Meiotic recombination and chromosome segregation in Schizosaccharomyces pombe

Abstract

In most organisms homologous recombination is vital for the proper segregation of chromosomes during meiosis, the formation of haploid sex cells from diploid precursors. This review compares meiotic recombination and chromosome segregation in the fission yeast Schizosaccharomyces pombe and the distantly related budding yeast Saccharomyces cerevisiae, two especially tractable microorganisms. Certain features, such as the occurrence of DNA breaks associated with recombination, appear similar, suggesting that these features may be common in eukaryotes. Other features, such as the role of these breaks and the ability of chromosomes to segregate faithfully in the absence of recombination, appear different, suggesting multiple solutions to the problems faced in meiosis.

Figure 1

Segregation of recombined chromosomes during the two meiotic divisions. Black and white lines represent homologous chromosomes. Gray circles represent cohesin; open circles represent kinetechores. Arrows represent the meiotic spindle. See text for explanation.

Figure 2

Control of the entry into meiosis. “Stress” includes starvation, DNA damage, high osmolarity, or heat shock, each of which can activate Atf1⋅Pcr1. Arrowheads indicate activation of the indicated protein or its gene or process; straight lines indicate inhibition or repression. See text for explanation.

Figure 3

Meiotic recombination initiated by a DNA double-strand break [after Szostak et al. (58)]. Thin and thick lines indicate single DNA strands of the parental chromatids. Dashed lines indicate newly synthesized DNA; arrowheads indicate 3′ ends. Alternative resolutions at the last step are not shown. See text for explanation.

Figure 4

Horsetail movement observed in live meiosis. Photomicrographs are of a single cell whose DNA was stained with Hoechst 33342. The numbers at the top are time in minutes. [Reproduced with permission from ref. (Copyright 1994, American Association for the Advancement of Science).]