|
|
The role of the cytoskeleton in morphogenesis of plant cells
Havelková, Lenka ; Schwarzerová, Kateřina (advisor) ; Hašek, Jiří (referee) ; Malínská, Kateřina (referee)
6. Conclusions ► The capability of ARPC2 protein (subunit of ARP2/3 complex) to bind microtubules was described in this study. Our results indicated that ARP2/3 complex may mediate direct interaction between microfilaments and microtubules in processes where the coordination of microtubule reorganization and actin mediated growth was required. ► We showed that cell-malforming effect of growth retardant ancymidol was based on its inhibitory action on cellulose synthesis. Microtubules played a passive role in this process and were not directly responsible for changes of the cell shape induced by ancymidol. ► Meristematic and suspensors cells in maturating somatic embryos differed in sensitivity to latrunculin B, probably due to different composition of actin isoforms in these cells. Application of low doses of latrunculin B resulted in selective death of suspensor cells and thus contributed to the development of high-quality embryos. ► Aluminium caused rapid cessation of root growth of Arabidopsis thaliana seedlings. We showed that the immediate reason of root growth cessation was plasma membrane rigidization and loss of endocytosis in root cells. Aluminium stabilized cortical microtubules within minutes and induced their loss within hours of treatment. However, the effect of aluminium on microtubules was not...
|
|
|
Nuclear import and export inhibitors analysis in plants
Haltuf, Josef ; Schwarzerová, Kateřina (advisor) ; Angelini, Jindřiška (referee)
Eukaryotic cells have a nucleus where DNA is stored. Transport between the nucleus and cytoplasm is extremely important for ensuring gene expression as well as for controlling and regulating nuclear processes and structures. During interphase, thousands of macromolecules are transported into and out of the nucleus through nuclear pores, and nucleocytoplasmic transport is essential for the viability of eukaryotic organisms. Transport between the nucleus and cytoplasm is tightly regulated, and specific inhibitors of nuclear transport are used to study this regulation. While nuclear transport inhibitors have been extensively studied in animal cell research, the activity of most of them has not been tested in plant cells. In this work the nuclear export inhibitors Leptomycin B (LMB) and the nuclear import inhibitors Importazole (IMZ) and Ivermectin (IVR) are tested in Arabidopsis thaliana plant roots and in isolated tobacco BY- 2 cells. This work also includes testing suitable markers for transport between the nucleus and cytoplasm. GFP-NES and NLS-GFP were found to be the best markers because they are stable and can diffuse spontaneously through nuclear pores. With these markers, I determined effective concentrations for LMB (100 nM in roots, 50 nM in isolated cells) and IMZ (75 μM in roots). IVR proved to be...
|
|
|
Analysis of the relationship between the function of the ARP2/3 protein complex and exocytosis in plant cells
Ničová, Klára ; Schwarzerová, Kateřina (advisor) ; Synek, Lukáš (referee)
Plant cells exhibit two types of growth: diffuse and apical. Mutation of the ARP2/3 complex, which is an actin nucleator, leads to phenotypic expression in both diffusely and apically growing cells. Many of these changes, such as impaired epidermal cell adhesion of hypocotyl cells or slower growth of pollen tubes, suggest that the observed phenotypes are cell wall related. Cell wall components are transported into the apoplastic space by exocytosis. Many factors are involved in controlled exocytosis, one of the most studied being the exocyst tethering complex. Mutants of the exocyst complex show phenotypes in both diffusely and apically growing cells, indicating that this complex is important for both types of growth. In addition, subunit EXO84b of the exocyst complex interacts with subunits of the ARP2/3 complex. In this thesis, I investigated the effect of mutation of ARP2/3 complex subunits on exocytosis of diffusely and apically growing cells by observing the localization and dynamics of the fluorescently labeled marker EXO84b-GFP. In epidermal hypocotyl cells (a model of diffuse growth), EXO84b-GFP had a shorter lifetime at the plasma membrane in ARP2/3 mutants compared to wild type. The pattern of its localization to the plasma membrane was also slightly different. It was not possible to...
