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1

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Quantification of total genomic DNA and selected repetitive sequences reveals concurrent changes in different DNA families in indica and japonica rice (2000)

Ohmido, N. ; Kijima, K. ; Akiyama, Y. ; [et al.]

Springer

Molecular genetics and genomics 263 (2000), S. 388-394

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ISSN: 1617-4623

Keywords: Key words Repetitive sequences ; Oryza sativa L. ; indica rice ; japonica rice ; Genome size

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract This paper describes a fluorescence in situ hybridization (FISH) analysis of three different repetitive sequence families, which were mapped to mitotic metaphase chromosomes and extended DNA fibers (EDFs) of the two subspecies of rice (Oryza sativa), indica and japonica (2n=2x=24). The repeat families studied were (1) the tandem repeat sequence A (TrsA), a functionally non-significant repeat; (2) the [TTTAGGG]n telomere sequence, a non-transcribed, tandemly repeated but functionally significant repeat; and (3) the 5S ribosomal RNA (5S rDNA). FISH of the TrsA repeat to metaphase chromosomes of indica and japonica cultivars revealed clear signals at the distal ends of twelve and four chromosomes, respectively. As shown in a previous report, the 17S ribosomal RNA genes (17S rDNA) are located at the nucleolus organizers (NORs) on chromosomes 9 and 10 of the indica cultivar. However, the japonica rice lacked the rDNA signals on chromosome 10. The size of the 5S rDNA repeat block, which was mapped on the chromosome 11 of both cultivars, was 1.22 times larger in the indica than in the japonica genome. The telomeric repeat arrays at the distal ends of all chromosome arms were on average three times longer in the indica genome than in the japonica genome. Flow cytometric measurements revealed that the nuclear DNA content of indica rice is 9.7% higher than that of japonica rice. Our data suggest that different repetitive sequence families contribute significantly to the variation in genome size between indica and japonica rice, though to different extents. The increase or decrease in the copy number of several repetitive sequences examined here may indicate the existence of a directed change in genome size in rice. Possible reasons for this phenomenon of concurrent evolution of various repeat families are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004380051182

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2

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Ribosomal DNAs: an exception to the conservation of gene order in rice genomes (2000)

Shishido, R. ; Sano, Y. ; Fukui, K.

Springer

Molecular genetics and genomics 263 (2000), S. 586-591

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ISSN: 1617-4623

Keywords: Key words rDNA locus ; Fluorescence in situ hybridization (FISH) ; Genus Oryza ; Comparative genomics

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract rDNA (18S-5.8S-25S rDNA) and 5S rDNA loci were visualized on the chromosomes of six species of the genus Oryza by fluorescence in situ hybridization (FISH) and the labeled rice chromosomes were identified based on their condensation patterns. As a result, the chromosomes harboring rDNA and/or 5S rDNA loci were determined in the complement for all the known rice genomes. Variation in the location of the rDNA loci indicated the transpositional nature of the rDNAs in the genus Oryza, as also suggested in Triticeae and Allium. Comparative analysis of the locations of rDNA loci among rice, maize and wheat revealed that variability in the physical location of the rDNA loci was characteristic of the genus Oryza and also of the genera of Gramineae. This variability in the location of the rDNA loci between evolutionarily related species is in sharp contrast to the conservation of the general order of genes in their genomes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004380051205

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3

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Quantitative chromosome maps and rDNA localization in the T subgenome of Nicotiana tabacum L. and its putative progenitors (2000)

Kitamura, S. ; Inoue, M. ; Ohmido, N. ; [et al.]

Springer

Theoretical and applied genetics 101 (2000), S. 1180-1188

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ISSN: 1432-2242

Keywords: Key words Quantitative idiogram ; Prometaphase chromosome ; Image analysis ; Fluorescence in situ hybridization ; T subgenome progenitor

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Using DAPI-stained prometaphase chromosomes, quantitative idiograms were constructed for the T subgenome of Nicotiana tabacum (2n = 4x = 48, SSTT) and two putative candidates for its T subgenome progenitor, Nicotiana otophora and Nicotiana tomentosiformis (both have 2n = 24, TT). The large chromosomes of the three karyotypes could be identified from the distributional pattern of the DAPI signal. Fluorescence in situ hybridization (FISH) with 5S rDNA gave not only good cytogenetical landmarks for identification of small chromosomes of the karyotypes but also phylogenetical information. In all three idiograms, 5S rDNA was localized in the proximal region of the long arm of a small submetacentric pair, but an additional 5S rDNA locus was detected terminally on the short arm of a small metacentric pair in N. otophora. The 18S rDNA locus detected here corresponded to satellite regions in all three karyotypes. Two satellited pairs in N. otophora and one satellited pair in N. tomentosiformis had single large subterminal DAPI blocks and two interstitial DAPI bands on their long arms, respectively. For the T subgenome component of N. tabacum, the single intense DAPI band was depicted on the center of the long arm of a satellited pair in the idiogram, although two interstitial bands were often detected on the long arm of the satellited pair in some spreads. Therefore, it was suggested that the T component of N. tabacum was more similar to that of N. tomentosiformis than N. otophora, especially in respect of the number and location of rDNA and the distributional patterns of DAPI signals.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s001220051595

