Ultrastructure of meiotic pairing in B chromosomes of Crepis capillaris. I. One-B and two-B pollen mother cells

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 611-621 ◽  
Author(s):  
G. H. Jones ◽  
J. A. F. Whitehorn ◽  
S. M. Albini
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Complex Surface ◽  
B Chromosome ◽  
B Chromosomes ◽  
Meiotic Pairing ◽  
Pollen Mother Cells ◽  
Crepis Capillaris ◽  
Axis Length ◽  
Mother Cells

Chromosome pairing of a small metacentric B chromosome in Crepis capillaris has been studied by synaptonemal complex surface spreading of pollen mother cells containing either one or two B chromosomes. The B-chromosome axis, on average, represents about 8.7% of the axis length of the standard A-chromosome set, which is less than the corresponding values for DNA content (10.6%) and mitotic chromosome volume (13.6%). Single B chromosomes commonly undergo fold-back pairing to give a symmetrical hairpin loop, which supports earlier suggestions that this B chromosome is an isochromosome. Two B chromosomes may show interarm pairing, exclusively, or interchromosome pairing, exclusively, or combinations of the two. Near the centromeres pairing occurs preferentially between arms of the same chromosome, but chromosome ends show random association. Some B chromosomes show anomalous pairing configurations, which may reflect further orders of reverse repeats within arms or, alternatively, nonhomologous pairing. The period of B-chromosome pairing is confined almost exclusively to zygotene, when the standard A chromosomes are pairing, but within this period their pairing is delayed relative to the A set. Individual B chromosomes at zygotene contain from one to three separate synaptonemal complex segments. These are widely distributed within the chromosomes, mainly in distal and interstitial regions; pairing is delayed around the centromere.Key words: B chromosomes, isochromosomes, synaptonemal complex.

The Effect of Spindle Inhibitors Applied before Meiosis on Meiotic Chromosome Pairing

1973 ◽  
Vol 12 (1) ◽  
pp. 143-161 ◽  
Author(s):  
G. A. DOVER ◽  
R. RILEY
Keyword(s):  
Chromosome Pairing ◽  
Chloral Hydrate ◽  
Control Mechanism ◽  
Meiotic Chromosome ◽  
Chiasma Formation ◽  
Meiotic Pairing ◽  
Mitotic Spindles ◽  
Pollen Mother Cells ◽  
Meiotic Chromosome Pairing ◽  
Mother Cells

Injection of 0.5% colchicine into immature tillers of genotypes of Triticum aestivum, T. aestivum x Aegilops mutica and T. aestivum x Secale cereale hybrids induces asynapsis at first meiotic metaphase irrespective of the homologous or homoeologous nature of the potential pairing chromosomes. The induction of asynapsis occurs at a time during and immediately following the last premeiotic mitosis of pollen mother cells. No disruption of synapsis and chiasma formation occurs in anthers having pollen mother cells originally at leptotene or immediately prior to leptotene when cultured in White's medium plus colchicine. Tetraploid and octaploid pollen mother cells resulting from the disruption of premeiotic spindles by colchicine show pairing of chromosomes only in bivalents, in genotypes normally having a degree of multivalent pairing configurations. The induction of multipolar mitotic spindles with 0.01% colchicine results in the development of pollen mother cell mosaics with different numbers of chromosomes. Such cells show high levels of chromosome pairing, including multivalents, in some genotypes that normally have very little chromosome pairing. The injection of 0.5% chloral hydrate during the last premeiotic mitosis of the archesporium causes no disturbances of meiotic pairing. The results are discussed with reference to the hypothesis that the control mechanism of meiotic chromosome pairing involves centromeric microtubules of the spindle (not affected by chloral hydrate) that are responsible for the positional adjustment, during the last mitotic anaphase, of potential pairing partners.

scholarly journals Meiosis in Oenothera missouriensis

1933 ◽  
Vol 113 (780) ◽  
pp. 57-70 ◽  
Keyword(s):  
Chromosome Pairing ◽  
Cytological Study ◽  
Stage Ii ◽  
Species Hybrid ◽  
Final Solution ◽  
Pollen Mother Cells ◽  
Closed Circle ◽  
Somatic Number ◽  
Mother Cells ◽  
Species Hybrids

