Meiotic chromosome association in diploid and tetraploid Avena strigosa Schrel.

In diploid Avena strigosa the frequency and distribution of open (rod) bivalents suggest that a limited number of chromosomes, possibly two, fail to have a chiasma in one (short) arm in over 60% of the cells. In the tetraploid these are expected to form bivalents instead of quadrivalents at metaphase I of meiosis in a high frequency. In addition, interstitial chiasmata are expected in the long arms of these chromosomes, when involved in quadrivalents. In the tetraploid the frequency of quadrivalents is indeed low, and the configurations with interstitial chiasmata are distributed as expected. However, application of Sybenga's models suggests that the pairing system rather than the chiasma system would be responsible for the low quadrivalent frequency. It is suggested that apparent negative chiasma interference across the point of pairing partner exchange, resulting from variation in its location, invalidates application of these models to the present material. Negative interference results in an even higher than expected open bivalent frequency, in combination with a relatively high ring quadrivalent frequency. In addition, not only the subacrocentric chromosomes but also the more metacentric chromsomes, by this same mechanism, tend to form open bivalents more often than in the diploid.Key words: meiosis, bivalent, quadrivalent, diploid, tetraploid, Avena strigosa

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A model of meiotic chromosome association in triploids

Genome ◽

10.1139/g89-414 ◽

1989 ◽

Vol 32 (1) ◽

pp. 82-98 ◽

Cited By ~ 16

Author(s):

Charles F. Crane ◽

David A. Sleper

Keyword(s):

Genome Analysis ◽

Meiotic Chromosome ◽

A Priori ◽

Chiasma Formation ◽

Chromosome Association ◽

Subsequent Formation ◽

Meiotic Analysis ◽

Partner Exchange ◽

Translocation Heterozygosity ◽

Metaphase I

A model was developed for chromosome association at meiotic metaphase I in triploids. Probabilities were estimated for each pachytene configuration and for subsequent formation of at least one chiasma in each combination of chromosome arms. Long and short arms were allowed to differ, but were related through an effective arm ratio so that the pattern of genomic affinity was the same for both arms. No other a priori assumptions were made about the pattern of genomic affinity. However, the usual assumptions of genome analysis were made including the following: identity of genomic-affinity pattern and chiasma frequency across homeologous groups, freedom from translocation heterozygosity, independence of chromosome arms, and absence of chiasma formation on both sides of a synaptic partner exchange within an arm. The model was statistically overparameterized and, therefore, had multiple solutions that yielded the same expected meiotic analysis. The range of these solutions can be found through repeated optimizations from randomly chosen starting values within the permitted ranges of the variables. It was convenient to express the optimized pattern of genomic affinity in terms of the proportions of metaphase I association due to each pairwise combination of genomes. Genomic affinity was analyzed in 16 triploid hybrids with the aid of the model.Key words: polyploidy, genome analysis, meiotic model.

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Cytogenetics of decaploid Agropyron elongatum (Elytrigia elongata) (2n = 70). I. Frequency of decavalent formation

Genome ◽

10.1139/g90-122 ◽

1990 ◽

Vol 33 (6) ◽

pp. 811-817 ◽

Cited By ~ 23

Author(s):

Mikio Muramatsu

Keyword(s):

High Frequency ◽

Chromosome Association ◽

Agropyron Elongatum ◽

Homologous Chromosomes ◽

Ring Shape ◽

Meiotic Configuration ◽

Multivalent Formation ◽

A Cell ◽

Chromosome Associations ◽

Metaphase I

The multivalents that appeared in the decaploid strain of Agropyron elongatum (2n = 10x = 70), a relative of wheat, ranged from trivalent to decavalent. Few univalents occurred. The metaphase I chromosome association in 12 cells where all configurations could clearly be identified averaged 0.42 ring X + 0.17 chain X + 0.42 ring VIII + 0.17 branched VIII + 0.25 chain VIII + 0.17 chain VII + 1.17 ring VI + 0.33 branched VI + 0.5 chain VI + 1.67 ring IV + 0.42 branched IV + 0.58 chain IV + 0.08 branched III + 0.17 chain III + 12.58 ring II + 3.75 open II + 0.25 I. The occurrence of decavalents, up to two in one cell, and of a cell with five multivalents, each of which involved more than five chromosomes, and many multivalents of ring shape indicated that the strain is autodecaploid.The chromosome associations of each cell can be interpreted as seven groups of 10 homologous chromosomes. The high frequency of bivalents indicated a tendency toward reduced multivalent formation, for which an explanation is suggested.Key words: Agropyron elongatum, meiotic configuration, decaploid, multivalent.

