Pcp1/pericentrin controls the SPB number in fission yeast meiosis and ploidy homeostasis

During sexual reproduction, the zygote must inherit exactly one centrosome (spindle pole body [SPB] in yeasts) from the gametes, which then duplicates and assembles a bipolar spindle that supports the subsequent cell division. Here, we show that in the fission yeast Schizosaccharomyces pombe, the fusion of SPBs from the gametes is blocked in polyploid zygotes. As a result, the polyploid zygotes cannot proliferate mitotically and frequently form supernumerary SPBs during subsequent meiosis, which leads to multipolar nuclear divisions and the generation of extra spores. The blockage of SPB fusion is caused by persistent SPB localization of Pcp1, which, in normal diploid zygotic meiosis, exhibits a dynamic association with the SPB. Artificially induced constitutive localization of Pcp1 on the SPB is sufficient to cause blockage of SPB fusion and formation of extra spores in diploids. Thus, Pcp1-dependent SPB quantity control is crucial for sexual reproduction and ploidy homeostasis in fission yeast.

Automated summary

This study reveals that fusion of spindle pole bodies (SPBs) in polyploid zygotes of the fission yeast is blocked, leading to the inability of cell proliferation through mitosis. Consequently, these polyploid zygotes generate supernumerary SPBs in subsequent meiosis, resulting in multipolar nuclear divisions and the production of extra spores. The persistent localization of Pcp1 protein on SPBs is the cause of SPB fusion blockage, which is crucial for sexual reproduction and ploidy homeostasis in the fission yeast.