Meiotic Aberrations Leading To Aneuploidy In Cauliflower (Brassica Oleracea L. var. Botrytis)

Abstract Aneuploid cauliflower plants (Brassica oleracea L. var. botrytis) display abnormal curd phenotypes causing serious commercial problems in offspring populations. Despite extensive breeding efforts, selection of genotypes producing euploid gametes remains unsuccessful due to unknown genetic and environmental factors. To reveal the origin of aneuploid gametes, we analyzed chromosome pairing, chiasma formation and chromosome segregation in pollen mother cells of selected cauliflower genotypes. To this end we compared different genotypes exhibiting Low with < 5%, Moderate with 5-10% and High with > 10% aberrant offspring. Microscopic observations revealed regular chromosome pairing at pachytene. However, cells at diakinesis and metaphase I showed variable numbers of univalents, suggesting that chiasma formation during meiotic prophase is incomplete or disrupted and results in a partial desynaptic phenotype. Cells at anaphase I – telophase II exhibited various degrees of unbalanced chromosome numbers explaining the aneuploid offspring. Immunofluorescence probed with an MLH1 antibody demonstrated fluorescent foci in all genotypes, but their lower numbers do not correspond to the putative sites of chiasmata. Interchromosomal connections between chromosomes and bivalents are common at diakinesis and metaphase I, and they contain centromeric and 45S rDNA tandem repeats, but such threads seemed not to affect proper disjoin of the half bivalents at anaphase I. Moreover, male meiosis in the arabidopsis APETALA1/ CAULIFLOWER double mutant with the typical cauliflower phenotype did show interchromosomal connections, but there were no indications for partial desynapsis. We now hypothesize that the occurrence of desynapsis in cauliflower is a developmental out-of-phase phenomenon partially or completely controlled by genes involved in flower and curd development.

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Analysis of synaptonemal complexes and chromosome pairing at metaphase I in the diploid intergeneric hybrid Lolium multiflorum × Festuca drymeja

Genome ◽

10.1139/g90-069 ◽

1990 ◽

Vol 33 (4) ◽

pp. 465-471 ◽

Cited By ~ 9

Author(s):

Hum M. Thomas ◽

W. G. Morgan

Keyword(s):

Chromosome Pairing ◽

Complex Analysis ◽

Lolium Multiflorum ◽

Intergeneric Hybrid ◽

Chiasma Formation ◽

Genotypic Effect ◽

Synaptonemal Complexes ◽

Dna Values ◽

Synaptonemal Complex Analysis ◽

Metaphase I

The synaptonemal complexes in the diploid hybrid Lolium multiflorum × Festuca drymeja were examined by the surface spreading technique, and chromosome pairing at metaphase I was analysed. Synaptonemal complex analysis revealed "illegitimate" pairing, including multivalents and foldback pairing. At metaphase I, most chiasmata were between chromosomes of the same genome, and again multivalents were found. It was concluded that most synaptonemal complexes resulted in chiasma formation. The effects of the large differences in DNA values of the two species and the possible genotypic effect of F. drymeja on chromosome pairing are discussed.Key words: Lolium-Festuca, synaptonemal complexes, nonhomologous pairing, DNA values.

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

Genome ◽

10.1139/g93-018 ◽

1993 ◽

Vol 36 (1) ◽

pp. 147-151 ◽

Cited By ~ 63

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.

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Interlocked bivalents in reconstructed metaphase I cells of bread wheat

Journal of Cell Science ◽

10.1242/jcs.75.1.85 ◽

1985 ◽

Vol 75 (1) ◽

pp. 85-92

Author(s):

J.S. Heslop-Harrison ◽

M.D. Bennett

Keyword(s):

Triticum Aestivum ◽

Light Microscopy ◽

Bread Wheat ◽

Chromosome Pairing ◽

Light Microscope ◽

Serial Sections ◽

Ring Bivalents ◽

Mother Cells ◽

I Cells ◽

Metaphase I

Complete reconstructions of all the bivalents were made from electron micrographs of serial sections through six pollen mother cells at metaphase I of meiosis in Triticum aestivum (hexaploid bread wheat). At least two of these metaphases contained interlocked pairs of bivalents. In one, two ring bivalents were interlocked, while in another a rod bivalent ran through the centre of a ring bivalent. Two other groups of bivalents were too closely appressed to allow separation into individual bivalents and may have contained interlocks. Meiosis in other anthers of the same plants examined by light microscopy was considered normal. The frequency of interlocking found was much higher than reported from light-microscope spreads. Not all interlocks in metaphase I cells need adversely affect meiosis, but knowledge of their regularity and form may facilitate understanding the processes of chromosome pairing.

