Synaptonemal complex formation in pollen mother cells of Tradescantia

Hasenkampf, Clare A.

doi:10.1007/bf00287035

Cited by 55 publications

(36 citation statements)

References 27 publications

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“…These changes correlate with changes in chromosome movements, which at the beginning ofzygotene are extensive but cease at pachytene (63). A reasonable hypothesis accounting for these findings could be that synaptonemal complex formation is entirely unspecific (17), its assembly being triggered in any region of alignment which has been maintained for a sufficient length of time. As a stable alignment at early zygotene with its vigorous movements is only possible in the presence of a high degree of homology between the aligned segments, synapsis will be specific while a stable alignment can occur between regions of low homology provided the chromosomes do not move.…”

Section: Specificity Of Synapsismentioning

confidence: 87%

The effect of chromosome 5B on synapsis and chiasma formation in wheat, triticum aestivum cv. Chinese Spring

Holm

Wang

1988

Carlsberg Res. Commun.

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The present paper summarizes and discusses the results obtained from a series of ultrastructural investigations of the effect of chromosome 5B on chromosome pairing and synaptonemal complex formation in wheat, T. aestivum cv. Chinese Spring. The material comprises hexaploid wheat nullisomic for chromosome 5B, monosomic for 5B, euploid wheat, wheat where chromosomes 5B have been replaced by one, two or three copies of an isochromosome for the long arm of chromosome 5B; trihaploid wheat with and without 5B and hybrids between Chinese Spring wheat and diploid rye with chromosome 5B, without 5B or carrying an isochromosome for the long arm of 5B. It is shown that nullisomy for chromosome 5B in hexaploid wheat results in a two-to threefold increase in the number of lateral components in multiple associations already from the beginning of zygotene and in trihaploid wheat and wheat-rye hybrids in a two-to threefold increase in the number of pairing partner exchanges per lateral component involved in synapsis. Only nullisomy for chromosome 5B and triisosomy for the long arm of chromosome 5B permit crossing over between the homoeologous chromosomes of wheat. It is inferred that the product of the Ph locus on chromosome 5B affects both synapsis and crossing over. As these timewise separated processes are assumed both to be initiated by heteroduplex formation, this might provide the common link in the action of the Ph gene. The results obtained with the genotypes containing different dosage of the Ph gene disprove both the hypothesis that Ph influences a premeiotic chromosome rearrangement (t 3, 14, 15) and the hypothesis (18, 82) that Ph controls the timing of crossing over with respect to the process of correction of multiple pairing associations.

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Section: Specificity Of Synapsismentioning

confidence: 87%

The effect of chromosome 5B on synapsis and chiasma formation in wheat, triticum aestivum cv. Chinese Spring

Holm

Wang

1988

Carlsberg Res. Commun.

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“…It is also clear that this is not the only mechanism, however. For example, plants with very long chromosomes have more SC initiation sites than crossovers (45,46); SC initiation sites without associated recombination nodules are observed near telomeres in S. macrospora (29); SC formation can occur in spo11 mutants in mice, albeit between nonhomologous chromosomes (14,15); and SC formation occurs normally in the absence of recombination in a number of organisms (see Introduction).…”

Section: Discussionmentioning

confidence: 99%

Tying synaptonemal complex initiation to the formation and programmed repair of DNA double-strand breaks

Henderson

Keeney

2004

Proc. Natl. Acad. Sci. U.S.A.

140

152

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During meiosis, homologous chromosomes recombine and become closely apposed along their lengths within the synaptonemal complex (SC). In part because Spo11 is required both to make the double-strand breaks (DSBs) that initiate recombination and to promote normal SC formation in many organisms, it is clear that these two processes are intimately coupled. The molecular nature of this linkage is not well understood, but it has been proposed that SC formation initiates locally at the sites of ongoing recombination and in particular at the subset of sites that will eventually give rise to crossovers. To test this hypothesis, we examined further the relationship between DSBs and SC formation in Saccharomyces cerevisiae. SCs were monitored in a series of spo11 missense mutants with varying DSB frequencies. Alleles that blocked DSB formation gave SC phenotypes indistinguishable from a deletion mutant, and partial loss-of-function mutations with progressively more severe DSB defects caused corresponding defects in SC formation. These results strongly correlate SC formation with Spo11 catalytic activity per se. Numbers of Zip3 complexes on chromosomes, thought to represent the sites of SC initiation, also declined when Spo11 activity decreased, but in a markedly nonlinear fashion: hypomorphic spo11 alleles caused larger defects in DSB formation than in Zip3 complex formation. This nonlinear response of Zip3 closely paralleled the response of crossover recombination products. The quantitative relationship between Zip3 foci, SC formation, and crossing over strongly implicates crossover-designated recombination intermediates as the sites of SC initiation.T wo prominent features of meiotic prophase are homologous recombination and formation of the synaptonemal complex (SC). Recombination establishes physical connections between homologous chromosomes in the form of crossovers, which help orient chromosomes properly on the meiosis I spindle. The widely conserved SC connects homologous chromosomes along their lengths during a portion of meiotic prophase and consists of two lateral elements, each formed along the axis connecting a pair of sister chromatids, and a central element linking the lateral elements together (reviewed in refs. 1 and 2).Chromosome synapsis is tightly coupled to homologous recombination in many organisms. The DNA double-strand breaks (DSBs) that initiate recombination occur before synapsis begins in budding yeast (3), and cytological features (e.g., histone H2AX phosphorylation and formation of strand exchange protein complexes) indicate that the same is true in other fungi, higher plants, and mammals (4-8). DSBs are created by the Spo11 protein (9, 10), and spo11 null mutants in many organisms are defective for SC formation (11-16). In some cases, exogenous DSBs can at least partially substitute for Spo11 in SC formation (15)(16)(17). Moreover, mutations that block processing of DSBs once they are formed (e.g., rad50S, dmc1) also cause defects in SC formation (18)(19)(20). These results place Spo11 action...

