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CURRENT KNOWLEDGE AND RESEARCH PERSPECTIVES OF THE SHELL FORMATION PROCESS IN THE GENUS ARCELLA (ARCELLINIDA: AMOEBOZOA)
стр.3-14
Porfírio-Sousa A.L., Lahr D.J.G.
Arcellinida is an Amoebozoa lineage characterized by the presence of an external shell. A comprehensive cyto-morphological description of the shell structure and formation (thecagenesis) process has been generated due to publications in the time span of more than a century. Recently, few works have advanced our understanding of the thecagenesis process or discussed this rich literature; however, several aspects of the shell formation and structure are still puzzles, as remains the relationship between genes and shell formation morphogenesis. Here we present an overview of the literature about shell formation and structure, focusing on the genus Arcella , the best-studied lineage. We show that some aspects regarding shell formation are still open questions. Moreover, based on the current knowledge, we can establish new frameworks, to address such issues as the origin and evolution of the shell in Arcellinida.
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PREDATORY FLAGELLATES - THE NEW RECENTLY DISCOVERED DEEP BRANCHES OF THE EUKARYOTIC TREE AND THEIR EVOLUTIONARY AND ECOLOGICAL SIGNIFICANCE
стр.15-22
Predatory protists are poorly studied, although they are often representing important deep-branching evolutionary lineages and new eukaryotic supergroups. This short review/opinion paper is inspired by the recent discoveries of various predatory flagellates, which form sister groups of the giant eukaryotic clusters on phylogenetic trees, and illustrate an ancestral state of one or another supergroup of eukaryotes. Here we discuss their evolutionary and ecological relevance and show that the study of such protists may be essential in addressing previously puzzling evolutionary problems, such as the origin of multicellular animals, the plastid spread trajectory, origins of photosynthesis and parasitism, evolution of mitochondrial genomes.
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HETEROLOGOUS EXPRESSION OF NOSEMA BOMBYCIS HEXOKINASE IN THE BACULOVIRUS-SF9 INSECT CELL SYSTEM CONFIRMS ITS ACCUMULATION IN THE HOST NUCLEI AND SECRETION BY THE MICROSPORIDIAN PARASITE
стр.23-31
Senderskiy I.V., Tsarev A.A., Zhuravlyov V.S., Pavlova O.A., Dolgikh V.V.
Hexokinase is one of the most interesting proteins secreted by entomopathogenic microsporidia into an infected cell. Its accumulation in the insect host nuclei suggests that the hexose-phosphorylating enzyme may also be involved in the regulation of transcription of host genes. In this study, a hexokinase of microsporidia Nosema bombycis was expressed in Sf9 lepidopteran cells using the baculovirus system. In contrast to green fluorescence protein and gluten-hydrolyzing proteinase of Sunn pest Eurygaster integriceps , expressed as the control proteins, the microsporidian recombinant enzyme without N-terminal signal peptide was accumulating in the nuclei of insect cells during heterologous expression. This result one more time confirms the nuclear localization of hexokinases secreted by microsporidia into the insect host cells and suggests that a model used is a convenient one to study an impact of N. bombycis hexokinase on the lepidopteran cells. Surprisingly, despite the elimination of signal peptide, the parasite enzyme was effectively secreted into the culture medium by Sf9 cells. Previously, we expressed several secretory proteins with their own or baculoviral glycoprotein gp67 signal peptides, but none of them was secreted as effectively as N. bombycis hexokinase. This unexpected result raises the question about signal sequences and mechanisms of protein secretion in microsporidia.
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THE ROLE OF THE CYTOSKELETON IN THE ECDYSIS OF THE DINOFLAGELLATE PROROCENTRUM MINIMUM
стр.38-44
Kalinina V., Berdieva M., Matantseva O.
Actin filaments (actomyosin system) and microtubules form highly organized cytoskeleton structures in unicellular organisms, particularly in dinoflagellates. The cytoskeleton organization of Prorocentrum minimum (Pavillard) Schiller, a bloom forming species, differs from that of most other studied dinoflagellates. While the cortical microtubules are absent, a dense layer of actin filaments is located beneath the cell covering. A previous study has shown that cytoskeleton likely plays an essential role in the ecdysis, the process of cell covering reorganization including shedding of the plasma membrane, outer amphiesmal vesicle membranes and thecal plates, of P. minimum . In this study, the involvement of cytoskeleton in the ecdysis process was investigated using specific drugs influencing cytoskeleton arrangement and functioning. P. minimum cells were treated with cytochalasin D, 2,3-butanedione monoxime (BDM) or nocodazole, and ecdysis was induced by centrifugation, a potent ecdysis trigger. The application of drugs significantly affected the rate of ecdysis induced by centrifugation. Cytochalasin D, an inhibitor of actin polymerization, impaired the last step of ecdysis, i.e. leaving the old thecal plates. BDM, a myosin function inhibitor, and nocodazole, a tubulin disrupting agent, delayed this process, but did not inhibit it. Taken together, our data suggest that inP. minimum the cortical actin is a crucial cytoskeleton element, which is required for the final step of the ecdysis process. Apparently, it could enable opening of the old thecal plates, and squeezing of the ecdysing cell between them.
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CAN MICROPLASTICS TRANSFER TOXOPLASMA GONDIIPARASITES TO MARINE FOODWEBS?
стр.45-46
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