Synaptonemal complexes of triploid (ZZW) chickens: Z–Z pairing predominates over Z–W pairing

Genome ◽  
1991 ◽  
Vol 34 (5) ◽  
pp. 718-726 ◽  
Author(s):  
Alberto J. Solari ◽  
M. H. Thorne ◽  
B. L. Sheldon ◽  
C. B. Gillies
Keyword(s):  
Synaptonemal Complex ◽  
Central Region ◽  
Sex Chromosomes ◽  
W Chromosome ◽  
Synaptonemal Complexes ◽  
Early Pachytene ◽  
Recombination Nodule ◽  
Recombination Nodules ◽  
Central Regions ◽  
Partial Elimination

Twelve triploid, ZZW chickens of ages ranging from day 19 of incubation to 15 days after hatching were used for oocyte analysis. Oocytes show 117 axes per nucleus. At early pachytene, most axes form double synaptonemal complexes (triplets). An average of 27 triplets, 12 bivalents, and 12 univalents was observed. Later, a partial elimination of triplets occurs, as they are converted into typical trivalents or bivalents and univalents. The number of recombination nodules per nucleus (52.7) is similar to that of diploids. These nodules can occur in register in both central regions of a triplet (no lateral interference), and they probably stabilize the central region. Among 31 oocytes, 29 had a regular ZZ bivalent and a W univalent, and only 2 had triple pairing between a ZZ bivalent and a terminal region of the W axis (less than 1 μm in length and having a terminal recombination nodule). Competition for pairing between the gonosomes results in a large (93.5% of cases) predominance of Z–Z pairing, because of a relatively minor homology between the W and Z chromosomes. The prevailing pairing failure of the W chromosome may lead to early oocyte loss.Key words: sex chromosomes, triploids, synaptonemal complex, Z–W pairing, chicken, recombination nodules.

Recombination nodule mapping and chiasma distribution in spermatocytes of the pigeon, Columba livia

Genome ◽  
1999 ◽  
Vol 42 (2) ◽  
pp. 308-314 ◽  
Author(s):  
M I Pigozzi ◽  
A J Solari
Keyword(s):  
Synaptonemal Complex ◽  
Random Distribution ◽  
Phosphotungstic Acid ◽  
Columba Livia ◽  
Complex Karyotype ◽  
Synaptonemal Complexes ◽  
Recombination Nodules ◽  
Chiasma Distribution ◽  
The Mean ◽  
Good Agreement

Pigeon spermatocytes were processed with a drying-down technique and their synaptonemal complex (SC) complements were analyzed by electron microscopy. The synaptonemal complex karyotype of the macrobivalents shows an excellent correspondence with the mitotic karyotype. The number and distribution of recombination nodules (RNs) were scored in complete nuclei stained with phosphotungstic acid. The average number of RNs per nucleus is 64.7. The number of nodules per bivalent shows a clear linear relationship with SC length in the 10 longest synaptonemal complexes, while the microbivalents usually bear a single RN. The location of RNs has a non-random distribution along the largest synaptonemal complexes, with lower frequencies near kinetochores and higher frequencies toward the telomeres. The ZZ bivalent is the fourth in size and shows free recombination, having on average 3.8 RNs. The mean number of nodules per cell and the mean number of nodules in the largest bivalents show very good agreement with the corresponding number of chiasmata scored in metaphase-I spermatocytes. It is concluded that the recombination nodules provide a good check for reciprocal exchanges in this and other species of birds. Additionally, a new morphology for the recombination nodules is presented, consisting of groups of electron-dense particles measuring 43 nm in diameter.Key words: meiosis, chiasmata, recombination nodules, pigeon spermatogenesis.

scholarly journals The Synaptonemal Complex Central Region Modulates Crossover Pathways and Feedback Control of Meiotic Double-strand Break Formation

2020 ◽  
Author(s):  
Min-Su Lee ◽  
Mika T. Higashide ◽  
Hyungseok Choi ◽  
Ke Li ◽  
Soogil Hong ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Central Region ◽  
Genetic Recombination ◽  
Strand Break ◽  
Late Prophase ◽  
Interacting Protein ◽  
Recombination Proteins ◽  
Central Regions ◽  
Chromosome Iii ◽  
Double Holliday Junction

