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  • 1
    ISSN: 1573-6849
    Keywords: chromosome polymorphism ; genome evolution ; in-situ hybridization ; repetitive DNA ; wheat–rye addition and substitution lines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a study of polymorphism and stability in rye chromosomes, three rye varieties and the sets of wheat-rye addition and substitution lines were compared using two non-homologous highly repetitive DNA families, pSc200 and pSc250. The rye varieties, Petkus, Imperial and Onohoiskaya, showed polymorphism for the presence and the size of the pSc200 in-situ hybridization signals on chromosome pairs, 2R, 4R and 7R, and the pSc250 signals on chromosomes, 5R, 6R and 7R. Chromosome 1R was heteromorphic within the Onohoiskaya variety. Differences in the distribution of chromosome polymorphisms imply that intervarietal changes to these highly repetitive DNA families occurred independently, despite their juxtaposition or even overlapping locations in subtelomeric heterochromatic regions. In the set of Saratovskaya 29 wheat/Onohoiskaya substitution lines, only chromosome 2R was altered relative to its counterpart in the parental rye variety due to amplification of the pSc250 signal on the long arm, although this did not exceed intervarietal polymorphism. In the set of Chinese Spring wheat/Imperial addition lines, only two Imperial chromosomes, 4R and 6R, were unchanged. We detected the loss of one or both rye homologous chromosomes, the loss of one arm, and the deletion of subtelomeric heterochromatin accompanied by the loss of the pSc200 signal. The results show that Saratovskaya 29/Onohoiskaya chromosome substitution lines possess increased chromosome stability compared with Chinese Spring/Imperial addition lines.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5060
    Keywords: C-banding ; fluorescent in situ hybridization ; metaphase I bonds ; translocation ; triticale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bronco 90 is an advanced line of hexaploid triticale and was reported to be a 2D(2R) chromosome substitution type. In F1 hybrids of this triticale with bread wheat, however, a meiotic configuration of 16 bivalents and 10 univalents was frequently observed indicating the presence of an additional D(R) chromosome substitution or D/R translocation. To determine the chromosome constitution of Bronco 90, C-banding and fluorescent in situ hybridization techniques were applied to somatic and meiotic metaphase chromosomes. These analyses revealed that in Bronco 90, the terminal 7% of the long arm of rye chromosome 5R is derived from the long arm of chromosome 4D. This translocated chromosome (5RS.5RL-4DL) and telosome 4DL formed metaphase I bonds at a frequency of 71%, demonstrating the significance of small terminal chromosome segments for pairing. This novel rye-wheat translocation is probably generated by homoeologous crossing-over because the distal region of 5RL is known to be homoeologous to that of 4DL. Possible association of this translocation with the absence of hairy peduncle character in Bronco 90 is discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-6849
    Keywords: Nicotiana tabacum ; nucleosome positioning ; Progenitor-specific probes ; repetitive DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Members of a new family of highly repetitive DNA sequences called GRS were isolated fromNicotiana tabacum L. genomic DNA and characterized. Cloned, sequenced monomeric units (180–182 bp) of GRS exhibit properties characteristic of molecules that possess a stable curvature. The GRS family represents about 0.15% of total genomic DNA (104 copies per haploid genome) and could be derived from eitherNicotiana tomentosiformis orNicotiana otophora, two possible ancestors of the T genome of the amphidiploidN. tabacum. Sequence homology between the HRS60 (Koukalováet al. 1989) and the GRS family has been estimated to be 57%.In situ hybridization was used to localize GRS on mitotic chromosomes. Hybridization signals were obtained on five pairs of chromosomes at intercalary sites of the longer chromosome arms. The majority of GRS sequences appeared to be organized in tandem arrays and a minority were found to be dispersed through the genome in short clusters, interspersed with other types of DNA repeats, including 25S rDNA sequences. Several loci containing both GRS and HRS60 were also found. Such hybrid loci may indicate intergenomic transfer of the DNA in the amphidiploidN. tabacum. GRS sequences, like HRS60 (Fajkuset al. 1992), were found to specify the location of nucleosomes. The position of the nucleosome core has been mapped with respect to a conservedMbol site in the GRS sequence and an oligo A/T tract is a major centre of the DNA curvature.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5028
    Keywords: sugar beet (Beta vulgaris) ; LINEs ; non-LTR retrotransposons ; reverse transcriptase gene ; in situ hybridization ; genome organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated and characterized conserved regions of the reverse transcriptase gene from non-LTR retrotransposons, also called long interspersed nuclear elements (LINEs), from Beta vulgaris, B. lomatogona and B. nana. The novel elements show strong homology to other non-LTR retrotransposons from plants, man and animals. LINEs are present in all species of the genus Beta tested, but there was variation in copy number. Analysis by Southern hybridization and fluorescent in situ hybridization revealed the clustered organization of these retroelements in beet species. PCR amplification using degenerate primers to conserved motifs of the predicted LINE protein sequence enabled the cloning of LINEs from both Monocotyledonae (Allium cepa, Oryza sativa and Secale cereale) and Dicotyledonae (Nicotiana tabacum and Antirrhinum majus) indicating that LINEs are a universal feature of plant genomes. A dendrogram of fifteen new and six previously isolated sequences showed the high level of sequence divergence while revealing families characteristic of some genera. The genomic organization of non-LTR retrotransposons was examined more detailed in A. majus and O. sativa.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 36 (1998), S. 149-161 
    ISSN: 1573-5028
    Keywords: chromatin ; nucleosome organization ; nucleosome phasing ; plant telomeres ; repetitive DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Analysis of the structure of chromatin in cereal species using micrococcal nuclease (MNase) cleavage showed nucleosomal organization and a ladder with typical nucleosomal spacing of 175–185 bp. Probing with a set of DNA probes localized in the authentic telomeres, subtelomeric regions and bulk chromatin revealed that these chromosomal regions have nucleosomal organization but differ in size of nucleosomes and rate of cleavage between both species and regions. Chromatin from Secale and Dasypyrum cleaved more quickly than that from wheat and barley, perhaps because of their higher content of repetitive sequences with hairpin structures accessible to MNase cleavage. In all species, the telomeric chromatin showed more rapid cleavage kinetics and a shorter nucleosome length (160 bp spacing) than bulk chromatin. Rye telomeric repeat arrays were shortest, ranging from 8 kb to 50 kb while those of wheat ranged from 15 kb up to 175 kb. A gradient of sensitivity to MNase was detected along rye chromosomes. The rye-specific subtelomeric sequences pSc200 and pSc250 have nucleosomes of two lengths, those of the telomeric and of bulk nucleosomes, indicating that the telomeric structure may extended into the chromosomes. More proximal sequences common to rye and wheat, the short tandem-repeat pSc119.2 and rDNA sequence pTa71, showed longer nucleosomal sizes characteristic of bulk chromatin in both species. A strictly defined spacing arrangement (phasing) of nucleosomes was demonstrated along arrays of tandem repeats with different monomer lengths (118, 350 and 550 bp) by combining MNase and restriction enzyme digestion.
    Type of Medium: Electronic Resource
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