Relationships between mitotic cycle duration, S period duration and the average rate of DNA synthesis in the root meristem cells of several plants
TL;DR: The average mitotic cycle duration of root meristem cells of several plants was measured with 3H-thymidine and showed that the cycle duration increases with an increase in the DNA content per cell and the average rate of DNA synthesis increased.
About: This article is published in Experimental Cell Research.The article was published on 1965-08-01. It has received 299 citations till now. The article focuses on the topics: DNA synthesis.
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TL;DR: This paper lists absolute nuclear DNA amounts for 753 angiosperm species, primarily for reference purposes, and so the species are listed in alphabetical order, as this was felt to be more helpful to cyto- and biochemists whom, it is anticipated, will be among its major users.
Abstract: The number of angiosperm species for which nuclear DNA amount estimates have been made has nearly trebled since the last collected lists of such values were published, and therefore, publication of a more comprehensive list is overdue. This paper lists absolute nuclear DNA amounts for 753 angiosperm species. The data were assembled primarily for reference purposes, and so the species are listed in alphabetical order, as this was felt to be more helpful to cyto- and biochemists whom, it is anticipated, will be among its major users. The paper also reviews aspects of the history, nomenclature, methods, accuracy and problems of nuclear DNA estimation in angiosperms. No attempt is made to reconsider those aspects of nuclear DNA estimation which have been fully revised previously, although the bibliography of such aspects is given. Instead, the paper is intended as a source of basic information regarding the terminology, practice and limitations of nuclear DNA estimation, especially by Feulgen microdensitometry, as currently practiced.
1,552 citations
TL;DR: It is shown that the mean cell cycle time and the mean meiotic duration in annual species is significantly shorter than in perennial species, and that satellite DNA is significant in its nucleotypic effects on developmental processes.
Abstract: Many components of cell and nuclear size and mass are correlated with nuclear DNA content in plants, as also are the durations and rates of such developmental processes as mitosis and meiosis. It is suggested that the multiple effects of the mass of nuclear DNA which affect all cells and apply throughout the life of the plant can together determine the minimum generation time for each species. The durations of mitosis and of meiosis are both positively correlated with nuclear DNA content and, therefore, species with a short minimum generation time might be expected to have a shorter mean cell cycle time and mean meiotic duration, and a lower mean nuclear DNA content, than species with a long mean minimum generation time. In tests of this hypothesis, using data collated from the literature, it is shown that the mean cell cycle time and the mean meiotic duration in annual species is significantly shorter than in perennial species. Furthermore, the mean nuclear DNA content of annual species is significantly lower than for perennial species both in dicotyledons and monocotyledons. Ephemeral species have a significantly lower mean nuclear DNA content than annual species. Among perennial monocotyledons the mean nuclear DNA content of species which can complete a life cycle within one year (facultative perennials) is significantly lower than the mean nuclear DNA content of those which cannot (obligate perennials). However, the mean nuclear DNA content of facultative perennials does not differ significantly from the mean for annual species. It is suggested that the effects of nuclear DNA content on the duration of developmental processes are most obvious during its determinant stages, and that the largest effects of nuclear DNA mass are expressed at times when development is slowest, for instance, during meiosis or at low temperature. It has been suggested that DNA influences development in two ways, directly through its informational content, and indirectly by the physical-mechanical effects of its mass. The term 'nucleotype' is used to describe those conditions of the nucleus which effect the phenotype independently of the informational content of the DNA. It is suggested that cell cycle time, meiotic duration, and minimum generation time are determined by the nucleotype. In addition, it may be that satellite DNA is significant in its nucleotypic effects on developmental processes.
710 citations
TL;DR: Eukaryote DNA can be divided into genic DNA, which codes for proteins (or serves as recognition sites for proteins involved in transcription, replication and recombination), and nucleoskeletal DNA (S-DNA), which exists only because of its nucleoskeleton role in determining the nuclear volume.
