Nuclear DNA amount and genome downsizing in natural and synthetic allopolyploids of the genera Aegilops and Triticum

Genome ◽  
2008 ◽  
Vol 51 (8) ◽  
pp. 616-627 ◽  
Author(s):  
T. Eilam ◽  
Y. Anikster ◽  
E. Millet ◽  
J. Manisterski ◽  
M. Feldman
Keyword(s):  
Genome Size ◽  
Dna Sequences ◽  
First Generation ◽  
Nuclear Dna ◽  
Chromosome Doubling ◽  
Intergeneric Hybridization ◽  
Dna Amount ◽  
B Genome ◽  
Nuclear Dna Amount ◽  
Dna Amounts

Recent molecular studies in the genera Aegilops and Triticum showed that allopolyploidization (interspecific or intergeneric hybridization followed by chromosome doubling) generated rapid elimination of low-copy or high-copy, non-coding and coding DNA sequences. The aims of this work were to determine the amount of nuclear DNA in allopolyploid species of the group and to see to what extent elimination of DNA sequences affected genome size. Nuclear DNA amount was determined by the flow cytometry method in 27 natural allopolyploid species (most of which were represented by several lines and each line by several plants) as well as 14 newly synthesized allopolyploids (each represented by several plants) and their parental plants. Very small intraspecific variation in DNA amount was found between lines of allopolyploid species collected from different habitats or between wild and domesticated forms of allopolyploid wheat. In contrast to the constancy in nuclear DNA amount at the intraspecific level, there are significant differences in genome size between the various allopolyploid species, at both the tetraploid and hexaploid levels. In most allopolyploids nuclear DNA amount was significantly less than the sum of DNA amounts of the parental species. Newly synthesized allopolyploids exhibited a similar decrease in nuclear DNA amount in the first generation, indicating that genome downsizing occurs during and (or) immediately after the formation of the allopolyploids and that there are no further changes in genome size during the life of the allopolyploids. Phylogenetic considerations of the origin of the B genome of allopolyploid wheat, based on nuclear DNA amount, are discussed.

Genome size in natural and synthetic autopolyploids and in a natural segmental allopolyploid of several Triticeae species

Genome ◽  
2009 ◽  
Vol 52 (3) ◽  
pp. 275-285 ◽  
Author(s):  
T. Eilam ◽  
Y. Anikster ◽  
E. Millet ◽  
J. Manisterski ◽  
M. Feldman
Keyword(s):  
Genome Size ◽  
Dna Sequences ◽  
Nuclear Dna ◽  
Reduction Process ◽  
Distribution Area ◽  
Meiotic Pairing ◽  
Dna Amount ◽  
Similar Reduction ◽  
Nuclear Dna Amount ◽  
Hordeum Murinum

Nuclear DNA amount (1C) was determined by flow cytometry in the autotetraploid cytotype of Hordeum bulbosum , in the cytologically diploidized autotetraploid cytotypes of Elymus elongatus , Hordeum murinum subsp. murinum and Hordeum murinum subsp. leporinum, in Hordeum marinum subsp. gussoneanum, in their progenitor diploid cytotypes, and in a newly synthesized autotetraploid line of E. elongatus. Several lines collected from different regions of the distribution area of every taxon, each represented by a number of plants, were analyzed in each taxon. The intracytotype variation in nuclear DNA amount of every diploid and autotetraploid cytotype was very small, indicating that no significant changes have occurred in DNA amount either after speciation or after autopolyploid formation. The autotetraploid cytotypes of H. bulbosum and the cytologically diploidized H. marinum subsp. gussoneanum had the expected additive amount of their diploid cytotypes. On the other hand, the cytologically diploidized autotetraploid cytotypes of E. elongatus and H. murinum subsp. murinum and H. murinum subsp. leporinum had considerably less nuclear DNA (10%–23%) than the expected additive value. Also, the newly synthesized autotetraploid line of E. elongatus showed similar reduction in DNA as its natural counterpart, indicating that the reduction in genome size occurred in the natural cytotype during autopolyploidization. It is suggested that the diploid-like meiotic behavior of these cytologically dipolidized autotetraploids is caused by the instantaneous elimination of a large number of DNA sequences, different sequences from different homologous pairs, leading to differentiation of the constituent genomes. The eliminated sequences are likely to include those that participate in homologous recognition and initiation of meiotic pairing. A gene system determining exclusive bivalent pairing by utilizing the differentiation between the two groups of homologues has been presumably superimposed on the DNA reduction process.

