INTRASPECIFIC VARIATION OF RIBOSOMAL GENE REDUNDANCY IN ZEA MAYS

ABSTRACT Ribosomal genes in eukaryotes are highly redundant. Considerable variation in the level of redundancy among species, especially in higher plants, has been reported; but except for deletion and duplication mutants, it is generally accepted that intraspecific variability in redundancy level is small. We have examined the level of redundancy in several lines of maize by DNA-rRNA saturation hybridization. The amount of nuclear DNA which hybridizes with rRNA in the ten lines examined varied from 0.24% to 0.50%. The number of rRNA genes per diploid genome thus ranges from 1.12 × 104 to 2.32 × 104. Results also indicate that the level of redundancy is genetically transmitted.

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RIBOSOMAL GENE LOCALIZATION AND DISTRIBUTION (ARRANGEMENT) WITHIN THE NUCLEOLAR ORGANIZER REGION OF ZEA MAYS

Genetics ◽

10.1093/genetics/80.3.505 ◽

1975 ◽

Vol 80 (3) ◽

pp. 505-518

Author(s):

Samuel A Ramirez ◽

John H Sinclair

Keyword(s):

Zea Mays ◽

Organizer Region ◽

Nucleolar Organizer Region ◽

Nucleolar Organizer ◽

B Chromosome ◽

Ribosomal Gene ◽

Ribosomal Genes ◽

Rrna Genes ◽

Gene Localization ◽

Chromosome 6

ABSTRACT Cytogenetic and molecular hybridization techniques were used to examine the arrangement of rRNA genes at the nucleolar organizer region (NOR) of maize. TB-6a stocks involving a reciprocal translocation between a B chromosome and the NOR of chromosome 6 were used. The amount of rDNA in the different stocks used varied from 1.5 to 4 NOR equivalents depending on the number of B6 choromosomes present. Cytological measurements show that the medial break through the NOR results in an equal partitioning of the heterochromatic knob (the NOR) between chromosome 6 and the B chromosome to which it was translocated. DNA-rRNA hybridization experiments show a linear relationship between the amount of rRNA capable of hybridizing with DNA and the number of NOR equivalents present. The data confirm McClintock's conclusion that the heterochromatic knob, rather than the constricted portion, is the true NOR region. Further, they show that the number of ribosomal genes is correlated with the amount of cytologically visible NOR, suggesting a uniform distribution of genes throughout the locus.

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The Ribosomal Gene Loci—The Power behind the Throne

Genes ◽

10.3390/genes12050763 ◽

2021 ◽

Vol 12 (5) ◽

pp. 763

Author(s):

Konstantin I. Panov ◽

Katherine Hannan ◽

Ross D. Hannan ◽

Nadine Hein

Keyword(s):

Genome Stability ◽

Cell Cycle Progression ◽

Global Gene Expression ◽

Cell Types ◽

Ribosomal Gene ◽

Cellular Growth ◽

Rrna Genes ◽

Dynamic Regulation ◽

Pol I ◽

Polymerase I

Nucleoli form around actively transcribed ribosomal RNA (rRNA) genes (rDNA), and the morphology and location of nucleolus-associated genomic domains (NADs) are linked to the RNA Polymerase I (Pol I) transcription status. The number of rDNA repeats (and the proportion of actively transcribed rRNA genes) is variable between cell types, individuals and disease state. Substantial changes in nucleolar morphology and size accompanied by concomitant changes in the Pol I transcription rate have long been documented during normal cell cycle progression, development and malignant transformation. This demonstrates how dynamic the nucleolar structure can be. Here, we will discuss how the structure of the rDNA loci, the nucleolus and the rate of Pol I transcription are important for dynamic regulation of global gene expression and genome stability, e.g., through the modulation of long-range genomic interactions with the suppressive NAD environment. These observations support an emerging paradigm whereby the rDNA repeats and the nucleolus play a key regulatory role in cellular homeostasis during normal development as well as disease, independent of their role in determining ribosome capacity and cellular growth rates.

