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FUNCTIONAL ANAYSIS OF SELECTED EXO70 EXOCYST SUBUNITS IN PLANTS
Kubátová, Zdeňka ; Kulich, Ivan (advisor) ; Grossmann, Guido (referee) ; Lichtscheidl-Schultz, Irene (referee)
Arabidopsis thaliana trichomes are large unicellular epidermal outgrowths with a specific development and intriguing shape, which makes them an excellent cell type for our research of cell polarization mecha- nisms. Cell polarity is essential for plant development and the exocyst complex is one of its key regulators. It is an octameric protein complex that mediates polarized exocytosis and growth by targeted tethering of secretory vesicles to the plasma membrane. Its EXO70 subunit functions as a landmark for exocytosis site and physically binds the target membrane through interaction with phospholipids. A remarkable multipli- cation of EXO70 subunit paralogs in land plant genomes is well documented, but the functional diversity of these paralogs remains to be described. In trichomes we revealed the specific role of the EXO70H4 paralog in secondary cell wall deposi- tion, especially in callose synthase delivery. We documented formation of a thick secondary cell wall during the maturation phase of wild type trichome development and a lack of it in the exo70H4 mutant. Moreover, we showed evidence for silica deposition dependency on callose synthesis. Further, we unveiled the formation of apical and basal plasma membrane domains, which differ in their phospholipid compo- sition and ability to bind...
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The role of adhesion of the plasma membrane to the cell wall in the development and function of the root system
Králíková, Dagmar ; Tylová, Edita (advisor) ; Schwarzerová, Kateřina (referee)
Adhesion between the plasma membrane and the cell wall and the existence of the continuum of these two compartments is needed for signal transmission, e.g. under pathogen attack, during cell expansion and cell wall growth, or in response to environmental conditions. This adhesion is, in addition to the turgor, provided by physical connection of both compartments. One of the best-known examples of physical connection is found in the root system, in the Caspary strip region, where it is required to maintain apoplastic barriers of the root system, even under adverse conditions and consequent plasmolysis. There is little information about the physical interconnection and the participating macromolecules but there are candidates, which could participate in this interaction. The diploma thesis deals with arabinogalactan (AGP) proteins with fasciclin-like domain (namely FLA9 and FLA2). These proteins may play a role in the adhesion of plasma membrane and cell wall and may be involved in the growth regulation and development of the root system. Both genes are are relatively strongly expressed in the roots, especially in the elongation zone and in the cortex, including the endodermis (according to chip data). Also, to a smaller extent, the thesis deals with integrin-like At14A protein. The most interesting...
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Molecular basis for regulation of cell wall pH in Arabidopsis thaliana
Bogdan, Michal ; Fendrych, Matyáš (advisor) ; Retzer, Katarzyna (referee)
The cell wall is one of the defining parts of the plant cell. Cell walls resist turgor pressure, give plants their rigidity and still allow the cell to grow despite their stiffness. The plant cell wall is a composite material that consists of different elements; thus, the knowledge of the plant cell wall composition helps us understand the impact of the mentioned pH changes. Alterations of plant cell wall properties result in a change of plant cell growth rate. A prime example of this is the modification of wall properties by pH change, termed the acid growth. Although acid growth has been studied for a long time, we still do not fully understand the underlying mechanisms, as we have not yet identified all the agents involved in acid growth and our ability to determine apoplastic pH is limited. Local cell wall pH fluctuations arise also due to plant organs having different roles and being affected by a diverse range of stimuli. Despite the fact that new pH measurement techniques, such as genetically encoded fluorescent probes, were developed in the last two decades, there is still a need to provide a higher spatiotemporal resolution of pH analysis. Key words: Arabidopsis, apoplastic pH, cell growth, acid growth theory, cell wall, auxin, apoplastic pH measurement
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Analysis of CESA complexes dynamics in plant cytoskeletal mutants
Dubenecká, Kamila ; Schwarzerová, Kateřina (advisor) ; Malínská, Kateřina (referee)
The basis of this study are mutant plants with ARP2/3 complex lacking in one of its subunits (arpc5 and arp2). These plants also express CSC subunit CESA6 of primary cell wall tagged by YFP. Thanks to modern imaging technologies, it is possible to observe the movement of tagged cellulose synthase complexes in vivo at plasmatic membrane. Kymograph analyses was used to measure the velocity of CESA complexes. In addition to observing CESA complexes directly on the plasma membrane, experiments were made to regenerate cell walls of protoplasts of Arabidopsis thaliana plants arpc5 and WT. It was found, that observed mutants arpc5 and arp2 have reduced velocity of CESA complexes in comparison to WT and arpc5 protoplasts regenerate cellulose mesh of cell wall slower. Keywords: Cellulose synthesis, ARP2/3 complex, CESA, CSC velocity, arpc5, arp2, Arabidopsis thaliana.
