Rapid cytological diploidization in newly formed allopolyploids of the wheat (Aegilops-Triticum) group

Genome ◽  
2009 ◽  
Vol 52 (11) ◽  
pp. 926-934 ◽  
Author(s):  
Hakan Ozkan ◽  
Moshe Feldman
Keyword(s):  
Chromosome Pairing ◽  
Dna Sequences ◽  
Meiotic Metaphase ◽  
Epigenetic Changes ◽  
Noncoding Dna ◽  
Ploidy Levels ◽  
Seed Fertility ◽  
Positive Linear Relationship ◽  
Competitive Species ◽  
Homoeologous Chromosomes

Recent studies in the genera Aegilops and Triticum showed that allopolyploid formation triggers rapid genetic and epigenetic changes that lead to cytological and genetic diploidization. To better understand the consequences of cytological diploidization, chromosome pairing and seed fertility were studied in S1, S2, and S3generations of 18 newly formed allopolyploids at different ploidy levels. Results showed that bivalent pairing at first meiotic metaphase was enhanced and seed fertility was improved during each successive generation. A positive linear relationship was found between increased bivalent pairing, improved fertility, and elimination of low-copy noncoding DNA sequences. These findings support the conclusion that rapid elimination of low-copy noncoding DNA sequences from one genome of a newly formed allopolyploid, different sequences from different genomes, is an efficient way to quickly augment the divergence between homoeologous chromosomes and thus bring about cytological diploidization. This facilitates the rapid establishment of the raw allopolyploids as successful, competitive species in nature.

Rapid genomic changes in newly synthesized amphiploids of Triticum and Aegilops. I. Changes in low-copy noncoding DNA sequences

Genome ◽  
1998 ◽  
Vol 41 (2) ◽  
pp. 272-277 ◽  
Author(s):  
B Liu ◽  
J M Vega ◽  
G Segal ◽  
S Abbo ◽  
M Rodova ◽  
...  
Keyword(s):  
Dna Sequences ◽  
High Frequency ◽  
Noncoding Dna ◽  
Ploidy Levels ◽  
Chromosome Differentiation ◽  
Genomic Changes ◽  
Parental Lines ◽  
Copy Dna ◽  
Homoeologous Chromosomes ◽  
Specific Sequences

We recently reported that allopolyploid formation in wheat was accompanied by rapid nonrandom elimination of specific low-copy, noncoding DNA sequences. These sequences occur in all diploid progenitors but are chromosome- or genome-specific at the polyploid level. To further investigate this phenomenon, we studied nine of these sequences, six chromosome-specific sequences and three genome-specific sequences, all isolated from common wheat. The various sequences were hybridized to DNA derived from nine newly synthesized amphiploids at different ploidy levels and to DNA from their parental lines. Although sequences homologous to the probes occur in all parental lines, a nonrandom loss of hybridization fragments was found at a high frequency in all amphiploids studied. In addition, a "loss/gain" of a hybridization fragment(s) was noticed in some of the amphiploids at lower frequency. Neither the type nor the frequency of changes was affected by intergenomic recombination or DNA methylation. It is suggested that rapid genomic changes culminated in a "programmed" pattern of elimination and (or) modification of specific low-copy DNA sequences following allopolyploidization. These events augmented the differentiation of homoeologous chromosomes, thus providing the physical basis for the diploid-like cytological behavior of polyploid wheat.Key words: wheat, allopolyploidy, genome evolution, chromosome- or genome-specific sequences, sequence elimination, homoeologous chromosome differentiation.

