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

Genome ◽  
1991 ◽  
Vol 34 (1) ◽  
pp. 109-120 ◽  
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.

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

Genome ◽  
1989 ◽  
Vol 32 (1) ◽  
pp. 72-81 ◽  
Author(s):  
J. H. de Jong ◽  
J. van Eden ◽  
J. Sybenga
Keyword(s):  
Complex Formation ◽  
Synaptonemal Complex ◽  
Secale Cereale ◽  
Chiasma Formation ◽  
Terminal Segment ◽  
Pachytene Nucleus ◽  
Synaptonemal Complexes ◽  
Synaptonemal Complex Formation ◽  
Chromosome 1R ◽  
Metaphase I

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.

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

Genome ◽  
1989 ◽  
Vol 32 (6) ◽  
pp. 983-991 ◽  
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.

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

Genome ◽  
1995 ◽  
Vol 38 (4) ◽  
pp. 764-771 ◽  
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.

Synaptonemal complex formation and metaphase I bond distribution at low temperatures in nullisomic 5D – tetrasomic 5B hexaploid wheat

Genome ◽  
1992 ◽  
Vol 35 (3) ◽  
pp. 498-502 ◽  
Author(s):  
L. Morais ◽  
A. Queiroz ◽  
W. Viegas ◽  
A. Roca ◽  
T. Naranjo
Keyword(s):  
Synaptonemal Complex ◽  
Low Temperatures ◽  
Low Frequency ◽  
Banding Technique ◽  
C Banding ◽  
Nonrandom Distribution ◽  
Chromosome Arm ◽  
Synaptonemal Complex Formation ◽  
I Cells ◽  
Metaphase I

Nullisomic 5D – tetrasomic 5B wheat plants were grown at 20 and 16 °C, and the level of paired and unpaired lateral elements in synaptonemal complex (SC) spreads was quantified in early-mid prophase I cells to ascertain the origin of the low frequency of metaphase I associations observed in plants held at 16 °C in the absence of the Ltp1 gene located on the long arm of chromosome 5D. The distribution of chromosome arm associations in metaphase I cells was studied using the C-banding technique. The results obtained confirm that asynapsis was the main cause of the reduction in the level of association in metaphase I at low temperature. Although a nonrandom distribution of chromosome arm associations at metaphase I was observed at both temperatures, this tendency was more visible at 16 °C, leading to the suggestion that at low temperatures differences in the specific ability of chromosome arms to form SCs and chiasmata are enhanced.Key words: synaptonemal complex, Ltp1 gene, metaphase I bonds, wheat, C-banding.

Rye C-banding patterns and meiotic stability of hexaploid triticale (× Triticosecale) selections differing in kernel shriveling

Genome ◽  
1990 ◽  
Vol 33 (5) ◽  
pp. 686-689 ◽  
Author(s):  
Charles M. Papa ◽  
R. Morris ◽  
J. W. Schmidt
Keyword(s):  
Secale Cereale ◽  
Chromosome Banding ◽  
Agronomic Performance ◽  
Hexaploid Triticale ◽  
Kernel Development ◽  
Banding Patterns ◽  
C Banding ◽  
Meiotic Stability ◽  
Metaphase I

Two winter hexaploid triticale populations derived from the same cross were selected on the basis of grain appearance and agronomic performance. The five lines from 84LT402 showed more kernel shriveling than the four lines from 84LT401. The derived lines were analyzed for aneuploid frequencies, rye chromosome banding patterns, and meiotic stability to detect associations with kernel development. The aneuploid frequencies were 16% in 84LT401 and 18% in 84LT402. C-banding showed that both selection groups had all the rye chromosomes except 2R. The two groups had similar telomeric patterns but differed in the long-arm interstitial patterns of 4R and 5R. Compared with lines from 84LT402, those from 84LT401 had significantly fewer univalents and rod bivalents, and more paired arms at metaphase I; fewer laggards and bridges at anaphase I; and a higher frequency of normal tetrads. There were no significant differences among lines within each group for any meiotic character. Since there were no differences within or between groups in telomeric banding patterns, the differences in kernel shriveling and meiotic stability might be due to genotypic factors and (or) differences in the interstitial patterns of 4R and 5R. By selecting plump grains, lines with improved kernel characteristics along with improved meiotic stability are obtainable.Key words: triticale, meiotic stability, C-banding, Secale cereale, heterochromatin.

Evidence of nonchiasmate bonds at metaphase I in inbred rye

1984 ◽  
Vol 26 (4) ◽  
pp. 409-414 ◽  
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.

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.

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

Genome ◽  
1990 ◽  
Vol 33 (6) ◽  
pp. 914-926 ◽  
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.

The relation between pairing preference and chiasma frequency in tetrasomics of rye

Genome ◽  
2004 ◽  
Vol 47 (1) ◽  
pp. 122-133 ◽  
Author(s):  
E Benavente ◽  
J Sybenga
Keyword(s):  
Secale Cereale ◽  
Chiasma Frequency ◽  
Active Sites ◽  
Chiasma Formation ◽  
Long Distance ◽  
Association Pattern ◽  
Chromosome 1R ◽  
Favorable Conditions ◽  
Pairing Initiation ◽  
Effective Pairing

The association pattern of marked tetrasomes of Secale chromosome 1R at meiotic first metaphase was analyzed. Two of the four chromosomes were identical with terminal C-bands at both arms; the other two were also identical but lacked C-bands and were homologous or homeologous with the first two. Four different types of heterozygotes for 1R were studied: (i) autotetraploid hybrids between genetic variants within Secale cereale subsp. cereale, (ii) tetraploid hybrids between subspecies of Secale cereale, (iii) tetraploid hybrids between species of Secale, and (iv) autotetrasomes of S. cereale in a wheat background. Earlier observations that heterozygous associations (banded with unbanded) had consistently higher chiasma frequencies than homozygous associations were extended and confirmed. To analyze this phenomenon more closely, the possible relations between this correlation and several other meiotic phenomena were studied. For this analysis, three genetically different autotetraploid hybrids within S. cereale were selected that differed with respect to the relation between pairing type and chiasma frequency. Special attention was given to different patterns of interference and other meiotic phenomena in the two chromosome arms of chromosome 1R. No relations between such phenomena and the relation between pairing type and chiasma frequency could be established. A hypothesis is formulated assuming that long-distance homologue attraction is concentrated in a limited number of sites and that in different genotypes, different patterns of active sites are present. Moderately weak attraction sites can pair with strong homologous sites under favorable genetic conditions, but two weak sites cannot. Then, heterozygotes have more effective pairing initiation and consequently chiasma formation than homozygotes. Under less favorable conditions, only strong sites are effective, and then, homozygotes pair better, but the chiasma frequency is lower. A model of the forces involved in homologue attraction is presented.Key words: autopolyploids, preferential pairing, chiasma frequency, homologue attraction, Secale.

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