A cytological study of the meiotic phenomena in Oenothera may not need an excuse in spite of the exhaustive studies of the genus made by numerous competent cytologists of this century. Up to the present time, all the investigators of Oenothera cytology have been successful in establishing that the basic ( n ) number of chromosomes in this genus is 7; although tetraploid (Gates, 1911), triploid (Cathcheside, 1931), and trisomic numbers might occur either naturally (by mutation) or could be produced by experiment. It is also known that the somatic number of chromosomes corresponds with the number of chromosome bodies in the diakinesis and metaphase of the heterotypic division.. Thus in diploid Oenothera species, hybrid, or mutant at the diakinesis of pollen mother cells 14 chromosomes have been shown to exist, withouth any doubt, in the configuration of a closed circle, in 7 ring pairs, or a mixtrue of free pairs and closed circles. Mathematically, there are 15 possible configurations in which 14 chromosomes can arrange themselves in the form of closed circle, ring pairs, or a combination of ring pairs and closed circles (Cleland and Blakeslee, 1931; Darlington, 1931). Of these 15 Possible configurations 13 have already been reported in various Oenothera species, hybrids and mutants (Darlington, 1931). Regarding the origin and significance of these chromosome configurations invsestigators have not yet reached an agreed opinion. Apart from the genetical significance, the much disputed cytological question of parasynaptic and telosynaptic methods of chromosome pairing is yet far from a final solution. In oenothera both the methods of pairing have strong sup-porters in consideration of observed cytological facts. The fact are (i) the continuous spireme (in leptotene stage); (ii) the pachynema and the diakinesis consisting of the 14 chromosomes arranged end to end. This arragement, known as catenation of chromosomes, favours the telosynaptic rather than the parasynaptic union. Wheras (i) double threads at the prophase, (ii) the looping of the threads, and (iii) the half number of bodies (7 ring pairs) at the diakinesis support the parasynaptic method of pairing of chromosomes. The occurence of a complete catenation of 14 chromosomes in some Oenotheras and the presence of 7 free pairs in others naturally suggests the question-whether they can be correlated with the two methods of chromosome-pairing in the meiosis of Oenothera .

Genome constitution of the Australian hexaploid grass Elymus scabrus (Poaceae: Triticeae)

Genome ◽  
1993 ◽  
Vol 36 (1) ◽  
pp. 147-151 ◽  
Author(s):  
J. Torabinejad ◽  
R. J. Mueller
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Intergeneric Hybrid ◽  
Meiotic Pairing ◽  
Genome Constitution ◽  
Psathyrostachys Juncea ◽  
Hybrid Plants ◽  
Thinopyrum Bessarabicum ◽  
Mother Cells ◽  
Metaphase I

Eight intergeneric hybrid plants were obtained between Elymus scabrus (2n = 6x = 42, SSYY??) and Australopyrum pectinatum ssp. retrofractum (2n = 2x = 14, WW). The hybrids were vegetatively vigorous but reproductively sterile. Examination of pollen mother cells at metaphase I revealed an average of 16.63 I, 5.29 II, 0.19 III, and 0.05 IV per cell for the eight hybrids. The average chiasma frequency of 6.77 per cell in the above hybrids strongly supports the presence of a W genome from A. pectinatum ssp. retrofractum in E. scabrus. Meiotic pairing data of some other interspecific hybrids suggest the existence of the SY genomes in E. scabrus. Therefore, the genome constitution of E. scabrus should be written as SSYYWW. Two other hybrid plants resulted from Elymus yezoensis (2n = 4x = 28, SSYY) crosses with A. pectinatum ssp. pectinatum (2n = 2x = 14, WW). Both were weak and sterile. An average of 0.45 bivalents per cell were observed at metaphase I. This clearly indicates a lack of pairing between W genome of Australopyrum and S or Y genomes of E. yezoensis. In addition, six hybrid plants of E. scabrus with Psathyrostachys juncea (2n = 2x = 14, NN) and one with Thinopyrum bessarabicum (2n = 2x = 14, JJ) were also obtained. The average bivalents per cell formed in both combinations were 2.84 and 0.70, respectively. The results of the latter two combinations showed that there is no N or J genome in E. scabrus.Key words: wide hybridization, chromosome pairing, genome analysis, Australopyrum, Elymus.