Rapid genomic changes in newly synthesized amphiploids ofTriticumandAegilops. II. Changes in low-copy coding DNA sequences

Genome ◽  
1998 ◽  
Vol 41 (4) ◽  
pp. 535-542 ◽  
Author(s):  
B Liu ◽  
J M Vega ◽  
M Feldman
Keyword(s):  
Dna Methylation ◽  
Dna Sequences ◽  
Gene Dosage ◽  
Restriction Enzymes ◽  
Noncoding Dna ◽  
Ploidy Levels ◽  
Coding Sequences ◽  
Genomic Changes ◽  
Cdna Sequences ◽  
Specific Sequences

We recently reported that formation of allopolyploid wheat was accompanied by rapid nonrandom changes in low-copy noncoding DNA sequences. In this report we show that following allopolyploidization, changes also occurred in coding sequences. Genomic DNA of nine different newly synthesized amphiploids of different ploidy levels and their parental lines was digested with five restriction enzymes and probed with 43 coding sequences. The sequences, 19 genomic and 24 cDNA sequences, are group (homoeologous) specific and represent the proximal and distal regions of the short and long arms of the seven homoeologous groups of the Triticeae. We revealed three types of changes: disappearance of a parental hybridization fragment(s), appearance of a novel fragment(s), and simultaneous disappearance of a parental fragment(s) and appearance of a novel fragment(s). No elimination of sequences took place, since in every sequence studied the parental hybridization fragments were present in at least one of the enzyme digests. Variations in pattern among individual plants of the same amphiploid, as well as between several synthetic and natural amphiploids, indicated that at least some of the genomic changes occurred at random. Intergenomic recombination was not the cause of the observed changes. Evidence was obtained, however, that changes were also brought about by DNA methylation. Methylation may cause inactivation of genes or modify their expression levels in some of the newly synthesized amphiploid plants, leading to genetic diploidization and gene-dosage compensation and thus increasing variation among individuals.Key words: wheat, allopolyploidy, DNA methylation, genetic diploidization, genome evolution, group (homoeologous) specific sequences.

Chromosome pairing and chiasma formation in autopolyploids of different Lathyrus species

Genome ◽  
1997 ◽  
Vol 40 (6) ◽  
pp. 937-944 ◽  
Author(s):  
H. I. T. Khawaja ◽  
J. Sybenga ◽  
J. R. Ellis
Keyword(s):  
Gene Flow ◽  
Chromosome Pairing ◽  
Chiasma Frequency ◽  
Chiasma Formation ◽  
Meiotic Metaphase ◽  
Lathyrus Sativus ◽  
Ploidy Levels ◽  
Lathyrus Odoratus ◽  
Mixed Populations ◽  
Tetraploid Level

Chromosome pairing and chiasma formation were studied in natural and induced tetraploids (2n = 28) of Lathyrus odoratus (induced), Lathyrus pratensis (natural and induced), Lathyrus sativus (induced), and Lathyrus venosus (natural), as well as in triploids of L. pratensis and diploids of L. odoratus, L. pratensis, and L. sativus. All natural tetraploids appeared to be autotetraploids and their meiotic metaphase I behaviour was very similar to that of the induced autotetraploids, with average numbers of pairing partner switches exceeding 4 or even 5. Multivalent frequencies were high, but the numbers of chiasmata were not much higher than necessary to maintain the configurations. Interstitial chiasmata were common, but not predominant. Fertility was reduced, but sufficient for predominantly vegetatively reproducing species. The triploids of L. pratensis had an even higher multivalent frequency than the tetraploids, but still produced some viable progeny at or close to the tetraploid level, suggesting that in mixed populations of diploids and tetraploids, triploids can contribute to gene flow between the ploidy levels. There was no significant correlation between chiasma frequency and ring bivalent frequency in the diploids and multivalent frequency in the corresponding tetraploids. In the tetraploids, chiasma frequency and multivalent frequency were negatively correlated.Key words: Lathyrus, natural, induced, autotetraploid, triploid, meiosis.

scholarly journals Rapid Elimination of Low-Copy DNA Sequences in Polyploid Wheat: A Possible Mechanism for Differentiation of Homoeologous Chromosomes

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1381-1387 ◽  
Author(s):  
Moshe Feldman ◽  
Bao Liu ◽  
Gregorio Segal ◽  
Shahal Abbo ◽  
Avraham A Levy ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Hexaploid Wheat ◽  
Tetraploid Wheat ◽  
Diploid Species ◽  
Noncoding Dna ◽  
Polyploid Wheat ◽  
Genomic Changes ◽  
Group I ◽  
Group Ii ◽  
Homoeologous Chromosomes