Abstract: The 40,000-fold variation in eukaryote haploid DNA content is unrelated to organismic complexity or to the numbers of protein-coding genes. In eukaryote microorganisms, as well as in animals and plants, DNA content is strongly correlated with cell volume and nuclear volume, and with cell cycle length and minimum generation time. These correlations are simply explained by postulating that DNA has 2 major functions unrelated to its protein-coding capacity: (1) the control of cell volume by the number of replicon origins, and (2) the determination of nuclear volume by the overall bulk of the DNA: cell growth rates are determined by the cell volume and by the area of the nuclear envelope available for nucleocytoplasmic transport of RNA, which in turn depends on the nuclear volume and therefore on the DNA content. During evolution nuclear volume, and therefore DNA content, has to be adjusted to the cell volume to allow reasonable growth rates. The great diversity of cell volumes and growth rates, and therefore of DNA contents, among eukaryotes results from a varying balance in different species between r-selection, which favours small cells and rapid growth rates and therefore low DNA C-values, and K-selection which favours large cells and slow growth rates and therefore high DNA C-values. In multicellular organisms cell size needs to vary in different tissues: size differences between somatic cells result from polyteny, endopolyploidy, or the synthesis of nucleoskeletal RNA. Conflict between the need for large ova and small somatic cells explains why lampbrush chromosomes, nurse cells, chromatin diminution and chromosome elimination evolved. Similar evolutionary considerations clarify the nature of polygenes, the significance of the distribution of haploidy, diploidy and dikaryosis in life cycles and of double fertilization in angiosperms, and of heteroploidy despite DNA constancy in cultured cells, and other puzzles in eukaryote chromosome biology. Eukaryote DNA can be divided into genic DNA (G-DNA), which codes for proteins (or serves as recognition sites for proteins involved in transcription, replication and recombination), and nucleoskeletal DNA (S-DNA) which exists only because of its nucleoskeletal role in determining the nuclear volume (which it shares with G-DNA, and performs not only directly, but also indirectly by coding for nucleoskeletal RNA). Mechanistic and evolutionary implications of this are discussed.
646 citations
TL;DR: A detailed review of the debate surrounding the C‐value enigma, the various theories proposed to explain it, and the evidence in favour of a causal connection between DNA content and cell size is provided.
Abstract: Variation in DNA content has been largely ignored as a factor in evolution, particularly following the advent of sequence-based approaches to genomic analysis. The significant genome size diversity among organisms (more than 200 000-fold among eukaryotes) bears no relationship to organismal complexity and both the origins and reasons for the clearly non-random distribution of this variation remain unclear. Several theories have been proposed to explain this ‘C-value enigma’ (heretofore known as the ‘C-value paradox’), each of which can be described as either a ‘mutation pressure’ or ‘optimal DNA’ theory. Mutation pressure theories consider the large portion of non-coding DNA in eukaryotic genomes as either ‘junk’ or ‘selfish’ DNA and are important primarily in considerations of the origin of secondary DNA. Optimal DNA theories differ from mutation pressure theories by emphasizing the strong link between DNA content and cell and nuclear volumes. While mutation pressure theories generally explain this association with cell size as coincidental, the nucleoskeletal theory proposes a coevolutionary interaction between nuclear and cell volume, with DNA content adjusted adaptively following shifts in cell size. Each of these approaches to the C-value enigma is problematic for a variety of reasons and the preponderance of the available evidence instead favours the nucleotypic theory which postulates a causal link between bulk DNA amount and cell volume. Under this view, variation in DNA content is under direct selection via its impacts on cellular and organismal parameters. Until now, no satisfactory mechanism has been presented to explain this nucleotypic effect. However, recent advances in the study of cell cycle regulation suggest a possible ‘gene–nucleus interaction model’ which may account for it. The present article provides a detailed review of the debate surrounding the C-value enigma, the various theories proposed to explain it, and the evidence in favour of a causal connection between DNA content and cell size. In addition, a new model of nucleotypic influence is developed, along with suggestions for further empirical investigation. Finally, some evolutionary implications of genome size diversity are considered, and a broadening of the traditional ‘biological hierarchy’ is recommended.
640 citations
Cites background from "Relationships between mitotic cycle..."
...Moreover, DNA synthesis seldom takes up more than 50% of the cell cycle in eukaryotes (e.g. Van’t Hof, 1965; Evans & Rees, 1971; Evans et al., 1973)....
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...More recently, some specific examples of mechanisms operating to constrain DNA expansion have been reported which speak against this notion; not surprisingly, these occur in organisms such as flighted vertebrates among whom low DNA contents might be expected on physiological grounds (e.g. Tiersch & Wachtel, 1991; Baker et al., 1992; Van Den Bussche, Longmire & Baker, 1995; Primmer et al., 1997)....
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...This correlation between C-value and Sphase may result because of an imperfect scaling of replicon numbers with genome size (e.g. Van’t Hof, 1965; Evans & Rees, 1971; Evans et al., 1973) and}or as a function of a more asynchronous activation of dispersed replicons in genomes containing more DNA (e.g. Francis et al., 1985)....
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...…strong negative association with the rates of both meiotic and mitotic cell division in a variety of organisms (e.g. Van’t Hof & Sparrow, 1963; Van’t Hof, 1965; Bennett, 1971; Evans et al., 1973; Nagl, 1974; Grosset & Odartchenko, 1975a, b ; Price & Bachmann, 1976; Rees et al., 1982; Horner &…...
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...Early discussions suggested that this occurred because the extra DNA takes longer to replicate (that is, more DNA results in a longer Sphase) (Van’t Hof & Sparrow, 1963; Van’t Hof, 1965)....
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ENEA1
TL;DR: It was concluded that nuclear DNA content estimations performed with fluorochromes showing base preference should be interpreted with caution even when AT/GC ratios of the reference and the sample are equal.
