Germination conditions that require mitochondrial function in Saccharomyces cerevisiae: utilization of acetate and galactose.

Ascospores of Saccharomyces cerevisiae inherited at least one functioning mitochondrion as shown by their ability to germinate on nonfermentable carbon sources. After transfer to germination medium, the optical density of the culture at 600 nm decreased (phase-dark), reaching a minimum within 60 min in the presence of glucose and within 180 min after transfer to acetate medium; thereafter, the optical density increased. Budding cells first appeared 90 min after transfer to glucose and 150 min after transfer to acetate. Augmentation of respiratory components, respiratory activity, and macromolecular synthesis (except for DNA synthesis) started at about the same time on glucose and on acetate, although the highest values for all these processes were reached in the presence of glucose. Mitochondrial inhibitors which affected germination on acetate did not arrest germination on glucose. However, mitochondrial activity was required for germination on galactose in a strain carrying the mutated allele imp1 of the nucleomitochondrion-connecting gene IMP1.