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

Journal of Cell Science ◽

10.1242/jcs.12.1.143 ◽

1973 ◽

Vol 12 (1) ◽

pp. 143-161 ◽

Cited By ~ 1

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.

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Comparative analysis of female and male meiosis in three meiotic mutants of tomato

Genome ◽

10.1139/g97-814 ◽

1997 ◽

Vol 40 (6) ◽

pp. 879-886 ◽

Cited By ~ 6

Author(s):

Francis W. J. Havekes ◽

J. Hans de Jong ◽

Christa Heyting

Keyword(s):

Comparative Analysis ◽

Chromosome Pairing ◽

Meiotic Prophase ◽

Chiasma Frequency ◽

Chiasma Formation ◽

Male Meiosis ◽

Wild Type ◽

Female Meiosis ◽

Similar Reduction ◽

Meiotic Mutants

Female meiosis was analysed in squash preparations of ovules from three meiotic mutants and wild-type plants of tomato. In the completely asynaptic mutant as6, chromosome pairing and chiasma formation were virtually absent in both sexes. In the partially asynaptic mutant asb, with intermediate levels of chromosome pairing at pachytene, there were a higher number of chiasmate chromosome arms in female meiosis than in male meiosis, whereas in the desynaptic mutant as5 there were normal levels of chromosome pairing at pachytene and a similar reduction in chiasma frequency in the two sexes. In wild-type tomato, we found slightly higher numbers of chiasmate chromosome arms in female meiosis than in male meiosis. We propose that the higher female chiasma frequencies in mutant asb and wild-type tomato result from a longer duration of female meiotic prophase. This would allow chromosomes more time to pair and recombine. It is possible that a longer duration of prophase I does not affect mutants as5 and as6, either because the meiotic defect acts before the pairing process begins (in as6) or because it acts at a later stage and involves chiasma maintenance (in as5).Key words: female meiosis, tomato, chiasma, mutant.

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Chromosome pairing in triploid and tetraploid hybrids in Elytrigia (Triticeae; Poaceae)

Canadian Journal of Genetics and Cytology ◽

10.1139/g84-082 ◽

1984 ◽

Vol 26 (5) ◽

pp. 519-522 ◽

Cited By ~ 13

Author(s):

Patrick E. McGuire

Keyword(s):

Chromosome Pairing ◽

Genome Analysis ◽

Triploid Hybrid ◽

Pollen Mother Cells ◽

Tetraploid Hybrid ◽

A Genome ◽

Mother Cells ◽

Metaphase I

Mean chromosome pairing of 5.14I + 1.28II (rod) + 3.86II (ring) + 1.47III + 0.11IV (open) + 0.11V was observed in pollen mother cells at metaphase I in the triploid hybrid Elytrigia scirpea (K. Presl) Holub, 2n = 4x = 28 × E. bessarabica (Savul. et Rayss) Dubrovik, 2n = 4x = 14. Mean chromosome pairing of 3.71I + 2.29II (rod) + 1.82II (ring) + 2.64III + 0.29IV (open) was observed in the triploid hybrid E. curvifolia (Lange) Holub, 2n = 4x = 28 × E. bessarabica. Mean chromosome pairing of 3.00I + 0.93II (rod) + 1.57II (ring) + 1.36III + 1.79IV (open) + 1.I4IV (closed) + 0.79V was observed in the tetraploid hybrid E. junceiformis Löve et Löve, 2n = 4x = 28 × E. curvifolia. The first hybrid provides the first evidence by genome analysis that E. bessarabica possesses a genome (designated Eb) which is closely related to the genomes of E. scirpea (ES and ESC) and hence to the E genome of E. elongata (Host) Nevski, 2n = 2x = 14. The second and third hybrids provide the first evidence that the two genomes of E. curvifolia (designated EC and ECU) are related to the Eb genome of E. bessarabica and thus to the E genome of E. elongata.Key words: Elytrigia, homoeology, Triticum, phylogeny, triploid, tetraploid.