Variation in nuclear DNA amount between wild and cultivated populations of Milium effusum (2n = 28)

Genome ◽  
1992 ◽  
Vol 35 (6) ◽  
pp. 1050-1053 ◽  
Author(s):  
Simon T. Bennett ◽  
Michael D. Bennett
Keyword(s):  
Intraspecific Variation ◽  
Nuclear Dna ◽  
Environmental Changes ◽  
Natural Habitat ◽  
Practical Importance ◽  
Plant Conservation ◽  
Plant Responses ◽  
Dna Amount ◽  
Nuclear Dna Amount ◽  
Dna Amounts

Mean 2C DNA amounts varied by 35.6%, ranging from 7.52 to 10.20 pg, between 10 populations of the grass Milium effusum L. Such intraspecific variation occurred despite a constant chromosome number (2n = 28) and no obvious differences in karyotype. Plants originating from botanic garden populations growing in cultivation had significantly (P < 0.001) larger DNA amounts than plants collected from wild populations. Moreover, variation in DNA amount within either the "cultivated" or the "wild" groups was not significant. As the environment in which plants are kept in botanic gardens is clearly different to the natural habitat for M. effusum, it seems likely that the difference in nuclear DNA amount is causally related, perhaps through its nucleotypic effects, to microclimate adaptation. These results suggest that at least some genotypes of M. effusum are fluid and sensitive to environmental change. Such data may have broad practical importance regarding plant responses to various environmental changes such as a nuclear winter and global warming, and implications for plant conservation and reintroduction. Milium effusum is a potentially useful plant material for studying the nature of intraspecific variation in DNA amount.Key words: Milium effusum, nuclear DNA amounts, nucleotype, environmental adaptation.

Genome size and genome evolution in diploid Triticeae species

Genome ◽  
2007 ◽  
Vol 50 (11) ◽  
pp. 1029-1037 ◽  
Author(s):  
T. Eilam ◽  
Y. Anikster ◽  
E. Millet ◽  
J. Manisterski ◽  
O. Sagi-Assif ◽  
...  
Keyword(s):  
Genome Size ◽  
Intraspecific Variation ◽  
Dna Content ◽  
Nuclear Dna ◽  
Diploid Species ◽  
Nuclear Dna Content ◽  
Dna Amount ◽  
Nuclear Dna Amount ◽  
Speciation Event ◽  
Close Temporal Proximity

One of the intriguing issues concerning the dynamics of plant genomes is the occurrence of intraspecific variation in nuclear DNA amount. The aim of this work was to assess the ranges of intraspecific, interspecific, and intergeneric variation in nuclear DNA content of diploid species of the tribe Triticeae (Poaceae) and to examine the relation between life form or habitat and genome size. Altogether, 438 plants representing 272 lines that belong to 22 species were analyzed. Nuclear DNA content was estimated by flow cytometry. Very small intraspecific variation in DNA amount was found between lines of Triticeae diploid species collected from different habitats or between different morphs. In contrast to the constancy in nuclear DNA amount at the intraspecific level, there are significant differences in genome size between the various diploid species. Within the genus Aegilops , the 1C DNA amount ranged from 4.84 pg in A. caudata to 7.52 pg in A. sharonensis; among genera, the 1C DNA amount ranged from 4.18 pg in Heteranthelium piliferum to 9.45 pg in Secale montanum . No evidence was found for a smaller genome size in annual, self-pollinating species relative to perennial, cross-pollinating ones. Diploids that grow in the southern part of the group’s distribution have larger genomes than those growing in other parts of the distribution. The contrast between the low variation at the intraspecific level and the high variation at the interspecific one suggests that changes in genome size originated in close temporal proximity to the speciation event, i.e., before, during, or immediately after it. The possible effects of sudden changes in genome size on speciation processes are discussed.

Karyological analysis and genome size in Milium (Gramineae) with special reference to polyploidy and chromosomal evolution

Genome ◽  
1991 ◽  
Vol 34 (6) ◽  
pp. 868-878 ◽  
Author(s):  
Simon T. Bennett ◽  
Sandra M. Thomas
Keyword(s):  
Genome Size ◽  
Geographical Distribution ◽  
Dna Sequences ◽  
Chromosome Evolution ◽  
Nuclear Dna ◽  
Chromosomal Evolution ◽  
System Support ◽  
Strong Resemblance ◽  
First Time ◽  
Dna Amounts