SummaryThe synaptonemal complex (SC) is a proteinaceous structure that mediates homolog engagement and genetic recombination during meiosis. Zip-Mer-Msh (ZMM) proteins promote crossover (CO) formation and initiate SC formation. In SC elongation, the SUMOylated SC component Ecm11 and its interacting protein Gmc2 facilitate the polymerization of Zip1, a SC-central region component in budding yeast. Through physical recombination, cytological, and genetic analyses, we here demonstrate that ecm11 and gmc2 mutants exhibit chromosome-specific defects in meiotic recombination. CO frequencies were reduced on a short chromosome (chromosome III), whereas CO and non-crossover (NCO) frequencies were increased on a long chromosome (chromosome VII). Further, persistent double-strand breaks (DSBs) occurred in unsynapsed chromosome regions during the late prophase, suggesting the presence of a negative regulation of DSB formation. The Ecm11-Gmc2 (EG) complex could participate in joint molecule (JM) processing and/or double-Holliday junction resolution for CO-designated recombination of the ZMM-dependent pathway. However, absence of the EG complex ameliorated the JM-processing defect in zmm mutants, suggesting a role of these proteins in suppression of ZMM-independent recombination. Therefore, the EG complex fosters ZMM-dependent processing and resolution of JMs while suppressing ZMM-independent JM processing and late DSB formation. Hence, EG-mediated SC central regions, which display properties similar to those of liquid crystals, may function as a compartment for sequestering recombination proteins in and out of the process to ensure meiosis specificity during recombination.

scholarly journals SYNAPTONEMAL COMPLEX AND RECOMBINATION NODULES IN WILD-TYPE DROSOPHILA MELANOGASTER FEMALES

Genetics ◽  
1979 ◽  
Vol 92 (2) ◽  
pp. 511-541
Author(s):  
Adelaide T C Carpenter
Keyword(s):  
Drosophila Melanogaster ◽  
Synaptonemal Complex ◽  
Meiotic Recombination ◽  
Morphological Type ◽  
Wild Type ◽  
Recombination Nodule ◽  
Recombination Nodules ◽  
Recombination Processes ◽  
A Subunit ◽  
Serial Section Reconstruction

ABSTRACT Electron microscope serial section reconstruction analysis of all zygotene-pachytene nuclei of meiotic cells from three wild-type germaria (a subunit of the ovary containing the early meiotic stages arrayed in temporal developmental sequence) of Drosophila melanogaster females corroborates and extends earlier observations (CARPENTER 1975a) on the nature and sequence of ultrastructural events occurring during the time of meiotic recombination. Emphasis has been placed on (1) the time of appearance and disappearance of the synaptonemal complex (SC) and the changes in its dimensions that accompany a cell's progression through pachytene, and (2) the appearance, disappearance, number and chromosomal locations of recombination nodules (CARPENTER 1975b). For both the SC and the recombination nodule the availability of several developmental series has provided an estimate of the biological variability in the properties of these recombination-associated structures. The much more extensive data presented here substantiate the earlier hypothesis that recombination nodules occur at sites where reciprocal meiotic recombination will occur, has occurred, or is occurring. A second morphological type of recombination nodule is reported; it is suggested that the presence of the latter type of nodule may correlate with sites of gene conversion. The hypothesis that there may be two types of meiotic recombination processes is discussed.

Localized chiasmata and meiotic nodules in the tetraploid onion Allium porrum

Genome ◽  
1996 ◽  
Vol 39 (4) ◽  
pp. 770-783 ◽  
Author(s):  
Stephen M. Stack ◽  
Dick Roelofs
Keyword(s):  
Key Words ◽  
Synaptonemal Complex ◽  
Allium Porrum ◽  
Crossing Over ◽  
High Fertility ◽  
Unusual Behavior ◽  
Synaptonemal Complexes ◽  
Recombination Nodules ◽  
Metaphase I

Allium porrum L. (cultivated leek) (2n = 4x = 32) is a fertile tetraploid that forms bivalents with pericentric chiasmata at metaphase I. To investigate the basis of this unusual behavior for a tetraploid, we describe the karyotype, axial cores, synaptonemal complexes (SCs), and meiotic nodules of A. porrum. The karyotype appears to be autotetraploid. This conclusion is also supported by presynaptic alignment of axial cores in groups of four and partner trades between pairs of SCs. Numerous early nodules are distributed all along axial cores and SCs during zygonema, but they are lost by late zygonema – early pachynema. Late (recombination) nodules (RNs) are present on SCs near kinetochores throughout the remainder of pachynema. This pattern of RNs corresponds to the pattern of pericentric chiasmata. Pachytene quadrivalents usually are resolved into bivalents because partner trades between SC lateral elements rarely occur between RNs on the same segment of SC. Thus, the patterns of crossing-over and partner trades promote balanced disjunction and high fertility in autotetraploid A. porrum. Rare quadrivalents observed at metaphase I must be due to infrequent partner trades between RNs. Polycomplexes, unusual in their number and size, were observed during zygonema. Key words : synaptonemal complex, recombination nodules, localized chiasmata, polycomplex, Allium porrum.