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Morphology and cytology of induced hexaploid of Elymus canadensis and its backcross derivatives—pentaploids, tetrasomics, and trisomics

Genome ◽

10.1139/g90-059 ◽

1990 ◽

Vol 33 (3) ◽

pp. 389-394 ◽

Cited By ~ 2

Author(s):

C. H. Park ◽

P. D. Walton

Keyword(s):

Tissue Culture ◽

Chromosome Pairing ◽

Seed Set ◽

Chiasma Formation ◽

Tetraploid Species ◽

Genomic Constitution ◽

Stainable Pollen ◽

Pollen Mother Cells ◽

Elymus Canadensis ◽

Mother Cells

A tissue culture induced octoploid of Elymus canadensis was crossed with two accessions ("Canada" and "Montana") of the same tetraploid species to produce hexaploids. Hexaploid (2n = 42) and near-hexaploid progeny (2n = 43 or 40) obtained from the crosses were morphologically vigorous but either partially or completely sterile. Mean frequencies of univalents and trivalents in the hexaploid pollen mother cells at metaphase I were 3 or 4 and 2 to 4 per cell, respectively. In view of the genomic constitution of the parents, the hexaploids were expected to be genomically double triploids. Nevertheless, bivalents, averaging 14–17 per cell, predominated. This might be due to the failure of chiasma formation and chiasma terminalization. One hexaploid plant was backcrossed to the tetraploid. The progeny consisted of one pentaploid and five aneuploids including one tetrasomic and two trisomics. All of the progeny from the backcrosses were less vigorous than aneuploids at the near-hexaploid level. Tetrasomics and trisomics had stainable pollen and a 17–19% seed set. Two trisomic plants were morphologically indistinguishable from each other and predominantly showed chromosome pairing of 14 II + 1 I. This indicates failure of chiasma formation and chiasma terminalization between homologous chromosomes.Key words: Elymus canadensis, hexaploids, tetrasomics, trisomics, meiosis.

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Chromosome pairing in the allotetraploid Aegilops biuncialis and a triploid intergeneric hybrid

Genome ◽

10.1139/g96-084 ◽

1996 ◽

Vol 39 (4) ◽

pp. 664-670 ◽

Cited By ~ 4

Author(s):

N. Cuñado ◽

S. Callejas ◽

M. J. García ◽

J. L Santos ◽

A. Fernández

Keyword(s):

Synaptonemal Complex ◽

Chromosome Pairing ◽

Complex Analysis ◽

Intergeneric Hybrid ◽

Chiasma Formation ◽

Triploid Hybrid ◽

Homologous Chromosomes ◽

Prophase I ◽

Surface Spread ◽

Metaphase I

Chromosome pairing behaviour of the natural allotetraploid Aegilops biuncialis (genome UUMM) and a triploid hybrid Ae. biuncialis × Secale cereale (genome UMR) was analyzed by electron microscopy in surface-spread prophase I nuclei. Synaptonemal-complex analysis at zygotene and pachytene revealed that synapsis in the allotetraploid was mostly between homologous chromosomes, although a few quadrivalents were also formed. Only homologous bivalents were observed at metaphase I. In contrast, homoeologous and heterologous chromosome associations were common at prophase I and metaphase I of the triploid hybrid. It is concluded that the mechanism controlling bivalent formation in Ae. biuncialis acts mainly at zygotene by restricting pairing to homologous chromosomes, but also acts at pachytene by preventing chiasma formation in the homoeologous associations. In the hybrid the mechanism fails at both stages. Key words : Aegilops biuncialis, allotetraploid, intergeneric hybrid, pairing control, synaptonemal complex.

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Cytomictic Anomalous Male Meiosis and 2nPollen Grain Formation inMertensia echioidesBenth. (Boraginaceae) from Kashmir Himalaya

The Scientific World JOURNAL ◽

10.1155/2014/134192 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7 ◽

Cited By ~ 6

Author(s):

Reyaz Ahmad Malik ◽

Raghbir Chand Gupta ◽

Santosh Kumari ◽

Akhtar Hussain Malik

Keyword(s):

