Differentiation and ferritin synthesis in phvcomvces blakesleeanus; an ultrastructural and physiological study

Abstract

The first part of this investigation deals with the ultrastructural aspects of the dormant and germinating spores and the growing mycelia of the fungus Phycomvces blakesleeanus in submerged culture. Emphasis is focussed on the detection and behaviour of the protein ferritin in these stages particularly in the growing mycelia. The concomitant morphological and ultrastructural changes are described. Time course experiments on growing mycelia revealed that at certain stages of differentiation, detectable ferritin first disappeared in incipient germ hyphae. Its reappearance was found to depend upon the presence of added iron in the medium. A correlation between this reappearance and the availability of lipid droplets, in sections of mycelia, is described and discussed. Successive changes in the ultra- structure of mitochondria during growth and differentiation are also described. In the second part of this study, the electron microscopic observations of ferritin behaviour are backed with tangible biochemical evidences by isolating the protein at different times and conditions from the growing mycelia. The effect of the presence of high iron in the medium and other factors on ferritin synthesis are described. A sixfold de novo increase in apoferritin synthesis is attained by iron administration to growing mycelia. Factors affecting such a synthesis and radioactivity incorporation are described and discussed. By the use of polyacrylamide gel electrophoresis the subunit molecular weight of Phvcomvces ferritin has been determined as 20,200 daltons.