Can epigenetic control explain pronounced within-plant heterogeneity of meiosis in a translocation trisome of Secale L.?

Genome ◽  
2012 ◽  
Vol 55 (4) ◽  
pp. 257-264 ◽  
Author(s):  
J. Sybenga
Keyword(s):  
Chromosome Pairing ◽  
Sexual Differentiation ◽  
Reciprocal Translocation ◽  
Meiotic Metaphase ◽  
Homology Search ◽  
Crossing Over ◽  
Somatic Variation ◽  
Cell Lineages ◽  
Secale Cereale L ◽  
Plant Grown

Meiotic metaphase I configuration frequencies were determined in different tillers of genetically related plants of rye ( Secale cereale L.) heterozygous for reciprocal translocation T248W (between chromosome arms 1RS and 6RS) and with an additional (telocentric) arm 1RS. Seventeen different configurations could be recognized, grouped into three categories. Very different configuration frequencies were found not only between sister plants from the same parents but also between tillers of the same plant grown under identical conditions (climate chambers at 15 °C and 20 °C). The heterogeneity reflects variation in chromosome pairing and crossing over, and is variable and unpredictable. Anthers within florets were homogeneous. Between tiller heterogeneity is insufficient to explain differences between sister plants. It is ascribed to random somatic variation in the conditions of the chromatin which, at meiosis, govern chromosome pairing. During sexual differentiation, these conditions are fixed and subsequent cell lineages have the same pairing and crossing over characteristics. As homology search is an activity of DNA, this control of pairing and crossing over, consistent over long cell lineages, may be considered to be epigenetic even when no realistic suggestions concerning its character can be given.

On the mechanism of homologous synapsis in lycosid spiders

Genome ◽  
1995 ◽  
Vol 38 (3) ◽  
pp. 443-449 ◽  
Author(s):  
Dwayne A. Wise ◽  
Jeanne L. Taylor
Keyword(s):  
Nuclear Envelope ◽  
Chromosome Pairing ◽  
Sex Chromosomes ◽  
Simple Form ◽  
Wolf Spider ◽  
Homology Search ◽  
Crossing Over ◽  
Reciprocal Translocations ◽  
Backup System ◽  
Telocentric Chromosomes

Lycosid spiders have 13 pairs of telocentric chromosomes and 2 nonhomologous sex chromosomes in males. At leptotene, the kinetochore ends are attached to the nuclear envelope via thickened attachment plaques. Homologous synapsis begins at the attachment plaques and proceeds zipper-like through the length of the synaptonemal complex. We have tested whether or not this simple form of homologous synapsis is obligatory by inducing reciprocal translocations. Since we find many irradiated cells with quadrivalents at diakinesis–prometaphase and metaphase I, clearly a backup system exists that can bring together homologous segments disparate from each other in the nucleus. This mechanism apparently does not depend on end-initiated synapsis. Furthermore, we have found in previous studies that wolf spider bivalents are always unichiasmate, with either proximally or distally placed chiasmata. Since many chain quadrivalents, but no ring quadrivalents, were seen in this study, crossing over and chiasma placement obey a different set of rules when homologous segments are switched between chromosomes.Key words: chromosome pairing, zygotene, homology search, spiders.

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 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.

EFFECT OF RYE ON HOMOEOLOGOUS CHROMOSOME PAIRING IN WHEAT × RYE HYBRIDS

1977 ◽  
Vol 19 (3) ◽  
pp. 549-556 ◽  
Author(s):  
J. Dvořák
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Chinese Spring ◽  
Triticum Aestivum L ◽  
Homoeologous Chromosome ◽  
Wheat Genotype ◽  
Hybrid Plants ◽  
Homoeologous Chromosome Pairing ◽  
Secale Cereale L ◽  
Polygenic System

The number of chiasmata per cell at metaphase I was scored in eight haploid plants of Triticum aestivum L. emend. Thell. cv. 'Chinese Spring' and 100 hybrid plants of Chinese Spring × Secale cereale L. Mean chiasma frequency per cell ranged from 0.00 to 3.59 in the hybrids and from 0.17 to 0.35 in the haploids. Since the same wheat genotype was present in both the haploids and hybrids, it is concluded that some of the rye genotypes promoted homoeologous chromosome pairing. The absence of distinct segregation classes among the hybrids suggests that these genes constitute a polygenic system.