To study genome evolution in allopolyploid plants, we analyzed polyploid wheats and their diploid progenitors for the occurrence of 16 low-copy chromosome- or genome-specific sequences isolated from hexaploid wheat. Based on their occurrence in the diploid species, we classified the sequences into two groups: group I, found in only one of the three diploid progenitors of hexaploid wheat, and group II, found in all three diploid progenitors. The absence of group II sequences from one genome of tetraploid wheat and from two genomes of hexaploid wheat indicates their specific elimination from these genomes at the polyploid level. Analysis of a newly synthesized amphiploid, having a genomic constitution analogous to that of hexaploid wheat, revealed a pattern of sequence elimination similar to the one found in hexaploid wheat. Apparently, speciation through allopolyploidy is accompanied by a rapid, nonrandom elimination of specific, lowcopy, probably noncoding DNA sequences at the early stages of allopolyploidization, resulting in further divergence of homoeologous chromosomes (partially homologous chromosomes of different genomes carrying the same order of gene loci). We suggest that such genomic changes may provide the physical basis for the diploid-like meiotic behavior of polyploid wheat.

Long-range correlation properties of coding and noncoding DNA sequences: GenBank analysis

1995 ◽  
Vol 51 (5) ◽  
pp. 5084-5091 ◽  
Author(s):  
S. V. Buldyrev ◽  
A. L. Goldberger ◽  
S. Havlin ◽  
R. N. Mantegna ◽  
M. E. Matsa ◽  
...  
Keyword(s):  
Long Range ◽  
Dna Sequences ◽  
Noncoding Dna ◽  
Range Correlation ◽  
Correlation Properties

scholarly journals Chloroplast Noncoding DNA Sequences Reveal Genetic Distinction and Diversity between Wild and Cultivated Prunus yedoensis

2017 ◽  
Vol 142 (6) ◽  
pp. 434-443
Author(s):  
Eun Ju Cheong ◽  
Myong-Suk Cho ◽  
Seung-Chul Kim ◽  
Chan-Soo Kim
Keyword(s):  
United States ◽  
Dna Sequences ◽  
The United States ◽  
Jeju Island ◽  
Noncoding Dna ◽  
Noncoding Regions ◽  
Naturally Occurring ◽  
Prunus Yedoensis ◽  
History Of ◽  
Ornamental Trees

Cultivated flowering cherries (Prunus subgenus Cerasus), which are one of the most popular ornamental trees around the world, have been developed through artificial hybridizations among wild flowering cherries. Among the hundreds of cultivars of flowering cherries, Prunus ×yedoensis ‘Somei-yoshino’ is the most common and widespread. However, its origin and genetic relationship to wild P. yedoensis, naturally occurring on Jeju Island, South Korea, have long been debated. We used sequence polymorphisms in eight chloroplast DNA (cpDNA) noncoding regions to distinguish wild and cultivated flowering cherries among 104 individuals (55 accessions). We were able to distinguish two distinct groups, one corresponding to wild P. yedoensis collections from Jeju Island and the other collections of cultivated P. ×yedoensis from Korea, Japan, and the United States. The chlorotype diversity of wild P. yedoensis in Jeju Island and cultivated P. ×yedoensis collections in the United States was quite high, suggesting multiple natural hybrid origins and long history of cultivation from different original sources, respectively.

THE MEIOTIC BEHAVIOR OF ANEUPOLYHAPLOIDS OF THE CULTIVATED OAT AVENA SATIVA (2n = 6x = 42)

1977 ◽  
Vol 19 (4) ◽  
pp. 651-656 ◽  
Author(s):  
J. M. Leggett
Keyword(s):  
Genetic Control ◽  
Chromosome Pairing ◽  
Avena Sativa ◽  
Meiotic Behavior ◽  
Homoeologous Chromosomes

Chromosome pairing and the frequency of secondary associations in two aneupolyhaploid plants of A. sativa are described. There was little evidence of pairing between homoeologous chromosomes in either plant. The results are discussed in relation to the genetic control of bivalent pairing in A. sativa and the possible divergence between the constituent genomes.