Meiosis in triploid Lolium. I. Synaptonemal complex formation and chromosome configurations at metaphase I in aneuploid autotriploid L. multiflorum

Genome ◽  
1994 ◽  
Vol 37 (2) ◽  
pp. 181-189 ◽  
Author(s):  
Huw M. Thomas ◽  
Barry J. Thomas
Keyword(s):  
Complex Formation ◽  
Synaptonemal Complex ◽  
Lolium Multiflorum ◽  
Synaptonemal Complexes ◽  
Pollen Mother Cells ◽  
Partner Exchange ◽  
Synaptonemal Complex Formation ◽  
Mother Cells ◽  
Axial Element ◽  
Metaphase I

A spreading technique for synaptonemal complexes (SCs) was applied to pollen mother cells of two aneuploid genotypes of autotriploid Lolium multiflorum (2n = 3x + 1 = 22). In the earliest nuclei analyzed the axial elements are in six groups of 3 and one group of 4. Most groups have formed multivalents with from one to five pairing partner exchanges, but there are also groups that have formed bivalents and univalents. Some axial elements have formed triple associations, in one case for the length of the trivalent. Unsynapsed axial elements remain aligned with their homologous SCs into pachytene, but this alignment is abolished as these axes pair heterologously among themselves until the entire axial element complement is synapsed. At metaphase I most chromosomes are associated as trivalents and quadrivalents.Key words: Lolium, triploid, pairing partner exchange, chiasma, multivalent.

Ultrastructure of meiotic pairing in B chromosomes of Crepis capillaris

Chromosoma ◽  
1991 ◽  
Vol 100 (3) ◽  
pp. 193-202 ◽  
Author(s):  
G. H. Jones ◽  
S. M. Albini ◽  
J. A. F. Whitehorn
Keyword(s):  
B Chromosomes ◽  
Meiotic Pairing ◽  
Crepis Capillaris

Synaptonemal complex analysis of hybrid cattle. III. Meiotic pairing mechanisms in F1 Brahman × Hereford hybrids

Genome ◽  
1991 ◽  
Vol 34 (2) ◽  
pp. 228-235 ◽  
Author(s):  
A. E. Dollin ◽  
J. D. Murray ◽  
C. B. Gillies
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Complex Analysis ◽  
Bos Taurus ◽  
Bos Indicus ◽  
Meiotic Pairing ◽  
Homoeologous Chromosome ◽  
Homoeologous Chromosome Pairing ◽  
Synaptonemal Complex Analysis ◽  
Complex Hybrid

The mechanisms of homoeologous chromosome pairing were studied in synaptonemal complex (SC) spreads of F1 Brahman (Bos indicus) × Hereford (Bos taurus) cattle. The most common SC abnormalities were bivalents with partial pairing failure and interlocks. While C-band polymorphisms could underlie most of the SC abnormalities observed in the full-blood cattle, other causes seem also to be contributing in the hybrids. The pattern of the abnormalities indicates that genie differences between the species were probably involved. Pachytene substaging data suggest that in some spreads, early pachytene bivalents with partial pairing failure may achieve complete synapsis or may be converted to interlocks by late pachytene.Key words: synaptonemal complex, hybrid cattle, interlocks.

Genomic constitution of the allo-octoploid Elymus tenuis (Poaceae: Triticeae) of New Zealand

2010 ◽  
Vol 23 (5) ◽  
pp. 381 ◽  
Author(s):  
Hai-Qin Zhang ◽  
Xue Bai ◽  
Bao-Rong Lu ◽  
Henry E. Connor ◽  
Yong-Hong Zhou
Keyword(s):  
New Zealand ◽  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Genomic Constitution ◽  
Pollen Mother Cells ◽  
Mother Cells

Elymus tenuis (Buch.) Á.Löve et Connor is a perennial octoploid (2n = 56) wheatgrass endemic to New Zealand. To investigate its genomic constitution, four artificial interspecific hybrids between E. tenuis and E. enysii (2n = 4x = 28, HW), and E. solandri (2n = 6x = 42, StYW) and E. multiflorus (2n = 6x = 42, StYW) were studied cytologically. Meioses in pollen mother cells (PMCs) of the hybrids showed relatively high chromosome pairing, with an average of 13.50 in E. enysii × E. tenuis, 20.22 in E. solandri × E. tenuis, 19.62 in E. multiflorus × E. tenuis, and 20.00 in E. tenuis × E. multiflorus bivalents per cell, respectively. The results indicate that E. tenuis is an allo-octoploid species, with the new and unique genomic constitution StYHW. An autochthonous origin is proposed for it.