Localized recombination nodules and sex chromosome behavior in the male mole cricket, Neocurtilla hexadactyla

Genome ◽  
1989 ◽  
Vol 32 (2) ◽  
pp. 275-281 ◽  
Author(s):  
B. Spyropoulos ◽  
D. Wise ◽  
P. B. Moens
Keyword(s):  
Synaptonemal Complex ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Chromosome X ◽  
Chromosome Behavior ◽  
Autosomal Bivalents ◽  
Electron Dense Material ◽  
Recombination Nodules ◽  
The Third ◽  
Mole Cricket

During meiotic prophase, the 10 metacentric autosomal bivalents of the mole cricket, Neocurtilla hexadactyla Perty, formed synaptonemal complexes only at their ends. These complexes were of similar morphology to those of other species. Virtually all of these distal synaptonemal complex segments contained one or more recombination nodules. There was complete correlation between the locations of the synaptonemal complex segments at pachytene and chiasmata at diplotene. The sex chromosomal bivalent X2 and Y, formed a synaptonemal complex at one end only. While no apparent physical or spatial connection was found during prophase between the X2Y bivalent and the third sex chromosome, X1, electron-dense material covered the centromeres of X1 and Y and to a lesser extent X2, thus differentiating the centromeres of the sex chromosomes from those of the autosomes.Key words: localised pairing, recombination nodules, chiasmata, sex chromosomes.

The synaptonemal complex karyotype from spread spermatocytes of a dipteran (Aedes aegypti)

1983 ◽  
Vol 25 (4) ◽  
pp. 361-369 ◽  
Author(s):  
Annelise Wandall ◽  
Allan Svendsen
Keyword(s):  
Electron Microscope ◽  
Aedes Aegypti ◽  
Light Microscopy ◽  
Synaptonemal Complex ◽  
Complex Karyotype ◽  
Synaptonemal Complexes ◽  
Recombination Nodules ◽  
The One ◽  
Mitotic Cells

Synaptonemal complexes (SCs) from the spermatocytes of the mosquito, Aedes aegypti, were spread on a 0.3 M sucrose hypophase and analyzed in the electron microscope. The SC karyotype was similar to the one known from light microscopy of mitotic cells in both relative lengths and in centromere positions. All pachytene nuclei retained their bouquet configuration during spreading; the telomeres were polarized and clustered, and the three centromeric regions were close together. The kinetochores differentiated during pachytene, those of bivalent No. 1 (the sex bivalent) before the others. Recombination nodules were preserved in some spreads; out of 35 nodules, whose distal or proximal location on the SC arms could be determined, 27 were located in the distal one-third of the arms. No SC arm had more than one nodule.

Quadrivalent formation in a tetraploid chicken oocyte

Genome ◽  
1988 ◽  
Vol 30 (6) ◽  
pp. 900-902 ◽  
Author(s):  
A. J. Solari ◽  
N. S. Fechheimer
Keyword(s):  
Electron Microscopy ◽  
Synaptonemal Complex ◽  
Complex Analysis ◽  
W Chromosome ◽  
Autosomal Bivalents ◽  
Initiation Point ◽  
Recombination Nodule ◽  
Synaptonemal Complex Analysis ◽  
Threshold Length ◽  
Pairing Initiation

Synaptonemal complex analysis of an exceptional tetraploid oocyte from a diploid chicken heterozygous for the MN t (Z;1) rearrangement was performed by electron microscopy of a spread preparation. Ten separate quadrivalents (26% of the chromosomal axes) were analyzed, as well as 50 autosomal bivalents. All the axes less than 2.5 μm in length formed bivalents (38) only, while axes in the 2.5–4.2 μm range formed 5 quadrivalents and 12 bivalents. The longer, separate axes formed quadrivalents only. Partner switches in excess of one were documented. The two identical W chromosomes paired only at the ends of their short arms. Quadrivalent formation may require a threshold length (2.5 μm), at least in this species. The tip of the short arm of the W chromosome may be a pairing initiation point, and it corresponds to the region associated with a localized recombination nodule previously described in diploid oocytes.Key words: quadrivalent, tetraploid, synaptonemal complex, chicken oocyte.

KARYOTYPE, SYNAPTONEMAL COMPLEXES AND POSSIBLE RECOMBINATION NODULES OF THE OOMYCETE FUNGUS SAPROLEGNIA

1982 ◽  
Vol 24 (4) ◽  
pp. 385-396 ◽  
Author(s):  
Kenji Tanaka ◽  
I. Brent Heath ◽  
Peter B. Moens
Keyword(s):  
Synaptonemal Complex ◽  
Nuclear Dna ◽  
Central Element ◽  
Nuclear Dna Content ◽  
Mean Value ◽  
Synaptonemal Complexes ◽  
Recombination Nodules ◽  
Section Electron ◽  
Serial Section Electron Microscopy ◽  
Complex Length

