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  • Articles  (23)
  • Transformation  (23)
  • Springer  (23)
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  • Articles  (23)
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  • Springer  (23)
  • Cambridge University Press
  • Nature Publishing Group
  • Periodicals Archive Online (PAO)
  • Springer Nature
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  • 2020-2024
  • 2005-2009
  • 2000-2004
  • 1985-1989  (23)
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  • Biology  (23)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 10 (1986), S. 767-775 
    ISSN: 1432-0983
    Keywords: Aspergillus ; Transformation ; Recombinant plasmids ; Autonomously replicating sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A pyrG − Aspergillus strain was transformed with plasmid pDJB-1, derived from pBR325 by insertion of the Neurospora crassa pyr4 gene (orotidine 5′-phosphate carboxylase), giving mitotically unstable transformants. Aspergillus DNA which acted as an “autonomously replicating sequence” (ARS) in yeast was inserted into pDJB-1 and the resulting construct, pDJB12.1, gave mitotically stable transformants when introduced into Aspergillus. Transformants obtained with pDJB-1 and pDJB12.1 gave few pyr − progeny in crosses to a pyrG + strain. Southern hybridisation analysis of pyr + transformants obtained with pDJB-1 revealed restriction fragments expected for integrated plasmid but transformants obtained with pDJB12-1 showed only bands derived from free plasmid. pDJB-1 and derivatives of pDJB12.1 could be recovered from transformants. These derivatives could not be explained by straightforward excision of integrated pDJB12.1 sequences but could result from recombination between plasmid molecules. Hybridisation of undigested transformant DNAs showed that the transforming DNA was present in a high molecular weight form. These results suggest: (1) pDJB12.1 derivatives and possibly pDJB-1 can replicate autonomously in Aspergillus; (2) A. nidulans DNA acting as an ARS in yeast enhances replication and/or segregation of transforming plasmids in Aspergillus; and (3) recombinant plasmids may undergo rearrangements when introduced into Aspergillus.
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  • 2
    ISSN: 1432-0983
    Keywords: Transformation ; Recombinant plasmids ; H. polymorpha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary For the transformation of the yeast Hansenula polymorpha we have constructed a set of hybrid plasmids carrying the LEU2 gene of Saccharomyces cerevisiae as a selective marker and fragments of mitochondrial DNA of Candida utilis and H. polymorpha or chromosomal DNA fragments of H. polymorpha as replicator sequences. The replication properties of chimeric plasmids in the yeast H. polymorpha were investigated. We showed that for plasmids propagated autonomously in this yeast the plasmid monomers could be detected in the transformants only during the immediate time after the transformation event. Further growth under selective conditions led to the selection of polymeric forms of plasmid DNA as it was clearly shown for transformants carrying cosmid pL2 with mtDNA fragment of C. utilis. Such transformants carrying polymerized plasmids showed a remarkably increased stability of the transformed phenotype. Cosmid pL2 was able to shuttle between Escherichia coli, S. cerevisiae and H. polymorpha, whereas plasmids with DNA fragments from H. polymorpha did not transform S. cerevisiae effectively.
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  • 3
    ISSN: 1432-0983
    Keywords: Recombinant DNA ; Cross hybridization ; 2D-electrophoresis ; Hybrid selection translation ; Transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using the structural gene for the ribosomal protein L3 from Saccharomyces cerevisiae as a probe, we isolated a homologous fragment from genomic DNA of Schizosaccharomyces pombe. Analysis of the plasmid carrying this fragment by hybridization selection and 2D-electrophoresis revealed a 31 kDa ribosomal protein. Transformation of the vector pDB248x containing this fragment into Schizosaccharomyces pombe leads to an increased level of mRNA suggesting that we have cloned the entire and actively transcribed gene.