Karyotypes, nuclear DNA amounts, and meiotic behaviour are presented for Milium effusum L. (2n = 28), Milium montianum Parl. (2n = 22), and two cytotypes of Milium vernale Bieb. (2n = 8, 10). The bimodal karyotype of M. montianum (8 large and 14 small chromosomes) is described for the first time. Evidence from C-banding and geographical distribution suggests an ancient interracial allopolyploid origin for M. effusum (2n = 28). Although M. montianum is undoubtedly allopolyploid, its parentage is unconfirmed. A strong resemblance between the M. vernale (2n = 8) karyotype and the eight large chromosomes in M. montianum suggests a common ancestry. It is possible that a diploid form of M. effusum contributed the remaining 14 chromosomes. A selective loss of DNA sequences from the smaller chromosomes during the subsequent reorganization of the allopolyploid genome may have enhanced the bimodality of the karyotype. Geographical distribution and a change in the breeding system support the direction of the change x = 5 to x = 4 in M. vernale. Allopolyploidy appears to have played a central role in the chromosome evolution and speciation of Milium.Key words: Milium (Gramineae), karyotype analysis, genome size, polyploidy, chromosome evolution.

scholarly journals Genome Size in Diploids, Allopolyploids, and Autopolyploids of Mediterranean Triticeae

2010 ◽  
Vol 2010 ◽  
pp. 1-12 ◽  
Author(s):  
T. Eilam ◽  
Y. Anikster ◽  
E. Millet ◽  
J. Manisterski ◽  
M. Feldman
Keyword(s):  
Flow Cytometry ◽  
Genome Size ◽  
Nuclear Dna ◽  
Biological Significance ◽  
Physical Basis ◽  
Meiotic Behavior ◽  
Dna Amount ◽  
Nuclear Dna Amount ◽  
Tribe Triticeae ◽  
Natural And Synthetic

Nuclear DNA amount, determined by the flow cytometry method, in diploids, natural and synthetic allopolyploids, and natural and synthetic autopolyploids of the tribe Triticeae (Poaceae) is reviewed here and discussed. In contrast to the very small and nonsignificant variation in nuclear DNA amount that was found at the intraspecific level, the variation at the interspecific level is very large. Evidently changes in genome size are either the cause or the result of speciation. Typical autopolyploids had the expected additive DNA amount of their diploid parents, whereas natural and synthetic cytologically diploidized autopolyploids and natural and synthetic allopolyploids had significantly less DNA than the sum of their parents. Thus, genome downsizing, occurring during or immediately after the formation of these polyploids, provides the physical basis for their cytological diploidization, that is, diploid-like meiotic behavior. Possible mechanisms that are involved in genome downsizing and the biological significance of this phenomenon are discussed.

Evolution of genome size across some cultivated Allium species

Genome ◽  
2005 ◽  
Vol 48 (3) ◽  
pp. 511-520 ◽  
Author(s):  
A Ricroch ◽  
R Yockteng ◽  
S C Brown ◽  
S Nadot
Keyword(s):  
Flow Cytometry ◽  
Genome Size ◽  
Internal Transcribed Spacer ◽  
Life Form ◽  
Nuclear Dna ◽  
Gc Content ◽  
Nuclear Dna Content ◽  
Dna Amount ◽  
Allium Species ◽  
Nuclear Dna Amount

Allium L. (Alliaceae), a genus of major economic importance, exhibits a great diversity in various morphological characters and particularly in life form, with bulbs and rhizomes. Allium species show variation in several cytogenetic characters such as basic chromosome number, ploidy level, and genome size. The purpose of the present investigation was to study the evolution of nuclear DNA amount, GC content, and life form. A phylogenetic approach was used on a sample of 30 Allium species, including major vegetable crops and their wild allies, belonging to the 3 major subgenera Allium, Amerallium, and Rhizirideum and 14 sections. A phylogeny was constructed using internal transcribed spacer (ITS) sequences of 43 accessions representing 30 species, and the nuclear DNA amount and the GC content of 24 Allium species were investigated by flow cytometry. For the first time, the nuclear DNA content of Allium cyaneum and Allium vavilovii was measured, and the GC content of 16 species was measured. We addressed the following questions: (i) Is the variation in nuclear DNA amount and GC content linked to the evolutionary history of these edible Allium species and their wild relatives? (ii) How did life form (rhizome or bulb) evolve in edible Allium? Our results revealed significant interspecific variation in the nuclear DNA amount as well as in the GC content. No correlation was found between the GC content and the nuclear DNA amount. The reconstruction of nuclear DNA amount on the phylogeny showed a tendency towards a decrease in genome size within the genus. The reconstruction of life form history showed that rhizomes evolved in the subgenus Rhizirideum from an ancestral bulbous life form and were subsequently lost at least twice independently in this subgenus.Key words: Allium, nuclear DNA amount, GC content, flow cytometry, internal transcribed spacer (ITS), phylogeny, life form.

