Mitochondrial suppressor of a nuclear gene in Paramecium

Abstract

THE biogenesis of mitochondria depends on two sources of genetic information: one in the nucleus and the other within the mitochondria. An important question raised by this situation is how information from the two sources becomes integrated to form a functional organelle^4,11. Products coded by both mitochondrial and nuclear DNA have been shown to be assembled in the mitochondrial inner membrane to form complex enzymes such as ATPase, cytochrome oxidase, cytochrome b and mutations in either genome can affect enzyme activity^2,6,7,14. Since the activity of such enzymes depends on molecular interactions between their component subunits, it is conceivable that a defect in one subunit can be, at least partly, corrected by a mutation affecting another subunit. A nuclear mutation suppressing the effect of a mutated mitochondrial gene has been studied in Neurospora⁸. We report here the reverse situation.