Evolutionary dynamics and chromosomal distribution of repetitive sequences on chromosomes of Aegilops speltoides revealed by genomic in situ hybridization

Since 1987 cytological evidence has arisen in our laboratory, pointing to x = 5 as the original basic chromosome number of maize and its related wild species. This paper deals with the analysis of the meiotic behavior of F1 hybrids Zea luxurians × Z. diploperennis (2n = 20) and Z. luxurians × Z. perennis (2n = 30). In the first hybrid the most frequent configuration was 8ll + 4l and in the latter was 5lll + 5ll + 5l. Applying GISH (genomic in situ hybridization) to mitotic chromosomes of Z. luxurians we found that DAPI (4', 6-diamidino-2-phenylindole) positive bands located in all telomeric regions of this species did not hybridize with either Z. perennis or Z. diploperennis genomic probe. Therefore, Z. luxurians has a repetitive sequence that can be used in fluorescent staining to identify its chromosomes. When GISH was employed on metaphase I of the 2n = 30 hybrid, all the univalents showed distinctive telomeres of Z. luxurians, while the bivalents did not present any signal. These findings show that the formation of bivalent-univalent configurations is not a random event. The bivalents tend to be spatially separated and are very often observed forming an independent group of 5II. Finally, trivalents were composed by one chromosome labeled in its telomeric regions, and two smaller and unlabeled ones. The use of chromosome markers of Z. luxurians demonstrated to be a good step forward in interpreting the nature of meiotic configurations in 2n = 30 Zea spp. hybrids. They can help to clarify the relationship between genomes and provide a useful addition to the taxonomic classification in the genus Zea.Key Words: Zea hybrids, evolution, cytogenetics, repetitive sequences, heterochromatic knobs.

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Coevolution of A and B genomes in allotetraploid Triticum dicoccoides

Genome ◽

10.1139/g00-060 ◽

2000 ◽

Vol 43 (6) ◽

pp. 1021-1026 ◽

Cited By ~ 18

Author(s):

Alexander Belyayev ◽

Olga Raskina ◽

Abraham Korol ◽

Eviatar Nevo

Keyword(s):

In Situ Hybridization ◽

Repetitive Sequences ◽

Triticum Dicoccoides ◽

Genomic In Situ Hybridization ◽

Banding Technique ◽

Genome Sequences ◽

Polyploid Evolution ◽

B Genome ◽

A Genome

Data is presented on the coevolution of A and B genomes in allotetraploid wheat Triticum dicoccoides (2n = 4x = 28, genome AABB) obtained by genomic in situ hybridization (GISH). Probing chromosomes of T. dicoccoides with DNA from the proposed A/B diploid genome ancestors shows evidence of enriching A-genome with repetitive sequences of B-genome type. Thus, ancestral S-genome sequences have spread throughout the AB polyploid genome to a greater extent than have ancestral A-genome sequences. The substitution of part of the A-genome heterochromatin clusters by satellite DNA of the B genome is detected by using the molecular banding technique. The cause may be interlocus concerted evolution and (or) colonization. We propose that the detected high level of intergenomic invasion in old polyploids might reflect general tendencies in speciation and stabilization of the allopolyploid genome.Key words: Triticum, polyploid, evolution, genomic in situ hybridization, repetitive sequences.

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Synthesis and cytological characterization of trigeneric hybrids of durum wheat with and without Ph1

Genome ◽

10.1139/g04-082 ◽

2004 ◽

Vol 47 (6) ◽

pp. 1173-1181 ◽

Cited By ~ 28

Author(s):

Prem P Jauhar ◽

M Doğramaci ◽

T S Peterson

Keyword(s):