|
|
|
ARP2/3 complex interaction with plant secretory pathway components
Voloshina, Mariia ; Schwarzerová, Kateřina (advisor) ; Oulehlová, Denisa (referee)
The ARP2/3 complex is an evolutionarily conserved protein complex involved in actin nucleation. In animals, the loss of function of ARP2/3 subunits is usually lethal. In contrast, arp2/3 plants are viable and exhibit certain morphological defects. One of the characteristic traits of arp2/3 plants is impaired cell adhesion. This suggests a role for the ARP2/3 complex in plant cell wall secretion, specifically pectins. However, the exact molecular mechanism of ARP2/3 function in this pathway has not been elucidated yet. Preliminary results suggest a possible interaction of ARP2/3 with the secretory pathway proteins GNL1, COPI, and COG. This work combines two methods - TIRFM/VAEM and co-immunoprecipitation - to study the interaction of ARP2/3 with selected markers. However, neither colocalization nor physical interaction was demonstrated. This work also characterises COPI, COG and GNL1 with TIRFM/VAEM and shows that there is an interaction between GNL1 and endocytic markers. Key words: ARP2/3, COPI, COG, GNL1, secretory pathway
|
|
|
Thermal imaging as a tool for evaluation of plant's cooling effect in green façades
Nohová, Michaela ; Lhotáková, Zuzana (advisor) ; Schwarzerová, Kateřina (referee)
Urbanisation and global warming are gaining momentum, and with it the need to improve the thermal comfort of urban citizens is growing. Due to the geometry of the city and the thermal properties of the materials from which the city consists, the so-called urban heat island effect occurs, which causes the temperature in city centres to be higher than in rural areas. One possible way to mitigate the urban heat island effect is to incorporate vegetation into the urban infrastructure. Green architecture is designed to do just that, and in this thesis I specifically focus on green facades and their cooling effect. Since green facades are usually large areas of green surface, this thesis focuses on thermal imaging and its use to measure the cooling rate of buildings and ambient air by green facades. It is the use of thermal cameras that is characterized by the ability to image large areas and record their temperature in real time, making thermal cameras an ideal tool for green facade research. As this topic is very specific and not yet so widespread in the literature, I discuss thermography from several perspectives in the context of its use for research on plant physiological parameters, and I also discuss the various methods and pitfalls of working with thermal image data. Key words: abiotic stress,...
|
|
|
Cell inclusions in microscopic eukaryotes
Pilátová, Jana ; Schwarzerová, Kateřina (advisor) ; Gierlinger, Notburga (referee) ; Prášil, Ondřej (referee)
This thesis reports, for the first time, a systematic study identifying various cell inclusions across the broad diversity of all major eukaryotic supergroups. Raman microspectroscopy technique was employed as a powerful technique, which is becoming the method of the first choice for such studies. In Chapter 1, the spatial reconstruction of chloroplasts of the unicellular zygnematophyte Cylindrocystis sp. (Streptophyta) revealed "empty spaces" inside. Subsequent analysis showed massive accumulations of polyphosphate, which is not located in the cytoplasm as in other species, but inside the chloroplasts. This newly discovered ability of the zygnematophytes, a sister group of terrestrial plants, to accumulate polyphosphate leads us to speculate about a possible adaptation to extreme Arctic conditions or even a preadaptation leading to plant terrestrialization. Chapter 2 summarizes the serendipitous discovery of purine crystalline inclusions in dinoflagellates and other microalgae. Investigated dinoflagellate species comprised zooxanthellae, the endosymbionts of reef-building corals, and the species causing toxic algal blooms. Purine crystals were further shown to act as dynamic high-capacity nitrogen storage. To show how widespread purine inclusions are, a revision of crystalline inclusions in all...
