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Cellular processes in twining plants and tendrils
Šimečková, Jana ; Krtková, Jana (advisor) ; Skokan, Roman (referee)
This work focuses on the twining of stems and tendrils of vines and the underlying cellular processes involved. Vines, comprising a diverse group, require support for their growth and are known as "climbers." Successful coiling depends on the contact between the plant and the support, this contact is facilitated by movements such as skototropism and circumnutation. Once in contact with the support, coiling occurs. Specialized G-fiber cells appear to play a crucial role in the coiling process. Additionally, microtubules and cellulose microfibrils are extensively studied in the context of helical growth. Although the complete picture of cellular signaling during coiling remains elusive, numerous chemical substances influencing coiling have been identified, including jasmonates and other plant hormones. Many significant plants fall into the category of climbing plants, yet much remains unknown about their coiling mechanisms.
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The Plant Experimental Models in Centuries - till 1918
Bršťáková, Hana ; Krtková, Jana (advisor) ; Lipavská, Helena (referee)
By 1918, many studies in plant organisms were performed. These laid fundamental building blocks for today's advanced research. To perform the experiments, many plant species were used. My thesis describes, first, which plant species were used in the experiments and second, what kind of discovery was made using them. I focus on plant processes and research fields that were of interest for the scientists then and this strucrure is also followed in my thesis. Each chapter describing individual process or research field is then written in chronological order. Specifically, the discovery of plant cell, selected plant movements such as nutation, phototropism, gravitropism, hydrotropism, plant nutrition and also the first scientific observation of Arabidopsis thaliana are discussed. The goal of this thesis is to introduce the history of selected discoveries in plants and to explain in which plant species the appropriate findings were achieved.
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Phototropic memory in early plant development
Šišková, Michaela ; Konrádová, Hana (advisor) ; Krtková, Jana (referee)
This thesis was inspired by controversial published results on the existence and reliability of a memory trace of the direction of the last illumination in young dicots. The theoretical part first covers phototropism, it briefly summarizes current knowledge about this growth movement, phototropins, and the mechanism of phototropic bending, including the role of auxin and its transporters. It also discusses the effect of previous light exposure on hypocotyl bending. Another section of the theoretical part is focused on the question of the existence of memory in plants. The experiments performed in the practical part are based on the assumption that plants are able to store a memory trace of previous light exposure. After the establishment of a system that made it possible to obtain a robust phototropic response to blue light, seedlings of the model plant Lepidium sativum were tested under different conditions to see if and how the direction of light affected the plants' response to subsequent phototropic stimulation. The results suggest that in at least one case, the final phototropic response could be interpreted as a formation of a specific memory trace in the tested plants. However, based on the results of this work, the existence of a memory trace of previous light exposure cannot be...
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Molecular base of plant HSP90-MT interaction
Benáková, Martina ; Krtková, Jana (advisor) ; Malcová, Ivana (referee)
Microtubules (MTs) are one of the essential cell structure that participate in a number of key events in the plant cells and their properties and functions are influenced and modified by many other proteins. These proteins belong to a group of microtubule- associated proteins (MAPs, microtubule-associated proteins). One of the MAPs, the molecular chaperone Hsp90, examines and fulfills a large number of different functions in the cell. Its colocalization with MTs has been demonstrated previously by Freudenreich and Nick (1998) and Petrášek et al. (1998). However, direct interaction with MTs was described only recently using cosedimentation assay. The specific cytosolic isoform of tobacco Hsp90 bound to MTs was called Hsp90_MT due to its ability to bind MTs. It has been also found that the binding to MTs is independent on the activity of ATP (Krtková et al., 2012). The authors also described a positive effect of Hsp90_MT on MT recovery after their exposure to cold stress. Although MT cytoskeleton dynamics is influenced by a large number of MAPs, it is surprising that the molecular mechanism of MAPs interaction with MTs and their MT-binding domains have not been described yet. Therefore, we decided to determine the tobacco Hsp90_MT MT-binding domain by production of a set of recombinant proteins...
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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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Endocytosis in plants
Svitáková, Lenka ; Krtková, Jana (advisor) ; Hála, Michal (referee)
Endocytosis is a process typical for eukaryotic cells. It is a mechanism that ensures invagination of the plasma membrane which leads to the creation of a membrane vesicle with specifically selected cargo. The vesicle is then internalized by the cell. Endocytosis has a crucial role in plant growth and development not only thanks to the reception of nutrients from the extracellular space but also by having a huge impact on the membrane composition which influences cellular signalling. There are few types of endocytosis known in plants. They differ from each other by the molecular machinery which ensures their process. The most studied type in plants is the clathrin-mediated endocytosis. Clathrin-coated vesicle formation proceeds through five stages. However, there are less details known about it in plant cells than in animal cells. In the first part of my bachelor thesis I describe recent knowledge of this topic and the most important participants in this process. I also mention the mechanisms of regulations that plant cells use to coordinate clathrin-mediated endocytosis. In the second part I summarize recently discovered types of endocytosis in plants that are independent from clathrin. These are endocytosis associated with microdomains and fluid- phase endocytosis. The details of these endocytic...
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