Synaptonemal complex formation and metaphase I configuration patterns in a translocation heterozygote of rye (Secale cereale)

Four rye plants heterozygous for translocation 248, involving chromosomes 1R and 6R, were used for a comparative study of synaptonemal complex formation at midprophase I and chromosome configurations at metaphase I. Synaptonemal complexes were obtained with a cell-spreading technique and studied with electron microscopy. The total length of the synaptonemal complexes in the 28 analyzable pachytene nuclei varied considerably, both within and among plants. The variation of synaptonemal complex lengths of the bivalents in a nucleus was partly stage dependent; i.e., it was greater at early than at late pachytene. In all but one pachytene nucleus, pairing in the quadrivalent was regular, and the four pairing arms were usually easy to identify. Most noticeable was the variation of pairing saturation at the breakpoint of the quadrivalent. Pairing in the breakpoint region was delayed with respect to the pairing in the bivalents. Variation in the arm lengths of the quadrivalent was the result of incomplete and nonhomologous pairing at the breakpoint as well as differential contraction rates among chromosome segments. It was shown that the completion of delayed pairing throughout pachytene is mainly long-arm pairing. The actual breakpoint was therefore not in the middle of the unpaired segments, but more distal. The analysis of metaphase I nuclei revealed that chiasma frequency in this material was higher than in similar material used in former studies. When one of the translocation segments lacked a chiasma, this was in most cases the short translocated segment 1RS, the terminal segment of the satellite of chromosome 1R. Positive chiasma interference was demonstrated between the interstitial and exchanged segment in 1RS. This agreed with the observation of a negative correlation in extent of pairing between these two segments. Other interference phenomena, which have been described for this translocation in other material, remained undetected because of lack of variation in chiasma formation owing to high chiasma frequency.Key words: Secale cereale, meiosis, translocation, synaptonemal complex, metaphase I.

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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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Synapsis and chiasma formation in a ditelo-substituted haploid of rye

Genome ◽

10.1139/g91-018 ◽

1991 ◽

Vol 34 (1) ◽

pp. 109-120 ◽

Cited By ~ 15

Author(s):

J. H. de Jong ◽

F. Havekes ◽

A. Roca ◽

T. Naranjo

Keyword(s):

Synaptonemal Complex ◽

Secale Cereale ◽

Chiasma Formation ◽

Chromosome Length ◽

C Banding ◽

Chromosome Associations ◽

Synaptonemal Complex Formation ◽

Chromosome 1R ◽

In Cells ◽

Metaphase I

Synapsis and chiasma formation were analyzed in a ditelo-substituted haploid of rye (Secale cereale), in which chromosome 1R was replaced by its telosomes. The study was made by comparing synaptonemal complex formation at early meiotic prophase I, chromosome associations at metaphase I, and recombinant chromosomes at anaphase I and prophase II. For the analysis of synaptonemal complexes, 41 nuclei at stages ranging from leptotene to early diplotene were selected. In the leptotene and early zygotene nuclei, numerous alignments of axial cores involving the same or different chromosomes were observed. Pairing initiation sites occurred at both interstitial and distal segments. Throughout zygotene the extent of pairing gradually increases, with values up to 84.8% at a stage that is morphologically comparable with late pachytene. Pairing-partner exchanges were frequently observed in zygotene nuclei, giving rise to multiple associations encompassing all or most of the chromosomes. In cells at metaphase I multivalents were very rare (2%), indicating elimination of most pairing-partner exchanges. In cells at metaphase I, anaphase I, and prophase II chromosome length, centromere position, and C-banding pattern enable the identification of the chromosomes 1RS, 1RL, 4R, 5R, and 6R, and the distinction of three metacentric chromosomes (RM1, RM2, and RM3). Metaphase I bonds were found to be nonrandomly distributed. Associations between the arms 4RL, 5RL, 6RL, and RM1L, all of them without telomeric C-bands, were more frequent than between the remaining arms. The bonds were mainly located at the distal parts of the chromosomes. The frequency of recombinant chromosomes at anaphase I or prophase II suggests that metaphase I bonds were true chiasmata.Key words: Secale cereale, haploid, synaptonemal complex, chiasmate bonds, C-banding.

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

Genome ◽

10.1139/g94-025 ◽

1994 ◽

Vol 37 (2) ◽

pp. 181-189 ◽

Cited By ~ 10

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.

