ADY1, a novel gene required for prospore membrane formation at selected spindle poles in Saccharomyces cerevisiae

ADY1 is identified in a genetic screen for genes on chromosome VIII of Sacc haromyces cerevisiae that are required for sporulation. ADY1 is not require d for meiotic recombination or meiotic chromosome segregation, but it is re quired for the formation of four spores inside an ascus. In the absence of ADY1, prospore formation is restricted to mainly one or two spindle poles p er cell. Moreover, the two spores in the dyads of the ady1 mutant are predo minantly nonsisters, suggesting that the proficiency to form prospores is n ot randomly distributed to the four spindle poles in the ady1 mutant. Inter estingly, the meiosis-specific spindle pole body component Mpc54p, which is known to be required for prospore membrane formation, is localized predomi nantly to only one or two spindle poles per cell in the ady1 mutant. A part ially functional Myc-Pfs1p is localized to the nucleus of mononucleate meio tic cells but not to the spindle pole body or prospore membrane. These resu lts suggest that Pfs1p is specifically required for prospore formation at s elected spindle poles, most likely by ensuring the functionality of all fou r spindle pole bodies of a cell during meiosis II.