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CHROMOSOME PAIRING IN HEXAPLOID HYBRIDS FROM BROMUS ERECTUS (2n = 28) × B. INERMIS (2n = 56)

Canadian Journal of Genetics and Cytology ◽

10.1139/g73-053 ◽

1973 ◽

Vol 15 (3) ◽

pp. 427-436 ◽

Cited By ~ 16

Author(s):

K. C. Armstrong

Keyword(s):

Chromosome Pairing ◽

Interspecific Hybrids ◽

Meiotic Chromosome ◽

The Other ◽

Meiotic Chromosome Pairing ◽

Hybrid Plants ◽

Quadrivalent Frequency ◽

Bromus Erectus ◽

Metaphase I

Meiotic chromosome pairing was studied at metaphase I of B. erectus (2n = 28), B. inermis (2n = 56) and interspecific hybrids from B. erectus × B. inermis (2n = 42). The B. erectus material averaged 2.08 IV + 0.11 III + 9.51 II + 0.35 I and B. inermis 0.05 VIII + 0.06 VI + 0.02 V + 2.25 IV + 0.11 III + 22.95 II + 0.25 I. The hybrid plants (2n = 42) averaged 0.18 VI + 1.90 IV + 0.19 III + 16.10 II + 0.39 I and one hybrid with 2n = 41 averaged 0.08 VI + 0.02 V + 0.95 IV + 0.50 III + 17.42 II + 0.72 I. Karyotype evidence supported the conclusion that B. erectus was an autotetraploid. The karyotype contains four large satellites and four subterminal chromosomes but the other four groups of four are median, with one group possibly a submedian. Since chromosome pairing in the hybrids was complete and the quadrivalent frequency in the parents and hybrids was similar, it was concluded that the genomic formula of B. erectus, B. inermis, and the hybrid was AAAA, AAAABBBB, and AAAABB, respectively.

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Comparison between synaptonemal complexes at pachytene and chromosome association at metaphase I in heterozygotes for a "nonreciprocal" translocation of rye

Genome ◽

10.1139/g89-542 ◽

1989 ◽

Vol 32 (6) ◽

pp. 983-991 ◽

Cited By ~ 6

Author(s):

T. Naranjo ◽

A. Roca ◽

P. G. Goicoechea ◽

J. H. de Jong ◽

W. D. Smilde

Keyword(s):

Complex Formation ◽

Synaptonemal Complex ◽

Secale Cereale ◽

Chiasma Formation ◽

Chromosome Association ◽

Simultaneous Occurrence ◽

Negative Interference ◽

Secale Cereale L ◽

Synaptonemal Complex Formation ◽

Metaphase I

A comparative analysis of synaptonemal complex formation at pachytene and chromosome association at metaphase I was carried out in heterozygotes for translocation T242W (2R/6R) of rye (Secale cereale L.). Synaptonemal complex formation supported earlier light microscopic observations that one exchanged segment of this translocation was very small and restricted to the telomere or had been lost. Negative interference between the interstitial segments with respect to chiasma formation was detected at metaphase I. This interference was apparently the result of the simultaneous occurrence of either asynapsis or nonhomologous pairing around the translocation point at pachytene. Negative interference detected across the centromere of 6R was attributed to nonhomologous pairing. The presence of an intercalary C-band in the interstitial segment 2RLi or in the 1RS arm had no apparent influence on synaptonemal complex formation. Unmatched ends of synaptonemal complex 1R and of the multivalent were in most cases associated with heterozygosity for the telomeric C-heterochromatin.Key words: Secale cereale, translocation, synapsis, interference, C-banding.

