Gamma Particles, Nadi-Positive Mitochondria, and Development in the Water Fungi Blastocladiella and Allomyces

Abstract

IN 1953, it was suggested¹ that genesis of ordinary colourless and orange thalli of Blastocladiella emersonii was related to the distribution of a hypothetic cytoplasmic factor, gamma, the rate of reproduction of which relative to growth of the protoplast was affected differentially by environmental factors. Later², a visible, Nadi-positive, cytoplasmic particle was detected, the distribution of which in the motile swarmers derived from ordinary colourless and orange plants corresponded with that predicted for the hypothetical factor, gamma; namely, a low number per spore for orange plants, and a higher number per spore for ordinary colourless plants. The number of these visible particles was, indeed, affected by environmental factors; furthermore, it appeared as if they might be transferred from one cell to another via temporary cytoplasmic bridges formed between orange and colourless motile cells³. In addition, studies with a mutant strain of B. emersonii which produced only orange plants revealed that: (a) the gamma content per mutant swarmer was the same as the gamma content of the wild-type orange swarmers from orange plants²; (b) such mutant, orange plants displayed a respiratory lesion in the tricarboxylic acid cycle; namely, they lacked the oxidative activity associated with α-ketoglutarate dehydrogenase normally found in the wild type^4,5. In recent years, it has begun to appear⁶ as if cytoplasmic control of differentiation of orange and colourless cells in the close relative Allomyces may also be related to the distribution of similar, Nadi-positive particles, particularly in view of the recent demonstration⁹ of a parallel sort of differential distribution of Nadi-positive ‘mitochondria’ in the unicellular orange and colourless sex organs of this fungus.