Spreading synaptonemal complexes of B isochromosomes in the grasshopper Omocestus burri

Meiotic pairing behaviour of one and two B isochromosomes (iso-Bs) in the grasshopper Omocestus burri was analysed by electron microscopy in surface-spread prophase I nuclei and compared with light microscopic observations of metaphase I. Iso-Bs display a peripheral location in the surface-spread nuclei and early pairing relative to that of the long members of the A set. Single iso-Bs undergo foldback pairing to give symmetrical hairpin loops. Two iso-Bs may show interarm pairing, mterchromosome pairing, or combinations of the two. Pericentromeric interarm pairing can be delayed in one or both Bs and this delay is mostly observed in bivalents with pairing partner switches. The iso-B bivalent frequencies observed in the three males analysed were 64, 44, and 41%, respectively; the two latter values were significantly lower than the 66% predicted by the random-end-pairing model. There is a reduction in the frequencies of iso-ring univalents (in 1B males) and bivalents (in 2B males) from pachytene to metaphase I. Similarities and differences between the pairing behaviour of iso-Bs from different species are also discussed.Key words: B isochromosomes, meiosis, grasshopper, synaptonemal complexes, pairing partner switches.

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Indiscriminate synapsis in achiasmate Allium fistulosum L. (Liliaceae)

Journal of Cell Science ◽

10.1242/jcs.103.2.415 ◽

1992 ◽

Vol 103 (2) ◽

pp. 415-422

Author(s):

G. Jenkins ◽

A. Okumus

Keyword(s):

Synaptonemal Complex ◽

Allium Fistulosum ◽

Cell Nuclei ◽

Male Sterile ◽

Allium Species ◽

Lateral Element ◽

Synaptonemal Complexes ◽

Independent Process ◽

Surface Spread ◽

Metaphase I

Seedlings of Allium fistulosum (2n=2x=16) were treated with aqueous colchicine with the intention of inducing tetraploidy. One treated, but undoubled, diploid mutant is described which consistently fails to form any chiasmata at diakinesis and metaphase I of meiosis. Electron microscopy of whole-mount surface-spread synaptonemal complex complements of pollen mother cell nuclei revealed that the achiasmate condition is probably due not only to the failure to complete synapsis, but also to the indiscriminate way in which the chromosomes form synaptonemal complexes during meiotic prophase. Synapsis begins and progresses with complete disregard to homology, with frequent exchanges of pairing partners resulting in the formation of multiple associations comprising heterologous chromosomes. Intrachromosomal synapsis is also evident as fold-back loops. Up to 78% of lateral element length is incorporated into synaptonemal complex, the morphology of which is not unlike that of normal A. fistulosum and other Allium species described previously. However, all the synaptonemal complexes are ineffective in terms of supporting chiasmata, since 16 univalents enter metaphase I and disjoin irregularly at anaphase I. The mutant is as a consequence completely male sterile. The synaptic behaviour observed confirms that the recognition of homology is an independent process and not a prerequisite for synaptonemal complex formation. It is hoped this mutant will be a valuable tool for probing the molecular basis of homology.

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Differences in the synaptic pattern in two autotetraploid cultivars of rye with different quadrivalent frequencies at metaphase I

Genome ◽

10.1139/g99-009 ◽

1999 ◽

Vol 42 (4) ◽

pp. 662-667

Author(s):

M Martínez ◽

C Cuadrado ◽

J Sybenga ◽

C Romero

Keyword(s):

Electron Microscopy ◽

Synaptonemal Complex ◽

Prophase I ◽

Quadrivalent Frequency ◽

Surface Spread ◽

Metaphase I

Synaptic behaviour of the two tetraploids rye cultivars Gigantón (G) and Tetrapico (T) displaying significant differences in their quadrivalent frequencies at metaphase I was analyzed by electron microscopy in surface-spread prophase I nuclei. A different behaviour was observed between the two cultivars; the synaptonemal complex (SC) quadrivalents frequency being significantly higher in G than in T at prophase I. Moreover, the G SC quadrivalents had more synaptic partner exchanges (SPEs) and their location was more distal than the T SC quadrivalents. However, inverse findings were found at metaphase I, the quadrivalent frequency was higher in T than in G. The role that different factors, mainly the number and location of the SPEs and the frequency and distribution of chiasmata, could play in the evolution from prophase I to metaphase I in both cultivars is discussed.Key words: autotetraploid rye, synaptonemal complex, spreading.

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Meiosis in Coprinus. VIII. A time-course study of the fusion and division of the spindle pole body during meiosis.