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Study of adhesive penetration into the wood cell wall
Janová, Petra ; Krbila, Jaromír (referee) ; Vaněrek, Jan (advisor)
This labor is based on penetration of adhesive into a wood cell walls. It focuse on adhesives basicly used for construction purposes, especially on epoxy resins. The labor contains the use of methods for precise detection adhesive in wood and methodics for choice of adhesive and wood basically used for bonding. It describes the experimentally detected dependence of contact angle on viscosity epoxy resins.
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Method´s analysis of submicroscopy structure of wood cell wall determination
Martinek, Radomír ; Kuklík,, Pavel (referee) ; Vaněrek, Jan (advisor)
The content of this study is focused on the influence of the structure of wood at microscopic and submicroscopic level on its mechanical properties. The wood cell wall consists of several layers, the dominant layer being layer S2, which occupies up to 80 % of the total thickness of the wood cell wall. Unique feature of this layer is that cellulose microfibrils placed in this layer are highly aligned and spirally wound around the cell axis. The inclination of these microfibrils is called microfibril angle (MFA) and is the key feature that affects mechanical properties of wood and its shrinkage. In theoretical part of this thesis methods for measuring microfibril angle are described. A method for measuring mechanical properties of the wood cell wall called nanoindentation is discussed in detail. In the practical part of this thesis, microfibril angle is measured by means of polarized light microscopy and mechanical properties of wood cell wall is determined by means of nanoindentation.
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Functions of the exocyst complex in secretion and cell wall biogenesis
Vukašinović, Nemanja ; Synek, Lukáš (advisor) ; Růžička, Kamil (referee) ; Kost, Benedikt (referee)
The mechanical strength of plant tissues and organs can be attributed to specific properties of the cell wall. In many cases, in order to establish their final shape, cells deposit various cell wall materials in a localized manner. This is achieved by highly organized action of the endomembrane system which is essential for biosynthesis and secretion of cell wall proteins and polysaccharides. The exocyst complex is a conserved tethering complex in eukaryotes and it is involved in tethering of secretory vesicles to the sites of secretion at the plasma membrane. In this study, we address several aspects of the plant exocyst complex architecture and cell wall development using molecular biology techniques and advanced confocal microscopy. We demonstrated that two SEC10 exocyst subunits are present in Arabidopsis thaliana and share redundant functions. We also showed that the architecture of the plant exocyst complex shares several structural features with the yeast one. We demonstrated the importance of the functional EXO84b exocyst subunit for normal tracheary element development and showed that the main constituents of the secondary cell walls are deposited normally in exocyst mutants. We described a clear difference in the exocyst microtubule-independent dynamics in epidermal cells vs. cell type...
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The effect of desiccation on streptophyte algae - mechanisms of stress resistance
Pošmourný, Martin ; Pichrtová, Martina (advisor) ; Vosolsobě, Stanislav (referee)
In this thesis I dealt streptophyta algae resistance against desiccation. Even though the area previously devoted only a few people. Considerable amount of work in recent years has been published on the subject. They were found interesting information and discovered new facts. Research continues on and on, and it would be useful to look at what was observed. I believe that understanding this phenomenon is the key to understanding some of the events in the evolution of nature and realizing how tough life can be on the very border of its possible occurrence. I tried to sort out the current knowledge about the mechanisms of stress resistance streptophyta algae and hope that I obtained an overview will help me understand better this issues. So far, it has been observed several approaches to defend against drying. Preventing drying, adaptation to water shortage and tolerance to desiccation. Among the preventive methods of defense include creating clusters of cells, multi-layered mats or secretion mucilage. As an adaptation to the lack of water algae evolved more complex answers in the form of changes in ultrastructure, or regulation of physiological processes. Klebsormidium is capable of half an hour to start the production of significant quantities callose and incorporate it into the cell wall. This...
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Isolation of plant organelles and study of transport mechanisms
Kettnerová, Dana ; Martin, Jan (advisor) ; Tůmová, Lenka (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of Pharmacognosy Diploma thesis Author: Dana Kettnerová Supervisor: PharmDr. Jan Martin, Ph.D. Title of diploma thesis: Isolation of plant organelles and study of transport mechanisms Key words: isolation, chloroplast, protoplast, vacuole, cell wall Isolation of plant organelles and other cellular components is essential for the study of physiological and pathological processes within the plant cell. It is possible to analyze cell structures, detect accumulation of certain metabolites, ions, enzymes and other substances thanks to the isolation. The goal of this diploma thesis was to provide an overview of isolation methods used for the isolation of cell wall, protoplasts, chloroplasts and vacuoles of plant cells. Isolation processes used for individual types of cell structures, the pros and cons of the various isolation methods, components of used media and their functions, as well as the structure and function of individual plant structures were described.
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