Mitochondrial fragmentation during germination in Blastocladiella emersonii

Abstract

Mitochondrial morphology, shape changes, and fragmentation were studied in the water mold Blastocladiella emersonii by means of complete serial sections through a number of cells at different stages of development during germination. The various stages can be identified by simple criteria with regard to surface morphology, disposition of flagellar axoneme, presence of nuclear cap, existence of germ tube (see Soll et al., 1969). Models of mitochondria of each cell stage except for the germling were reconstructed from serial thin sections. The results are reported as follows: 1. 1. The zoospore contains a single, cup-shaped mitochondrion. 2. 2. In the round cell I stage, the mitochondrion is still single. 3. 3. Beginnings of mitochondrial branching can be observed in the cell intermediate between round cell I and round cell II. 4. 4. In round cell II, this branching is greatly pronounced and separate mitochondrial fragments can be observed. Changes in mitochondrial morphology are discussed in relation to macromolecular events accompanying these alterations.