Differences in meiotic pairing induction between the A genomes of Triticum boeoticum Boiss. and T. urartu Tum. using diploid species of the subtribe Triticineae as analysers

Genome ◽  
1987 ◽  
Vol 29 (6) ◽  
pp. 891-893 ◽  
Author(s):  
H. Lucas ◽  
J. Jahier
Keyword(s):  
Interspecific Hybrids ◽  
Diploid Species ◽  
Distinct Species ◽  
The Other ◽  
Meiotic Behaviour ◽  
Meiotic Pairing ◽  
Haynaldia Villosa ◽  
Pollen Mother Cells ◽  
Triticum Boeoticum ◽  
Mother Cells

The number of associations between chromosome arms in the pollen mother cells of the hybrid Triticum boeoticum × T. urartu is similar to that in the pollen mother cells of the parental accessions. The latter two species were crossed with the following diploid species: T. tauschii, T. comosum, T. umbellulatum, and Haynaldia villosa. The meiotic behaviour of the hybrids showed that the chromosomes of T. urartu share more homology with the diploid Triticum species than do those of T. boeoticum. On the other hand, there is more pairing in the hybrid T. boeoticum × H. villosa than in T. urartu × H. villosa. These results confirm that T. boeoticum and T. urartu are distinct species. Key words: Triticineae, interspecific hybrids, meiotic behaviour, speciation.

Initiation and progression of homologous chromosome synapsis in Crepis capillaris: Variations on a theme

Genome ◽  
1999 ◽  
Vol 42 (5) ◽  
pp. 867-873 ◽  
Author(s):  
R Banerjee ◽  
G H Jones
Keyword(s):  
Synaptonemal Complex ◽  
Plant Species ◽  
Homologous Chromosome ◽  
Chromosome Length ◽  
Large Sample ◽  
Crepis Capillaris ◽  
Chromosome Synapsis ◽  
Meiotic Synapsis ◽  
Mother Cells ◽  
Variations On A Theme

The model cytogenetic plant species Crepis capillaris (2x = 6), in which all 3 chromosomes are readily distinguished, was used to analyse the initiation and progression of meiotic synapsis in a large sample of spread and silver-stained pollen mother cells. Particular emphasis was placed on detecting general patterns or trends of synaptic order, both among different bivalents and within (along) individual bivalents, and investigating the consistency or otherwise of these synaptic patterns. The order of synaptic progression and completion was partly related to chromosome length; as in other species, shorter bivalents tended to complete synapsis ahead of longer ones. Individual bivalents also showed distinct patterns of synapsis, with a tendency for subterminal regions to initiate synapsis early, followed by multiple synaptic initiations in internal bivalent regions. However, the analysis showed that these synaptic patterns are only general trends and significant variations in synaptic order and pattern, among and within bivalents, occur in individual cells.Key words: meiosis, synapsis, synaptonemal complex, Crepis.

Meiotic synapsis of the Allium porrum B chromosome: evidence for a derived isochromosome origin

Genome ◽  
1996 ◽  
Vol 39 (6) ◽  
pp. 1199-1204 ◽  
Author(s):  
K. A. Khazanehdari ◽  
G. H. Jones
Keyword(s):  
B Chromosome ◽  
B Chromosomes ◽  
Allium Porrum ◽  
Chromosome Synapsis ◽  
Hairpin Loops ◽  
Different Types ◽  
Centric Shift ◽  
Meiotic Synapsis ◽  
Surface Spread ◽  
Mother Cells

Ultrastructural analysis of B chromosome synapsis in surface-spread (2B) pollen mother cells of the leek, Allium porrum, has clarified their structural organization and shed new light on their origin. In pachytene cells containing two B chromosomes, these chromosomes either formed a pair of univalents showing foldback hairpin loops or synapsed together to form bivalents of several different types. The synaptic configurations of univalents and bivalents indicate that these B chromosomes have a basically isochromosome organization, but this is modified by a slight centric shift giving an arm ratio of 1.1:1. This analysis adds to the growing number of B chromosomes that have been shown to be isochromosomes or isochromosome derivatives. Key words : Allium porrum, B chromosomes, synapsis, synaptonemal complex, isochromosome.

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