The nucleolus organizer region of maize (Zea mays L.): Chromosomal site of DNA complementary to ribosomal RNA

Phillips, Ronald L.; Kleese, Roger A.; Wang, S. S.

doi:10.1007/bf00326423

Cited by 100 publications

(34 citation statements)

References 12 publications

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“…The complete separation of the rRNA genes from the main band with 20 x 106 dalton, double-stranded DNA, indicates that these genes are present in clusters of at least three or four sequence repeats. This, together with the absence of rRNA genes within the main band, is consistent with the conclusion that all the rRNA genes are clustered within the nucleolar organizer DNA (11,23). This is in contrast to results obtained with wheat which suggested that the rRNA genes were scattered throughout the genome (13).…”

Section: Discussionsupporting

confidence: 88%

The Genes for Cytoplasmic Ribosomal Ribonucleic Acid in Higher Plants

Scott

Ingle²

1973

Plant Physiol.

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The genes for cytoplasmic ribosomal RNA are partially resolved from the bulk of the DNA by CsCI equilibrium centrifugation. Although in some plants the buoyant density of the ribosomal RNA genes is as expected from the base composition of ribosomal RNA, others show a large discrepancy which cannot be due to the presence of low G-C spacer-DNA. The crosshybridization observed with 1.3 and 0.7 X 100 molecular weight ribosomal RNAs and DNA, which varies greatly with different plant species, is not due to contamination of the ribosomal RNAs, and is specific for the ribosomal DNA of each species, probably largely restricted to those sequences coding for the two stable ribosomal RNAs. The double reciprocal plot may be used for the extrapolation of saturation values only with caution, because in these cases such plots are not linear over the whole of the hybridization reaction. stages of the reaction are therefore advantageous. The observation that the plot of reciprocal of hybridization against reciprocal of time fitted a straight line (9), which could be extrapolated to infinite time, suggested how saturation values could be obtained from measurements of the initial reaction. This should minimize problems of cross-hybridization. The use of this double reciprocal plot also eliminated the problem of RNA concentration-dependence of the saturation value, since analysis of the hybridization of complementary RNA and DNA from E. coli showed that the hybridization value obtained by extrapolation was essentially independent of the RNA concentration employed (9). This relationship has also been shown to hold for the hybridization of B. subtilis rRNA and DNA (6). The theoretical basis of this double reciprocal plot is not clear (9), but it represents a convenient, concentration-independent way of estimating a saturation value from the early part of the hybridization reaction.This paper describes some of the properties of the rRNA genes in higher plants and considers the nature of the crosshybridization observed between the 1.3 X 106 and 0.7 X 106 mol wt rRNAs. Some of the problems involved in the determination of a saturation value are discussed. Molecular hybridization of RNA to DNA has become an increasingly useful technique for studying many aspects of the genome. The stability and homogeneity of rRNA, which allows the preparation of highly purified molecules in relatively large amounts, has facilitated investigations of the rRNA genes by this method. The rRNA genes from Xenopus were the first genes to be isolated (8), and there is now a considerable knowledge of their fine structure (5, 7). Much less is known about rRNA genes in plants, and determination of the absolute redundancy of these genes is complicated by the apparent cross-hybridization between the two high molecular weight rRNAs (1.3 and 0.7 X 106) and their complementary sequences in the DNA, which confuses the determination of saturation levels (15). Similar cross-hybridization has been noted with the rRNAs from Escherichia coli (1, 4, 21), yeast (25), ra...

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Section: Discussionsupporting

confidence: 88%

The Genes for Cytoplasmic Ribosomal Ribonucleic Acid in Higher Plants

Scott

Ingle²

1973

Plant Physiol.

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“…This phenomenon, known as nucleolar dominance (1)(2)(3)(4), was initially discovered as a change in chromosome structure (5). At nucleolus organizer regions (NORs), the loci where nucleoli form during interphase (6,7), and where genes encoding the precursor transcript for 18S, 5.8S, and 25S rRNA are tandemly arrayed (8)(9)(10), NOR-bearing chromosomes in pure species (nonhybrids) display thin ''secondary constrictions'' at metaphase (6,7). Navashin noted that in numerous interspecies hybrids, only the chromosomes of one parent display these secondary constrictions (5).…”

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confidence: 99%

Natural variation in nucleolar dominance reveals the relationship between nucleolus organizer chromatin topology and rRNA gene transcription in Arabidopsis

Pontes¹,

Lawrence²,

Neves³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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In genetic hybrids, nucleolus formation on chromosomes inherited from only one parent is the epigenetic phenomenon, nucleolar dominance. By using Arabidopsis suecica, the allotetraploid hybrid of Arabidopsis thaliana and Arabidopsis arenosa, natural variation in nucleolar dominance was found to occur, providing a unique opportunity to examine homologous nucleolus organizer regions (NORs) in their active and inactive states. In A. suecica strain LC1, NORs derived from A. arenosa are active, whereas A. thalianaderived NORs are silenced. In A. suecica strain 9502, NORs of both parental species are active. When active, NORs are partially, but not fully, decondensed. Both active and inactive LC1 NORs colocalize with the nucleolus, contradicting the long-standing assumption that rRNA gene transcription drives nucleolus association. Collectively, these observations clarify the relationships among NOR chromatin topology, rRNA gene transcription, and NOR-nucleolus associations. A. suecica strains LC1 and 9502 have each lost one pair of A. thaliana NORs during evolution, and amplified fragmentlength polymorphism analysis further indicates that these strains are genetically very similar. These data suggest that nucleolar dominance can result from subtle genetic or epigenetic variation but is not a trait fundamental to a given interspecies hybrid combination.

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“…Nucleolus organizer regions (NORs) are the sites of rRNA genes in the chromosomes of animal (Ritossa and Spiegelman, 1965;Wallace and Birnstiel, 1966;Henderson et al, 1972Henderson et al, , 1974 and plant species (Phillips et al, 1971;Flavell and O'Dell, 1975;Hutchinson and Miller, 1982). Methods have been developed for the selective staining of these chro mosomal regions both in animals (Goodpasture and Bloom, 1975;Howell et al, 1975;Verma and Babu, 1984) and plants (Hizume et al, 1980;Lacadena et al, 1984;Mehra et al, 1985;Cunado et al, 1986).…”

Section: N Bandingmentioning

confidence: 99%