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 both gametes is blocked in polyploid zygotes.As a result,the polyploid zygotes cannot proliferate mitotically and frequently form supernumerary SPBs during subsequent zygotic 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/pericentrin,which,in normal diploid zygotic meiosis,exhibits a dynamic association with SPB when the cells are committed to sexual differentiation.Artificially induced constitutive localization of Pcp1 on SPB is sufficient to result in blockage of SPB fusion and formation of extra spores in diploid zygotic meiosis,which can be rescued in the case of defective Pcp1 function on SPB.Thus,Pcp1-dependent SPB quantity control is crucial for sexual reproduction and ploidy homeostasis in fission yeast.