scholarly journals Three-dimensional Ultrastructure of Saccharomyces cerevisiae Meiotic Spindles

2005 ◽  
Vol 16 (3) ◽  
pp. 1178-1188 ◽  
Author(s):  
Mark Winey ◽  
Garry P. Morgan ◽  
Paul D. Straight ◽  
Thomas H. Giddings ◽  
David N. Mastronarde
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Chromosome ◽  
Three Dimensional ◽  
Structural Basis ◽  
Mitotic Spindles ◽  
Yeast Saccharomyces Cerevisiae ◽  
Homologous Chromosomes ◽  
Sister Chromatids ◽  
Single Nucleus ◽  
Meiotic Spindles

Meiotic chromosome segregation leads to the production of haploid germ cells. During meiosis I (MI), the paired homologous chromosomes are separated. Meiosis II (MII) segregation leads to the separation of paired sister chromatids. In the budding yeast Saccharomyces cerevisiae, both of these divisions take place in a single nucleus, giving rise to the four-spored ascus. We have modeled the microtubules in 20 MI and 15 MII spindles by using reconstruction from electron micrographs of serially sectioned meiotic cells. Meiotic spindles contain more microtubules than their mitotic counterparts, with the highest number in MI spindles. It is possible to differentiate between MI versus MII spindles based on microtubule numbers and organization. Similar to mitotic spindles, kinetochores in either MI or MII are attached by a single microtubule. The models indicate that the kinetochores of paired homologous chromosomes in MI or sister chromatids in MII are separated at metaphase, similar to mitotic cells. Examination of both MI and MII spindles reveals that anaphase A likely occurs in addition to anaphase B and that these movements are concurrent. This analysis offers a structural basis for considering meiotic segregation in yeast and for the analysis of mutants defective in this process.

scholarly journals Three-dimensional ultrastructural analysis of the Saccharomyces cerevisiae mitotic spindle.

1995 ◽  
Vol 129 (6) ◽  
pp. 1601-1615 ◽  
Author(s):  
M Winey ◽  
C L Mamay ◽  
E T O'Toole ◽  
D N Mastronarde ◽  
T H Giddings ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitotic Spindle ◽  
Mother Cell ◽  
Early Stage ◽  
Three Dimensional ◽  
The Other ◽  
Mitotic Spindles ◽  
Yeast Saccharomyces Cerevisiae ◽  
Computer Aided ◽  
Anaphase B

The three dimensional organization of microtubules in mitotic spindles of the yeast Saccharomyces cerevisiae has been determined by computer-aided reconstruction from electron micrographs of serially cross-sectioned spindles. Fifteen spindles ranging in length from 0.6-9.4 microns have been analyzed. Ordered microtubule packing is absent in spindles up to 0.8 micron, but the total number of microtubules is sufficient to allow one microtubule per kinetochore with a few additional microtubules that may form an interpolar spindle. An obvious bundle of about eight interpolar microtubules was found in spindles 1.3-1.6 microns long, and we suggest that the approximately 32 remaining microtubules act as kinetochore fibers. The relative lengths of the microtubules in these spindles suggest that they may be in an early stage of anaphase, even though these spindles are all situated in the mother cell, not in the isthmus between mother and bud. None of the reconstructed spindles exhibited the uniform populations of kinetochore microtubules characteristic of metaphase. Long spindles (2.7-9.4 microns), presumably in anaphase B, contained short remnants of a few presumed kinetochore microtubules clustered near the poles and a few long microtubules extending from each pole toward the spindle midplane, where they interdigitated with their counterparts from the other pole. Interpretation of these reconstructed spindles offers some insights into the mechanisms of mitosis in this yeast.

scholarly journals Shugoshin Promotes Sister Kinetochore Biorientation in Saccharomyces cerevisiae

