Characterization of the rapidly reassociating deoxyribonucleic acid of Cucurbita pepo and the sequences complementary to ribosomal and transfer ribonucleic acids

Thornburg, William; Siegel, Albert

doi:10.1021/bi00738a032

Cited by 8 publications

(7 citation statements)

References 28 publications

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“…If we assume the haploid genome size of muskmelon is about that of the closely related pumpkin, 5.1 X 1011 daltons (38), the number of copies of the 33% and 40% components per genome is estimated to be 6.1 X 108 and 310, respectively (satellite is 30% of total DNA).…”

Section: Resultsmentioning

confidence: 99%

“…Essentially all of pumpkin nuclear DNA complementary to ribosomal RNA (rDNA) (2.2-2.4% of nuclear DNA) was found in a satellite (38,44) of similar density to that of the muskmelon satellite. Since pumpkin and muskmelon are in the same family, Cucurbitaceae, our satellite may contain a similar amount of rDNA.…”

Section: Discussionmentioning

confidence: 99%

“…Since pumpkin and muskmelon are in the same family, Cucurbitaceae, our satellite may contain a similar amount of rDNA. Thus, muskmelon rDNA could account for perhaps 15% of the satellite (assuming one strand is transcribed and 30% of the total DNA for the satellite) with a complexity of 4 to 6 X 106 daltons (38). Spacer and rRNA precursor DNA would add to this complexity figure.…”

Section: Discussionmentioning

confidence: 99%

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Novel Properties of Satellite DNA from Muskmelon

Bendich¹,

Anderson²

1974

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

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The purified dense satellite of muskmelon (Cucumis melo L.) represents 30% of the total DNA and forms a sharp, unimodal peak in both neutral and alkaline CsCl gradients. Spectrophotometric melting and DNA reassociation analyses revealed that one-third of the satellite is high melting and has a complexity of about 2.5 X 105 daltons, while the remaining two-thirds of the satellite melts 80 lower and has a complexity of about 5 X 108 daltons. The thermal stability of reassociated satellite DNA indicates that the multiple copies of the two melting fractions are essentially identical. The sharp, unimodal peak in Cs2SO4 becomes two distinct peaks when either silver or mercuric ions are included in the Cs2 S04 gradient One or more extremely rapidly reassociating components of nuclear DNA are present in many animals, often detectable as "satellite" bands in CsCl gradients (1). The kinetics of strand reassociation and the stability of these reformed duplexes are interpreted to mean that the multiple DNA segments are highly reiterated and are closely similar copies (2-4). Although its function is not known, some satellite DNA in mice (5) and insects (6, 7) hybridizes primarily with the centromeric regions of chromosomes in cytological preparations. It is enriched in heterochromatin of guinea pig (8), mouse, crab (9) and calf (10), and in mouse nucleoli (11). The mouse satellite does not appear to be transcribed (12). These unusual properties have led to the suggestion that satellite DNA may have a structural function in chromosome folding, pairing, and movement (12,13).From its reassociation kinetics, mouse satellite was estimated to contain about a million very similar copies comprising some 10% of the total mouse DNA (2, 14). The repeating unit in guinea pig a-satellite DNA has been estimated from oligonucleotide digestion products to be six nucleotides long (somewhat longer in the mouse) with about 12% nucleotide changes in the repeating units (15). Sequencing techniques have also provided length estimates of ten in a kangaroo rat satellite (16) and seven for each of three satellites in Drosophila virilis (17). The original complexity estimate (2) for mouse satellite of 300-400 nucleotide pairs (np) was considered too large after estimates were made of the marked influence of mispairing on reassociation rate (18,19

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Novel Properties of Satellite DNA from Muskmelon

Bendich¹,

Anderson²

1974

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

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“…8). Indeed, in some plants, sequences complementary to ribosomal RNA appear to be concentrated in the satellite band (4,10). These have been estimated to account for perhaps 15%o of the satellite in muskmelon (8), and to contain cistrons for both cytoplasmic and chloroplastic rRNAs in pumpkin (11).…”

Section: Discussionmentioning

confidence: 99%

“…In this regard, several higher plants, including cucumber, have previously been shown to contain particularly large amounts (up to 44%) of satellite DNAs in neutral CsCl (4)(5)(6)(7)(8). These large plant satellites-in analogy with the satellite DNAs of animal cells (9)-have variously been reported to be rapidly renaturing (4,7,8,10), associated with the genes for rRNA (4,11) and of nuclear origin (7,10,12). The relationship between cytoplasmic organelle DNA and the large plant satellites, however, was not seriously investigated.…”