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Relation between loss of chromosome associations at metaphase I and interference estimates in rye

Genome ◽

10.1139/g88-004 ◽

1988 ◽

Vol 30 (1) ◽

pp. 19-24

Author(s):

A. Roca ◽

T. Naranjo ◽

P. G. Goicoechea ◽

R. Giraldez

Keyword(s):

Secale Cereale ◽

Translocation Breakpoint ◽

Negative Interference ◽

Secale Cereale L ◽

Chromosome Associations ◽

I Cells ◽

Chiasma Interference ◽

Metaphase I

Interference between metaphase I associations (bonds) in specific segments of the chromosomes involved in translocation T242W of rye has been studied. Different values of coincidence were obtained at mid- and late metaphase I for all segment pairs analyzed. At mid-metaphase I there is negative interference between segments opposite to the translocation breakpoint and there is no cross-centromere interference. At late metaphase I there is negative interference in all these segment pairs. The comparison between mid- and late metaphase I cells also indicated that the frequency with which some of these segments are associated decreases along this stage. The possible causes of this decrease and its relation to the differences in coincidence estimates are discussed.Key words: Secale cereale L., translocations, chiasma interference.

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Pachytene pairing and metaphase I configurations in a tetraploid somatic Lycopersicon esculentum × L. peruvianum hybrid

Genome ◽

10.1139/g94-007 ◽

1994 ◽

Vol 37 (1) ◽

pp. 54-60 ◽

Cited By ~ 13

Author(s):

J. Sybenga ◽

E. Schabbink ◽

J. van Eden ◽

J. H. de Jong

Keyword(s):

Significant Negative Correlation ◽

Chiasma Formation ◽

Pericentric Heterochromatin ◽

Lower Probability ◽

Sharp Drop ◽

Late Pachytene ◽

Recombination Nodules ◽

Partner Exchange ◽

Quadrivalent Frequency ◽

Metaphase I

In the tetraploid somatic hybrid between the diploid Lycopersicon species L. esculentum (tomato) and L. peruvianum, synaptonemal complexes formed quadrivalents in 73 of the 120 sets of four chromosomes (60.8%) in 10 cells studied in detail at pachytene. Of these, 43 had one pairing partner exchange, 22 had two, and 8 had three, very close to a Poisson distribution. The points of pairing partner exchange were concentrated at the middle of the two arms. The frequency per arm corresponded with physical arm length. There was a sharp drop around the centromere, and pericentric heterochromatin had a slightly lower probability of being involved in pairing partner exchange than euchromatin. The chromosomes align before pairing and there are several points of pairing initiation, with concentrations at or near the ends and the centromere. From zygotene to late pachytene the quadrivalent frequency decreased considerably. At late pachytene it was lower than expected with the observed high frequency of pairing partner exchange. Pairing affinity between species was only slightly lower than affinity within species, in spite of considerable genetic differentiation. The frequency of recombination nodules increased from early to late zygotene and then decreased strongly to full pachytene. There is a highly significant negative correlation between percent pairing and SC length. At metaphase I the frequency of quadrivalents was 0.444, and branched quadrivalents were rare, probably caused by interference and restriction of chiasma formation to distal euchromatin. Metaphase I quadrivalent frequency is a relatively good indication of pairing affinity in this material.Key words: Lycopersicon, tetraploid hybrid, synaptonemal complex, pairing partner exchange, diakinesis/metaphase I.

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A model of meiotic chromosome association in tetraploids

Genome ◽

10.1139/g89-500 ◽

1989 ◽

Vol 32 (4) ◽

pp. 691-707 ◽

Cited By ~ 6

Author(s):

Charles F. Crane ◽

David A. Sleper

Keyword(s):