In Situ Hybridization ◽

Chromosome Pairing ◽

Genetic Recombination ◽

Genomic In Situ Hybridization ◽

Homoeologous Pairing ◽

Alien Gene Transfer ◽

Chromosome 5B ◽

Alien Gene ◽

Trigeneric Hybrids

Wild grasses in the tribe Triticeae, some in the primary or secondary gene pool of wheat, are excellent reservoirs of genes for superior agronomic traits, including resistance to various diseases. Thus, the diploid wheatgrasses Thinopyrum bessarabicum (Savul. and Rayss) Á. Löve (2n = 2x = 14; JJ genome) and Lophopyrum elongatum (Host) Á. Löve (2n = 2x = 14; EE genome) are important sources of genes for disease resistance, e.g., Fusarium head blight resistance that may be transferred to wheat. By crossing fertile amphidiploids (2n = 4x = 28; JJEE) developed from F1 hybrids of the 2 diploid species with appropriate genetic stocks of durum wheat, we synthesized trigeneric hybrids (2n = 4x = 28; ABJE) incorporating both the J and E genomes of the grass species with the durum genomes A and B. Trigeneric hybrids with and without the homoeologous-pairing suppressor gene, Ph1, were produced. In the absence of Ph1, the chances of genetic recombination between chromosomes of the 2 useful grass genomes (JE) and those of the durum genomes (AB) would be enhanced. Meiotic chromosome pairing was studied using both conventional staining and fluorescent genomic in situ hybridization (fl-GISH). As expected, the Ph1-intergeneric hybrids showed low chromosome pairing (23.86% of the complement), whereas the trigenerics with ph1b (49.49%) and those with their chromosome 5B replaced by 5D (49.09%) showed much higher pairing. The absence of Ph1 allowed pairing and, hence, genetic recombination between homoeologous chromosomes. Fl-GISH analysis afforded an excellent tool for studying the specificity of chromosome pairing: wheat with grass, wheat with wheat, or grass with grass. In the trigeneric hybrids that lacked chromosome 5B, and hence lacked the Ph1 gene, the wheat–grass pairing was elevated, i.e., 2.6 chiasmata per cell, a welcome feature from the breeding standpoint. Using Langdon 5D(5B) disomic substitution for making trigeneric hybrids should promote homoeologous pairing between durum and grass chromosomes and hence accelerate alien gene transfer into the durum genomes.Key words: alien gene transfer, chiasma (xma) frequency, chromosome pairing, fluorescent genomic in situ hybridization (fl-GISH), homoeologous-pairing regulator, specificity of chromosome pairing, wheatgrass.

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Genome constitutions ofRoegneriaalashanica,R.elytrigioides,R.magnicaespesandR.grandis(Poaceae: Triticeae) via genomic in-situ hybridization

Nordic Journal of Botany ◽

10.1111/j.1756-1051.2009.00611.x ◽

2010 ◽

Vol 28 (2) ◽

pp. 206-211 ◽

Cited By ~ 7

Author(s):

Hai-Qing Yu ◽

Chun Zhang ◽

Chun-Bang Ding ◽

Hai-Qin Zhang ◽

Yong-Hong Zhou

Keyword(s):

In Situ Hybridization ◽

Genomic In Situ Hybridization

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A Centromeric Tandem Repeat Family Originating From a Part of Ty3/gypsy-Retroelement in Wheat and Its Relatives

Genetics ◽

10.1093/genetics/164.2.665 ◽

2003 ◽

Vol 164 (2) ◽

pp. 665-672 ◽

Cited By ~ 4

Author(s):

Zhi-Jun Cheng ◽

Minoru Murata

Keyword(s):

In Situ Hybridization ◽

Tandem Repeats ◽

Diploid Species ◽

Upstream Region ◽

Aegilops Speltoides ◽

Repeat Family ◽

B Genome ◽

Intervening Sequences ◽

Wild Diploid Species

AbstractFrom a wild diploid species that is a relative of wheat, Aegilops speltoides, a 301-bp repeat containing 16 copies of a CAA microsatellite was isolated. Southern blot and fluorescence in situ hybridization revealed that ∼250 bp of the sequence is tandemly arrayed at the centromere regions of A- and B-genome chromosomes of common wheat and rye chromosomes. Although the DNA sequence of this 250-bp repeat showed no notable homology in the databases, the flanking or intervening sequences between the repeats showed high homologies (>82%) to two separate sequences of the gag gene and its upstream region in cereba, a Ty3/gypsy-like retroelement of Hordeum vulgare. Since the amino acid sequence deduced from the 250 bp with seven CAAs showed some similarity (∼53%) to that of the gag gene, we concluded that the 250-bp repeats had also originated from the cereba-like retroelements in diploid wheat such as Ae. speltoides and had formed tandem arrays, whereas the 300-bp repeats were dispersed as a part of cereba-like retroelements. This suggests that some tandem repeats localized at the centromeric regions of cereals and other plant species originated from parts of retrotransposons.

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