FIBRILLAR ACTIN IN THE NUCLEAR APPARATUS OF THE CILIATE PARAMECIUM CAUDATUM
K. A. Benken, E. V. Sabaneyeva
St. Petersburg State University, Department of Cytology and Histology;
e-mail: saban@mail333.com
Due to their nuclear dualism, ciliates provide a good model for studying the role of actin in spatial organization
and transcription activity of the nucleus. The actin in the nuclear apparatus of the ciliate Paramecium caudatum
was studied using fluorescently labeled phalloiodin and indirect immunocytochemistry. Fibrillar actin
was demonstrated in both of the nuclei. Actin was revealed in the chromatin areas, and was often associated with
the periphery of the amplified nucleoli in the macronucleus. Redistribution of actin was observed depending on
different physiological state of the cells. Stable infection of the macronulear with the intranuclear endobionts
Holospora obtusa led to the loss of nuclear actin accompanied by significant nuclear fragility and redistribution
of the phosphorylated form of the actin-binding protein cofilin. Spherical bodies resembling karyosphere were
found in the macronuclear anlagen.
Key words: nuclear actin, ciliates, nuclear dualism, macronucleus, amplified nucleoli, cofilin, intranuclear endobionts
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