Protistology 1 (3) 92–100 (2000)
Cell architecture during the morphogenesis of coenocytic alga Vaucheria sessilis. II. Organization of
microfilament system in the course of germination
Olga V. Gavrilova, Elena E. Rudanova and Natalia N. Petrova
Laboratory of Microbiology, Biology Research Institute of St. Petersburg State University, Russia
Summary
The architecture of microfilaments during the morphogenesis of Vaucheria sessilis (Vauch.) D.C. was investigated by fluorescence
microscopy of (un)fixed cells using fluorescein-labelled phalloidin (FITS) and differential interference contrast (D.I.C.). The organization
of F-actin system varies during aplanospore germination. In intact aplanospore, the arrangement of short fine microfilaments is irregular.
Cortical girding band lies beneath the cell membrane and persists during germination. Fine microfilaments rearrange themselves into
thick bundles which gradually reorient in axial direction. Cortical band, which is typical for vegetative thallome, is forming de novo in the
secondary projection. At the same time, dense and fine actin network appears in the apical zone. Final phase of germination (formation of
the vegetative branch) is characterized by active migration of organelles, and by formation of an apical cluster of nuclei. This process is
accompanied by the reorganization of apical microfilament ring into a honeycomb-like network. Controversies with F-actin structure, revealed
by many scientists who examined apical growth, can be explained by an extremely dynamic organization of microfilaments in the tip-growing
cells. Moreover, the pattern of F-actin architecture strongly depends on the physiological status of the cell.
Key words: microfilaments, cytoskeleton, germination, morphogenesis, Vaucheria, apical growth
|