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4

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Assembly of plasmid DNA and chromatophore inRhodospirillum rubrum (2000)

Iwano, M. ; Ogasawara, Y. ; Hase, A. ; [et al.]

Springer

Protoplasma 214 (2000), S. 158-165

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ISSN: 1615-6102

Keywords: Chromatophore ; In situ hybridization ; Photosynthetic bacterium ; Plasmid

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Rhodospirillum rubrum, a photosynthetic bacterium, contains many photosynthetic vesicular membranous structures called chromatophores. The organism contains a 55 kb specific plasmid which is essential for photosynthesis, but the exact relationship between the chromatophore and the plasmid is uncertain. In this study we examined the precise localization of the plasmids, especially in relation to the chromatophores. Fluorescence in situ hybridization indicated that there are several copies of the plasmid per cell and that some plasmids are localized close to the cellular envelope. In situ hybridization at the electron-microscopic level further revealed that the plasmid localized to the periphery of the chromatophore close to the envelope. Moreover, when the chromatophore fraction was purified from cells, the plasmid DNA was observed as a cluster around the chromatophore vesicles. The assembly of the plasmid and chromatophore may be related to chromatophore formation by invagination of cell membrane.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01279060

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5

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Molecular orbital theory of reactivity in radical polymerization. Part II (1956)

Hayashi, K. ; Yonezawa, T. ; Nagata, C. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Polymer Science 20 (1956), S. 537-550

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ISSN: 0022-3832

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: Several problems in the process of radical polymerization, e.g., the relation between the chemical structure of vinyl monomer and its chemical reactivity, the prevalence of head-to-tail configuration, the reactivity of initiator radicals, the alternation tendency in heteropolymerization, and the relative ease of coupling in several cases of homopolymerization, are treated by the theory previously proposed by the present authors, in which reactivity is represented by the magnitude of stabilization energy due to π conjugation between a monomer and a radical in the transition state. In addition, a brief discussion on the existing theories of reactivity and some applications of Hush's method to the problem of termination are presented. The agreement between results of calculation and experiment is shown to be almost statisfactory.

Additional Material: 2 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pol.1956.120209612

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6

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Molecular orbital theory of reactivity in ionic polymerizations (1957)

Yonezawa, T. ; Higashimura, T. ; Katagiri, K. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Polymer Science 26 (1957), S. 311-321

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ISSN: 0022-3832

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: The stabilization energy due to the conjugation taking place between a monomer and an ion in the transition state is calculated by the LCAO perturbation theory, in the same way in which the reactivity in radical copolymerization has previously been treated. In terms of this stabilization energy, the reactivity ratios of several monomer pairs in ionic copolymerization are satisfactorily interpreted. It is noted that, by the present method, both the radical and ionic copolymerization can be treated in a unified manner, whereas it is difficult in existing empirical methods. The positions of attack in polymer ions as well as in monomers, which are predicted by the frontier electron densities, are shown to agree well with experimental facts. The relative reactivities of vinyl monomers in ionic homopolymerization is also explained successfully by the magnitude of the localization energy computed by the LCAO method.

Additional Material: 1 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pol.1957.1202611406

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7

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Theoretical considerations on the mechanism of stereospecific cationic polymerization in homogeneous systems (1959)

Higashimura, T. ; Yonezawa, T. ; Okamura, S. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Polymer Science 39 (1959), S. 487-492

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ISSN: 0022-3832

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: A theoretical interpretation of the mechanism of stereospecific cationic polymerization in a homogeneous system at low temperature is given. The existance of a counterion in the vicinity of a charged carbon atom of a growing polymer ion is assumed and a repulsive interaction is considered to be between the substituent of the attacking monomer and that of the polymer. The most probable geometrical conformation of a monomer and a polymer ion in the transition state is determined by the magnitude of stabilization due to the overlap between atomic orbitals of ion and monomer. Our experimental results can be explained satisfactorily by this mechanism.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pol.1959.1203913540

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