Cytochromes and the Succinic Acid Oxidase System of Poky Strains of Neurospora

Abstract

Recent investigations in this laboratory (1) have demonstrated that in Neurospora crassa growth characteristics representing at least two stable states are possible with the same constitution of nuclear genes. If a slow growing strain, designated poky, functions in a cross to wild type as the maternal or protoperithecial parent, then all progeny from the cross exhibit the poky character. If the cross is made in the reverse, or reciprocal manner, that is, with the wild type strain functioning as a protoperithecial parent, then all progeny are normal in growth rate. During the course of the work on inheritance it was observed that mycelial pads from poky were characterized by a red color reminiscent of that of the heme pigments. Examinations of suspensions and extracts of the mold with a spectroscope yielded the information that poky mycelium contains large quantities of a substance having the absorption spectrum characteristic of cytochrome c, whereas the bands corresponding to cytochromes o and b were not visible. All three of these components were detected easily in the wild type strain. The experimental results presented here provide more precise information on the similarities and differences between these two strains with respect to the cytochrome and the succinic acid oxidase systems. Preliminary observations suggested that poky in Neurospora is analogous to petite in yeast (2) in which abnormalities in the succinic acid oxidase system have been reported, but this analogy is shown here to be only a partial one