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Synaptic abnormalities in spread nuclei of Secale. I. Inbred lines

Genome ◽

10.1139/g95-097 ◽

1995 ◽

Vol 38 (4) ◽

pp. 764-771 ◽

Cited By ~ 3

Author(s):

M. Martínez ◽

C. Cuadrado ◽

C. Romero

Keyword(s):

Complex Formation ◽

Synaptonemal Complex ◽

Secale Cereale ◽

Inbred Lines ◽

Meiotic Behaviour ◽

Synaptonemal Complex Formation ◽

Metaphase I

The meiotic behaviour at metaphase I of two inbred lines of Secale cereale showed a decrease in the frequency of bound arms and the presence of univalents. The study of synaptonemal complex formation revealed that these inbred lines had asynapsis and many nuclei did not complete the pairing process. Synaptic abnormalities such as fold-back loops, short pairing partner switches, interstitial nonhomologous pairing regions, and asynchrony between bivalents were associated and correlated with interlocking. It is suggested that the asynapsis is due to a failure in the interlocking repair. All these abnormalities could affect the formation and maintenance of chiasmata and so could explain the metaphase I behaviour of these inbred lines and the differences between them.Key words: inbred lines, Secale cereale, synaptonemal complex, spreading, synaptic abnormalities.

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Synaptonemal complex formation in male scorpions exhibiting achiasmate meiosis and structural heterozygosity

Genome ◽

10.1139/g90-138 ◽

1990 ◽

Vol 33 (6) ◽

pp. 914-926 ◽

Cited By ~ 11

Author(s):

Catherine M. Shanahan ◽

David L. Hayman

Keyword(s):

Complex Formation ◽

Synaptonemal Complex ◽

Meiotic Chromosome ◽

Male Meiosis ◽

Late Prophase ◽

Maintenance System ◽

Structural Heterozygosity ◽

Synaptonemal Complex Formation ◽

And Inversion ◽

Metaphase I

Synaptonemal complex (SC) formation was studied in testicular material from individuals of a number of species from two families of Australian scorpions; Buthidae and Scorpionidae. These scorpions exhibit unusual cytogenetic features including achiasmate male meiosis, interchange heterozygosity, and centromeric fusion–fission and inversion heterozygosity. The synaptic behaviour of chromosomes involved in these rearrangements was studied from zygotene to metaphase I, using both meiotic chromosome preparations and techniques for examination of the SCs. Multivalent associations present during the achiasmate meiosis of both buthid and scorpionid scorpions are retained from prophase to metaphase I, unlike those present in polyploid achiasmate Bombyx females. Further evidence suggests that synaptic adjustment does not occur generally in achiasmate scorpionid inversion heterozygotes. However, for some inversions, pairing is seen to become more heterosynaptic from late prophase to metaphase I and this may be related to the pairing maintenance system during achiasmate meiosis in these specialized organisms.Key words: synaptonemal complex, achiasmate meiosis, heterozygosity, interchange, inversion.

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Meiosis in Bombyx mori females

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1977.0022 ◽

1977 ◽

Vol 277 (955) ◽

pp. 343-350 ◽

Cited By ~ 25

Keyword(s):

Complex Formation ◽

Nuclear Envelope ◽

Bombyx Mori ◽

Synaptonemal Complex ◽

Crossing Over ◽

Limited Region ◽

Homologous Chromosomes ◽

Synaptonemal Complexes ◽

Envelope Material ◽

Synaptonemal Complex Formation

Grossing over is absent in oocytes of the silkworm, Bombyx mori . Synaptonemal complexes are present during pachytene between the paired chromosomes. At leptotene, lateral components of the synaptonemal complex are attached in a bouquet to a limited region of the nuclear envelope. Before completion of lateral components, synaptonemal complex formation begins at the nuclear envelope. With synaptonemal complex formation proceeding from both ends bivalents occasionally become interlocked. After pairing is completed, the bouquet arrangement is dissolved possibly as a result of a flow of the inner membrane of the nuclear envelope thereby separating the telomeres. After the telomeres are released from the nuclear envelope, material is deposited onto the lateral components of the synaptonemal complex. The modified synaptonemal complexes are retained by the bivalents until metaphase I. It is suggested that these modified synaptonemal complexes substitute for chiasmata in order to ensure regular disjunction of homologous chromosomes in the absence of crossing over.

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Chromosome-autonomous feedback down-regulates meiotic DNA break competence upon synaptonemal complex formation

Genes & Development ◽

10.1101/gad.342873.120 ◽

2020 ◽

Vol 34 (23-24) ◽

pp. 1605-1618 ◽

Cited By ~ 1

Author(s):

Xiaojing Mu ◽

Hajime Murakami ◽

Neeman Mohibullah ◽

Scott Keeney

Keyword(s):

Complex Formation ◽

Synaptonemal Complex ◽

Synaptonemal Complex Formation ◽

Dna Break

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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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