Differential Genome Size and Repetitive DNA Evolution in Diploid Species of Melampodium sect. Melampodium (Asteraceae)

Abstract Heavy metals can affect the morphology, physiology and evolution of plants. Asplenium viride is a diploid species, belonging to the largest genus of the cosmopolitan fern family Aspleniaceae, and occurring on various types of alkaline rocks. It is known to colonize sites with high concentrations of heavy metals, exhibiting changes in frond morphology. Microevolutionary processes, manifesting as changes in genome size and new genotype formation, can ultimately lead to the formation of new subspecies and speciation. This study aimed to evaluate the morphological and genetic diversity of A. viride, and to test for a potential correlation between variability and heavy metal concentration. Analysis of A. viride specimens, from one metalliferous site and five non-metalliferous localities, showed no apparent variation in genome size between plants from affected and non-affected sites. There was no significant correlation between genetic variability and heavy metal concentration. This was possibly due to intragametophytic selfing, caused by patchy habitats and subsequent founder effects, resulting from long-distance colonization by single spores.

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Genome size and genome evolution in diploid Triticeae species

Genome ◽

10.1139/g07-083 ◽

2007 ◽

Vol 50 (11) ◽

pp. 1029-1037 ◽

Cited By ~ 46

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.

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The evolution of genome size and rDNA in diploid species ofChenopodium s.l.(Amaranthaceae)

Botanical Journal of the Linnean Society ◽

10.1111/boj.12321 ◽

2015 ◽

Vol 179 (2) ◽

pp. 218-235 ◽

Cited By ~ 11

Author(s):

Bozena Kolano ◽

Dorota Siwinska ◽

Jamie McCann ◽

Hanna Weiss-Schneeweiss

Keyword(s):

Genome Size ◽

Diploid Species

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Evolution of Genome Size in Conifers

Silvae Genetica ◽

10.1515/sg-2005-0020 ◽

2005 ◽

Vol 54 (1-6) ◽

pp. 126-137 ◽

Cited By ~ 73

Author(s):

M. Raj Ahuja ◽

David B. Neale

Keyword(s):

Genome Size ◽

Repetitive Dna ◽

Gene Families ◽

Gene Duplications ◽

Large Genome ◽

Repeat Units ◽

Conifer Genome ◽

Large Genome Size ◽

Highly Repetitive Dna ◽

Open Question

AbstractConifers are the most widely distributed group of gymnosperms in the world. They have large genome size (1C-value) compared with most animal and plant species. The genome size ranges from ~6,500 Mb to ~37,000 Mb in conifers. How and why conifers have evolved such large genomes is not understood. The conifer genome contains ~75% highly repetitive DNA. Most of the repetitive DNA is composed of non-coding DNA, including ubiquitous transposable elements. Conifers have relatively larger rDNA repeat units, larger gene families generated by gene duplications, larger nuclear volume, and perhaps larger genes, as compared to angiosperm plants. These genomic components may partially account for the large genome size, as well as variation in genome size, in conifers. One of the major mechanisms for genome size expansion and evolution of species is polyploidy, which is widespread in angiosperms, but it is rare in conifers. There are only a few natural polyploids in one family of conifers, Cupressaceae. Other conifers, including well-studied pines, are nearly all diploids. Whether ancient polyploidy has played a role in the evolution of genome size in conifers still remains an open question. The mechanisms that account for the variation and evolution of genome size in conifers are addressed in this review.

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Associated chromosomal DNA changes in polyploids

Genome ◽

10.1139/g94-080 ◽

1994 ◽

Vol 37 (4) ◽

pp. 560-564 ◽

Cited By ~ 27

Author(s):

S. N. Raina ◽

A. Parida ◽

K. K. Koul ◽

S. S. Salimath ◽

M. S. Bisht ◽

...

Keyword(s):

Genome Size ◽

Dna Content ◽

Nuclear Dna ◽

Seed Set ◽

Diploid Species ◽

Expected Value ◽

Chromosomal Dna ◽

Seed Fertility ◽

Dna Loss ◽

Dna Amounts

The 2C and 4C nuclear DNA amounts were estimated in eight diploid species, belonging to three diverse genera (Vicia, Tephrosia, and Phlox) and their corresponding colchitetraploids. In P. drummondii, T. purpurea, and T. oxygona tetraploids the deviation from the expectation was highly significant. The DNA in P. drummondii was further discarded in subsequent (C1, C2) generations, thus attaining an overall reduction of about 25%. The DNA content in the subsequent generations was the same as that of C2. It is concluded that rapid DNA loss in the first and subsequent generations was not only associated with the substantial increase (30–66%) in the seed set, but it also helped in the establishment and stabilization of the tetraploid. The possible relationship between such a nucleotypic change and success of polyploids is discussed. The DNA change from the expected value in the P. drummondii tetraploid was achieved by equal decrement to each chromosome independent of size, i.e., small chromosomes loose the same amount of DNA as the large chromosomes.Key words: colchitetraploid, genome size, DNA loss, seed fertility, stability, DNA distribution.

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Cytogenetic studies of interspecific hybrids between diploid species of Festuca

Canadian Journal of Genetics and Cytology ◽

10.1139/g86-128 ◽

1986 ◽

Vol 28 (6) ◽

pp. 921-925 ◽

Cited By ~ 6

Author(s):

W. G. Morgan ◽

Hugh Thomas ◽

M. Evans ◽

M. Borrill

Keyword(s):

Genome Size ◽

Chromosome Pairing ◽

Dna Content ◽

Interspecific Hybrids ◽

Parental Species ◽

Diploid Species ◽

Chromosome Size ◽

Cytogenetic Studies ◽

The Difference

Chromosome pairing in hybrids between diploid species of Festuca is described. The chromosome complements of the species from different taxonomic sections vary in chromosome size and DNA content. In interspecific hybrids involving species of the section Montanae there was a relationship between the difference in DNA content of the parental species and chromosome pairing in the F1 hybrids. The larger the difference between the DNA content of the parental species, the more pronounced the failure of chromosome pairing in the F1 hybrids. Factors other than divergence in genome size were also shown to have an effect on chromosome pairing in other hybrid combinations.Key words: chromosome pairing, DNA content, Festuca, hybrids (interspecific).

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