Mitochondrial inheritance is required for MEN-regulated cytokinesis in budding yeast

Mitochondrial inheritance, the transfer of mitochondria from mother to daughter cell during cell division, is essential for daughter cell viability. The mitochore, a mitochondrial protein complex containing Mdm10p, Mdm12p, and Mmm1p, is required for mitochondrial motility leading to inheritance in budding yeast. We observe a defect in cytokinesis in mitochore mutants and another mutant (mmr1Delta gem1Delta) with impaired mitochondrial inheritance. This defect is not observed in yeast that have no mitochondrial DNA or defects in mitochondrial protein import or assembly of beta-barrel proteins in the mitochondrial outer membrane. Deletion of MDM10 inhibits contractile-ring closure, but does not inhibit contractile-ring assembly, localization of a chromosomal passenger protein to the spindle during early anaphase, spindle alignment, nucleolar segregation, or nuclear migration during anaphase. Release of the mitotic exit network (MEN) component, Cdc14p, from the nucleolus during anaphase is delayed in mdm10Delta cells. Finally, hyperactivation of the MEN by deletion of BUB2 restores defects in cytokinesis in mdm10Delta and mmr1Delta gem1Delta cells and reduces the fidelity of mitochondrial segregation between mother and daughter cells in wild-type and mdm10Delta cells. Our studies identify a novel MEN-linked regulatory system that inhibits cytokinesis in response to defects in mitochondrial inheritance in budding yeast.