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Dynamics and role of the Arabidopsis thaliana IAA17/AXR3 protein in regulation of root growth by auxin
Kubalová, Monika ; Fendrych, Matyáš (advisor) ; Glanc, Matouš (referee)
Auxin is phytohormone that regulates several developmental processes and environmental responses. One of the most well-described outcome of the auxin signalling pathway is regulation of gene transcription. Aux/IAA proteins play an important role in this process, acting as transcriptional repressors. Recent studies revealed that several root growth responses are too rapid to be explained by changes in the level of transcription. The correlation between the amount of Aux/IAAs and the root growth rate suggests that these proteins might be involved in root growth regulation, especially during rapid growth responses that are not associated with transcriptional reprogramming. This work is focused on one of the 29 Arabidopsis Aux/IAA proteins - the IAA17/AXR3 protein. First, we produced stable transgenic lines of Arabidopsis thaliana expressing different combinations of fluorescently labelled AXR3-1 proteins and/or fused to subcellular localization tags under the control of different tissue-specific promoters, in order to characterize the subcellular localization of the studied protein. Subsequent visualization by confocal microscopy methods confirmed information about the role of IAA17/AXR3 protein in root growth responses, its involvement in auxin signalling, and gravitropism. Next, we showed that the...
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Gravitropism mechanisms in single-celled organs and multicellular organs of plants
Nehasilová, Martina ; Fendrych, Matyáš (advisor) ; Kurtović, Katarina (referee)
Plants react to various environmental stimuli by oriented growth. The growth responses are called tropisms. Gravitropism is a directed growth concerning the gravity vector. Plant shoots grow up, negatively gravitropically, to catch the light. Roots are positively gravitropic; they grow down to anchor the plant in the substrate and seek water and minerals. The process of gravitropism consists of three stages: signal perception, signal transmission, and growth response. These stages can all occur in a single cell or separately in different parts of a multicellular organ. Single-cell gravitropic systems are represented by algal rhizoids or moss protonemata. They need minimal signal transmission because gravity vector perception and growth response happen in the same cell. The multicellular systems, represented here by angiosperm roots, have a more robust signal transmission phase. This thesis compares mechanisms of plant gravitropism based on the two categories - single-cell vs. multicellular. Despite their different cellular arrangements, single-cell and multicellular gravitropism share several characteristics, such as statolith sedimentation, Ca2+ fluxes, pH changes, and altered vesicular trafficking. Still, the lack of knowledge about the single-cell systems and high inner variability within the...
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Tissue-specific knockout of starch synthesis in columella cells of Arabidopsis thaliana and gravitropic response
Bogdan, Michal ; Fendrych, Matyáš (advisor) ; Retzer, Katarzyna (referee)
Since the studies of plant gravitropism by Charles Darwin, the identity of specific sensors of gravity in plants has been uncertain. To this date, statoliths - starch granules in the root tips - are considered to play a key role in gravity sensing. The role of statoliths as organelles that mediate the gravity sensing ability of plant roots is based on research that uses plants which have severely impaired ability to synthesize starch in general or have their cells that contain statoliths removed or damaged. This represents methodical imperfections that give rise to alternative explanations, like disturbed auxin flow due to heavy damage to the root tip or unknown involvement of starch from other parts of the plant in gravity perception. Thanks to advances in the field of CRISPR/Cas9 technology, we are now able to produce tissue-specific mutants that might help with clarification of whether starch granules in the root tip are involved in sensing gravity and if so, how significant is this involvement. This diploma thesis aimed to answer these questions by adapting the tissue-specific CRISPR/Cas9 system and using it for the creation of mutants that are starchless specifically in the columella cells. Using this approach, we generated one tissue non-specific mutant line and three tissue-specific mutant...
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Dynamics and role of the Arabidopsis thaliana IAA17/AXR3 protein in regulation of root growth by auxin
Kubalová, Monika ; Fendrych, Matyáš (advisor) ; Glanc, Matouš (referee)
Auxin is phytohormone that regulates several developmental processes and environmental responses. One of the most well-described outcome of the auxin signalling pathway is regulation of gene transcription. Aux/IAA proteins play an important role in this process, acting as transcriptional repressors. Recent studies revealed that several root growth responses are too rapid to be explained by changes in the level of transcription. The correlation between the amount of Aux/IAAs and the root growth rate suggests that these proteins might be involved in root growth regulation, especially during rapid growth responses that are not associated with transcriptional reprogramming. This work is focused on one of the 29 Arabidopsis Aux/IAA proteins - the IAA17/AXR3 protein. First, we produced stable transgenic lines of Arabidopsis thaliana expressing different combinations of fluorescently labelled AXR3-1 proteins and/or fused to subcellular localization tags under the control of different tissue-specific promoters, in order to characterize the subcellular localization of the studied protein. Subsequent visualization by confocal microscopy methods confirmed information about the role of IAA17/AXR3 protein in root growth responses, its involvement in auxin signalling, and gravitropism. Next, we showed that the...
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Evolutionary and theoretical aspects of the biological work of Bohumil Němec
Loginov, Ivan ; Hermann, Tomáš (advisor) ; Žárský, Viktor (referee)
Plant physiologist Bohumil Němec is one of the most important people in the history of Czech science. In this thesis, crucial concepts and theories that B. Němec developed in his scientific and popularizing publications are described and put in context. In addition, materials from the personal fond of B. Němec located in the Archive of the CAS were used. Particular questions tackled in this thesis are those of stimuli transmission in plants, the starch-statolith theory of gravitropism, morphaesthesia, organogenes, Němec's approach to evolutionary theory, and genetics, and the division of organisms in two groups. Moreover, Němec's role in the contemporary debates about vitalism, mechanism, and the effect of these two philosophies on the approach towards scientific research is indicated. By that, Němec's transition from the mechanism to the so-called physiology of stimuli (Rheizphysiologie) is illustrated. The outcome of the thesis is broadening the knowledge in the history of plant physiology, especially the history of the natural sciences in the Czech context.
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Scientific and Institutional Activities of Bohumil Němec at Charles University
Loginov, Ivan ; Hermann, Tomáš (advisor) ; Žárský, Viktor (referee)
Bohumil Němec ranks among the most remarkable figures of Czech science. At the beginning of the 20th century he made a significant contribution to the explanation of plant gravitropism and to the establishment of the Institute for plant physiology at the Faculty of Science at Charles University. Besides that he also studied plant regeneration, fertilization and nuclear division. In my thesis I processed scientific and popular scientific articles by Němec and used secondary sources to analyze his overall activity at the university in historical context. Thesis output is structured overview of Bohumil Němec's activities which can be used for the follow-up research.
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