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Protistology ■ 9
NUCLEUS-ASSOCIATED ACTIN IN DIFFERENT STAGES OF AMOEBA PROTEUS CELL CYCLE
Berdieva M.A., Bogolyubov D.S., Demin S.Y.,
Podlipaeva Y.I., Goodkov A.V.
Institute of Cytology of the Russian Academy of
Sciences, St. Petersburg, Russia
Despite of plenty of the reports and reviews there are still a lot of blank spots in the matter of the organization and functioning of Amoeba proteus nuclear apparatus. According to our 3D-reconstruction of its chromatin compartment, it has a complicated and highly dynamic structure (Demin et al., 2016). Actin was shown to be a key protein actor in providing different nuclear processes. Immunocytochemical study has shown an actin meshwork strongly co-localized with chromatin fibrils. On the other hand, the amoeba nucleus appears embraced by a basket-like structure formed by F-actin that in turn is connected with cytoplasmic actin filaments. 3D-observations of the nucleus during the cell cycle indicate a regular process of the chromatin extrusion/elimination ofthe part ofthe chromatin "excess" to the cytoplasm. Based on the 3D-reconstruction ofphalloidin-stained cells, we suppose the existence of specific chromatin-binding sites interacting with actin filaments meshwork. We also propose a hypothesis that the chromatin extrusion is provided by actin filaments which may pull out the chromatin fibrils from the nucleus. Funded by the Russian Foundation for Basic Research, projects 15-0403451, 15-04-01857, and the granting program "Molecular and Cell Biology" of the Presidium of RAS.
INFLUENCE OF SALINITY STRESS ON DNA SYNTHESIS AND CHROMOSOME FINE STRUCTURE OF DINOFLAGELLATES PRO-ROCENTRUM MINIMUM (PAVILLARD) SCHILLER
Berdieva M.A.1, Filatova N.A.1, Knyazev N.A.12, Skarlato S.O.1
1 - Institute of Cytology of the Russian Academy of Sciences, St. Petersburg, Russia
2 - Nanotechnology Research and Education Centre, Russian Academy of Sciences, St. Petersburg, Russia [email protected]
Prorocentrum minimum is a common planktonic potentially toxic bloom-forming dinoflagellate. Being widely distributed, this species demonstrates high adaptive capacity to different factors, particularly salinity. We studied cellular and biochemical aspects of physiological adaptation of this dino-
flagellate. The basic culture of P. minimum, isolated from the Black Sea, was grown in 17 psu f/2 medium (cultivation conditions described in Pozdnyakov et al., 2014). Experiments were carried out by inoculation of cells into 4, 8, 35 psu f/2 medium and 17 psu as a control for 30 min. Then cells were returned to the basic medium, incubated for 24 h and fixed for flow cytometry or transmission electron microscopy. We detected DNA concentration value (1.2 pg/cell) and fine structure of chromosomes in control series. After inoculation of cells into 8 psu f/2 medium we observed the highest DNA concentration (1.5 pg/cell) and the lowest cell mortality rates. Chromosomes became more condensed, local unwound sites increased in number and appeared more distinct. Transfer into the medium with native for these organisms salinity 35 psu (the World ocean level) did not caused any reliable differences in DNA concentration (1,3 pg/ cell). At the ultrastructural level, we observed total splitting of chromosomes in most cases. Inoculation of cells into 4 psu f/2 did not caused any significant changes in DNA concentration value, but led to high cell mortality rates. Our results are in agreement with the protistan species maximum concept for the horohalinicum. Funded by the Russian Science Foundation, project 16-14-10116.
FINDING AND ANALYSIS OF AMOEBO-ZOA-SPECIFIC GENES TO STUDY ENVIRONMENTAL DIVERSITY OF AMOEBAE Bondarenko N.I., Smirnov A.V. Department of Invertebrate Zoology, Faculty of Biology, Saint-Petersburg State University, Saint-Petersburg, Russia [email protected]
Amoebozoa is a one of the supergroups of eukaryo-tes, which includes naked and testate lobose amoebae, pelobionts, mycetozoa, and several groups of flagellated organisms. In environmental DNA surveys done on traditional DNA barcodes (SSU-rDNA, Cox I gene) amoebozoan genes normally constitutes a minor part of the total gene diversity and represent only the most abundant lineages. To resolve this problem, we attempted to find Amoebozoa-specific genes and gene families with low level of paralogy appropriate for the application as a DNA barcodes for this group of protists. We analyzed the Amoebozoa RNA-Seq data which were available from MMETSP (http://www.moore.org/). First, we analyzed assembled transcriptomes from MMETSP and found transcripts with unusually big size (more than 50 000 bp) in several assemblies. This led us to the decision to repeat data assembly de novo.
