A Nuclear Gene Suppressor of a Cytoplasmically Inherited Character in Neurospora crassa

SUMMARY: The cytoplasmically inherited trait in poky, Neurospora crassa, is recognized by certain defects in the cytochrome system accompanied by a low growth rate. In the presence of the gene, f, the growth rate of a poky strain becomes nearly normal but the defective cytochrome system remains unchanged, as if the defects were being compensated for by an increase in activity of some other enzyme system. When the f allele of this gene is replaced by its normal counterpart the poky character is again fully expressed. The allele, f, is apparently without effect on another cytoplasmically inherited character, mi 3, similar in its properties to poky. Nor do the nuclear gene mutants, C115 and C117, also similar in phenotype, appear to respond to f. A nuclear gene suppressor of the mutant, C115, restores to normal not only the growth rate but also the cytochrome system of this mutant. No effect of this suppressor on poky, mi 3 and C117 has been detected.