Abstract：
:During meiotic prophase in the ciliate Tetrahymena thermophila micronuclei dramatically elongate and form thread-like crescents. The arrangement of the chromosomes within the crescent as well as the timing of chromosome pairing and recombination with respect to the elongation process have been subjects of ongoing debate. Here, we addressed these issues by means of fluorescence in situ hybridization, labeling of individual chromosomes by BrdU (BrdU-painting) and by immunostaining of the recombination protein, Rad51. BrdU-painting indicated that chromosomes are arranged as parallel bundles within the crescent, and telomere-directed fluorescent in situ hybridization (FISH) revealed that most if not all telomeres are assembled near one end of the developing crescent. Prior to full crescent formation, Rad51 localizes to chromatin as numerous foci. Locus-specific FISH demonstrated that close pairing of homologues only occurs in the full crescent. Meiotic DNA double-strand break formation and the initiation of recombination thus seem to precede close pairing. A synaptonemal complex was not detected. We conclude that the chromosomes adopt a polarized arrangement within the crescent, probably resembling the classical bouquet arrangement. Furthermore, we propose that the elongated shape of meiotic micronuclei promotes the parallel arrangement of chromosomes and supports the juxtaposition of homologous regions in the absence of a synaptonemal complex. Several pieces of evidence indicate the presence of one to four chiasmata per bivalent, which would call for crossover interference to explain regular bivalent formation in spite of this low mean number. Tetrahymena might, therefore, pose a case of interference in the absence of a synaptonemal complex.
journal_name
J Cell Scijournal_title
Journal of cell scienceauthors
Loidl J,Scherthan Hdoi
10.1242/jcs.01504keywords:
subject
Has Abstractpub_date
2004-11-15 00:00:00pages
5791-801issue
Pt 24eissn
0021-9533issn
1477-9137pii
jcs.01504journal_volume
117pub_type
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journal_title：Journal of cell science
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更新日期：2008-11-15 00:00:00
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journal_title：Journal of cell science
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doi：
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更新日期：2016-05-01 00:00:00
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