Pollen Grains ◽

Male Meiosis ◽

Kashmir Himalaya ◽

Open Chain ◽

Chromatin Material ◽

Translocation Heterozygosity ◽

Mother Cells ◽

Chromatin Transfer ◽

First Time ◽

Metaphase I

PresentlyMertensia echioidesBenth. (Boraginaceae) collected from Kashmir Himalaya, India, is cytologically analyzed for the first time revealing2n=2x=24(diploid). Interestingly we found 4.3–6.2% syncytic meiocytes/PMCs with2n=4x=48(tetraploid) in addition to normal meiocytes (2n=24) during male meiosis. These comparatively larger PMCs (pollen mother cells) lead to the formation of fertile giant2npollen grains. A frequency of 6.4–13.3% PMCs shows transfer of chromatin material at prophase-I and, therefore, results in aneuploid meiocytes. Whole chromatin transfer by the process of cytomixis could also have led to the formation of tetraploid cells. Translocation heterozygosity is also evident in the form of multivalents in 12–17% diploid (2x) meiocytes at diakinesis and metaphase-I and is reported for the first time in this species. The syncytes formed depict open chain hexavalent and quadrivalent formation in the three populations with different frequencies. Moreover chromatin stickiness at metaphase-I is observed in 45% of PMCs in population-1 (P-1). Syncyte or unreduced PMC formation leading to unreduced fertile gametes is here speculated to act as a possible way out for infraspecific polyploidization in the species.

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Homoeologous chromosome pairing at metaphase I of meiosis in Hordeum vulgare L. × H. bulbosum L. triploid hybrids (HvHbHb)

PLANT BIOTECHNOLOGY AND BREEDING ◽

10.30901/2658-6266-2020-2-o2 ◽

2020 ◽

Vol 3 (2) ◽

pp. 6-15

Author(s):

G. I. Pendinen ◽

M. Scholz

Keyword(s):

Chromosome Pairing ◽

Parental Species ◽

Homoeologous Pairing ◽

Hybrid Plants ◽

Homoeologous Chromosome Pairing ◽

A Genome ◽

Cultivated Barley ◽

Gish And Fish ◽

Mother Cells ◽

Metaphase I

Background. One of the ways to use the genetic potential of bulbous barley, which is characterized by a number of valuable traits, is interspecific hybridization. In crosses of H. vulgare (2x) × H. bulbosum (2x) and H. vulgare (4x) × H. bulbosum (4x) with a genome ratio of 1Hv: 1Hb in a hybrid embryo, elimination of bulbous barley chromosomes is observed in many cases, and the intensity of the process and the result of the crossing depend on the genotypes of the parental forms. This limits the possibility of including a significant variety of parental forms in crosses. Сrossing of diploid forms of H. vulgare with tetraploid accessions of H. bulbosum (4x) results in the formation of triploid hybrids (HvHbHb) with stable chromosomal composition in pollen mother cells (PMCs) at metaphase I (MI) of meiosis. These triploid hybrids can serve as a basis for obtaining series of introgressive lines of cultivated barley. One of the tasks of this type of work is to estimate the involvement of various chromosomes and their arms in homoeologous associations. The aim of this work was to study the possibility of homoeologous pairing of chromosomes of parental species at MI of meiosis in triploid hybrids using GISH and FISH with chromosome-specific markers, as well as to register the participation of individual arms of the cultivated barley chromosomes in homoeologous associations with the chromosomes of bulbous barley in triploid hybrids (HvHbHb).Materials and methods. Seven triploid hybrids of H. vulgare × H.bulbosum (HvHbHb) obtained in four combinations of crosses with the participation of three diploid cultivars of cultivated barley and two tetraploid accession of bulbous barley were used in this study. The features of homoeologous pairing of chromosomes at MI were studied using the method of fluorescent in situ hybridization (GISH and FISH) with chromosome-specific markers.Results All the studied hybrid plants are characterized by a stable chromosomal composition in PMCs at the MI stage of meiosis. Meiotic configurations formed by homoeologous chromosomes of the parental species, ranging from 0.87 to 1.40 on average per cell, were identified in all the studied plants. Among them, vbb trivalents prevailed. Analysis of chromosome pairing at MI in triploid hybrids revealed the participation of all chromosome arms of H. vulgare in homoeologous Hv-Hb associations, except for the short arm of chromosome 1H. In all the studied triploid hybrids, there is a tendency for a higher frequency of involvement of the long arms of chromosomes in the formation of homoeologous associations; this feature is most clearly manifested in case of chromosome 5H.Conclusions Intergenomic associations with the participation of all arms of H. vulgare chromosomes, except for the short arm of chromosome 1H, were revealed at MI in H. vulgare × H. bulbosum triploid hybrids (HvHbHb). Chromosome 5H, as well as any other cultivated barley chromosome, is characterized by a higher involvement of its long arm in homoeologous associations Hv-Hb, as compared to the short arm.

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