potato plants were transformed with the cassava GBSS cDNA in antisense orientation fused between the potato GBSS promoter and the nopaline synthase terminator. The expression of the endogenous GBSS gene in these transgenic potato plants was partially or completely inhibited. Complete inhibition of GBSS activity by the cassava antisense gene resulted in absence of GBSS protein and amylose giving rise to almost complete amylose-free potato starch. This shows that also heterologous genes can be used to achieve antisense effects in other plant species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021811
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  • 9
    Electronic Resource
    Electronic Resource
    Transformation of homozygous diploid potato with an Agrobacterium tumefaciens binary vector system by adventitious shoot regeneration on leaf and stem segments (1989)
    Springer
    Plant molecular biology 12 (1989), S. 329-337 
    Details
    ISSN: 1573-5028
    Keywords: Agrobacterium tumefaciens ; adventitious shoot regeneration ; transformation ; homozygous potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transformed potato (Solanum tuberosum) plants were obtained from homozygous diploid potato by using a transformation procedure in combination with an adventitious shoot regeneration method. Leaf and stem explants were inoculated with an Agrobacterium tumefaciens strain which contained a binary vector (pVU 1011) carrying the neomycin phosphotransferase gene. Shoot regeneration most effectively on stem explants, occurred within six weeks directly from the explants without introducing a callus phase. A strong seasonal influence on transformation efficiencies was observed. Analysis of a number of randomly selected regenerated shoots for their ability to root and form shoots on kanamycin-containing medium shows that over 90% of the regenerated shoots obtained are transformed. In a number of shoots transformation was confirmed by a test for the presence and expression of the NPT-II gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00043210
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  • 10
    Electronic Resource
    Electronic Resource
    Introduction of sense and antisense cDNA for branching enzyme in the amylose-free potato mutant leads to physico-chemical changes in the starch (1996)
    Springer
    Planta 198 (1996), S. 340-347 
    Details
    ISSN: 1432-2048
    Keywords: Antisense inhibition ; Branching enzyme (potato) ; Co-suppression (gene activity) ; Gene activity (branching enzyme) ; Solanum (branching enzyme) ; Starch physico chemical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract One isoform of the branching enzyme (BE; EC 2.4.1.18) of potato (Solarium tuberosum L.) is known and catalyses the formation of α-1,6 bonds in a glucan chain, resulting in the branched starch component amylopectin. Constructs containing the antisense or sense-orientated distal 1.5-kb part of a cDNA for potato BE were used to transform the amylose-free (amf) mutant of potato, the starch of which stains red with iodine. The expression of the endogenous BE gene was inhibited either largely or fully as judged by the decrease or absence of the BE mRNA and protein. This resulted in a low percentage of starch granules with a small blue core and large red outer layer. There was no effect on the amylose content, degree of branching or λmax of the iodine-stained starch. However, when the physico-chemical properties of the different starch suspensions were assessed, differences were observed, which although small indicated that starch in the transformants was different from that of theamf mutant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620049
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