J. Bahler et al., UNUSUAL NUCLEAR-STRUCTURES IN MEIOTIC PROPHASE OF FISSION YEAST - A CYTOLOGICAL ANALYSIS, The Journal of cell biology, 121(2), 1993, pp. 241-256
Earlier results from sectioned nuclei indicating that Schizosaccharomy
ces pombe does not develop a classical tripartite synaptonemal complex
(SC) during meiotic prophase are confirmed by spreading of whole nucl
ei. The linear elements appearing during prophase I resemble the axial
cores (SC precursors) of other organisms. The number of linear elemen
ts in haploid, diploid, and tetraploid strains is always higher than t
he chromosome number, implying that they are not formed continuously a
long the chromosomes. Time course experiments reveal that the elements
appear after DNA replication and form networks and bundles. Later the
y separate and approximately 24 individual elements with a total lengt
h of 34 mum are observed before degradation and meiotic divisions. Par
allel staining of DNA reveals changes in nuclear shape during meiotic
prophase. Strains with a mei4 mutation are blocked at a late prophase
stage. In serial sections we additionally observed a constant arrangem
ent of the spindle pole body, the nucleolus, and the presumptive centr
omere cluster. Thus, S. pombe manages to recombine and segregate its c
hromosomes without SC. This might correlate with the absence of crosso
ver interference. We propose a mechanism for chromosome pairing with i
nitial recognition of the homologs at the centromeres and suggest func
tions of the linear elements in preparation of the chromosomes for mei
osis I disjunction. With the spreading technique combined genetic, mol
ecular, and cytological approaches become feasible in S. pombe. This p
rovides an opportunity to study essential meiotic functions in the abs
ence of SCs which may help to clarify the significance of the SC and i
ts components for meiotic chromosome structure and function.