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  • nucleolar dominance  (2)
  • Triticum aestivum cv  (1)
  • 1
    ISSN: 1573-6849
    Keywords: B chromosomes ; genomicin situ hybridization ; nuclear architecture ; Secale cereale ; Triticum aestivum cv ; Lindström
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The B chromosomes (Bs) of rye (Secale cereale) have been studied at interphase in terms of their chromatin organization, patterns of nuclear disposition and physical association in plants with two, three, and four Bs. The study was made in the Lindström strain of hexaploid wheat, which carries the rye Bs as an addition line, byin situ hybridization with a B-specific probe and by genomicin situ hybridization (GISH) with rye genomic DNA, enabling whole chromosome painting. Repetive sequences common to the As and Bs of rye allow for visualization of the rye B at interphase in the wheat background. A B-specific probe enables the orientation of two or more Bs to be determined, and the combination of both probes used together gives information on the disposition of the Bs and on their patterns of physical association within the nucleus. The Bs form linear ‘strings’, and the ends of their long arms, which can be detected by the B-specific probe, are usually located within the hemisphere of the nucleus that has the least condensed chromatin. There is dose-dependent association, and even numbers (2B, 4B) have a greater preference for association than odd ones (3B).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromosome research 5 (1997), S. 125-131 
    ISSN: 1573-6849
    Keywords: gene expression ; nucleolar dominance ; rDNA ; substitution lines ; triticale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hybrid plants and animals often show suppression of activity of ribosomal genes (rDNA) originating from one of the parental or ancestral species. In the wheat × rye amphiploid triticale, containing 28 chromosomes of wheat origin and 14 from rye, rDNA of rye origin (on chromosome 1R) is not normally expressed, while the 1B- and 6B-origin rDNA from wheat shows strong expression. Expression of rDNA can be accurately assessed by the silver staining method, which stains both interphase nucleoli and metaphase rDNA sites that were actively expressed at the previous interphase. We show here that substitution of another rye chromosome, 2R, by a chromosome from hexaploid wheat, 2D(triticale-2D(2R)), prevents suppression of the rye-origin rDNA, and leads to activity of all six major rDNA loci. These results were found in two different triticales and supported by rDNA behaviour in wheat—rye chromosomal addition lines. Models for chromosomal interactions leading to control of rDNA expression are presented.
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  • 3
    ISSN: 1573-6849
    Keywords: meiotic reprogramming ; microspores ; nucleolar dominance ; rDNA expression ; rye NOR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To test the hypothesis that interspecific genomic and chromosome interactions leading to nucleolar dominance could be reprogrammed in meiosis, we compared the expression of distinct nucleolar organizing region (NOR) loci in hexaploid triticale root tip meristematic cells, pollen mother cells and young pollen grains. Interphase and metaphase cells were silver stained to quantify nucleoli and active NOR loci respectively. A marked difference in the ribosomal RNA gene activity of each locus was observed when different types of cells were compared: in somatic and pollen mother cells, rRNA gene activity was mainly restricted to major wheat NORs (1B and 6B) with only a small contribution from rye NORs (1R). In contrast, in young pollen grains, all NORs present, including the 1R NORs, were consistently active. The expression of all NORs just after meiosis is considered to be a consequence of meiotic reprogramming of rye origin rDNA. Gene reprogramming mediated by the resetting of methylation patterns established early in embryogenesis is suggested to be responsible for the differential expression of the NORs of rye origin in distinct developmental stages of triticale.
    Type of Medium: Electronic Resource
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