Effect of chromosome 1B, chromosome 6B, and low temperature on the frequency of chromosome pairing at first meiotic metaphase in hexaploid triticale

1983 ◽  
Vol 25 (3) ◽  
pp. 278-282
Author(s):  
Julian B. Thomas ◽  
P. J. Kaltsikes ◽  
S. Shigenaga
Keyword(s):  
Low Temperature ◽  
Common Wheat ◽  
Chromosome Pairing ◽  
Meiotic Metaphase ◽  
The Other ◽  
Hexaploid Triticale ◽  
Other Hand

Chromosome 1B in 'Rosner' and chromosome 6B in line 125 both reduced the frequency with which chromosomes were paired at first meiotic metaphase of hexaploid triticale. On the other hand, chromosome 6B in 'Rosner' and chromosomes 1B and 6B in line 110 had no such effect. The 1B pairing suppressor in 'Rosner' was located on the short arm of the chromosome (1Bs). Between 10 and 30 °C, pairing frequency was quite stable in 'Rosner' triticale in comparison with common wheat, although the level was consistently lower in the triticale. Some reduction of pairing frequency was noted at 10 °C in 'Rosner'. This effect of low temperature did not interact with 1B dosage to cause a disproportionate decrease in pairing frequency when plants with high 1B dosage were grown at 10 °C.

scholarly journals Chromosome pairing in altered constitutions and models of synapsis and crossing-over

1968 ◽  
Vol 12 (1) ◽  
pp. 21-27 ◽  
Author(s):  
Marjorie P. Maguire
Keyword(s):  
Chromosome Pairing ◽  
Direct Relationship ◽  
Crossing Over ◽  
Chromosome 2 ◽  
Similar Material ◽  
Maize Chromosome ◽  
Theoretical Considerations

Metaphase trivalent frequencies from a number of new chromosomal constitutions (various combinations of maize chromosome 2-Tripsacum homeologue primary and secondary interchanges) are presented and compared to previous findings from similar material. It is suggested than an underlying direct relationship may exist between extent of gentic map present in duplicate and triplicate and expectation from a sharing of map probability of crossing-over among all homologues. Theoretical considerations are discussed.

scholarly journals Interfered Chromosome Pairing Promotes Meiosis Instability of Autotetraploid Arabidopsis by High Temperatures

2021 ◽  
Author(s):  
Huiqi Fu ◽  
Jiayi Zhao ◽  
Ziming Ren ◽  
Ke Yang ◽  
Chong Wang ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Chromosome Pairing ◽  
Environmental Temperature ◽  
Oryza Sativa L ◽  
Male Meiosis ◽  
Crossing Over ◽  
Autotetraploid Rice ◽  
Increased Temperature ◽  
Chromosome Separation ◽  
The Impact

Alterations of environmental temperature affect multiple meiosis processes in flowering plants. Polyploid plants derived from whole genome duplication (WGD) have enhanced genetic plasticity and tolerance to environmental stress, but meanwhile face a challenge for organization and segregation of doubled chromosome sets. In this study, we investigated the impact of increased environmental temperature on male meiosis in autotetraploid Arabidopsis thaliana. Under low to mildly-increased temperatures (5-28°C), irregular chromosome segregation universally takes place in synthesized autotetraploid Columbia-0 (Col-0). Similar meiosis lesions occur in autotetraploid rice (Oryza sativa L.) and allotetraploid canola (Brassica napus cv. Westar), but not in evolutionary-derived hexaploid wheat (Triticum aestivum). As temperature increases to extremely high, chromosome separation and tetrad formation are severely disordered due to univalent formation caused by suppressed crossing-over. We found a strong correlation between tetravalent formation and successful chromosome pairing, both of which are negatively correlated with temperature elevation, suggesting that increased temperature interferes with crossing-over prominently by impacting homolog pairing. Besides, we showed that loading irregularities of axis proteins ASY1 and ASY4 co-localize on the chromosomes of syn1 mutant, and the heat-stressed diploid and autotetraploid Col-0, revealing that heat stress affects lateral region of synaptonemal complex (SC) by impacting stability of axis. Moreover, we showed that chromosome axis and SC in autotetraploid Col-0 are more sensitive to increased temperature than that of diploid Arabidopsis. Taken together, our study provide evidence suggesting that WGD without evolutionary and/or natural adaption negatively affects stability and thermal tolerance of meiotic recombination in Arabidopsis thaliana.

scholarly journals THE MANIFESTATION OF CHROMOSOME REARRANGEMENTS IN UNORDERED ASCI OF NEUROSPORA

Genetics ◽  
1974 ◽  
Vol 77 (3) ◽  
pp. 459-489
Author(s):  
David D Perkins
Keyword(s):  
Reciprocal Translocation ◽  
Chromosome Aberrations ◽  
Visual Inspection ◽  
Break Point ◽  
Crossing Over ◽  
Reciprocal Translocations ◽  
Analytical Technique ◽  
Large Numbers ◽  
Pericentric Inversions ◽  
Break Points

