Nuclear suppressors of the [poky] cytoplasmic mutant in Neurospora crassa. I. Genetics and respiratory properties.

Six nuclear suppressors of the (poky) cytoplasmic mutant (sup-1, sup-3, sup-4, sup-5, sup-10, sup-14) have been obtained in Neurospora crassa. The sup genes suppress the slow growth phenotype of (poky), and alleviate, at least partially, the deficiency of cyanide sensitive respiratory activity in the mycelium of this cytoplasmic mutant. The six suppressors are nonallelic, suppress the phenotypic effects of (stp-Bl) in addition to (poky), but have no effect on the phenotype expression of the (mi-3) cytoplasmic mutant. On the basis of experimentally established molecular defects in (poky) and on the basis of hypothetical consideration, it is proposed that the sup mutations affect the structure and properties of mitochondrial ribosomal proteins.