Abstract: Flow cytometric estimation of nuclear DNA content was performed in six plant species employing three fluorochromes showing different DNA base preferences: propidium iodide (no base preference), 4′,6-diamidino-2-phenylindole (DAPI; AT preference), and mithramycin (GC preference). Nuclei isolated from human leukocytes were used as a primary reference standard. While nuclear DNA contents estimated using propidium iodide were in agreement with published data obtained using other techniques, the values obtained using fluorochromes showing base preference were significantly different. It was found that the differences were caused by the differences in overall AT/GC ratios, and by the species-specific differences in binding of these fluorochromes to DNA. It was concluded that nuclear DNA content estimations performed with fluorochromes showing base preference should be interpreted with caution even when AT/GC ratios of the reference and the sample are equal. The use of intercalting dyes (e.g. propidium iodide) is recommended for this purpose. On the other hand, comparison of the staining behaviour of intercalating dyes with that of dyes showing base preference may give additional information on chromatin structural differences and arrangement of molecule pairs in DNA.
569 citations
References
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TL;DR: The present study arose from the observation that a more intense colour was sometimes produced if, instead of being heated at 1000 for 10 min., the reaction mixture was allowed to stand overnight at room temperature.
Abstract: Of the colour reactions available for the determination and identification of deoxyribonucleic acid (DNA), the reaction with diphenylamine in a mixture of acetic and sulphuric acids at 1000 (Dische, 1930) has been perhaps the most widely used. The present study arose from the observation that a more intense colour was sometimes produced if, instead of being heated at 1000 for 10 min., the reaction mixture was allowed to stand overnight at room temperature. As a result of this observation the procedure has been modified, principally by adding acetaldehyde to the reagents and by allowing the solution to stand for about 17 hr. at 30° instead of heating it at 1000. The modified method is 3-5 times as sensitive as Dische's original procedure, and several substances which interfere in the original method do not do so in the modified procedure. Some observations on the mechanism of the reaction have been made; in particular it was discovered that there is a liberation of inorganic orthophosphate from DNA during the early stages of the reaction. This finding has a bearing on the structure of DNA. The modified method has already been used in an investigation of nucleic acid metabolism during bacteriophage multiplication (Burton, 1955).
13,649 citations
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01 Jan 1955
TL;DR: Nucleic Acid is a complex biomolecule that stores genetic information in the form of a code that is necessary for life.
Abstract: Nucleic Acids are another important type of organic compound that is necessary for life. A nucleic acid is a complex biomolecule that stores genetic information in the form of a code. Nucleic acids are so named because they arise from the nucleus of the cell. The nucleus is often referred to as the “control center” of the cell because the nucleic acids within contain the coded instruction for all of the cell’s (and therefore the organism’s) activities.
2,080 citations
TL;DR: Cell mass, the average number of nuclei/cell and the content of RNA and DNA were studied in Salmonella typhimurium during balanced (steady state) growth in different media, indicating that this organism exists in one of a large number of possible stable physiological states.
Abstract: Cell mass, the average number of nuclei/cell and the content of RNA and DNA were studied in Salmonella typhimurium during balanced (steady state) growth in different media. These quantities could be described as exponential functions of the growth rates afforded by the various media at a given temperature. The size and chemical composition characteristic of a given medium were not influenced by the temperature of cultivation. Thus, under conditions of balanced growth, this organism exists in one of a large number of possible stable physiological states. The variations in mass/cell are due to changes in the number of nuclei/cell as well as in mass/nucleus. An increase in the number of ribonucleoprotein particles at higher growth rates could, it appears, largely account for the increase in mass/nucleus. Calculations indicate that the rate of protein synthesis per unit RNA is nearly the same at all growth rates.
1,419 citations
1,399 citations
TL;DR: Tritiated thymidine autoradiography has been applied to several renewing epithelial tissues of the adult mouse to determine the average time required for DNA synthesis, indicating that DNA synthetic time may be a temporal constant, of considerable potential utility to studies of cell proliferation.
Abstract: Tritiated thymidine autoradiography has been applied to several renewing epithelial tissues of the adult mouse in order to determine (a) the average time required for DNA synthesis; and (b) the temporal relationship of the synthesis period to the progenitor cycles of these populations. The average duration of DNA synthesis has been computed from curves describing the rates of appearance and disappearance of labeled metaphase figures in epithelia of colon, ileum, duodenum, esophagus, and oral cavity, in both normal and colchicine-treated animals. In general, application of colchicine does not significantly influence the derived values for DNA synthesis duration. The DNA synthetic time is remarkably similar in the tissues examined, despite wide differences in the times required for completion of the progenitor cycle (and for tissue renewal). Synthesis of DNA in these epithelial cells of the mouse requires approximately 7 hours. Agreement between this value and those derived by other investigators for mammalian cells in vivo and in vitro indicates that DNA synthetic time may be a temporal constant, of considerable potential utility to studies of cell proliferation. The advantages and shortcomings of this experimental approach to problems of cell population kinetics in vivo are discussed.
170 citations