Synthesis of mitochondrial and nuclear DNA in anerobically grown yeast during the development of mitochondrial function in response to oxygen

Abstract

When Saccharomyces cerevisiae is grown anerobically in the presence of a fermentable substrate, oxidative mitochondrial function disappears. When such anerobic cells are exposed to oxygen, even in a medium which does not support growth for lack of an assimilable nitrogen source, mitochondrial functional development proceeds rapidly. Tritium-labeled adenine was rapidly incorporated into mitochondrial DNA during respiratory oxygen adaptation. The specific activity of mitochondrial DNA was 6 to 30 times greater than that of nuclear DNA. Incorporation of radioactivity into mitochondrial DNA was maximal during the first 30 minutes after exposure to oxygen, declining rapidly thereafter. DNA synthesis preceded the development of respiratory enzyme activity which continued to rise for at least nine hours. The early DNA synthesis persisted during a two-hour pre-incubation period in adaptation medium in a nitrogen atmosphere, but an additional burst of DNA synthesis appeared after exposure to air. High glucose concentration in the oxygen adaptation medium inhibited both mitochondrial DNA synthesis and the development of respiratory activity. We estimate that 10 to 35% of the mitochondrial DNA replicates during oxygen adaptation. A respiratory-deficient mutant showed a similar response to oxygen and glucose with respect to DNA synthesis although oxidative enzyme activity was absent. Cycloheximide and chloramphenicol blocked the development of respiratory activity in response to oxygen. Cycloheximide did not inhibit mitochondrial DNA synthesis. Chloramphenicol had either no effect or inhibited both mitochondrial and nuclear DNA synthesis symmetrically.