Biogenesis of Mitochondria in Germinating Peanut Cotyledons II. Changes in Cytochromes and Mitochondrial DNA

Abstract

Biogenesis of mitochondria occurs in the germinating cotyledons of peanuts. This process was demonstrated by measuring both constitutive and enzymatic properties of mitochondria as a function of germination time. Direct counting by phase contrast microscopy of sucrose density gradient preparations showed that the number of mitochondria increased markedly during germination. DNA with a buoyant density distinct from the major cellular DNA was associated with these mitochondrial preparations. During germination the amount of this DNA in mitochondrial pellets increased. This increase closely paralleled the increase in number of mitochondria.Succinoxidase and succinic dehydrogenase increased during germination. Both activities were confined to the mitochondrial fraction. The rate of increase of succinoxidase activity was significantly greater than the rate of increase of succinic dehydrogenase and both increased at least initially at a greater rate than the amount of mitochondrial DNA or numbers of mitochondria.The amounts of cytochromes present in mitochondrial preparations were measured spectrophotometrically. All of the cytochromes increased in amount during germination. The rate of increase of cytochrome a - a(3) very close to the rate of increase in succinoxidase activity.