ABSTRACT Rapid, effective techniques have been developed for detecting and characterizing chromosome aberrations in Neurospora by visual inspection of ascospores and asci. Rearrangements that are detectable by the presence of deficient, nonblack ascospores in test crosses make up 5 to 10% of survivors after UV doses giving 10-55% survival. Over 135 rearrangements have been diagnosed by classifying unordered asci according to numbers of defective spores. (These include 15 originally identified or analyzed by other workers.) About 100 reciprocal translocations (RT's) have been confirmed and mapped genetically, involving all combinations of the seven chromosomes. Thirty-three other rearrangements generate viable nontandem duplications in meiosis. These consist of insertional translocations (IT's) (15 confirmed), and of rearrangements that involve a chromosome tip (10 translocations and 3 pericentric inversions). No inversion has been found that does not include the centromere. A reciprocal translocation was found within one population in nature. When pairs of RT's that involve the same two chromosome arms were intercrossed, viable duplications were produced if the breakpoints overlapped in such a way that pairing resembled that of insertional translocations (27 combinations).—The rapid analytical technique depends on the following. Deficiency ascospores are usually nonblack (W: "white") and inviable, while nondeficient ascospores, even those that include duplications, are black (B) and viable. Thus RT's typically produce 50% black spores, and IT's 75% black. Asci are shot spontaneously from ripe perithecia, and can be collected in large numbers as groups of eight ascospores representing unordered tetrads, which fall into five classes: 8B:0W; 6B:2W, 4B:4W, 2B:6B, 0B:8W. In isosequential crosses, 90-95% of tetrads are 8:0. When a rearrangement is heterozygous, the frequencies of tetrad classes are diagnostic of the type of rearrangement, and provide information also on the positions of break points. With RT's, 8:0 (alternate centromere segregation) = 0:8 (adjacent-1), 4:4's require interstitial crossing over in a centromere-break point interval, and no 6:2's or 2:6's are expected. With IT's, duplications are viable, 8:0 = 4:4, 6:2's are from interstitial crossing over, 0:8's or 2:6's are rare. Tetrads from RT's that involve a chromosome tip resemble those from IT's, as do tetrads from intercrosses between partially overlapping RT's that involve identical chromosome arms.—Because viable duplications and other aneuploid derivatives regularly occur among the offspring of rearrangements such as insertional translocations, care must be taken in selecting stocks, and original strains should be kept for reference.

Location of the Ph1 locus in the metaphase chromosome map and the linkage map of the 5Bq arm of wheat

1986 ◽  
Vol 28 (4) ◽  
pp. 511-519 ◽  
Author(s):  
R. Jampates ◽  
J. Dvořák
Keyword(s):  
Linkage Map ◽  
Chromosome Pairing ◽  
Chinese Spring ◽  
Chromosome Rearrangement ◽  
Distal Region ◽  
Crossing Over ◽  
Chromosome 5B ◽  
Ph1 Locus ◽  
The Difference ◽  
Two Populations

Heterogenetic chromosome pairing in wheat is prevented by the Ph1 locus on the q (=L) arm of chromosome 5B. Two durum wheat cv. Cappelli structural mutants with rearranged 5Bq chromosome arms were investigated to determine the location of the Ph1 locus in the metaphase map and the linkage map of the arm. One of the mutants, Cap5Bq−, has a deletion of subregion 5Bq12.3 between C-bands 5Bq12.2 and 5Bq21 and the other one, Cap5Bq+, has the same subregion duplicated. Each mutant and standard cv. Cappelli were crossed with Aegilops kotschyi, Ae. ovata, Ae. cylindrica, Ae. ventricosa, Ae. juvenalis, and "Ae. crassa 6x." Hybrids involving Cap5Bq− had higher levels of chromosome pairing than those involving cv. Cappelli, whereas those involving Cap5Bq+ had lower levels of pairing than those involving cv. Cappelli. Cap5Bq− was crossed with cv. Cappelli and the F1 was hybridized with Ae. kotschyi and Ae. ventricosa. All hybrids with the 5Bq− chromosome had a higher level of chromosome pairing than those with the standard chromosome. Cap5Bq+ was crossed with cv. Cappelli and the F1 was hybridized with Ae. kotschyi. Most hybrids with the 5Bq+ chromosome had a lower level of chromosome pairing than those with the standard chromosome. Because the difference between the means of the two populations was small (0.43 chiasmata per cell) and the distributions overlapped, the strength of the linkage between the duplication and reduced pairing could not be determined; the data, nevertheless, showed that the reduced pairing must be strongly, if not completely, linked to the duplication. It is therefore concluded that the Ph1 locus is in the euchromatic subregion 5Bq12.3, 5Bq− is a null for Ph1, and 5Bq+ has two Ph1 loci. The 5Bq+ chromosome was substituted into Triticum aestivum cv. Chinese Spring, the substitution was crossed with cv. Chinese Spring ditelosomic 5Bq, and the F1 was crossed with cv. Chinese Spring monosomic 5B. Recombination of C-bands relative to each other and the centromere was determined with the objective of determining the distribution of crossing-over along the 5Bq arm and the linkage of the subregion 5Bq12.3 with the centromere. The distibution of crossing-over was greatly distorted, most occurred in the distal region of the arm. The subregion 5Bq12.3 showed a tight linkage with the centromere, even though it is in the middle of the 5Bq arm. It is proposed to designate the cv. Cappelli Ph1− mutation as ph1c.Key words: Triticum, map distortion, homoeologous pairing, chromosome pairing, chromosome rearrangement.

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