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  • 1
    ISSN: 0304-4211
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0378-1119
    Keywords: RNA polymeraseIII ; Recombinant DNA ; mung bean ; regulation of transcription ; termination
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0378-1119
    Keywords: Adzuki bean ; RNA polymerase I ; mung bean ; repetitive DNA ; retrotransposition ; termination of transcription ; unequal crossover
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2242
    Keywords: Repeated DNA ; Restriction satellite ; RFLP ; Solanaceae ; Species-specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Highly repeated DNA of potato (Solanum sp.) was characterized by cloning various major repeated elements of the nuclear genome. The percentage of the nuclear genome of the specific fractions and the restriction enzyme patterns were determined in order to show the distribution and organization of the respective repeats in the genome of Solanum tuberosum cultivars, dihaploid breeding lines and in wild species of Solanum. Several of the clones obtained were represented in a high copy number but showed no informative RFLP patterns. More information was gained from ‘restriction satellite’ repeats. The clone pR1T320 was found to contain satellite repeats (360 bp in length) that are proportionally present in the genome of all Solanum species at frequencies, between 0.5% and 2.6% and which are differently organized. This repeat was also found in the genera Lycopersicon, Datura and Nicotiana. With various restriction enzymes characteristic RFLP patterns were detected. A more or less genus-specific element for Solanum was the 183-bp repeat (clone pSA287; between 0.2–0.4% of the nuclear genome) that was present in the majority of the Solanum species analyzed except S. kurtzianum, S. bulbocastanum and S. pinnatisectum. In a few wild species (prominently in S. kurtzianum, S. demissum and S. acaule) a specific repeat type was detected (clone pSDT382; repeat length approximately 370 bp) that could be used to trace the wild species introduced into S. tuberosum cultivars. The repeats analyzed together with the 18S, 5.8S and 25S ribosomal DNA (1.9–5.2%, corresponding to 1800-5500 rDNA copies) comprised approximately 4–7% of the Solanum genome.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2242
    Keywords: Helictotrichon ; Oryza sativa ; Satellite DNA ; Genome-specificity ; Phylogenetic relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The taxonomic relationships among perennial oats (Helictotrichon Besser ex Schultes & Schultes, Aveninae, Aveneae, Poaceae) have been studied using highly repeated satellite DNA as a molecular marker. Highly repetitive sequences were isolated from restriction endonuclease digests of nuclear DNA of Helictotrichon convolutum, and satellite repeats (approximately 365 bp in length) were cloned, sequenced and compared among each other. They exhibited an intraspecific sequence variability of 6–9%. This satellite DNA, CON1, is differentially distributed within the genus Helictotrichon. In species of the subgenus Helictotrichon a high copy number is detectable, whereas in representatives of the subgenera Pratavenastrum and Pubavenastrum the number of copies per genome is rather low. Surprisingly, the satellite DNA repeat CON1 shows 74% sequence similarity to an A-genome specific repetitive DNA of Oryza (rice).
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  • 6
    ISSN: 1432-2242
    Keywords: Hybrid identification ; Molecular evolution ; Repetitive DNA elements ; Satellite DNA ; Solanaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Species-specific repetitive DNA probes are a useful tool for the molecular identification of somatic hybrids. Therefore, the distribution of three repetitive DNA elements of Solanum was investigated in Solanum wild species, Solanum breeding lines, and in more distantly related species of the genera Lycopersicon, Nicotiana, and Datura. The clone pSCH15, obtained from S. circaeifolium, represents a new 168-bp repetitive element; it shows 73–79% sequence similarity to repetitive elements of S. brevidens and Lycopersicon species. The 163-bp element in pSBH6, cloned from S. bulbocastanum, turned out to be very similar (95% sequence homology) to the Lycopersicon element pLEG15/TGRI previously regarded to be present only in species of the genus Lycopersicon and in S. lycopersicoides. Lower sequence similarity of approximately 80% was observed to repetitive elements of S. brevidens which are organized differently. The repeats exhibited different degrees of specificity: by Southern hybridization the element represented by the clone pSBH6 could be detected in almost all Solanum species investigated here but only after long exposure to X-ray film. The previously described “Solanum-specific” element represented by the clone pSA287 was also found, although in a very low copy number, in Lycopersicon esculentum. Therefore, detection of the repetitive elements pSA287 and pSBH6 in those species in which the respective repeat is less represented depends on exposure time. In contrast, the element pSCH15 is prominently present only in a small number of Solanum wild species and — to some extent — in the diploid breeding lines as revealed after long exposure. Use of these repeated elements for the identification of specific genomes in protoplast-fusion hybrids between Solanum wild species and Solanum breeding lines, or between two breeding lines, was evaluated.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2242
    Keywords: Key words Asymmetric somatic hybrids ; Flowcytometry ; RFLP ; Solanum tuberosum ; Wild species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The objective of this study was to evaluate the suitability of different techniques for a simple and rapid identification of asymmetric hybrids, without the use of selection markers and independent of the fusion partners used. Additionally, the degree of donor DNA elimination was determined. Among 473 viable plants obtained from asymmetric fusion experiments between three di-haploid breeding lines of potato (Solanum tuberosum) and diploid wild species (S. bulbocastanum, S. circaeifolium; X-ray treatment of the wild species) the most promising ones were investigated with three different methods: flow cytometry, RFLP analysis with an oligonucleotide probe (GATA)4, and with single-copy probes. Flow cytometry, which combines a high screening capacity with detailed information about the DNA content and allows a distinction between asymmetric hybrids and chimeras, detected 31 hypo-tetraploid and 42 hypo-hexaploid regenerates among 224 plants. With the oligonucleotide probe (GATA)4 only a few asymmetric hybrids were detected among all regenerates. More than 50% of these asymmetric regenerates were chimeras. Concerning the degree of DNA elimination, the results obtained by RFLP analysis with 17 single-copy probes were correlated with the results obtained by flow cytometry. The maximum DNA elimination of the donor genome was 52%. As a trend, an irradiation dosage of 210 Gy caused a higher DNA elimination in the wild species than a dosage of 70 Gy. No calli were obtained after irradiation of the wild species with 420 Gy.