Chromosome and nuclear DNA study on Luzula - a genus with holokinetic chromosomes

Genome ◽  
2004 ◽  
Vol 47 (2) ◽  
pp. 246-256 ◽  
Author(s):  
Elzbieta Kuta ◽  
Borut Bohanec ◽  
Ewa Dubas ◽  
Liliana Vizintin ◽  
Leslaw Przywara
Keyword(s):  
Genome Size ◽  
Nuclear Dna ◽  
Size Variation ◽  
Nuclear Genome ◽  
Dna Amount ◽  
Genome Size Variation ◽  
Chromosome Fusion ◽  
Holokinetic Chromosomes ◽  
Nuclear Dna Amount ◽  
Leaf Tissues

Chromosomes and nuclear DNA amount were analyzed in leaf tissues of Luzula nivea, Luzula luzuloides, and Luzula multiflora. Intra- and interspecific karyological variability was stated. Chromosome numbers in diploids ranged 2n = 8-24 in L. nivea and L. luzuloides and 2n = 12-84 in hexaploid L. multiflora. Karyological variability resulted mainly from chromosome fission (agmatoploidy) and aneusomaty; chromosome fusion (symploidy) and polyploidy were also involved. Flow cytometric determination of nuclear genome size using propidium iodide staining gave values of 1.584 pg in L. luzuloides, 1.566 pg in L. nivea, and 3.034 pg in L. multiflora. Variability in relative nuclear genome size within species was measured by 4',6-diamidino-2-phenylindole staining. In contrast with previous reports, variability was fairly small and ranged from 1.796 to 1.864 pg in L. luzuloides, from 1.783 to 1.847 pg and from 1.737 to 1.808 pg in two populations (S and F) of L. nivea, respectively, and from 3.125 to 3.271 pg in L. multiflora. An intraplant (interleaf) genome size variation was also observed and its possible causes are discussed.Key words: Luzula, holokinetic chromosomes, agmatoploidy, symploidy, polyploidy, nuclear DNA amount, intraplant genome size variability, flow cytometry.

scholarly journals Quantum patterns of genome size variation in angiosperms

2020 ◽  
Vol 15 ◽  
Author(s):  
Liaofu Luo ◽  
Lirong Zhang
Keyword(s):  
Genome Evolution ◽  
Genome Size ◽  
Evolution Operator ◽  
Nuclear Dna ◽  
Size Variation ◽  
Dna Amount ◽  
Genome Size Variation ◽  
A Genome ◽  
Eigen Value ◽  
Dna Amounts

Aims: The discontinuous pattern of genome size variation in angiosperms is an unsolved problem related to genome evolution. We introduce a genome evolution operator and solve the related eigen-value equation to deduce the discontinuous pattern. Background: Genome is a well-defined system for studying evolution of species. One of the basic problems is the genome size evolution. The DNA amounts for angiosperm species are highly variable differing over 1000-fold. One big surprise is the discovery of the discontinuous distribution of nuclear DNA amounts in many angiosperm genera. Objective: The discontinuous distribution of nuclear DNA amounts have certain regularity much like a group of quantum states in atomic physics. The quantum pattern has not been explained by all the evolutionary theories so far and we shall interpret it through the quantum simulation of genome evolution. Methods: We have introduced a genome evolution operator H to deduce the distribution of DNA amount. The nuclear DNA amount in angiosperms is studied from the eigen-value equation of the genome evolution operator H. The operator H is introduced by physical simulation and it is defined as a function of the genome size N and the derivative with respective to the size. Results: The discontinuity of DNA size distribution and its synergetic occurrence in related angiosperms species are successfully deduced from the solution of the equation. The results agree well with the existing experimental data of Aloe, Clarkia, Nicotiana, Lathyrus, Allium and other genera. Conclusion: The success of our approach may infer the existence of a set of genomic evolutionary equations satisfying classical – quantum duality. The classical phase of evolution means it obeying classical deterministic law, while the quantum phase means it obeying quantum stochastic law. The discontinuity of DNA size distribution provides fresh evidence on the quantum evolution of angiosperms. People realize that the discontinuous pattern is due to the existence of some unknown evolutionary constrains. However, our study indicates that these constrains on angiosperm genome are essentially of quantum origin.

Nuclear DNA amounts in angiosperms

1976 ◽  
Vol 274 (933) ◽  
pp. 227-274 ◽  
Keyword(s):  
Nuclear Dna ◽  
Basic Information ◽  
Dna Amount ◽  
Alphabetical Order ◽  
Comprehensive List ◽  
Nuclear Dna Amount ◽  
Angiosperm Species ◽  
Dna Amounts

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.

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