Increased ploidy and KAR3 and SIR3 disruption alter the dynamics of meiotic chromosomes and telomeres.
We investigated the sequence of chromosomal events during meiotic prophase in haploid, diploid and autotetraploid SK1 strains of Saccharomyces cerevisiae. Using molecular cytology, we found that meiosis-specific nuclear topology (i.e. dissolution of centromere clustering, bouquet formation and meiotic divisions) are significantly delayed in polyploid SK1 meiosis. Thus, and in contrast to the situation in plants, an increase in ploidy extends prophase I in budding yeast. Moreover, we found that bouquet formation also occurs in haploid and diploid SK1 meiosis deficient in the telomeric heterochromatin protein Sir3p. Diploid sir3Delta SK1 meiosis showed pleiotropic defects such as delayed centromere cluster resolution in a proportion of cells and impeded downstream events (i.e. bouquet formation, homologue pairing and meiotic divisions). Meiotic telomere clustering occurred in diploid and haploid sir3Delta strains. Using the haploid system, we further show that a bouquet forms at the kar3Delta SPB. Comparison of the expression of meiosis-specific Ndj1p-HA and Zip1p in haploid control and kar3Delta time courses revealed that fewer cells enter the meiotic cycle in absence of Kar3p. Elevated frequencies of bouquets in kar3Delta haploid meiosis suggest a role for Kar3p in regulation of telomere dynamics.
Max-Planck-Institute for Molecular Genetics, Ihnestrasse 73, D-14195 Berlin, Germany.
Edgar
E
Trelles-Sticken
Josef
J
Loidl
Harry
H
Scherthan
D018797:Cell Cycle Proteins / Q000235:genetics; D002503:Centromere / Q000235:genetics; D023902:Chromosome Pairing / Q000235:genetics; D004171:Diploidy; D005854:Germ Cells / Q000378:metabolism; D006238:Haploidy; D008540:Meiosis / Q000235:genetics*; D008869:Microtubule-Associated Proteins / Q000172:deficiency / Q000235:genetics*; D009687:Nuclear Proteins; D011003:Ploidies; D011418:Prophase / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics*; D016615:Telomere / Q000235:genetics*
D018797:Cell Cycle Proteins; C063504:KAR3 protein, S cerevisiae; D008869:Microtubule-Associated Proteins; C433703:Ndj1 protein, S cerevisiae; D009687:Nuclear Proteins; C084122:SIR3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; C090118:Zip1 protein, S cerevisiae