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  • 8
    ISSN: 1432-2242
    Keywords: Cucumis sativus ; Satellite DNA ; Insertion ; Amplification ; Sequence homology ; Cucumis melo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Another satellite DNA repeat (type IV) in the genome of Cucumis sativus (cucumber) was found and investigated with respect to DNA sequence, methylation, and evolution. This satellite shows a repeat length of 360 bp and a GC-content of 47%. The repeats of type IV are highly conserved among each other. Evidence for CG and CNG methylation is presented. By comparison to the previously described satellites (type I/II and type III) from cucumber, it is evident that this repeat is created by an insertion of a 180 bp DNA sequence similar to type I–III into another DNA sequence (or vice versa), and subsequent amplification forming a new satellite repeat. The different satellites of the type I/II, type III, and the 180 bp insert of type IV show a sequence homology of 60%–70%, indicating that the complex satellite DNA of cucumber is originated from a common progenitor by mutation, additional insertion, and amplification events. Copies of a sequence similar to a part of type IV are present in the genome of the related species Cucumis melo (melon).
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2242
    Keywords: 5S rDNA ; Evolution ; Protoplast fusion ; Somatic hybrids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucleotide sequences of the 5S rRNA genes (5S rDNA) of two Solanum tuberosum breeding lines (R1 and B15) and of the Mexican wild species S. pinnatisectum were determined and compared with each other and to the 5S rDNA of other Solanaceae species (Lycopersicon esculentum, Nicotiana rustica and Petunia hybrida). The 5S rDNA repeats of the Solanum species are 324–329 bp in length, and they exhibit 91–95% sequence identity. Sequence variability is mainly located in a short region of the spacer separating the 5S rRNA coding regions. A synthetic 28-mer oligonucleotide constructed according to this region can be used as a specific hybridization probe to distinguish symmetric somatic hybrids between S. tubersosum breeding line B15 and S. pinnatisectum produced by protoplast fusion. Interestingly, the two Solanum breeding lines R1 and B15 differ also in this spacer region.
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  • 10
    ISSN: 1432-2242
    Keywords: Flow cytometry ; Protoplast fusion ; RFLP ; Species-specific repetitive elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Interspecific somatic hybrids between the 1EBN-wild species Solanum pinnatisectum (S. pnt) and four different diploid breeding lines of Solanum tuberosum (S. tbr) were produced by electrofusion. S. pnt exhibits resistance to Phytophthora infestans and Erwinia blackleg. Somatic hybrids were identified by RFLP analysis using the oligonucleotide (GATA)4 as a probe. In three of four combinations all regenerates obtained were somatic hybrids. All 86 somatic hybrids between the breeding line H256/1 and S. pnt were analyzed in detail with respect to morphological and molecular characters; 50% of the somatic hybrids showed normal intermediate leaf morphology. Tubers of somatic hybrid plants grown in the greenhouse as well as in the field were evenly shaped and remarkably similar to those of the S. tbr breeding line. Analysis of relative DNA content by flow cytometry revealed that 75% of the somatic hybrids were tetraploid, some were hypotetraploid and others polyploid or mixoploid. Slotblot and RFLP analyses were carried out using repetitive and some single-copy DNA probes. The genome portion of the S. tbr breeding line was determined by slot-blot analysis using the species-specific repetitive probe pSA287. Obviously, most somatic hybrids contain the complete genomes of both fusion partners. In some of the somatic hybrids, a significantly lower intensity of the S. pnt-specific hybridization signal indicated a certain degree of asymmetry.
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