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  • 1
    Electronic Resource
    Electronic Resource
    Stability of a rhizosphere microbial community exposed to natural and manipulated environmental variability (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 38 (2001), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Phospholipid fatty acid (PLFA) and artificial neural network analyses were used to examine the composition of the Spartina alterniflora rhizosphere microbial community after exposure to manipulations in the field designed to alter the availability of host plant-derived and abiotic nutrient resources. We also tracked the experiments over a sufficient duration to observe significant natural variability in edaphic variables. We determined the PLFA composition of axenic S. alterniflora roots in order to distinguish differences in PLFAs that were due to changes in the rhizosphere microbiota from those only due to variability in plant root mass among samples. There were no significant changes in the PLFA profiles in response to experimental treatments and little change over the 8-week duration of the experiments. The microbial communities in the S. alterniflora rhizosphere did not respond dramatically to changing environmental conditions in the absence of major physical or chemical disruptions of the rhizosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.2001.tb00883.x
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  • 2
    Electronic Resource
    Electronic Resource
    Sustained root culture for generation and vegetative propagation of transgenic Arabidopsis thaliana (1993)
    Springer
    Plant cell reports 12 (1993), S. 603-606 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Excised roots of wild-type and nitrate-reductase deficient mutant Arabidopsis thaliana (L.) Heynh. can be propagated as sustained root cultures in liquid medium. Culture initiation from a single seedling required a two-day indoleacetic acid treatment at 0.05 mg/l concentration. Indoleacetic acid facilitated subculture but was not essential for sustained growth. This procedure has allowed the clonal propagation of roots derived from individual wildtype and mutant seedlings for more than 21 months. The cultured roots retained their shoot regeneration ability; however, a controlled desiccation treatment was required to restore it to the level of freshly excised roots. The chromosome number remained diploid and no evidence for the accumulation of recessive mutations was observed. The cultured roots are competent for Agrobacterium-mediated transformation. The sustained root culture technology allowed the maintenance of transgenic tissues in which expression of a dominant, seed-lethal gene (seed-specific pea vicilin promoter fused to diphtheria toxin A chain gene) precluded generative propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232807
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  • 3
    Electronic Resource
    Electronic Resource
    Stimulation of shoot regeneration in Triticum aestivum and Nicotiana plumbaginifolia Viv. tissue cultures using the ethylene inhibitor AgNO3 (1987)
    Springer
    Plant cell reports 6 (1987), S. 1-4 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Silver nitrate effectively promoted shoot regeneration in wheat (Triticum aestivum L.) callus cultures derived from immature embryos. This effect could be observed in both weakly and strongly regenerating cultivars, and in using material from both field and greenhouse grown plants. The role of silver ions as an inhibitor of ethylene action was supported by a reversal of the inhibitory effects of 2,4-D and ethylene on morphogenesis in wheat callus cultures. Enhancement of shoot regeneration by silver nitrate was also observed in callus cultures of non-regenerating or weakly regenerating mutants of Nicotiana plumbaginifolia Viv. derived from cell cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00269725
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  • 4
    Electronic Resource
    Electronic Resource
    T-DNA-insert-independent mutations induced in transformed plant cells duringAgrobacterium co-cultivation (1994)
    Springer
    Transgenic research 3 (1994), S. 317-325 
    Details
    ISSN: 1573-9368
    Keywords: Agrobacterium ; mutagenesis ; Nicotiana plumbaginifolia ; nitrate reductase ; ploidy ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transformation frequencies were determined for 1n, 2n, and 4n Nicotiana plumbaginifolia protoplast cultures inAgrobacterium-mediated gene transfer experiments. An unexpected large drop (50%) in plating efficiencies was observed in the non-selected (control) 1n populations after transformation treatment with virulent strains. This effect was not observed in the 2n or 4n cultures or in the 1n cultures when treated with avirulent bacteria. The mortality was disproportionally high and could not be explained by the low (0.1–0.5%) transformation efficiency in the 1n population, indicating mutagenesis of the cell populations independently from the T-DNA insertions. Mutagenesis was also indicated in gene tagging experiments where nitrate reductase-deficient (NR−) mutants were selected from haploidNicotiana plumbaginifolia protoplasts, as well as from leaf disc cultures or protoplasts of diploid plants that were heterozygotic for a mutation either in the NR apoenzyme gene (nia/wt) or one of the molybdenum-containing cofactor genes (cnxA/wt), afterAgrobacterium co-cultivation. The chlorate-resistant isolates were tested for the T-DNA-specific kanamycin resistance trait only after NR-deficiency had been established. Thirty-nine independent NR-deficient mutants were analysed further by Southern blot hybridization. There was no indication of integrated T-DNA sequences in the mutated NR genes, despite the fact that NR-deficient cells were found more frequently in cell populations which became transformed during the treatment than in the populations which did not. These observations suggest that transformation-competent cells undergo mutagenesis during theAgrobacterium gene transfer process not only as a result of stable integration events, but also through accompanying events that do not result in major changes in the mutated loci. The nature of these changes at the molecular level remains to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01973592
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  • 5
    Electronic Resource
    Electronic Resource