Meiotic Chromosome ◽

A Priori ◽

Meiotic Metaphase ◽

Chromosome Association ◽

Preferential Pairing ◽

Subsequent Formation ◽

Meiotic Analysis ◽

Basic Assumptions ◽

The Relationship ◽

Metaphase I

A model is constructed for chromosome association at meiotic metaphase I in tetraploids. Probabilities are estimated for each pachytene configuration and for subsequent formation of at least one chiasma in each combination of chromosome arms. Long and short arms can differ but are related through an effective arm ratio so as to maintain the same pattern of genomic affinity for both arms. No other a priori assumptions are made about the pattern of genomic affinity, but the same basic assumptions are made as in our preceding model for triploids. The model is statistically overparameterized and therefore has multiple solutions whose range can be found through repeated optimization from different starting points. In some cases the same expected meiotic analysis can arise from quite different genomic structures, which therefore cannot be distinguished on the basis of unmarked chromosomes. Solutions to the model are conveniently expressed in terms of the proportion of metaphase I association due to each pairwise combination of genomes. Interpretation of model solutions is also aided by the use of numerical indices that reflect closeness to 11 particular genomic structures or that reveal properties of the relationship among variables. The model differs from that of Kimber and Alonso in its handling of two chiasmatically bound arms in a randomly pairing homologous group, and frequently as well in its optimized pattern of genomic affinity upon application to 3:1 and 2:1:1 genomic structures. With the aid of the model, genomic affinity is analyzed in 20 individuals, representing hybrids, amphiploids, and species.Key words: polyploidy, genome analysis, preferential pairing, meiotic model.

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Synaptonemal complex proteins: occurrence, epitope mapping and chromosome disjunction

Journal of Cell Science ◽

10.1242/jcs.107.10.2749 ◽

1994 ◽

Vol 107 (10) ◽

pp. 2749-2760 ◽

Cited By ~ 48

Author(s):

M.J. Dobson ◽

R.E. Pearlman ◽

A. Karaiskakis ◽

B. Spyropoulos ◽

P.B. Moens

Keyword(s):

Synaptonemal Complex ◽

Fusion Proteins ◽

Epitope Mapping ◽

Core Protein ◽

Binding Capacity ◽

Polyclonal Antibodies ◽

Meiotic Chromosome ◽

Immunogold Labelling ◽

Chromosome Disjunction ◽

Metaphase I

We have used polyclonal antibodies against fusion proteins produced from cDNA fragments of a meiotic chromosome core protein, Cor1, and a protein present only in the synapsed portions of the cores, Syn1, to detect the occurrence and the locations of these proteins in rodent meiotic prophase chromosomes. The 234 amino acid Cor1 protein is present in early unpaired cores, in the lateral domains of the synaptonemal complex and in the chromosome cores when they separate at diplotene. A novel observation showed the presence of Cor1 axial to the metaphase I chromosomes and substantial amounts of Cor1 in association with pairs of sister centromeres. The centromere-associated Cor1 protein becomes dissociated from the centromeres at anaphase II and it is not found in mitotic metaphase centromeres. The extended presence of Cor1 suggests that it may have a role in chromosome disjunction by fastening chiasmata at metaphase I and by joining sister kinetochores, which ensures co-segregation at anaphase I. Two-colour immunofluorescence of Cor1 and Syn1 demonstrates that synapsis between homologous cores is initiated at few sites but advances rapidly relative to the establishment of new initiation sites. If the rapid advance of synapsis deters additional initiation sites between pairs of homologues, it may provide a mechanism for positive recombination interference. Immunogold epitope mapping of antibodies to four Syn1 fusion proteins places the amino terminus of Syn1 towards the centre of the synaptonemal complex while the carboxyl terminus extends well into the lateral domain of the synaptonemal complex. The Syn1 fusion proteins have a non-specific DNA binding capacity. Immunogold labelling of Cor1 antigens indicates that the lateral domain of the synaptonemal complex is about twice as wide as the apparent width of lateral elements when stained with electron-dense metal ions. Electron microscopy of shadow-cast surface-spread SCs confirms the greater width of the lateral domain. The implication of these dimensions is that the proteins that comprise the synaptic domain overlap with the protein constituents of the lateral domains of the synaptonemal complex more than was apparent from earlier observations. This arrangement suggests that direct interactions might be expected between some of the synaptonemal complex proteins.

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Varietal variation and chromosome behaviour during meiosis in Solanum tuberosum

Heredity ◽

10.1038/s41437-020-0328-6 ◽

2020 ◽

Vol 125 (4) ◽

pp. 212-226 ◽

Cited By ~ 3

Author(s):

Anushree Choudhary ◽

Liam Wright ◽

Olga Ponce ◽

Jing Chen ◽

Ankush Prashar ◽

...