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Inhibition of δ-Aminolevulinic Acid Synthesis by Glyphosate

Weed Science ◽

10.1017/s004317450006375x ◽

1981 ◽

Vol 29 (5) ◽

pp. 571-577 ◽

Cited By ~ 21

Author(s):

Lynn M. Kitchen ◽

William W. Witt ◽

Charles E. Rieck

Keyword(s):

Carbon Dioxide ◽

Zea Mays ◽

Aminolevulinic Acid ◽

Higher Plants ◽

Acid Synthesis ◽

The Other ◽

Porphyrin Ring ◽

Fresh Weight ◽

Ring Compounds ◽

Site Of Action

The effect of glyphosate [N-(phosphonomethyl) glycine] on barley (Hordeum vulgareL.) and corn (Zea maysL.) shoot δ-aminolevulinic acid (ALA) production was examined by monitoring ALA content in the tissue and measuring incorporation of14C precursors into ALA and chlorophylla. Barley shoot ALA content was significantly decreased by 1 mM glyphosate after 9, 11, and 15 h of illumination. ALA production by treated barley shoots was 30 nmoles•g fresh weight-1•h-1at each interval tested, compared with 75 to 120 nmoles•g fresh weight-1•h-1for the control. In corn shoots, ALA content was reduced 32, 45, and 58% by 0.1, 1.0, and 10.0 mM glyphosate, respectively, after 12 h illumination. Incorporation studies with14C-glutamate,14C-α-ketoglutarate, and14C-glycine into ALA showed a 77, 92, and 91% inhibition, respectively, in barley shoots treated with 1 mM glyphosate. Incorporation of14C-ALA into chlorophyllawas not affected by 1 mM glyphosate. Thus, the site of action of glyphosate may involve two enzyme pathways:one controlling the conversion of α-ketoglutarate to ALA, and the other controlling the condensation of glycine with succinyl CoA to form ALA and carbon dioxide. Inhibition of ALA synthesis blocks synthesis of chlorophyll, as well as all other porphyrin ring compounds found in higher plants. Thus, inhibition of ALA synthesis may be an integral component of the herbicidal mode of action of glyphosate.

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Detection of a variable number of 18S-5.8S-26S and 5S ribosomal DNA loci by fluorescent in situ hybridization in diploid and tetraploid Arachis species

Genome ◽

10.1139/g98-092 ◽

1999 ◽

Vol 42 (1) ◽

pp. 52-59 ◽

Cited By ~ 27

Author(s):

S N Raina ◽

Y Mukai

Keyword(s):

In Situ Hybridization ◽

5S Rdna ◽

Gene Families ◽

Ribosomal Gene ◽

Rrna Genes ◽

Tetraploid Species ◽

Arachis Species ◽

26S Rdna ◽

Rdna Loci

In order to obtain new information on the genome organization of Arachis ribosomal DNA, more particularly among A. hypogaea and its close relatives, the distribution of the 18S-5.8S-26S and 5S ribosomal RNA gene families on the chromosomes of 21 diploid and tetraploid Arachis species, selected from six of nine taxonomic sections, was analyzed by in situ hybridization with pTa71 (18S-5.8S-26S rDNA) and pTa794 (5S rDNA) clones. Two major 18S-5.8S-26S rDNA loci with intense signals were found in the nucleolus organizer regions (NOR) of each of the diploid and tetraploid species. In addition to extended signals at major NORs, two to six medium and (or) minute-sized signals were also observed. Variability in the number, size, and location of 18S-5.8S-26S sites could generally distinguish species within the same genome as well as between species with different genomes. The use of double fluorescence in situ hybridization enabled us to locate the positions of 5S rRNA genes in relation to the chromosomal location of 18S-5.8S-26S rRNA genes in Arachis chromosomes which were difficult to karyotype. Two or four 5S rDNA loci and 18S-5.8S-26S rDNA loci were generally located on different chromosomes. The tandemly repeated 5S rDNA sites were diagnostic for T and C genomes. In one species, each of B and Am genomes, the two ribosomal gene families were observed to occur at the same locus. Barring A. ipaensis and A. valida, all the diploid species had characteristic centromeric bands in all the 20 chromosomes. In tetraploid species A. hypogaea and A. monticola only 20 out of 40 chromosomes showed centromeric bands. Comparative studies of distribution of the two ribosomal gene families, and occurrence of centromeric bands in only 20 chromosomes of the tetraploid species suggests that A. villosa and A. ipaensis are the diploid progenitors of A. hypogaea and A. monticola. This study excludes A. batizocoi as the B genome donor species for A. hypogaea and A. monticola.Key words: Arachis species, 5S rRNA, 18S-5.8S-26S rRNA, in situ hybridization, evolution.

