Asynaptic meiosis in fission yeast?

Abstract

Meiotic prophase has been studied by both light and electron microscopy in diploid cell lines (h+/h‐) of Schizosaccharomyces pombe. One wild‐type and one mutant strain were used, the latter (mei4‐B2) being blocked after premeiotic DNA synthesis and after commitment to meiosis. Meiosis and sporulation were induced in liquid culture by a shift to a sporulation medium devoid of a nitrogen source. The time course was determined from light‐microscopic preparations; most cells passing through meiotic prophase between 5 and 8 h after the shift. In samples from that interval, ca. 20% of the nuclei were elongate in shape, containing strands of chromatin in rough alignement with the long axis of the nucleus. This stage was found to accumulate in the mutant. A bundle of microtubules, just outside of the spindle plaque, apparently stabilized the elongated shape of the nuclei. Linear electron‐dense structures were observed to populate these nuclei. They resembled unpaired lateral elements of synaptonemal complexes in other organisms. Yet, at no times did we observe a tripartite complex or any other sign of chromosomal pairing in our material.

A large gene family in fission yeast encodes spore killers that subvert Mendel’s law

“…Four-spored asci represented about half of the cells 10 hr after shifting to SSL-N (Olson et al, 1978). Electron microscopy was performed as described (Sun et al, 2013).…”

Chromosome pairing and synapsis during Caenorhabditis elegans meiosis

“…In C. elegans , where there is normally only one CO per chromosome pair, the inhibitory effect acts robustly over the entire length of each chromosome [14, 68]. The SC was long considered a prime candidate to mediate CO interference, based on the absence of interference in some budding yeast mutants lacking SC [69], and on phylogenetic correlations: the fungi A. nidulans and S. pombe lack both SCs and CO interference [70, 71]. Evidence of non-random distribution of synapsis initiation sites in budding yeast mutants lacking SCs seems to negate this idea [72], but the debate about the role of the SC in crossover regulation is far from resolved [18].…”

SUMOylation is required for normal development of linear elements and wild-type meiotic recombination in Schizosaccharomyces pombe

“…Instead, thin thread-like structures, the so-called linear elements (LinEs) are present at the corresponding stages of meiosis (Olson et al 1978;Hirata and Tanaka 1982;Bähler et al 1993). LinEs are not continuous along chromosomes.…”