Keyword(s):

Solanum Tuberosum ◽

Meiotic Chromosome ◽

In Situ Hybridisation ◽

Fluorescence In Situ Hybridisation ◽

Form Complex ◽

Meiotic Chromosomes ◽

Varietal Variation ◽

Reference Map ◽

Allelic Segregation ◽

Metaphase I

Abstract Naturally occurring autopolyploid species, such as the autotetraploid potato Solanum tuberosum, face a variety of challenges during meiosis. These include proper pairing, recombination and correct segregation of multiple homologous chromosomes, which can form complex multivalent configurations at metaphase I, and in turn alter allelic segregation ratios through double reduction. Here, we present a reference map of meiotic stages in diploid and tetraploid S. tuberosum using fluorescence in situ hybridisation (FISH) to differentiate individual meiotic chromosomes 1 and 2. A diploid-like behaviour at metaphase I involving bivalent configurations was predominant in all three tetraploid varieties. The crossover frequency per bivalent was significantly reduced in the tetraploids compared with a diploid variety, which likely indicates meiotic adaptation to the autotetraploid state. Nevertheless, bivalents were accompanied by a substantial frequency of multivalents, which varied by variety and by chromosome (7–48%). We identified possible sites of synaptic partner switching, leading to multivalent formation, and found potential defects in the polymerisation and/or maintenance of the synaptonemal complex in tetraploids. These findings demonstrate the rise of S. tuberosum as a model for autotetraploid meiotic recombination research and highlight constraints on meiotic chromosome configurations and chiasma frequencies as an important feature of an evolved autotetraploid meiosis.

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Cytogenetic abnormalities of cotton somaclones from callus cultures

Genome ◽

10.1139/g89-509 ◽

1989 ◽

Vol 32 (5) ◽

pp. 762-770 ◽

Cited By ~ 36

Author(s):

David M. Stelly ◽

D. W. Altman ◽

R. J. Kohel ◽

T. S. Rangan ◽

E. Commiskey

Keyword(s):

Cell Culture ◽

Tissue Culture ◽

Somaclonal Variation ◽

High Frequency ◽

Chromosomal Abnormalities ◽

Callus Cultures ◽

Meiotic Abnormalities ◽

High Frequencies ◽

Field Environment ◽

Metaphase I

Somaclonal variation occurs among regenerants from tissue culture of many plant species. Our objective was to determine whether cytogenetic variation contributes to somaclonal variation in cotton (Gossyptum hirsutum L.,2n = 4x = 52). Of 117 somaclones of cotton regenerated from 18-month-old callus cultures of 'SJ-2' and 'SJ-5' cultivars, 35 were analyzed for meiotic abnormalities. The population of somaclones was extremely varied in phenotype, most plants being strikingly aberrant in phenotype. Fertility was generally poor: 84% failed to set bolls and only 5% set 10 or more bolls in a field environment. Only one of the somaclones (3%) formed 26 bivalents at metaphase I. Fourteen were nonsynaptic to partially synaptic at metaphase I. Synaptic abnormalities impaired fertility and precluded thorough metaphase analysis. Chromosome numbers obtained for 32 plants ranged from 49 to 53, and only 1 plant was hyperaneuploid. No plant was polyploid. Chromosomal abnormalities in plants with normal metaphase pairing included univalents, unequal bivalents, rod bivalents, trivalents, open quadrivalents, and centric fragments. Seventeen hypoaneuploid plants formed a V-shaped trivalent at metaphase I, constituting a high frequency of tertiary monosomy. The high frequencies of aneuploidy and tertiary monosomy indicate that cytogenetic anomalies are a major source of somaclonal variation in cotton. It is hypothesized that (i) primary cytogenetic events during cotton cell culture give rise to breakage – fusion – bridge (BFB) cycles, (ii) BFB cycles accrue during culture, (iii) BFB cycles cause loss of chromatin, and (iv) BFB cycles are resolved by the formation of stable tertiary chromosomes with mono-centric activity. The hypothesis accounts mechanistically for the coincidence of chromatin deficiencies and chromatin exchange involved implicitly in tertiary monosomy, as well as for the relatively high frequency of tertiary monosomy among somaclones.Key words: aneuploid, monosomic, synaptic, sterility, Gossypium.

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