A review of the fern genus Pellaea (Pteridaceae) in Australasia

2020 ◽  
Author(s):  
Patrick J. Brownsey ◽  
Daniel J. Ohlsen ◽  
Lara D. Shepherd ◽  
Whitney L. M. Bouma ◽  
Erin L. May ◽  
...  
Keyword(s):  
New Zealand ◽  
Chloroplast Dna ◽  
Dna Sequences ◽  
Sequence Data ◽  
Indigenous Species ◽  
Ploidy Levels ◽  
Dna Sequence Data ◽  
Australian Species ◽  
The Status ◽  
Chloroplast Dna Sequences

Five indigenous species of Pellaea in Australasia belong to section Platyloma. Their taxonomic history is outlined, morphological, cytological and genetic evidence for their recognition reviewed, and new morphological and chloroplast DNA-sequence data provided. Australian plants of P. falcata (R.Br.) Fée are diploid and have longer, narrower pinnae than do New Zealand plants previously referred to P. falcata, which are tetraploid. Evidence indicates that P. falcata does not occur in New Zealand, and that collections so-named are P. rotundifolia (G.Forst.) Hook. Chloroplast DNA sequences are uninformative in distinguishing Australian P. falcata from New Zealand P. rotundifolia, but show that Australian P. nana is distinct from both. Sequence data also show that Australian and New Zealand populations of P. calidirupium Brownsey & Lovis are closely related, and that Australian P. paradoxa (R.Br.) Hook. is distinct from other Australian species. Although P. falcata is diploid and P. rotundifolia tetraploid, P. calidirupium, P. nana (Hook.) Bostock and P. paradoxa each contain multiple ploidy levels. Diploid populations of Pellaea species are confined to Australia, and only tetraploids are known in New Zealand. Evolution of the group probably involved hybridisation, autoploidy, alloploidy, and possibly apomixis. Further investigation is required to resolve the status of populations from Mount Maroon, Queensland and the Kermadec Islands.

Homologous chromosome pairing in meiosis of higher eukaryotes—still an enigma?

Genome ◽  
2020 ◽  
Vol 63 (10) ◽  
pp. 469-482
Author(s):  
J. Sybenga
Keyword(s):  
Chromosome Pairing ◽  
Dna Sequences ◽  
Homologous Chromosome ◽  
Homology Search ◽  
Size Difference ◽  
Primary Role ◽  
Dna Double Strand Breaks ◽  
Homologous Chromosome Pairing ◽  
Higher Eukaryotes

Meiosis is the basis of the generative reproduction of eukaryotes. The crucial first step is homologous chromosome pairing. In higher eukaryotes, micrometer-scale chromosomes, micrometer distances apart, are brought together by nanometer DNA sequences, at least a factor of 1000 size difference. Models of homology search, homologue movement, and pairing at the DNA level in higher eukaryotes are primarily based on studies with yeast where the emphasis is on the induction and repair of DNA double-strand breaks (DSB). For such a model, the very large nuclei of most plants and animals present serious problems. Homology search without DSBs cannot be explained by models based on DSB repair. The movement of homologues to meet each other and make contact at the molecular level is not understood. These problems are discussed and the conclusion is that at present practically nothing is known of meiotic homologue pairing in higher eukaryotes up to the formation of the synaptonemal complex, and that new, necessarily speculative models must be developed. Arguments are given that RNA plays a central role in homology search and a tentative model involving RNA in homology search is presented. A role of actin in homologue movement is proposed. The primary role of DSBs in higher eukaryotes is concluded to not be in pairing but in the preparation of Holliday junctions, ultimately leading to chromatid exchange.

Rapid genomic changes in newly synthesized amphiploids of Triticum and Aegilops. I. Changes in low-copy noncoding DNA sequences

Genome ◽  
1998 ◽  
Vol 41 (2) ◽  
pp. 272-277 ◽  
Author(s):  
B. Liu ◽  
J.M. Vega ◽  
G. Segal ◽  
S. Abbo ◽  
M. Rodova ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Noncoding Dna ◽  
Genomic Changes
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