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confidence: 99%

Satellite-Rich DNA in Cucumber: Hormonal Enhancement of Synthesis and Subcellular Identification

Kadouri¹,

Atsmon²,

Edelman³

1975

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

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Cucumber hypocotyl DNA in neutral CsCl distributes into a mainband comprising 59% of the total, and two large satellite bands which contribute 41%to the DNA pattern. Organelle enrichment studies show that the densities of mitochondrial and chloroplast DNA coincide with those of the satellite bands. At least 12-19% of total cucumber DNA is associated with the cytoplasmic organelles. These In prior studies, gibberellin-induced elongation of the cucumber hypocotyl was correlated with an increased incorporation of [3H]thymidine into DNA (1). Autoradiographic and fractionation experiments (2) further suggested that much of this synthesis might be extranuclear, reflecting a hormoneenhanced multiplication of chloroplasts in the elongating zone (3). This possibility has now been investigated at the level of different DNA density peaks by CsCl gradient centrifugation. In this regard, several higher plants, including cucumber, have previously been shown to contain particularly large amounts (up to 44%) of satellite DNAs in neutral CsCl (4-8). These large plant satellites-in analogy with the satellite DNAs of animal cells (9)-have variously been reported to be rapidly renaturing (4,7,8,10), associated with the genes for rRNA (4, 11) and of nuclear origin (7,10,12). The relationship between cytoplasmic organelle DNA and the large plant satellites, however, was not seriously investigated.In the present report we demonstrate that a considerable fraction of the large satellite DNAs in cucumber are associated with chloroplasts and mitochondria. We further show that in elongating hypocotyl tissue the rates of synthesis of organelle-rich satellite DNA and mainband DNA respond in vivo to hormone treatments by increasing markedly. Alternatively (method 2), hypocotyl sections were processed as described by Tautvydas (17) except that steeping was carried out at 0-2°in 4% gum arabic, 0.4 M sucrose, 6 mM Mg acetate, 0.3 mM dithiothreitol, and 5 mM morpholinoethane sulfonate, pH 6.4. Resuspension buffer was without gum arabic and contained 0.15% 2-ethyl-1-hexanol. Method 3 was identical to method 2 except that 0.1% Triton X-100 was included during the steeping procedure. For the isolation of chloroplasts the filtered homogenate was centrifuged at 1000 X g, and the pellet was dispersed in modified Honda medium supplemented with 40 mM Mg+2 and incubated with DNase (70 ug/ml) at 0°for 15-20 min. After addition of 0.1 M EDTA, discontinuous sucrose gradient centrifugation was carried out (2). For the isolation of mitochondria filtered homogenate was centrifuged at 5000 X g for 5 min and the supernatant was recentrifuged at 23,500 X g for 20 min.The 23,500 X g pellet was treated with DNase as described for chloroplasts and then rinsed in Tris-saline-EDTA.

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Characterization of repetitive elements in several Cucurbita species

Leclerc

Siegel

1987

Plant Mol Biol

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About 1.3×10(5) copies of a tandemly arranged, 351 base pair element constitute from 4 to 8% of the Cucurbita pepo genome. A homologous, high copy number repetitive element is present in the genomes of C. moschata and C. foetidissima, but not in C. maxima or Cucumis sativus. Array lengths of at least 65 members have been detected for C. pepo, and 140 for C. moschata. The nucleotide sequence of six C. pepo repeat units were determined and each was found to be unique, differing from the others at from 7 to 23 positions. The element was composed of highly modified DNA as evidenced by the fact that only one of its two Hpa I restriction sites is subject to digestion and by the observation that all internal Cs and about half of the external Cs of its single Hpa II site are methylated. At least 5 cellular RNA species contain sequences complementary to one of the DNA strands of the element. These have discrete sizes of 3.0, 2.3, 1.8, 1.3 and 0.5 kb. Such transcripts are detected in C. pepo, C. moschata and C. foetidissima stem and/or leaf RNA, but not root RNA and are probably not polyadenylated. No transcripts were found which contain sequences complementary to the other DNA strand of the element.

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Characterization of the rapidly reassociating deoxyribonucleic acid of Cucurbita pepo and the sequences complementary to ribosomal and transfer ribonucleic acids

Cited by 8 publications

References 28 publications

Novel Properties of Satellite DNA from Muskmelon

Novel Properties of Satellite DNA from Muskmelon

Satellite-Rich DNA in Cucumber: Hormonal Enhancement of Synthesis and Subcellular Identification

Characterization of repetitive elements in several Cucurbita species

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