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Molecular mechanism of mechanoreception in plants
Jelínková, Barbora ; Martinek, Jan (advisor) ; Fendrych, Matyáš (referee)
Plant, as sedentary organism, does not have many possibilities to physically escape it's unpleasant surroundings, instead it adapts oneself. One of many plant senses that are crucial for tracking environment changes is mechanoreception. Plant senses and differentiates between many mechanical cues, some of them affecting plant immunity and morphogenesis. The whole plant cell reacts to mechanical cues and many cellular structures are involved in mechanoreception. Any change in cell wall - a borderline between the cell and it's surroundings - is transduced to plasma membrane, then to the cytoskeleton and potentially to other structures. Concept of this cell wall-plasma membrane-cytoskeleton continuum and it's use as an instrument to illuminate molecular mechanisms of mechanoreception in plants are the key topics of my thesis.
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Non-traditional roles of formins besides actin nucleation
Metlička, Jáchym ; Cvrčková, Fatima (advisor) ; Opatrný, Zdeněk (referee)
Formin homology 2 (FH2) domaincontaining proteins (formins) have, since their discovery in 1990, been observed in all analyzed species of eukaryotic kingdoms. Our knowledge of structure and function of the defining FH2 domain has greatly increased over the last couple of years. Its function in nucleation, polymerization and processive capping of actin filaments designates formin protein family an important cytoskeletonremodelling factor. But FH2 domain is just one part of the puzzle additional optional conserved peptide structures surrounding it, as well as concrete variation of the FH2 domain itself, greatly influence the functional properties and cellular localization of the resultant formin protein. Formins have been implicated in variety of cellular processes, which often (but not always) involve the cytoskeleton e.g. Factin network management, crosstalk of Factin filaments and microtubules or plasma membrane. They also partake in processes integral to cell division, function in conserved signalling pathways and much more. This thesis explains the structure and function of FH2 and FH1 domains, outlines the main formin phylogenetic clades in multicellular eukaryotes and reviews various roles that formins fulfill or are thought to fulfill. Such goal, however, is very bold and (considering the...
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Cytoplasmic membrane and tonoplast dynamics during closing and opening of stomata
Röder, Matěj ; Žárský, Viktor (advisor) ; Albrechtová, Jana (referee)
Stomata are epidermal structures mediating regulated contact of plant apoplast with surrounding environment via stomatal opening. Change of turgor plays crucial part in initiation of stomatal opening or closure. During stomatal movement, guard cell undergo considerable and repetitive changes in cell volume and consequently surface area over a period of minutes. Alteration in the surface of membrane must occurs due to limited stretching capability of the plasma membrane. It can be achieved through membrane invaginations and endocytosis of small vesicles. Microscopy and electrophysiology techniques have proven that both processes are happening in guard cells. These processes are controlled and managed by complex web of signal pathways in which actin and microtubular cytoskeletons, SNARE proteins, ion channels and others molecules have crucial parts. The aim of this work is to summarize current knowledge on the processes and mechanisms of these membranes surface changes and their molecular principle.
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Role of cytoskeleton in plant cell morphogenesis
Miklánková, Pavlína ; Schwarzerová, Kateřina (advisor) ; Sekereš, Juraj (referee)
The cells are able to acquire variety of shapes, in which cytoskeleton plays an important role. Cytoskeleton influences deposition of cell wall materials, regulates vesicle movement in cell, participates in exocytosis and endocytosis. Cortical microtubules affect celulose accumulation in cell wall and determine direction of cell expansion, although the exact connection between microtubules and cellulose remains unclear. Actin promotes growth and contributes to its spatial regulation in both tip ang diffuse growing cells. Actin is important for secretion in expanding cells but its exact functions in cell growth regulation are not explained yet. Analysis of mutants, spectroscopic methods, cytoskeletal drugs, fluorescence proteins and other methods are used to better understand how actin and microtubule cytoskeleton are integrated during plant cell morphogenesis. Epidermal and trichome cells of Arabidopsis thaliana are a good model of research and they are used for most studies.
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Interactions of Mitochondria with Other Cellular Structures
Vinopalová, Martina ; Doležal, Pavel (advisor) ; Voleman, Luboš (referee)
In cells, mitochondria fulfil diverse set of roles, including a production of energy-rich molecules, which are necessary for proper functioning of the cell, calcium homeostasis, apoptosis and even biosynthesis of Fe-S centres, heme and steroids. To coordinate some of these processes with events occurring in the rest of the cell, mitochondria need to communicate with the other cellular structures through their physical contacts. Resulting intracellular platforms give rise to additional mitochondrial functions. This thesis summarizes current findings from the cells of mammalian model organisms and the budding yeast Saccharomyces cerevisiae about the interactions of this semiautonomous organelle with other cellular components and about the functions, which these interactions mediate.