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  • 4
    ISSN: 1432-0983
    Keywords: Neurospora crassa ; Transformation ; Cosmid library ; inl locus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We constructed a Neurospora crassa gene library in a cosmid vector and used the cosmid-pool DNA to transform an inl, rg Neurospora crassa strain to inositol prototrophy. The inl + colonies obtained in this experiment proved to be integrative type transformants. Genetic analysis revealed that the integration event occurred at or near the inl locus. In one of the transformants the inl + trait exhibited mitotic and meiotic instability. In hybridization experiments free plasmids were detected in the F1 progeny of the transformants. We were able to recover eleven different plasmids from the F1 progeny of the transformants. None of these plasmids proved to carry a functional copy of the inl + gene as judged by its transforming ability. Possible explanations for the observed phenomena are discussed.
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  • 5
    ISSN: 1432-0983
    Keywords: ARS ; Transformation ; Non-homologous recombination ; Integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the fission yeast, Schizosaccharomyces pombe, transformation with recombinant plasmids always results in a high proportion of mitotically unstable transformants. This suggested that specialised (ARS) sequences might not be required for autonomous replication of plasmids in S. pombe, contrary to the situation in Saccharomyces cerevisiae. We have shown that specialised ARS sequences, analogous to those in S. cerevisiae, do exist in S. pombe, supporting the view that ARS elements are a general feature of eukaryotes. In addition, there is a further mechanism of plasmid maintenance which involves homologous and non-homologous integration into, and excision from the genome.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 10 (1986), S. 593-599 
    ISSN: 1432-0983
    Keywords: Transformation ; Aspergillus nidulans ; Ornithine carbamoyl transferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Thirty-three argB− to argB+ transformants of Aspergillus nidulans have been subjected to genetic and molecular analysis. Two showed high levels of mitotic instability although it is suggested that this is a consequence of heterokaryosis rather than instability of the transformation event. Most transformants resulted from the integration of the transforming DNA in tandem with the chromosomal argB locus. The maximum number of inserted sequences was two, to generate three copies of the argB locus. The other main transformant type showed replacement of the argB− mutation by the wild-type allele present on the transforming plasmid. Transformants were also recovered in which the transforming DNA had integrated into non-homologous chromosomal regions. Selfed or hybrid cleistothetica from all transformants, except the gene replacement types gave arginine requiring recombinants. Most transformants showed low levels of meiotic instability. Others displayed varying levels which in some cases differed between selfed and hybrid cleistotheticia. There was some correlation between meiotic instability and the nature of the transformation event. Diploid parasexual and aneuploid analysis located the integrated DNA in each transformant to chromosome III. Two transformants were isolated as heterozygous diploids. A third diploid was isolated as a stable mitotic segregant from one of the mitotically unstable transformants.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 72 (1986), S. 53-58 
    ISSN: 1432-2242
    Keywords: Agrobacterium tumefaciens ; Forage legumes ; Crowngall ; Transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Galls were induced in six species of forage legumes following inoculation with wild-type strains of A. tumefaciens. The plant species was more influential than the bacterial strain in determining the type of tumour produced. Inoculation of Medicago sativa resulted in small, disorganised tumours. The three Trifolium species, T. repens, T. hybridum and T. pratense, formed galls which tended to produce roots and both Onobrychis viciifolia and Lotus corniculatus produced teratomatous galls. The shoots elongated in the latter species only. In L. corniculatus, tissues that were infected by five bacterial strains were capable of shoot regeneration when cultured on a hormone-free medium. The transformed nature of these shoots was confirmed by their failure to root, the production of callus from leaves cultured on hormone-free medium and the presence of opines.