The Journal of Cell Biology ◽

10.1083/jcb.76.3.761 ◽

1978 ◽

Vol 76 (3) ◽

pp. 761-766 ◽

Cited By ~ 17

Author(s):

B C Lu

Keyword(s):

Electron Microscopy ◽

Time Course ◽

Spindle Pole Body ◽

Spindle Pole ◽

Coprinus Cinereus ◽

Synaptonemal Complexes ◽

Pole Body ◽

Spindle Pole Bodies ◽

Time Course Study ◽

Metaphase I

The time-course study of meiosis in the fungus Coprinus cinereus (C. lagopus) by electron microscopy reveals that two monoglobular spindle pole bodies (SPB's) of prekaryogamy nuclei come together during karyogamy and are fused. The fusion SPB of postkaryogamy nucleus persists through zygotene and pachytene as evidenced by the presence of axial components and synaptonemal complexes. At early diplotene, the SPB divides. The divided SPB takes on a diglobular form, which grows in size to form two daughter SPB's. These separate and move to opposite poles at metaphase I.

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Chromosome structure and pairing preferences in autotetraploid rye (Secale cereale)

Genome ◽

10.1139/g94-112 ◽

1994 ◽

Vol 37 (5) ◽

pp. 784-793 ◽

Cited By ~ 12

Author(s):

G. Jenkins ◽

R. Chatterjee

Keyword(s):

Electron Microscopy ◽

Secale Cereale ◽

Homologous Chromosome ◽

Chromosome Structure ◽

Structural Similarity ◽

The Other ◽

Whole Mount ◽

Structural Divergence ◽

Surface Spread ◽

Pairing Behaviour

The influence of chromosome structure upon pairing behaviour during meiosis was investigated by comparing four autotetraploid genotypes of rye (Secale cereale) containing homologous chromosome sets with different degrees of structural similarity. The series provided a range of genotypes that, at one extreme, contained structurally identical chromosome sets and, at the other extreme, sets that are certainly more heterozygous in the genic sense and probably also more diverse from a purely structural viewpoint. Relative frequencies of pairing configurations at meiotic prophase and metaphase I were compared by electron microscopy of whole-mount surface-spread synaptonemal complex complements and light microscopy of squash preparations. Despite unexpectedly low quadrivalent frequencies over all four genotypes, higher mean bivalent frequencies appeared to be associated with greater homologue diversity. In other words, greater structural divergence between chromosome sets appears to facilitate more efficient discrimination between homologous and identical chromosomes that drives the formation of bivalents. Statistical comparisons were not able to confirm in some cases the significance of the observed pattern of pairing behaviour.Key words: autotetraploid, rye, synapsis, chiasmata.

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The Effect of Homoeologous Meiotic Pairing in Tetraploid Hordeum bulbosum L. × H. vulgare L. Hybrids on Alien Introgressions in Offspring

Cytogenetic and Genome Research ◽

10.1159/000455141 ◽

2016 ◽

Vol 150 (2) ◽

pp. 139-149 ◽

Cited By ~ 1

Author(s):

Margret Scholz ◽

Galina Pendinen

Keyword(s):

Interspecific Hybrids ◽

In Situ Hybridisation ◽

Basic Material ◽

Meiotic Pairing ◽

Hordeum Bulbosum ◽

Homoeologous Pairing ◽

Introgression Breeding ◽

The Individual ◽

Pairing Behaviour

The pairing behaviour of the individual chromosome arms of Hordeum vulgare (Hv) with their homoeologous arms of H. bulbosum (Hb) at metaphase I of meiosis in tetraploid Hb × Hv hybrids and the frequencies of recombined Hv chromosome arms in selfed offspring were studied on differentially visualized chromosomes after fluorescent in situ hybridisation. The frequencies of paired Hv-Hb arms in the F2 and F3 hybrids were correlated with the frequencies of recombined Hv chromosomes in progenies. Self-generation of hybrids, the number of Hv and Hb chromosomes, and the number of recombined Hv chromosomes of the hybrids strongly influenced the Hv-Hb pairing frequency in meiosis. Within the offspring of F2 and F3 hybrids both Hv plants and hybrids were detected. In contrast, all progenies of the F4 hybrid were hybrids which exhibited centromere misdivisions. The highest frequencies of homoeologous pairing in hybrids and most recombinants were obtained for the barley chromosome 1HL. Recombinants for 4HL, 5HS, 6HS, and 7HS were rarely found. Meiotic pairing and recombinants involving chromosome 1HS were never observed. The results of this study demonstrate that fertile tetraploid interspecific hybrids with a high intergenomic pairing at meiosis are valuable basic material for introgression breeding in barley.