2008 ◽  
Vol 19 (3) ◽  
pp. 1199-1209 ◽  
Author(s):  
Brendan M. Kiburz ◽  
Angelika Amon ◽  
Adele L. Marston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Segregation ◽  
Minor Role ◽  
Meiotic Cell ◽  
Homologous Chromosomes ◽  
Cell Divisions ◽  
Sister Chromatids ◽  
Sister Kinetochore ◽  
A Minor ◽  
Meiosis I

Chromosome segregation must be executed accurately during both mitotic and meiotic cell divisions. Sgo1 plays a key role in ensuring faithful chromosome segregation in at least two ways. During meiosis this protein regulates the removal of cohesins, the proteins that hold sister chromatids together, from chromosomes. During mitosis, Sgo1 is required for sensing the absence of tension caused by sister kinetochores not being attached to microtubules emanating from opposite poles. Here we describe a differential requirement for Sgo1 in the segregation of homologous chromosomes and sister chromatids. Sgo1 plays only a minor role in segregating homologous chromosomes at meiosis I. In contrast, Sgo1 is important to bias sister kinetochores toward biorientation. We suggest that Sgo1 acts at sister kinetochores to promote their biorientation.

scholarly journals Absence of microtubule sliding and an analysis of spindle formation and elongation in isolated mitotic spindles from the yeast Saccharomyces cerevisiae.

1982 ◽  
Vol 94 (2) ◽  
pp. 341-349 ◽  
Author(s):  
S M King ◽  
J S Hyams ◽  
A Luba
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Mitotic Spindles ◽  
Microtubule Organization ◽  
Yeast Saccharomyces Cerevisiae ◽  
Spindle Formation ◽  
Detailed Model ◽  
Thin Sections ◽  
Gold Thioglucose

Mitotic spindles were isolated from a cell division cycle mutant of the budding yeast Saccharomyces cerevisiae by the lysis of sphateroplasts on an air:buffer interface and were negatively stained with 1% gold thioglucose. Isolated spindles were incubated under conditions which promoted the sliding disintegration of parallel preparations of Tetrahymena axonemes, namely the addition of ATP to 20 microM. In no experiment was a corresponding change in microtubule organization of the spindle observed even when spindles were first pretreated with either 1-10 microgram/ml trypsin or 0.2-2% Triton X-100. During these experiments a number of spindles were isolated from cells that had passed through the imposed temperature block, and from the images obtained a detailed model of spindle formation and elongation has been constructed. Two sets of microtubules, one from each spindle pole body (SPB), completely interdigitate to form a continuous bundle, and a series of discontinuous microtubules are then nucleated by each SPB. As the spindle elongates, the number of microtubules continuous between the two SPBs decreases until, at a length of 4 micrometer, only one remains. The spindle, composed of only one microtubule, continues to elongate until it reaches the maximal nuclear dimension of 8 micrometer. The data obtained from negatively stained preparations have been verified in thin sections of wild-type cells. We suggest that, as in the later stages of mitosis only one microtubule is involved in the separation of the spindle poles, the microtubular spindle in S. cerevisiae is not a force-generating system but rather acts as a regulatory mechanism controlling the rate of separation.

scholarly journals Genetic Interactions Between HOP1, RED1 and MEK1 Suggest That MEK1 Regulates Assembly of Axial Element Components During Meiosis in the Yeast Saccharomyces cerevisiae

Genetics ◽  
1997 ◽  
Vol 147 (1) ◽  
pp. 33-42 ◽  
Author(s):  
Nancy M Hollingsworth ◽  
Lisa Ponte
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Genetic Interactions ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Sister Chromatids ◽  
Cytological Data ◽  
Negative Effect ◽  
Two Hybrid ◽  
Axial Element ◽  
Putative Protein Kinase