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  • 8
    ISSN: 1432-2242
    Keywords: Agrobacterium tumefaciens “shooter” mutants ; Transformation ; Shoot regeneration ; Protoplasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Alternative methods for shoot regeneration in protoplast derived cultures were developed in Nicotiana paniculata and Physalis minima. In both species protoplast derived callus is not regeneratable to shoots by conventional methods, e.g. hormone treatment. Leaf discs and stem segments of N. paniculata and P. minima were incubated with Agrobacterium tumefaciens “shooter” strains harbouring pGV 2215 or pGV 2298 or wildtype strain B6S3. After 36 h of co-incubation protoplasts were prepared. (Leaf disc and stem segment cloning). Co-cultivation experiments were also undertaken with protoplasts of both species. Transformed clones, characterized by their hormone independent growth and octopine production, could be isolated after about two months. Transformation frequencies of “leaf disc and stem segment cloning” and co-cultivation experiments varied from 5×10−3 to 5×10−5. After about one year of cultivation on hormone-free culture medium, shoots could be recovered from colonies of N. paniculata, transformed by the strain harbouring pGV 2298. In protoplast derived colonies of P. minima, shoot induction was obtained only after transformation by bacteria carrying pGV 2215. This demonstrates the importance of the particular “shooter” mutant, as well as the response of the host plant. Transformed shoots of P. minima produced octopine, whereas octopine production in transformed shoots and callus of N. paniculata was undetectable after one year of cultivation, though T-DNA was still present in the plant genome. Transformed shoots of N. paniculata and P. minima do not produce any roots. Shoots of N. paniculata have an especially tumerous phenotype. Shoots of both species were successfully grafted to normal donor plants of N. tabacum.
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  • 9
    ISSN: 1432-2242
    Keywords: Lycopersicon esculentum ; Transformation ; Hairy-root ; A. tumefaciens ; A. rhizogenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cultivated tomato was genetically transformed using two procedures. In the first procedure, punctured cotyledons were infected with “disarmed” Agrobacterium tumefaciens strain LBA4404 or with A. rhizogenes strain A4, each containing the binary vector pARC8. The chimeric neomycin phosphotransferase (NPT II) gene on pARC8 conferred on transformed plant cells the ability to grow on medium containing kanamycin. Transformation reproducible yielded kanamycin-resistant transformants in different tomato genotypes. NPT II activity was detected in transformed calli and in transgenic plants. All of these plants were phenotypically normal, fertile and set seeds. Using the second procedure, inverted cotyledons, we recovered transformed tomato plants from A. rhizogenes-induced hairy roots. In this case, all of the transgenic plants exhibited phenotypes similar to hairy root-derived plants reported for other species. Southern blot analysis on these plants revealed that the plant DNA hybridized with both probes representing pARC8-T-DNA, and the T-DNAs of the A4 Ri-plasmid. However, southern analysis on those phenotypically normal transgenic plants from the first procedure revealed that only the pARC8-T-DNA was present in the plant genome, thus indicating that the pARC8-T-DNA integrated into the plant genome independently of the pRi A4-T-DNA. Genetic analysis of these phenotypically normal transgenic plants for the kanamycin-resistance trait showed Mendelian ratios, 3∶1 and 1∶1, for selfed (R1) and in crossed progeny, respectively.
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  • 10
    ISSN: 1617-4623
    Keywords: Methylotrophic yeasts ; Transformation ; ARS sequence ; Plasmid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A high frequency transformation system for the methylotrophic yeast Hansenula polymorpha has been developed. This system depends on complementation of isolated uracil auxotrophs by the URA3 gene of Saccharomyces cerevisiae. Maintenance of the uracil prototrophy is based on integration of plasmid YIp5 at random sites within the H. polymorpha genome and on autonomously replicating plasmids containing ARS1 of S. cerevisiae or related sequences cloned from the host DNA. The sequence of one autonomously replicating sequence (HARS1) from H. polymorpha has been determined showing an AT-rich region of 9 bp with some similarity to the consensus sequence of known eukaryotic replication origins. Mitotic loss of autonomously replicating sequences is high; selection for stable uracil prototrophs yields multiple tandem arrangement of the transformed DNA with no detectable loss of the phenotype on non-selective medium. These features offer the possibility for extensive gene expression in H. polymorpha.
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