The cytoskeleton in the unique cell reproduction by conidiogenesis of the long-neck yeast Fellomyces (Sterigmatomyces) fuzhouensis |
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Authors: | M Gabriel M Kopecká M Yamaguchi A Svoboda K Takeo S Yoshida M Ohkusu T Sugita T Nakase |
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Institution: | (1) Department of Biology, Faculty of Medicine, Masaryk University, Brno;(2) Research Center for Pathogenic Fungi and Microbial Toxicoses, Chiba University, Chiba;(3) Department of Microbiology, Meiji Pharmaceutical University, Kiyose;(4) Department of Biotechnology, National Institute of Technology and Evaluation, Kisarazu |
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Abstract: | Summary. The morphology of conidiogenesis and associated changes in microtubules, actin distribution and ultrastructure were studied
in the basidiomycetous yeast Fellomyces fuzhouensis by phase-contrast, fluorescence, and electron microscopy. The interphase cell showed a central nucleus with randomly distributed
bundles of microtubules and actin, and actin patches in the cortex. The conidiogenous mother cell developed a slender projection,
or stalk, that contained cytoplasmic microtubules and actin cables stretched parallel to the longitudinal axis and actin patches
accumulated in the tip. The conidium was produced on this stalk. It contained dispersed cytoplasmic microtubules, actin cables,
and patches concentrated in the cortex. Before mitosis, the nucleus migrated through the stalk into the conidium and cytoplasmic
microtubules were replaced by a spindle. Mitosis started in the conidium, and one daughter nucleus then returned to the mother
via an eccentrically elongated spindle. The cytoplasmic microtubules reappeared after mitosis. A strong fluorescence indicating
accumulated actin appeared at the base of the conidium, where the cytoplasm cleaved eccentrically. Actin patches then moved
from the stalk together with the retracting cytoplasm to the mother and conidium. No septum was detected in the long neck
by electron microscopy, only a small amount of fine “wall material” between the conidium and mother cell. Both cells developed
a new wall layer, separating them from the empty neck. The mature conidium disconnected from the empty neck at the end-break,
which remained on the mother as a tubular outgrowth. Asexual reproduction by conidiogenesis in the long-neck yeast F. fuzhouensis has unique features distinguishing it from known asexual forms of reproduction in the budding and fission yeasts. Fellomyces fuzhouensis develops a unique long and narrow neck during conidiogenesis, through which the nucleus must migrate into the conidium for
eccentric mitosis. This is followed by eccentric cytokinesis. We found neither an actin cytokinetic ring nor a septum in the
long neck, from which cytoplasm retracted back to mother cell after cytokinesis. Both the conidium and mother were separated
from the empty neck by the development of a new lateral wall (initiated as a wall plug). The cytoskeleton is clearly involved
in all these processes.
Correspondence and reprints: Department of Biology, Faculty of Medicine, Masaryk University, Tomešova 12, 602 00 Brno, Czech
Republic. |
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Keywords: | : Basidiomycetes Fellomyces fuzhouensis Conidiogenesis Cytoskeleton Immunofluorescence Electron microscopy |
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