    Frequent collinear long transfer of DNA inclusive of the whole binary vector during Agrobacterium-mediated transformation (1997)
    Springer
    Plant molecular biology 34 (1997), S. 913-922 
    Details
    ISSN: 1573-5028
    Keywords: Agrobacterium tumefaciens ; Arabidopsis thaliana ; Nicotiana plumbaginifolia ; root transformation ; T-DNA transfer ; vacuum infiltration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When Agrobacterium was used to transform Nicotiana plumbaginifolia protoplasts and Arabidopsis thaliana roots and seedlings, a large number of plants were found in which not only the T-region defined by the border repeat sequences but the entire binary vector was integrated, as determined by both PCR and Southern analysis techniques. N. plumbaginifolia protoplast co-cultivation experiments yielded 3 out of 5 transformants with collinear sequence past the left border. In Arabidopsis root transformation experiments, 33% (6/18) of the transformants had T-DNA which exceeded the left border repeat. Vacuum infiltration of Arabidopsis seedlings produced even a greater percentage of transformants with sequences outside the left border repeat (62%, 39/63). The long transfer DNA cosegregated with the T-region encoded hygromycin resistance in the T2 progeny eliminating the possibility that long transfer DNA was of extrachromosomal or Agrobacterium origin. The high frequency of long transfer after vacuum infiltration of A. thaliana needs to be considered when analyzing T-DNA tagged mutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005849303333
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  • 6
    Electronic Resource
    Electronic Resource
    Differential manifestation of seed mortality induced by seed-specific expression of the gene for diphtheria toxin A chain in Arabidopsis and tobacco (1992)
    Springer
    Molecular genetics and genomics 235 (1992), S. 33-40 
    Details
    ISSN: 1617-4623
    Keywords: Arabidopsis ; Diphtheria toxin ; Embryogenesis ; Genetic ablation ; Pea vicilin promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A pea vicilin promoter-diphtheria toxin A (DTx-A) chain gene fusion was introduced into Arabidopsis and tobacco. The chimeric Dtx-A gene behaves as a dominant, seed-lethal, Mendelian factor, and the segregation ratios are consistent with the numbers of integrated copies as revealed by Southern blotting. Germination deficiency results from distinct developmental abnormalities, thus allowing genetic dissection of seed development. The endosperm is affected first in both species. In Arabidopsis, full cellularization of the initially syncytial endosperm does not take place, which results in shrinkage and a shriveled appearance of the mature dry seed. The embryo, which appears structurally normal and lacks visible lesions, ceases to develop at the partially recurved cotyledon stage and does not use the remaining endosperm. In tobacco, peripheral degeneration and premature termination of cellular endosperm development occurs at the cotyledon initiation stage. Lesions appear in the cotyledons at the advanced cotyledon stage, but the embryo continues to grow and attains nearly the same size and level of differentiation as mature wild-type embryos before degeneration and intracellular disintegration take place throughout. Accumulation of protein bodies and other cytoplasmic inclusions is very limited and occurs only in few cells. The timing and distribution of lesions follow a pattern typical for accumulation of protein bodies in wild-type seeds. These observations are consistent with expression of the vicilin promoter in the enlargement phase of cell differentiation. A novel tissue interaction arises, when the embryo uses up all the arrested endosperm: the embryo proves to be capable of absorbing the parenchyma layers of the integument, which are normally obliterated by, and incorporated into, the endosperm. The mature seed thus consists of a seed coat of one rigid cell layer, and a degenerated embryo. The genetic ablation technique has thus contributed to the establishment of the sequence of events and elucidation of the role of different cell lineages and tissues in seed development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286178
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  • 7
    Electronic Resource
    Electronic Resource
    Independent integration and seed-transmission of the TR-DNA of the octopine Ti plasmid pTi Ach5 in Nicotiana plumbaginifolia (1986)
    Springer
    Plant molecular biology 6 (1986), S. 101-109 
    Details
    ISSN: 1573-5028
    Keywords: Agrobacterium tumefaciens ; agropine ; coculture transformation ; TR-DNA inheritance ; TR-DNA integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary After co-cultivation of diploid Nicotiana plumbaginifolia protoplasts with an octopine-type Agrobacterium tumefaciens strain (LBA 4013) putative transformants were selected for hormone-independent growth, and were tested for T-DNA markers. The number of transformants expressing only TL-DNA markers, i.e. phytohormone autotrophy and octopine synthase, was an order of magnitude higher than that of the cell lines which were simultaneously positive for both TL- and TR-DNA markers (the latter being mannopine and agropine). In one transformant, line no. 101, only the TR-DNA markers were found. Not each of the TL-, or TR-DNA markers were expressed in each transformant resulting in a variety of phenotypes. It included the unorganized or the shoot-teratoma type of growth combined with the presence or absence of opines; e.g. agropine was absent from some of the transformants containing its precursor, mannopine. 5-Azacytidine did not induce agropine synthesis in these lines. Southern blot analysis showed that the TR-DNA region coding for agropine synthesis was rearranged or absent in one of these lines. Similar variation in the expression of agropine and mannopine production was observed in transformants obtained with the leucinopine-type strain A281. From line 101 plants could be easily regenerated with the ability to synthesize agropine and mannopine. The segregation in the self-progeny fitted to a 3:1 ratio, indicating that the TR-DNA was carried by a single chromosome. The Southern blot analysis showed that only opine-positive plants contained TR-DNA. It also confirmed the absence of the TL-DNA, demonstrating the independent integration of the TR-region of the octopine-type Ti plasmid pTi Ach5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027303
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