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Ultrastructural karyology of Spongospora subterranea (Plasmodiophoromycetes)

Canadian Journal of Botany ◽

10.1139/b92-155 ◽

1992 ◽

Vol 70 (6) ◽

pp. 1228-1233 ◽

Cited By ~ 5

Author(s):

James P. Braselton

Keyword(s):

Electron Microscopy ◽

Single Unit ◽

Spongospora Subterranea ◽

Unit Membrane ◽

Potato Tubers ◽

Haploid Chromosome Number ◽

Synaptonemal Complexes ◽

Transmission Electron ◽

Host Parasite ◽

Section Analysis

Sporogenic (cystogenous) stages of development of Spongospora subterranea (Wallroth) Lagerheim f.sp. subterranea Tomlinson infecting potato tubers were examined with transmission electron microscopy. Volume of nuclei in transitional Plasmodia was 28.2 ± 8.3 μm3. Serial section analysis revealed 37 synaptonemal complexes, hence the haploid chromosome number was considered to be 37. Total length of synaptonemal complexes per nucleus was 74.6 ± 1.4 μm, with individual synaptonemal complexes ranging in length from 1.34 ± 0.07 μm to 3.48 ± 0.17 μm. No polycomplexes were observed in transitional nuclei. Electron-opaque thickenings of lateral elements occurred irregularly. Additional ultrastructural features of sporogenic plasmodia included end-to-end paired centrioles defining the poles of the nuclei and a host–parasite boundary of a single unit membrane. Key words: karyotype, Plasmodiophoromycetes, Spongospora, synaptonemal complex.

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Trachelomonas volzii vs T. dubia (Euglenophyceae)—one or two separate species? Study on similarities and differences of the species

Phytotaxa ◽

10.11646/phytotaxa.357.1.1 ◽

2018 ◽

Vol 357 (1) ◽

pp. 1 ◽

Cited By ~ 1

Author(s):

MAŁGORZATA PONIEWOZIK ◽

KONRAD WOŁOWSKI ◽

JOLANTA PIĄTEK

Keyword(s):

Electron Microscopy ◽

The Other ◽

New Combinations ◽

Separate Species ◽

Phenotypic Changes ◽

The World ◽

Key Features ◽

Similarities And Differences ◽

Species Study ◽

Scanning Electron

This study concerns the two species Trachelomonas volzii and T. dubia which were examined for similarities and dissimilarities of their loricae and monads organization. We specifically focused on the key features of both species that were originally used to separate one from the other: annular thickening at the base of collar and dimensions and ornamentation of loricae. Loricae of specimens were examined by light and scanning electron microscopy and the results were compared with the literature data describing these taxa and reported occurrences in the world. The species together with their varieties and forms do not appear to have strong characteristics distinguishing them, rather the variability observed fits natural phenotypic changes. Based on evidence from this study, we recommend combining these two taxa and propose T. volzii as the single taxon. We also examined a set of varieties of original T. volzii since the species contained several varieties that were almost identical in relation to lorica structure and occurrence. As a result of these observations, we propose the following varieties: Trachelomonas volzii var. volzii as a nominative variety, T. volzii var. australis, T. volzii var. sulcata, T. volzii var. inflata, T. volzii var. acidophila. Furthermore, we propose reclassifying some taxa and the new combinations such as: T. dubia var. ornata to T. volzii var. ornata and T. dubia var. colliundulata to T. volzii var. colliundulata. In our opinion, T. dubia fo. acuminata should be included with the species T. hexangulata due to its unique, hexagonal shaped lorica.

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Evidence of nonchiasmate bonds at metaphase I in inbred rye

Canadian Journal of Genetics and Cytology ◽

10.1139/g84-066 ◽

1984 ◽

Vol 26 (4) ◽

pp. 409-414 ◽

Cited By ~ 7

Author(s):

M. C. Cermeño ◽

J. Orellana ◽

J. R. Lacadena

Keyword(s):

Secale Cereale ◽

Chiasma Frequency ◽

Meiotic Pairing ◽

Secale Cereale L ◽

Chromosome 1R ◽

Metaphase I

The loss of bound chromosome arms through early, middle, and late metaphase I has been analyzed in a plant of inbred rye (Secale cereale L.) heterozygous for a terminal heterochromatic C-band of the long arm of chromosome 1R. From the increase in the number of univalent pairs due to bound arm loss, and from the comparison between the frequencies of bound arms at metaphase I and recombinant chromosomes at anaphase I, it is concluded that some of the chromosome bonds appearing at metaphase I are actually nonchiasmate associations that can be considered as remnants of prophase pairing. Conclusions concerning recombination obtained solely from the analysis of chiasma frequency measured as bound arms may be invalid.Key words: inbred rye, C-heterochromatin, meiotic pairing, nonchiasmate bonds.

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Scanning electron microscopy of basidiospores of species of Strobilomycetaceae

Canadian Journal of Botany ◽

10.1139/b71-177 ◽

1971 ◽

Vol 49 (8) ◽

pp. 1259-1261 ◽

Cited By ~ 11

Author(s):

Larry F. Grand ◽

Royall T. Moore

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

North American ◽

North American Species ◽

Surface Features ◽

The Family ◽

Similarities And Differences ◽

Scanning Electron

Basidiospores of 13 North American species of Strobilomycetaceae were examined by scanning electron microscopy. Similarities and differences of surface features among species are discussed in relation to their possible role in the taxonomy of the family.

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