Recombination nodules and synaptonemal complex in recombination-defective females of Drosophila melanogaster

Chromosoma ◽  
1979 ◽  
Vol 75 (3) ◽  
pp. 259-292 ◽  
Author(s):  
Adelaide T. C. Carpenter
Keyword(s):  
Drosophila Melanogaster ◽  
Synaptonemal Complex ◽  
Recombination Nodules

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.

Are there morphologically abnormal early recombination nodules in the Drosophila melanogaster meiotic mutant mei-218?

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 74-80 ◽  
Author(s):  
Adelaide T. C. Carpenter
Keyword(s):  
Drosophila Melanogaster ◽  
Synaptonemal Complex ◽  
Gene Conversion ◽  
Meiotic Recombination ◽  
Cytological Study ◽  
Specific Probe ◽  
Definitive Answer ◽  
Recombination Nodules ◽  
Defective Mutant ◽  
Meiotic Crossover

Early recombination nodules have been suggested to perform a role in meiotic gene conversion recombination events. The meiotic recombination-defective mutant mei-218 greatly reduces the frequency of meiotic crossover (reciprocal) recombination events and reduces the number of late recombination nodules to the same extent. However, it does not reduce the frequency of simple gene conversion events, although they are abnormal in having shorter coconversion tracts than controls. The original cytological study yielded somewhat fewer early nodules in mei-218 than in controls, although very abnormal ones might have been missed. The present study failed to identify a mei-218 specific abnormal category. However, because recombination nodules are at present recognizable only by their morphology, a definitive answer to this question must await a specific probe for recombination nodules. Moreover, the possibility remains that early nodules in mei-218 are more ephemeral than are early nodules in wild type.Key words: synaptonemal complex, recombination nodules, meiotic mutants, Drosophila melanogaster.

Solitary and synaptonemal complex-associated recombination nodules in pro-nurse cells during oogenesis in Drosophila melanogaster

Chromosoma ◽  
1993 ◽  
Vol 102 (6) ◽  
pp. 396-402 ◽  
Author(s):  
Karin Schmekel ◽  
Jacob Wahrman ◽  
Bertil Daneholt
Keyword(s):  
Drosophila Melanogaster ◽  
Synaptonemal Complex ◽  
Nurse Cells ◽  
Recombination Nodules

Normal Synaptonemal Complex and Abnormal Recombination Nodules in Two Alleles of the Drosophila Meiotic Mutant mei-W68

Genetics ◽  
2003 ◽  
Vol 163 (4) ◽  
pp. 1337-1356 ◽  
Author(s):  
Adelaide T C Carpenter
Keyword(s):  
Electron Microscopy ◽  
Synaptonemal Complex ◽  
High Frequency ◽  
Serial Section ◽  
The Other ◽  
Wild Type ◽  
Recombination Nodules ◽  
Section Electron ◽  
Serial Section Electron Microscopy ◽  
Section Electron Microscopy

Abstract The meiotic phenotypes of two mutant alleles of the mei-W68 gene, 1 and L1, were studied by genetics and by serial-section electron microscopy. Despite no or reduced exchange, both mutant alleles have normal synaptonemal complex. However, neither has any early recombination nodules; instead, both exhibit high numbers of very long (up to 2 μm) structures here named “noodles.” These are hypothesized to be formed by the unchecked extension of identical but much shorter structures ephemerally seen in wild type, which may be precursors of early recombination nodules. Although the mei-W68L1 allele is identical to the mei-W681 allele in both the absence of early recombination nodules and a high frequency of noodles (i.e., it is amorphic for the noodle phene), it is hypomorphic in its effects on exchange and late recombination nodules. The differential effects of this allele on early and late recombination nodules are consistent with the hypothesis that Drosophila females have two separate recombination pathways—one for simple gene conversion, the other for exchange.

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 Synaptonemal complex-deficient Drosophila melanogaster females exhibit rare DSB repair events, recurrent copy number variation, and an increased rate of de novo transposable element movement

2019 ◽  
Author(s):  
Danny E. Miller
Keyword(s):  
Drosophila Melanogaster ◽  
Copy Number Variation ◽  
Transposable Element ◽  
Synaptonemal Complex ◽  
Copy Number ◽  
De Novo ◽  
Wild Type ◽  
Dsb Repair ◽  
Number Variation ◽  
Element Movement

ABSTRACTGenetic stability depends on the maintenance of a variety of chromosome structures and the precise repair of DNA breaks. During meiosis, programmed double-strand breaks (DSBs) made in prophase I are normally repaired as gene conversions or crossovers. Additionally, DSBs are made by the movement of transposable elements (TEs), which must also be resolved. Incorrect repair of these DNA lesions can lead to mutations, copy number variations, translocations, and/or aneuploid gametes. In Drosophila melanogaster, as in most organisms, meiotic DSB repair occurs in the presence of a rapidly evolving multiprotein structure called the synaptonemal complex (SC). Here, whole-genome sequencing is used to investigate the fate of meiotic DSBs in D. melanogaster mutant females lacking functional SC, to assay for de novo CNV formation, and to examine the role of the SC in transposable element movement in flies. The data indicate that, in the absence of SC, copy number variation still occurs but meiotic DSB repair by gene conversion may occur only rarely. Remarkably, an 856-kilobase de novo CNV was observed in two unrelated individuals of different genetic backgrounds and was identical to a CNV recovered in a previous wild-type study, suggesting that recurrent formation of large CNVs occurs in Drosophila. In addition, the rate of novel TE insertion was markedly higher than wild type in one of two SC mutants tested, suggesting that SC proteins may contribute to the regulation of TE movement and insertion in the genome. Overall, this study provides novel insight into the role that the SC plays in genome stability and provides clues as to why SC proteins are among the most rapidly evolving in any organism.