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CYTOGENETIC EFFECTS OF 2,4-D AND AMITROLE IN RELATION TO NUCLEAR VOLUME AND DNA CONTENT IN SOME HIGHER PLANTS

Canadian Journal of Genetics and Cytology ◽

10.1139/g72-095 ◽

1972 ◽

Vol 14 (4) ◽

pp. 773-783 ◽

Cited By ~ 55

Author(s):

T. Mohandas ◽

W. F. Grant

Keyword(s):

Hordeum Vulgare ◽

Nuclear Dna ◽

Higher Plants ◽

Positive Control ◽

Root Tip ◽

Interphase Chromosome ◽

Dna Values ◽

Cytological Abnormalities ◽

Centaurea Jacea ◽

Chrysanthemum Leucanthemum

The cytological effects of 2,4-D and amitrole were studied for 12 species (Tradescantia clone 02, Allium cepa, Vicia faba, Triticum aestivum, T. dicoccum, Hordeum vulgare, Secale cereale, Centaurea jacea, Cirsium vulgare, Chrysanthemum leucanthemum, Plantago major and Erigeron canadensis). Ethyl methane sulfonate (EMS) was used as a positive control. The cytological abnormalities induced in root-tip cells by both 2,4-D and amitrole included chromosome bridges, fragments, lagging chromosomes, and chromatin bodies; 2,4-D also induced chromosome contraction, and C-mitoses. Studies following seed treatments of Hordeum vulgare on M2 seedlings showed that 2,4-D and EMS induced albina mutants. Interphase nuclear volumes of the various species were measured from root-tip meristems. Nuclear DNA values were determined cytophotometrically for seven species. The relative DNA values were found to be positively correlated with nuclear volumes. The lack of any clear relationship between the number of cytological abnormalities induced by the chemicals and the nuclear and interphase chromosome volumes of the plants probably reflects a lack of synchrony of the treated cell population.

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Inter- and intraspecific variation of nuclear DNA reassociation kinetics in the Gracilariales (Rhodophyta)

Journal of Applied Phycology ◽

10.1007/bf02179783 ◽

1990 ◽

Vol 2 (3) ◽

pp. 259-267 ◽

Cited By ~ 21

Author(s):

Julie A. Dutcher ◽

Donald F. Kapraun ◽

Ronald K. Sizemore

Keyword(s):

Intraspecific Variation ◽

Nuclear Dna ◽

Reassociation Kinetics ◽

Dna Reassociation ◽

Dna Reassociation Kinetics

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Intraspecific variation in nuclear DNA content in Collinsia verna nutt. (Scrophulariaceae)

Heredity ◽

10.1038/hdy.1984.25 ◽

1984 ◽

Vol 52 (2) ◽

pp. 235-242 ◽

Cited By ~ 15

Author(s):

Judith K Greenlee ◽

K S Rai ◽

Alton D Floyd

Keyword(s):

Intraspecific Variation ◽

Dna Content ◽

Nuclear Dna ◽

Nuclear Dna Content ◽

Collinsia Verna

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NUCLEAR DNA AND CYTOPLASMIC DNA FROM TISSUES OF HIGHER PLANTS

The Journal of Cell Biology ◽

10.1083/jcb.27.3.451 ◽

1965 ◽

Vol 27 (3) ◽

pp. 451-457 ◽

Cited By ~ 29

Author(s):

Yasuo Hotta ◽

Alix Bassel ◽

Herbert Stern

Keyword(s):

Inorganic Phosphate ◽

Nuclear Dna ◽

Higher Plants ◽

Soluble Fraction ◽

Buoyant Density ◽

Wheat Roots ◽

Cytoplasmic Dna ◽

Sucrose Medium

Young wheat roots were labeled with 32P-inorganic phosphate. Following the labeling period, roots were homogenized in a sucrose medium and fractionated into nuclei, cytoplasmic particles (including proplastids and mitochondria), and a soluble fraction containing most of the microsomes. DNA prepared from the particles had a higher buoyant density than that from the nuclei and showed a marked loss in total label if the roots were exposed to non-radioactive medium for 48 hours prior to fractionation of the cells.

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