The DNA content of cells in the root of

Deeley, E.M.; Davies, H.G.; Chayen, J.

doi:10.1016/0014-4827(57)90174-x

Cited by 74 publications

(18 citation statements)

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“…The validity of this method has been well established by comparisons between estimations of Feulgen stain values with chemically determined estimates of DNA in the same material (Deeley, Davies and Chayen, 1957;Ris and Mirsky, 1949;Leuchtenberger, 1954;McLeish and Sunderland, 1961).…”

Section: Experimental Techniques (A) Feulgen Photometrymentioning

confidence: 99%

Nuclear changes in flax

Evans

1968

Heredity

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Section: Experimental Techniques (A) Feulgen Photometrymentioning

confidence: 99%

Nuclear changes in flax

Evans

1968

Heredity

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“…Although it is common in plant roots for cells to stop dividing and differentiate from G1 and G2, the mechanisms responsible for the transition are unknown (5)(6)(7)11). Recent work with synchronized cells of pea roots showed that nascent replicons remain unattached until they reach late S and G2 phases (18).…”

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confidence: 99%

Cells of pea (Pisum sativum) that differentiate from G2 phase have extrachromosomal DNA.

Hof¹,

Bjerknes²

1982

Mol. Cell. Biol.

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Velocity sedimentation in an alkaline sucrose gradient of newly replicated chromosomal DNA revealed the presence of extrachromosomal DNA that was not replicated by differentiating cells in the elongation zone. The extrachromosomal DNA had a number average molecular weight of 12 x 106 to 15 x 106 and a weight average molecular weight of 25 x 106, corresponding to about 26 x 106 and 50 x 106 daltons, respectively, of double-stranded DNA. The molecules were stable, lasting at least 72 h after being formed. Concurrent measurements by velocity sedimentation, autoradiography, and cytophotometry of isolated nuclei indicated that the extrachromosomal molecules were associated with root-tip cells that stopped dividing and differentiated from G2 phase but not with those that stopped dividing and differentiated from G1 phase.Although it is common in plant roots for cells to stop dividing and differentiate from G1 and G2, the mechanisms responsible for the transition are unknown (5-7, 11). Recent work with synchronized cells of pea roots showed that nascent replicons remain unattached until they reach late S and G2 phases (18). At this time, the nascent molecules are joined and form mature, chromosomal-size DNA chains. Other experiments showed that cells arrested in G2 by carbohydrate starvation also have nascent replicons that are unattached and, when given sucrose, many of these replicons are not joined (23). The presence and persistence of smaller molecules that remain unattached and fail to reach chromosomal size in nuclei of the root tip is the topic of this paper. The experiments were designed to determine whether or not the nascent molecules, resolved under alkaline conditions, were products of single-stranded breaks or gaps that nevertheless remained with the chromosomal duplex, or whether they were products of other processes, such as amplification or nucleases indigenous to cells of the root tip. The results indicated that one or the other of the latter processes is involved, since the molecules are free of chromosomal DNA. It was also shown that cells that differentiate from G2 have extrachromosomal DNA that was not detectable in those that stop dividing and differentiate from G1. These results are the first of their kind in plant cell biology. MATERIALS AND METHODSCulture of root tips. Seeds of Pisum sativum (var. Alaska) were surface sterilized with Clorox, washed with distilled water, and aseptically germinated in petri dishes (150 by 20 mm) that contained three layers of Whatman no. 1 filter paper moistened with distilled water. After 4 days, seedlings with primary roots 2.5 to 4 cm long were selected, and the terminal 1 to 1.5 cm was removed, suspended in 50 ml of White medium with 2% sucrose, and cultured at 22 ± 1°C for up to 72 h on a reciprocal shaker at about 1 cycle per min. Seed germination and root culture were carried out in the dark and were only intermittently exposed to light, when isotope was added to the medium.Labeling of DNA. DNA labeling followed different protocols, depending on the experim...

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“…However, WooDARD et al (1961) recently reported that they had found a minor peak of DNA synthesis just preceding mitosis. Since the data available in the 274 KIHLMAN literature indicate that the total mitotic cycle is of the same duration in lateral roots as in main roots (e.g., REVELL 1953, DEELEY et al 1957, EvANS et al 1957, it was assumed that G 2 was also of the same duration in the two cases. (KIHLMAN 1962).…”

Section: The Effect Of Fudr In Combination With X-rays and Eocmentioning

confidence: 99%

The Production of Chromatid Aberrations by5-FluorodeoxyuridineAlone and in Combination with X-Rays and8-Ethoxycaffeine

Kihlman

1962

Caryologia

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The DNA content of cells in the root of

Cited by 74 publications

References 1 publication

Nuclear changes in flax

Nuclear changes in flax

Cells of pea (Pisum sativum) that differentiate from G2 phase have extrachromosomal DNA.

The Production of Chromatid Aberrations by5-FluorodeoxyuridineAlone and in Combination with X-Rays and8-Ethoxycaffeine

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