scholarly journals Crossover patterning through kinase-regulated condensation and coarsening of recombination nodules

2021 ◽  
Author(s):  
Liangyu Zhang ◽  
Weston Stauffer ◽  
David Zwicker ◽  
Abby F. Dernburg
Keyword(s):  
Synaptonemal Complex ◽  
Meiotic Recombination ◽  
Ring Domain ◽  
Homologous Chromosomes ◽  
Crossover Interference ◽  
C Elegans ◽  
Recombination Nodules

AbstractMeiotic recombination is highly regulated to ensure precise segregation of homologous chromosomes. Evidence from diverse organisms indicates that the synaptonemal complex (SC), which assembles between paired chromosomes, plays essential roles in crossover formation and patterning. Several additional “pro-crossover” proteins are also required for recombination intermediates to become crossovers. These typically form multiple foci or recombination nodules along SCs, and later accumulate at fewer, widely spaced sites. Here we report that in C. elegans CDK-2 is required to stabilize all crossover intermediates and stabilizes interactions among pro-crossover factors by phosphorylating MSH-5. Additionally, we show that the conserved RING domain proteins ZHP-3/4 diffuse along the SC and remain dynamic following their accumulation at recombination sites. Based on these and previous findings we propose a model in which recombination nodules arise through spatially restricted biomolecular condensation and then undergo a regulated coarsening process, resulting in crossover interference.

scholarly journals Synaptonemal Complex-Deficient Drosophila melanogaster Females Exhibit Rare DSB Repair Events, Recurrent Copy-Number Variation, and an Increased Rate of de Novo Transposable Element Movement

2019 ◽  
Vol 10 (2) ◽  
pp. 525-537 ◽  
Author(s):  
Danny E. Miller
Keyword(s):  
Drosophila Melanogaster ◽  
Copy Number Variation ◽  
Transposable Element ◽  
Synaptonemal Complex ◽  
Copy Number ◽  
De Novo ◽  
Wild Type ◽  
Dsb Repair ◽  
Number Variation ◽  
Element Movement

Genetic stability depends on the maintenance of a variety of chromosome structures and the precise repair of DNA breaks. During meiosis, programmed double-strand breaks (DSBs) made in prophase I are normally repaired as gene conversions or crossovers. DSBs can also be made by other mechanisms, such as the movement of transposable elements (TEs), which must also be resolved. Incorrect repair of these DNA lesions can lead to mutations, copy-number changes, translocations, and/or aneuploid gametes. In Drosophila melanogaster, as in most organisms, meiotic DSB repair occurs in the presence of a rapidly evolving multiprotein structure called the synaptonemal complex (SC). Here, whole-genome sequencing is used to investigate the fate of meiotic DSBs in D. melanogaster mutant females lacking functional SC, to assay for de novo CNV formation, and to examine the role of the SC in transposable element movement in flies. The data indicate that, in the absence of SC, copy-number variation still occurs and meiotic DSB repair by gene conversion occurs infrequently. Remarkably, an 856-kilobase de novo CNV was observed in two unrelated individuals of different genetic backgrounds and was identical to a CNV recovered in a previous wild-type study, suggesting that recurrent formation of large CNVs occurs in Drosophila. In addition, the rate of novel TE insertion was markedly higher than wild type in one of two SC mutants tested, suggesting that SC proteins may contribute to the regulation of TE movement and insertion in the genome. Overall, this study provides novel insight into the role that the SC plays in genome stability and provides clues as to why the sequence, but not structure, of SC proteins is rapidly evolving.

Two kinds of "recombination nodules" in Neurospora crassa

Genome ◽  
1989 ◽  
Vol 32 (2) ◽  
pp. 309-317 ◽  
Author(s):  
Maja Bojko
Keyword(s):  
Neurospora Crassa ◽  
Synaptonemal Complex ◽  
Nucleolus Organizer ◽  
Crossing Over ◽  
Dramatic Reduction ◽  
Recombination Nodules ◽  
Exchange Event ◽  
The Mean ◽  
Different Origin ◽  
Positive Interference

Two morphological types of recombination nodules, termed early and late, are recognized in Neurospora crassa. Eighty nuclei at different substages were used to determine numbers of nodules per nucleus, distribution of nodules along the nucleolus-organizing chromosome, and distribution of nodules among the two largest chromosomes. Early nodules appear at the synaptonemal complex at early zygotene and increase in number during zygotene until a dramatic reduction occurs at zygotene – pachytene transition. Thereafter early nodules are steadily eliminated until they disappear by diplotene. Late nodules are also present during zygotene. Their number doubles at the zygotene – pachytene transition and stays at this level until diplotene. The total number of nodules is rather constant through zygotene and pachytene. Distribution of bivalents with 0, 1, 2, etc. nodules follows a Poisson distribution at zygotene, but not at pachytene, where variance is less than the mean, indicating positive interference. Nodules are distributed nonrandomly along the nucleolus-organizer bivalent. The pattern differs slightly in nuclei of different origin. Nuclei with unusual synaptonemal complexes sustain normal levels of recombination by having the same amount of nodules as normal nuclei. In abnormal nuclei nodules are preferentially associated with normal segments. It is proposed that early nodules do not participate in any form of recombination but have a role in finding an appropriate site for a crossing-over event. Morphological change to the late type indicates that the site has been reached and the exchange event can be mediated by the late nodule.Key words: recombination nodules, Neurospora crassa, synaptonemal complex.

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