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“…For these reasons the maceration, swelling and fixation was performed at 0-4 ~ and high EDTA concentrations were used to inhibit nucleases. The brief post fixation with glutaraldehyde during washing was performed to stabilize the nuclei further before air drying and the inclusion of Ficoll in the washing medium has been reported to protect the nuclei during drying (25,47). Altogether these precautions appeared to reduce the frequency of lateral component breakage.…”

Section: The Spreading Proceduresmentioning

confidence: 99%

Chromosome pairing and chiasma formation in allohexaploid wheat, Triticum aestivum analyzed by spreading of meiotic nuclei

Holm

1986

Carlsberg Res. Commun.

133

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An ultrastructural analysis of spread, silver stained meiotic nuclei of wheat, Triticum aestivum, has been performed. Partial tracings of lateral components and synaptonemal complexes of a number ofleptotene and early zygotene nuclei, and complete tracings of eleven mid zygotene, seven late zygotene, twenty pachytene, twelve early diplotene, twenty-one mid diplotene and sixteen late diplotene nuclei have permitted the following observations and conclusions: 1) The chromosomes appear to be randomly distributed within the spread leptotene and early zygotene nuclei. 2) The complement length, i.e., the lateral component length of the three genomes, decreases from a mean of 2063 Ixm at mid zygotene to 1806 ~tm at late zygotene and 1474 ~tm at pachytene. 3) Chromosome pairing is initiated preferentially from the telomeres. These are aggregated during zygotene whereby a chromosome bouquet is established. Synaptonemal complex formation is thereafter also initiated interstitially, the mean number of synaptonemal complex segments being 156 per nucleus in the eleven mid zygotene nuclei where on the average 61% of the complement is paired. 4) Chromosome pairing and synaptonemal complex formation remain frequently incomplete. In most cases, however, more than 95% of the complement has synapsed. 5) Interlocking of lateral components and synaptonemal complexes is frequent at zygotene. Detailed analysis of one mid zygotene nucleus revealed more than 20 intedockings, most of them being bivalent interlockings. At late zygotene there was a mean of 5 bivalent intedockings per nucleus and a few chromosome intedockings. Some interlockings persist up to pachytene and a few may remain into diplotene. 6) Multiple associations of chromosomes, probably signifying pairing between homoeologues, are seen in eight of the eleven mid zygotene nuclei, in four of the seven late zygotene nuclei, in three of the 20 pachytene nuclei and possibly in one of the early diplotene nuclei. 7) Synaptonemal complex degradation is initiated at a limited number of sites at the pachytene to diplotene transition, the number of retained synaptonemal complex segments amounting to 89, 119 and 136 at early, mid and late diplotene. This exceeds thb number of chiasmata observable at metaphase I in the light microscope by a factor of two to three. 8) It is proposed that the diploid behaviour ofallohexaploid wheat results from: I) A high stringency of chromosome pairing at the beginning of zygotene whereby pairing preferentially is initiated between homologues. II) Transformation of multiple association into bivalents at the end of zygotene and during pachytene before crossing over occurs and/or III) a suppression of crossing over between paired segments of homoeologous chromosomes. The possible effect of the Ph gene(s) on the long arm of chromosome 5B is discussed.

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Synaptonemal complex formation in pollen mother cells of Tradescantia

Cited by 55 publications

References 27 publications

The effect of chromosome 5B on synapsis and chiasma formation in wheat, triticum aestivum cv. Chinese Spring

The effect of chromosome 5B on synapsis and chiasma formation in wheat, triticum aestivum cv. Chinese Spring

Tying synaptonemal complex initiation to the formation and programmed repair of DNA double-strand breaks

Chromosome pairing and chiasma formation in allohexaploid wheat, Triticum aestivum analyzed by spreading of meiotic nuclei

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