Abstract During meiosis, axial elements are generated by the condensation of sister chromatids along a protein core as precursors to the formation of the synaptonemal complex (X). Functional axial elements are essential for wild-type levels of recombination and proper reductional segregation at meiosis I. Genetic and cytological data suggest that three meiosis-specific genes, HOP1, RED1 and MEK1, are involved in axial element formation in the yeast Saccharomyces cerevisiae. HOP1 and RED1 encode structural components of axial elements while MEK1 encodes a putative protein kinase. Using a partially functional allele of MEK1, new genetic interactions have been found between HOP1, RED1 and MEK1. Overexpression of HOP1 partially suppresses the spore inviability and recombination defects of mekl-974; in contrast, overexpression of RED1 exacerbates the mek1-974 spore inviability. Co-overexpression of HOP1 and RED1 in mek1-974 diploids alleviates the negative effect of overexpressing RED1 alone. Red1p/Red1p as well as Hop1p/Red1p interactions have been reconstituted in two hybrid experiments. Our results suggest a model whereby Mekl kinase activity controls axial element assembly by regulating the affinity with which Hoplp and Redlp interact with each other.

scholarly journals Meiotic chromosome pairing in triploid and tetraploid Saccharomyces cerevisiae.

Genetics ◽  
1995 ◽  
Vol 139 (4) ◽  
pp. 1511-1520 ◽  
Author(s):  
J Loidl
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Complex Formation ◽  
Chromosome Segregation ◽  
Chromosome Pairing ◽  
Meiotic Chromosome ◽  
Low Frequency ◽  
Spore Viability ◽  
Homologous Chromosomes ◽  
Meiotic Chromosome Pairing ◽  
Synaptonemal Complex Formation

Abstract Meiotic chromosome pairing in isogenic triploid and tetraploid strains of yeast and the consequences of polyploidy on meiotic chromosome segregation are studied. Synaptonemal complex formation at pachytene was found to be different in the triploid and in the tetraploid. In the triploid, triple-synapsis, that is, the connection of three homologues at a given site, is common. It can even extend all the way along the chromosomes. In the tetraploid, homologous chromosomes mostly come in pairs of synapsed bivalents. Multiple synapsis, that is, synapsis of more than two homologues in one and the same region, was virtually absent in the tetraploid. About five quadrivalents per cell occurred due to the switching of pairing partners. From the frequency of pairing partner switches it can be deduced that in most chromosomes synapsis is initiated primarily at one end, occasionally at both ends and rarely at an additional intercalary position. In contrast to a considerably reduced spore viability (approximately 40%) in the triploid, spore viability is only mildly affected in the tetraploid. The good spore viability is presumably due to the low frequency of quadrivalents and to the highly regular 2:2 segregation of the few quadrivalents that do occur. Occasionally, however, quadrivalents appear to be subject to 3:1 nondisjunction that leads to spore death in the second generation.

scholarly journals Measurements of excision repair tracts formed during meiotic recombination in Saccharomyces cerevisiae

1992 ◽  
Vol 12 (4) ◽  
pp. 1805-1814
Author(s):  
P Detloff ◽  
T D Petes
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Recombination ◽  
High Frequency ◽  
Excision Repair ◽  
Yeast Saccharomyces Cerevisiae ◽  
Heteroduplex Dna ◽  
Homologous Chromosomes ◽  
His4 Gene

During meiotic recombination in the yeast Saccharomyces cerevisiae, heteroduplexes are formed at a high frequency between HIS4 genes located on homologous chromosomes. Using mutant alleles of the HIS4 gene that result in poorly repaired mismatches in heteroduplex DNA, we find that heteroduplexes often span a distance of 1.8 kb. In addition, we show that about one-third of the repair tracts initiated at well-repaired mismatches extend 900 bp.

scholarly journals Repair of specific base pair mismatches formed during meiotic recombination in the yeast Saccharomyces cerevisiae

1991 ◽  
Vol 11 (2) ◽  
pp. 737-745
Author(s):  
P Detloff ◽  
J Sieber ◽  
T D Petes
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Base Pair ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Homologous Chromosomes ◽  
Base Pair Mismatch ◽  
Dna Strands ◽  
Postmeiotic Segregation ◽  
Mutant Genes ◽  
His4 Gene