Pachytene nuclei of the fungus Saprolegnia ferax (Gruith.) Thuret were analyzed by serial section electron microscopy. These nuclei contained 21 synaptonemal complexes, all of which terminated at both ends on the nuclear envelope. These complexes range from 1.6 μm to 5.5 μm in length and are composed of two rather diffuse lateral elements, lack a continuous central element and contain discontinuous central nodes. These nodes occur at about 1 per μm of synaptonemal complex length, have a diameter of approximately 50 nm, are predominantly short (<200 nm) and appear to occur as multiples of a basic 50 nm length. These nodes are in many respects similar to previously reported recombination nodules. The complexes were not seen to form a bouquet stage. Based on nuclear DNA content and synaptonemal complex length, the chromosomes are calculated to contain 2C values of between 5.2 and 17.3 fg of DNA, with a mean value of 9.3 fg. Thus it seems that Saprolegnia has large chromosomes relative to other fungi and a haploid complement of 21.

Chiasmata and recombination nodules in Lilium longiflorum

Genome ◽  
1989 ◽  
Vol 32 (3) ◽  
pp. 486-498 ◽  
Author(s):  
Stephen M. Stack ◽  
Lorinda K. Anderson ◽  
Jamie D. Sherman
Keyword(s):  
Synaptonemal Complex ◽  
Average Length ◽  
Central Element ◽  
Lilium Longiflorum ◽  
Uranyl Acetate ◽  
Synaptonemal Complexes ◽  
Recombination Nodules ◽  
Acetate Lead ◽  
Complete Set ◽  
Late Diplotene

We determined the frequency of chiasmata at late diplotene in microsporocytes of Lilium longiflorum (lily). Because there are long, intimate associations of homologous chromosomes in addition to short associations that appear to be single chiasmata, the number of chiasmata counted depends on how the long associations are interpreted. Using a defined method, we determined that there was an average of 54.8 ± 6.0 chiasmata per complete set of diplotene bivalents. Recombination nodules are 100-nm ellipsoids that are found on the central element of synaptonemal complexes. There is correlative evidence that strongly indicates recombination nodules are located at the sites of crossing-over in late pachytene. Using spreads of synaptonemal complexes stained with uranyl acetate – lead citrate, we determined that the frequency of recombination nodules was 1/57.2 μm of synaptonemal complex. Using separate silver-stained spreads of synaptonemal complexes from lily microsporocytes, we determined that the average length of a complete set of pachytene synaptonemal complexes was 3149 ± 668 μm. Therefore, an average set of synaptonemal complexes would have 55.1 (3149 ÷ 57.2) recombination nodules, a number that closely matches the average number of chiasmata in a set of late diplotene bivalents.Key words: chiasmata, recombination nodules, synaptonemal complex, Lilium longiflorum.

Synaptonemal complex spreading in Allium cepa and Allium fistulosum. II. Pachytene observations: the SC karyotype and the correspondence of late recombination nodules and chiasmata

Genome ◽  
1988 ◽  
Vol 30 (3) ◽  
pp. 399-410 ◽  
Author(s):  
S. M. Albini ◽  
G. H. Jones
Keyword(s):  
Synaptonemal Complex ◽  
Allium Cepa ◽  
Positional Distribution ◽  
Allium Fistulosum ◽  
Dna Amount ◽  
Closely Related Species ◽  
Synaptonemal Complexes ◽  
Recombination Nodules ◽  
Surface Spreading ◽  
Metaphase I

Pachytene synaptonemal complexes and recombination nodules were analysed, by surface spreading, in the closely related species Allium fistulosum and Allium cepa (both 2n = 16), which show highly contrasting patterns of chiasma distribution. Pachytene observations show that all eight pairs of homologues are fully paired in both species, despite the pronounced localisation of chiasmata in A. fistulosum. Synaptonemal complex karyotype analysis reveals similar marker complexes in both species. These are presumed homoeologues, which, possibly due to the uneven distribution of the higher DNA amount found in A. cepa, rank in slightly different positions in the two karyotypes. Darkly staining ellipsoidal late recombination nodules were observed associated with PTA stained pachytene synaptonemal complexes. The positional distribution of late recombination nodules along synaptonemal complexes corresponds almost exactly to the distribution of chiasmata along metaphase I bivalents in the two species. These observations strongly support the proposal that late recombination nodules are involved in reciprocal meiotic recombination. The frequencies of late recombination nodules at pachytene showed deficits (30% in A. fistulosum, 70% in A. cepa) compared to metaphase I chiasma frequencies. It is suggested that the greater deficit of late recombination nodules in A. fistulosum could be related to a longer duration of meiosis in this species resulting from its greater genomic DNA content.Key words: synaptonemal complex, recombination nodules, Allium.

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