|
|
| |
|
|
Lignin and lignification mechanisms
Gargoš, Ondřej ; Tylová, Edita (advisor) ; Schwarzerová, Kateřina (referee)
Lignin is an essential compound of all vascular plants. Recent studies have also shown its presence in non-vascular plants. Lignin is important for plant growth and development, provides a mechanical support to plant tissues and is also a major player in the response of plants to various stresses. Lignin is an aromatic heteropolymer and comprises classical lignin units - guaiacyl (G), syringyl (S) and p-hydroxyfenyl (H). The amount and ratio of these lignin units varies among plant species, organs and cell types. Nontraditional monomer units that can be deposited in lignin also increase the variety of lignin. Lignification, i.e. the formation and deposition of lignin, is a complex and precisely controlled process involving the synthesis of monolignols in the cytoplasm, their transport into the cell wall and subsequent polymerization. A number of enzymes are involved in the lignification process, and recent studies are gradually revealing the mechanisms of lignification regulation in various cells of plant body. This bachelor thesis summarizes the knowledge of the importance, synthesis and deposition of lignin, and also compares the mechanisms regulating lignification in different types of plant cells - tracheary elements, sclerenchyma and endodermal cells. An interesting phenomenon of lignification...
|
|
|
The role of ARPC2 in plant cells
Šlajcherová, Kateřina ; Schwarzerová, Kateřina (advisor) ; Klíma, Petr (referee)
ARPC2 protein localization in a plant cell Kateřina Šlajcherová 1 Abstract Actin cytoskeleton is an ubiquitous structure which plays numerous irreplacable roles. Actin nucleation is, beside formins, performed by ARP2/3 complex (actin-related protein), comprising of seven subunits (ARP2, 3, C1-C5) and activated by protein SCAR/WAVE complex. ARP2/3 complex is attached to the membrane and branches existing microfilaments, apart from nucleating them de novo. ARP2/3 mutants in most organisms show severe defects. However, plant mutants exhibit only mild phenotype, for example, Arabidopsis thaliana ARPC2 mutant (dis2-1) has deformed trichomes and leaf epidermal cells, but its viability is not impaired. The aim of the thesis is to map ARPC2 localization within the cell and broaden our understanding of ARP2/3 complex role in plant cell morphogenesis. Tobacco ARPC2 (NtArpC2) subunit was visualized in Arabidopsis plants, using the GFP fusion protein as well as imunofluorescence and anti-ARPC2 antibody. Experiments were undertaken to collocalize the subunit with actin and microtubular cytoskeleton, with mitochondrions, endosomes and other membrane organelles. The specimens were observed in confocal and TIRF microscope. The GFP-NtARPC2 protein shows as motile dots; their movement, but not their existence, is dependent...
|
|
|
The effect of Arp2/3 complex on vacuolar structure, cytoplasmic streaming and dictyosome motility.
Semerák, Matěj ; Schwarzerová, Kateřina (advisor) ; Eliášová, Kateřina (referee)
In plant cells, actin filaments are nucleated in two different ways: The growth of single filaments or their bundles is enabled by various types of formins, whereas branched meshworks emerge due to Arp2/3 complex activity. Mutations in genes of these nucleators lead to various phenotypic traits. This thesis deals in the first place with influence of Arp2/3 complex subunits' dysfunction on intracellular motility (cytoplasmic streaming, stop-and-go movements of Golgi apparatus cisternae), since it had not been extensively studied before, and also attempts to quantify the already known impacts of mutations in genes for ARP2 and ARPC5 subunits on the vacuolar morphogenesis. For comparison, a few experiments with plants which carried a mutation in gene for FH1 formin were also realised when measuring the cytoplasmic streaming. The experiments were conducted with a model plant Arabidopsis thaliana. The methods particularly included transformation with fluorescent markers by Agrobacterium tumefaciens (or usage of a fluorescent dye), microscopy (both standard and confocal) and subsequent evaluation of the acquired data using a computer. During the cytoplasmic streaming research, effects of cytoskeletal drug latrunculin B were studied, too. The outputs did not prove that the Arp2/3 complex defects would manifest...
|
guest ::
RSS feed.