Perinuclear actin rings in the yeasts

Fellomyces fuzhouenesis is the basidiomycetous yeast that reproduces asexually by conidiogenesis [1, 2, 3]. F-actin during conidiogenesis was detected by rhodamine-phalloidin, nuclei were stained by DAPI. Results showed that F-actin cytoskeleton of Fellomyces fuzhounesis consisted of F-actin patches, cables and cytokinetic ring-like structures that were similar to those in Cryptococcus neoformans [4]. Actin patches accumulated at the apex of sterigma and in the area of formation of wall closure. Actin cables directed from conidiogenous mother cell to sterigma and conidium. Developing conidium had actin patches at the cortex. Mature conidium having nucleus was separated from sterigma by actin ring-like structure that was similar to Aureobasidium pullulans [5] and appeared at the base of conidium. Such F-actin cytoskeleton was detected during cultivation of F. fuzhounesis in YEPG, YNBG or PDBG medium. In some of these cells nucleus-associated F-actin ring was identified. The frequency of this perinuclear F-actin ring increased in a special radish-containing culture medium (S.Yoshida, unpublished data), and after the disappearance of microtubules in cells induced by the cytoskeletal inhibitor (M.Gabriel, M. Kopecka, unpublished data). The perinuclear actin rings were observed in various planes in the cells. Their function is not known. We can speculate that the perinuclear F-actin ring may be related to the migration of the nucleus into sterigma, to nuclear division or to cytokinesis, or it may be some reaction of the cell to the stress before start of apoptosis. The research was supported by grant No. 310/03/1195 of the Grant Agency of Czech Republic. [1] Fell, J. W. Ant. v. Leeuwenhoek 32, 99-104 (1966). [2] Banno I., Yamada, I. J. Gen. Appl. Microbiol. 30, 523-525 (1984). [3] Gabriel M. et al. Scripta Medica 73, 341-360 (2000). [4] Kopecka M., Gabriel M. et al. Eur. J. Cell Biol. 80, 303-311 (2001). [5] Kopecka M., Gabriel M. et al. Microbiology 149, 865-876 (2003).