Isolation and characterization of yeast mitochondrial mutants defective in spore germination.

This paper describes a new type of mitochondrial mutation. During germination of ascospores the mutants are blocked at the first budding stage and consequently die. However, vegetative growth on nonfermentable carbon sources and respiration are close to normal. The spores of the mutants which (like the wild type) contain very low amounts of mitochondrial cytochromes, do not synthesize cytochromes b and aa3 during germination.The mutants show a pleiotropic phenotype during the vegetative phase: they lack carbon catabolite repression of cytochromes on media containing 10% glucose. We discuss here the hypothesis that the mutation is located in a regulatory region on the mitochondrial genome which is needed for the reinitiation of mitochondrial genetic activity during germination of ascospores.