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Searching for mechanisms and functions of microtubular interactions with other plant cell structures
Krtková, Jana ; Schwarzerová, Kateřina (advisor) ; Vaňková, Radomíra (referee) ; Ovečka, Miroslav (referee)
Microtubular cytoskeleton is involved in many processes in plant cells, including cell division, growth and development. Other proteins enable its functions by modulation of its dynamics and organization and by mediation of functional and structural interaction with other cell structures. Identification of the mediating proteins and the functions of these interactions under specific conditions were the main aims of the thesis. Membrane proteins interacting with microtubules were identified using biochemical methods. Surprisingly, the identified proteins co-sedimenting with microtubules were not members of the "classical" microtubule associated proteins (MAPs). There were enzymes, chaperones and plant specific proteins among them. For further studies, the identified microtubule-associated heat-shock protein 90 (Hsp90_MT) was chosen. Recombinant Hsp90_MT binds directly to microtubules and tubulin dimers in vitro. The ATP-binding pocket is not responsible for this association. In BY-2, Hsp90_MT co-localizes with phragmoplast and cortical microtubules and is involved in microtubule recovery after their depolymerization during cold treatment. In plants, Hsp90 is involved in cell cycle progression, its inhibition causes cell-cycle arrest in G1 phase. Based on literature search for animal proteins...
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Microtubule-associated proteins in plants
Benáková, Martina ; Krtková, Jana (advisor) ; Vinopal, Stanislav (referee)
1. Abstract and key words MTs are one of the basic cellular protein structure. Their features and function are influenced and modified by group of other proteins, i.e. microtubule-associated proteins (MAPs). In the last decades, an extensive research on MAPs and their wide range of functions has been carried out. Therefore we are aware of the involvement of some of the MAPs in MT dynamics, other have been shown to have rather structural function. They bundle MTs with various cell structures, such as the other MTs, proteins, organelles, actin cytoskeleton or plasma membrane. Many described MAPs are homologous in the whole eukaryotic domain, for example MAP65 or EB1 (END BINDING 1) family, therefore it is interesting to follow if and how the functions of plant MAPs differ from their animal counterparts. On the other hand, there are many specific MAPs with unique functions in plants, e.g. ATK5 or SPR1 (SPIRAL 1). This Bachelor thesis is a survey on current knowledge of plant MAPs and it makes an effort to present their characteristic and functions in plant cell and organism. Key words: cytoskeleton, microtubules, microtubule-associated proteins, plant cell, growth and development
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Mechanisms of epidermal cells polarization in plants.
Vojtíková, Zdeňka ; Žárský, Viktor (advisor) ; Soukup, Aleš (referee)
Plant epidermal cells form contact area of the plant, they protect it from impacts of surrounding environment and they mediate the communication with its neighbourhood. In the epidermis there are evenly distributed several cell types with quite specialized morphology (pavement cells, trichomes and guard cells) due to the polarization mechanisms. The cytoskeleton and signal molecules of ROP GTPase family promote the polarized growth. Thanks to polarized growth the cells reach their shapes. The cytoskeleton responds to the signal by expanding the cell, helps with targeting of the secretion to the sites of active growth and mediates polarized formation of the cell wall. On the upper side of the epidermis the cuticle and layer of epicuticular waxex is secreted. The secretion of cuticular components is baso-apicaly polarized. This work summarizes the mechanisms of the polarization in plant epidermal cells discoverd untill now.
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Utilization of chemical cross-linking for studying intermediate filaments organization
Dlabolová, Lada ; Novák, Petr (advisor) ; Sabó, Ján (referee)
Intermediate filaments are cytoskeleton components formed by a large family of fibrous proteins specifically expressed in nearly all differentiated cells. Under physiological conditions, they spontaneously assemble into fibers in a process that involves several stages in the organization of subunits. These fibers provide elastic properties to the cells, allowing them to maintain their structural and mechanical integrity. While the structure of other cytoskeletal components is now well researched, detailed information on the structure of intermediate filaments at various stages of assembly is still not available. Thus, new insights into the structure of these proteins could be of great benefit in understanding of various pathological mechanisms associated with changes in their expression in cells. This thesis studies interactions of dimeric subunits in the tetrameric assembly of vimentin, class III protein of intermediate filaments. By chemical cross-linking of isotopically labeled and unlabeled tetrameric vimentin mixture, followed by proteolytic cleavage and mass spectrometry analysis, interdimeric, intradimeric and intrapeptide cross-linking products were identified. Quantification yielded information on interdimeric and intradimeric distance constraints, which allow the characterization of a...
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Mechanisms of Microtubules Dynamics and Nucleation in a Plant Cell
Mauerová, Zdeňka ; Schwarzerová, Kateřina (advisor) ; Žárský, Viktor (referee)
Nucleation of microtubules co-determines organization of this cytoskeleton component in cells and makes a significant contribution to shaping its dynamics. In plant cells, micro- tubules are mainly nucleated on preexisting ones and nucleation takes place in the cortex and also within the mitotic spindle and the fragmoplast. Recruiting the γTuRC, a pre- served universal nucleator, to the wall of microtubules is provided by augmin in cooperation with NEDD1/GCP-WD. The function of the γTuRC is at least in the case of nucleation in the spindle, but apparently in other situations as well further enhanced by XMAP215/MOR1, which raises efficiency of the γTuRC through its own polymerization activity, and TPX2, or its homologs, which for one thing, directly activates the complex and for another, locally increases concentration of tubulins by forming condensate with them, which also augments the probability of success of nucleation. Not much is known about regulatory pathways controlling this process, with the exception of the TTP complex, which is functional in the cortex. Overall, knowledge covering nucleation in plants is rather meager and information concerning the molecular mechanisms of functioning of mentioned factors comes mainly from research in animals. Keywords augmin, cytoskeleton, γTuRC,...
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