Homologous chromosome pairing in wheat

1999 ◽  
Vol 112 (11) ◽  
pp. 1761-1769 ◽  
Author(s):  
E. Martinez-Perez ◽  
P. Shaw ◽  
S. Reader ◽  
L. Aragon-Alcaide ◽  
T. Miller ◽  
...  
Keyword(s):  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Homologous Chromosome ◽  
Wild Type ◽  
Sister Chromatids ◽  
Homologous Chromosome Pairing ◽  
Tapetal Cells ◽  
Telomere Cluster ◽  
Diploid Cells ◽  
Degree Of Association

Bread wheat is a hexaploid (AABBDD, 2n=6x=42) containing three related ancestral genomes, each having 7 chromosomes, giving 42 chromosomes in diploid cells. During meiosis true homologues are correctly associated in wild-type wheat, but a degree of association of related chromosomes (homoeologues) occurs in a mutant (ph1b). We show that the centromeres are associated in non-homologous pairs in all floral tissues studied, both in wild-type wheat and the ph1b mutant. The non-homologous centromere associations then become homologous premeiotically in wild-type wheat in both meiocytes and the tapetal cells, but not in the mutant. In wild-type wheat, the homologues are colocalised along their length at this stage, but the telomeres remain distinct. A single telomere cluster (bouquet) is formed in the meiocytes only by the onset of leptotene. The sub-telomeric regions of the homologues associate as the telomere cluster forms. The homologous associations at the telomeres and centromeres are maintained through meiotic prophase, although, during leptotene, the two homologues and also the sister chromatids within each homologue are separate along the rest of their length. As meiosis progresses, first the sister chromatids and then the homologues associate intimately. In wild-type wheat, first the centromere grouping, then the bouquet disperse by the end of zygotene.

scholarly journals Regulating chromosomal movement by the cochaperone FKB-6 ensures timely pairing and synapsis

2017 ◽  
Vol 216 (2) ◽  
pp. 393-408 ◽  
Author(s):  
Benjamin Alleva ◽  
Nathan Balukoff ◽  
Amy Peiper ◽  
Sarit Smolikove
Keyword(s):  
Nuclear Envelope ◽  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Homologous Chromosome ◽  
Strand Break ◽  
Crossing Over ◽  
Chromosome Movement ◽  
Microtubule Network ◽  
Homologous Chromosome Pairing ◽  
Proper Movement

In meiotic prophase I, homologous chromosome pairing is promoted through chromosome movement mediated by nuclear envelope proteins, microtubules, and dynein. After proper homologue pairing has been established, the synaptonemal complex (SC) assembles along the paired homologues, stabilizing their interaction and allowing for crossing over to occur. Previous studies have shown that perturbing chromosome movement leads to pairing defects and SC polycomplex formation. We show that FKB-6 plays a role in SC assembly and is required for timely pairing and proper double-strand break repair kinetics. FKB-6 localizes outside the nucleus, and in its absence, the microtubule network is altered. FKB-6 is required for proper movement of dynein, increasing resting time between movements. Attenuating chromosomal movement in fkb-6 mutants partially restores the defects in synapsis, in agreement with FKB-6 acting by decreasing chromosomal movement. Therefore, we suggest that FKB-6 plays a role in regulating dynein movement by preventing excess chromosome movement, which is essential for proper SC assembly and homologous chromosome pairing.

Homologous chromosome pairing

1977 ◽  
Vol 277 (955) ◽  
pp. 245-258 ◽  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Homologous Chromosome ◽  
Crossing Over ◽  
Supporting Evidence ◽  
Mitotic Metaphase ◽  
Sister Chromatids ◽  
Homologous Chromosome Pairing ◽  
Attachment Sites ◽  
Crossover Site

Commonly accepted precepts are challenged : (1) that homologous chromosome pairing is normally mediated by nuclear envelope attachment sites; (2) that crossover site establishment awaits synaptic completion; and (3) that it is the function of the synaptonemal complex to hold homologues in register so that equal crossing over can occur, and perhaps to provide machinery for the crossover process. Although these views may eventually be shown to be true, it is felt that currently available evidence does not warrant their full acceptance, and that alternatives should be considered. As examples of alternatives the following ideas, with some supporting evidence, are suggested: (1) homologous chromsome pairing (in non-haplont organisms) may be accomplished by chance meeting of homologue segments (followed by establishment of invisible, elastic connectors) at congression for a mitotic metaphase (in many cases perhaps the premeiotic mitosis); (2) crossover sites may be established before, during, or immediately following initiation of synapsis; and (3) the synaptonemal complex may somehow function in the crossover process at the inception of its formation, but its complete deployment throughout each normal bivalent may serve some other role, such as mediation of the binding of sister chromatids apparently required for chiasma maintenance until anaphase I.

scholarly journals Bqt2p is essential for initiating telomere clustering upon pheromone sensing in fission yeast

2006 ◽  
Vol 173 (6) ◽  
pp. 845-851 ◽  
Author(s):  
Xie Tang ◽  
Ye Jin ◽  
W. Zacheus Cande
Keyword(s):  
Fission Yeast ◽  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Homologous Chromosome ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Meiotic Spindle ◽  
Meiotic Progression ◽  
Pole Body ◽  
Homologous Chromosome Pairing

The telomere bouquet, i.e., telomere clustering on the nuclear envelope (NE) during meiotic prophase, is thought to promote homologous chromosome pairing. Using a visual screen, we identified bqt2/im295, a mutant that disrupts telomere clustering in fission yeast. Bqt2p is required for linking telomeres to the meiotic spindle pole body (SPB) but not for attachment of telomeres or the SPB to the NE. Bqt2p is expressed upon pheromone sensing and colocalizes thereafter to Sad1p, an SPB protein. This localization only depends on Bqt1p, not on other identified proteins required for telomere clustering. Upon pheromone sensing, generation of Sad1p foci next to telomeres depends on Bqt2p. However, depletion of Bqt2p from the SPB is dispensable for dissolving the telomere bouquet at the end of meiotic prophase. Therefore, telomere bouquet formation requires Bqt2p as a linking component and is finely regulated during meiotic progression.

scholarly journals Dynamics of Homologous Chromosome Pairing during Meiotic Prophase in Fission Yeast

2004 ◽  
Vol 6 (3) ◽  
pp. 329-341 ◽  
Author(s):  
Da-Qiao Ding ◽  
Ayumu Yamamoto ◽  
Tokuko Haraguchi ◽  
Yasushi Hiraoka
Keyword(s):  
Fission Yeast ◽  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Homologous Chromosome ◽  
Homologous Chromosome Pairing

Non-homologous chromosome pairing during meiosis in haploid Brassica rapa

2021 ◽  
Author(s):  
Jiachen Yuan ◽  
Gongyao Shi ◽  
Yan Yang ◽  
Janeen Braynen ◽  
Xinjie Shi ◽  
...  
Keyword(s):  
Brassica Rapa ◽  
Chromosome Pairing ◽  
Homologous Chromosome ◽  
Homologous Chromosome Pairing

A cohesin-based structural platform supporting homologous chromosome pairing in meiosis

2016 ◽  
Vol 62 (3) ◽  
pp. 499-502 ◽  
Author(s):  
Da-Qiao Ding ◽  
Tokuko Haraguchi ◽  
Yasushi Hiraoka
Keyword(s):  
Chromosome Pairing ◽  
Homologous Chromosome ◽  
Homologous Chromosome Pairing

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.

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