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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Company
    Nature biotechnology 1 (1983), S. 262-269 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Agrobacterium tumefaciens has the natural ability to insert a specific part of its Ti (tumor–inducing) plasmid, called T–DNA, into the chromosomal DNA of host plant cells, causing tumorous growth. Foreign DNA artificially introduced into T–DNA is inserted into the plant genome by ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Double transformation ; Binary vector ; T-DNAs segregation ; Disarmed Ti-plasmid ; Agrobacterium tumefaciens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 200 kb Agrobacterium Ti-plasmid pTiT37 carries a 25 kb segment of T-DNA which it transfers to plant cells during crown-gall tumorigenesis. We have previously engineered into this T-DNA a pBR322-derived cloning vector which enabled us to rescue-clone full length T-DNA from the Ti-plasmid into a 36 kb MINI-Ti plasmid. We report here the deletion of oncogenes from MINI-Ti to produce Micro-Ti containing the nopaline synthase gene and the ampicillin resistance gene and origin of replication of pBR322, flanked by left and right T-DNA borders. Micro-Ti was recloned into the wide host range plasmid pRK290 and transformed into an A. tumefaciens strain carrying a helper plasmid that could supply Virulence (VIR) genes in trans. Using the octopine Ti-plasmid pTiB6-806 as a helper, transformed tobacco cells were obtained which produced both nopaline and octopine. Two cloned cell lines producing both opines were found to be hormone dependent and to produce fertile tobacco plants. We selfed one of these plants and found that the two opine markers segregated in the F1 progeny in a Mendelian fashion. This showed that the T-DNAs were not linked in the transformed plant genome. Southern blot analysis of the genomic DNA from the regenerated plant showed that only part of the (oncogenic) octopine T-DNA was present indicating that it had suffered a deletion in the auxin producing locus (tms region). Presence of the cytokinin autonomy locus presumably accounts for the abnormal rooting behavior of the F1 progeny seedlings containing this T-DNA.
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  • 3
    ISSN: 1573-5028
    Keywords: Arabidopsis thaliana ; cystathionine β-lyase ; double-stranded RNA ; gene silencing ; methionine biosynthesis ; RNA interference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Controlled down-regulation of endogenous plant gene expression is a useful tool, but antisense and sense silencing lack predictability. Recent studies show that expression of both antisense and sense RNA together is an effective means of inactivating reporter and viral genes in plants. We created transgenic plants expressing antisense and sense RNA together in a single `double-stranded RNA' (dsRNA) transcript. This approach shows great promise as a highly effective means for reducing gene function. With this approach, we demonstrated that the Arabidopsis cystathionine β-lyase gene, which encodes a methionine biosynthetic enzyme, is essential for viability. Inactivation of this gene was rescued by the addition of methionine to the growth medium. Compared to antisense and sense constructs, the dsRNA construct showed a much more consistent and complete suppression of gene activity. Additionally, expression of a transcript with a spacer sequence containing an unrelated gene between antisense and sense luciferase gene fragments led to stronger inactivation of a second luciferase transgene than did constructs with a minimal spacing between sense and antisense fragments. However, the gene in the spacer region was neither functionally expressed nor functional in silencing a second, unlinked homologous transgene.
    Type of Medium: Electronic Resource
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