Heteroduplexes formed between DNA strands derived from different homologous chromosomes are an intermediate in meiotic crossing over in the yeast Saccharomyces cerevisiae and other eucaryotes. A heteroduplex formed between wild-type and mutant genes will contain a base pair mismatch; failure to repair this mismatch will lead to postmeiotic segregation (PMS). By analyzing the frequency of PMS for various mutant alleles in the yeast HIS4 gene, we showed that C/C mismatches were inefficiently repaired relative to all other point mismatches. These other mismatches (G/G, G/A, T/T, A/A, T/C, C/A, A/A, and T/G) were repaired with approximately the same efficiency. We found that in spores with unrepaired mismatches in heteroduplexes, the nontranscribed strand of the HIS4 gene was more frequently donated than the transcribed strand. In addition, the direction of repair for certain mismatches was nonrandom.

scholarly journals An autonomous meiosis-specific region of yeast Nup2 (hNup50) promotes normal meiotic chromosome dynamics in Saccharomyces cerevisiae

2016 ◽  
Author(s):  
Daniel B. Chu ◽  
Sean M. Burgess
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Chromosome ◽  
Diploid Parent ◽  
Homologous Chromosomes ◽  
Chromosome Dynamics ◽  
Amino Acid Region ◽  
Cell Extracts ◽  
Pulling Forces ◽  
Dividing Cells ◽  
Necessary And Sufficient

ABSTRACTMeiosis is a specialized cellular program required to create haploid gametes from diploid parent cells. Prior to the first meiotic division, homologous chromosomes pair, synapse, and recombine to ensure their proper disjunction at anaphase I. Additionally, telomeres tethered at the nuclear envelope cluster in the bouquet configuration where they are subjected to dramatic pulling forces acting from outside of the nucleus. In Saccharomyces cerevisiae, the telomere-associated protein Ndj1 is required for bouquet formation. When Ndj1 is absent, these dramatic motions cease and multiple steps of meiosis I prophase progression are delayed. Here we identified Nup2 in a pool of enriched proteins that co-purify with tagged Ndj1 from meiotic cell extracts. Nup2 is a nonessential nucleoporin that functions in nuclear transport, boundary activity, and telomere silencing in mitotically dividing cells. We found that deletion of NUP2 delayed pairing and synapsis during meiosis, and led to decreased spore viability, similar to the ndj1Δ mutant phenotype. Surprisingly, the nup2Δ ndj1Δ double mutant failed to segregate chromosomes, even though the meiotic program continued. These results suggest that a physical impediment to nuclear division is created in the absence of Nup2 and Ndj1. Our deletion analysis of NUP2 identified a previously uncharacterized 125-amino acid region that is both necessary and sufficient to complement all of nup2Δ’s meiotic phenotypes, which we call the meiotic autonomous region (MAR). We propose that Ndj1 and Nup2 function in parallel pathways to promote the dynamic chromosome events of meiotic chromosome dynamics, perhaps through the establishment or maintenance of higher-order chromosome organization.

Chromosomal assignment of mutations by specific chromosome loss in the yeast Saccharomyces cerevisiae.

Genetics ◽  
1990 ◽  
Vol 125 (2) ◽  
pp. 333-340 ◽  
Author(s):  
L P Wakem ◽  
F Sherman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasmid Dna ◽  
High Frequency ◽  
Recessive Mutation ◽  
Chromosomal Assignment ◽  
Chromosome Loss ◽  
Specific Chromosome ◽  
Yeast Saccharomyces Cerevisiae ◽  
Homologous Chromosomes

Abstract Yeast 2-microns plasmids were integrated near the centromere of a different chromosome in each of 16 cir0 mapping strains of Saccharomyces cerevisiae. The specific chromosomes containing the integrated 2-microns plasmid DNA were lost at a high frequency after crossing the cir0 strains to cir+ strains. A recessive mutation in a cir+ strain can then be easily assigned to its chromosome using this set of mapping strains, since the phenotype of the recessive mutation will be manifested only in diploids having the integrated 2-microns plasmid and the unmapped mutation on homologous chromosomes.

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