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Rodina auxinových přenašečů PIN: funkční a evoluční pohled
Skůpa, Petr ; Zažímalová, Eva (advisor) ; Hejátko, Jan (referee) ; Opatrný, Zdeněk (referee)
Growth and development of plant body is dependent on correct and effective integration of information about current deployment of its body parts, as well as on perception and transduction of inputs from environment. Multiple developmental processes within plant body are determined by specific and tightly controlled distribution of molecule with unique signaling mission within plant development - auxin. Spatial distribution of auxin is co-determined by plethora of tightly controlled processes, and the polar auxin transport plays unique role among them. PIN proteins are the plant-specific family of secondary transporters driving movement of auxin across membranes. With their frequent asymmetrical localization within cells, specific expression patterns in developing tissues and their reactiveness to external cues they secure unique, dynamic and asymmetric distribution of auxin within the plant body. This dissertation thesis is focused on characterization of the role different PIN proteins play in determining cellular auxin homeostasis and consequent formation of auxin gradients. Controlled overexpression of PIN proteins in tobacco cells showed, that PIN4 and to some extent also PIN6, function as the direct auxin efflux carriers. In the cellular auxin transport they play the role analogous to other...
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New insights on auxin metabolism
Helusová, Lenka ; Müller, Karel (advisor) ; Ryšlavá, Helena (referee)
Auxin is the longest known phytohormone with many functions. It participates in the development of embryo, in vegetative and generative development, plant stress reaction, and also in their senescence and death. Activity of auxin in plant cells and tissues is quite often compared to the effect of morphogens, i.e. the effect of substances, whose concentrations induce a strictly defined response in tissue and organ formation. Apart from intercellular and intracellular auxin transport, the main determinants of auxin concentration gradients are its biosynthesis and metabolism. Regardless of the long-lasting study of auxin, the complexity of metabolic pathway regulation is still not well known. The aim of this thesis is to summarize current knowledge of the metabolism of auxin in plants, i.e. its biosynthetic pathways, conjugation and oxidation, and put them into a context with older results.
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The evolution of auxin homeostasis mechanisms
Skokan, Roman ; Petrášek, Jan (advisor) ; Buschmann, Henrik (referee) ; Holzinger, Andreas (referee)
The evolution of auxin homeostasis mechanisms Ph.D. thesis Roman Skokan, 2021 Abstract The streptophyte lineage consists of land plants (embryophytes) and several groups of primarily freshwater green algae called charophytes. While the phytohormone auxin is a conserved regulator of land plant development, little has been known of the possible origins of auxin response mechanisms in charophytes. We found that one of these mechanisms, the cellular auxin efflux via the PIN family of transport proteins, is most likely a deeply conserved feature in streptophytes. Additionally, we investigated the state of conservation in the green lineage (Viridiplantae) of the gene families known to be involved in auxin transport in land plants. We revealed that some families are deeply conserved outside land plants, but not others. We also helped uncover a unique radiation within the PIN family in Charophyceae. Striving to uncover the native significance of auxin transport in charophytes, we discovered a growth response to exogenously-applied auxin in Closterium, though the effort to produce stable mutant lines in the native PIN homolog is still underway. Altogether, we brought important insights into the evolution of auxin transport and response in the streptophyte lineage, though many questions still remain.
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The role of auxin in streptophyte algae
Schmidt, Vojtěch ; Petrášek, Jan (advisor) ; Pleskot, Roman (referee)
The phytohormone auxin is an important morphogen with an essential role in the development of land plants, where mechanisms of its action are well described. However, its role in green algae is poorly understood. Land plants are part of the phylum Streptophyta together with six closely related groups of predominantly freshwater green algae (charophytes). So far, the knowledge about the evolutionary origins of auxin action mechanism is mainly based on genomic information, and much less on experimental findings. In this work, the presence of auxin, its precursor, and catabolism products were shown in representative species of charophytes with varying levels measured compounds both produced endogenously and into the culture media. Thus, we gained a comprehensive insight into the possible strategies of auxin homeostasis across the non-land plant streptophytes. Also, an effect of exogenous auxin on the cell morphology and culture growth of the desmid Closterium was investigated. Image analysis of IAA-treated cells revealed a rather pleiotropic effect on cell morphology. The culture growth was inhibited by IAA. Additionally, IAA induced malformations in cell shape, and the extent of this phenomenon across individual cultures was dependent on the culture growth status. Lastly, we optimized the method of...
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Mechanisms coordinating auxin metabolism and transport
Novotná, Lenka ; Petrášek, Jan (advisor) ; Serre, Nelson Bernard Calixte (referee)
Auxin is a small molecule that functions as a plant hormone, and it exists in several forms, of which indole-3-acetic acid (IAA) is the most studied one. IAA modulates cell elongation, division, and differentiation by generating local gradients, and it is essential for almost every aspect of plant growth and development. These gradients are established by the cooperation of IAA biosynthesis, metabolism, and transport. A plant responds to both local auxin maxima and minima; thus, it is necessary to regulate auxin metabolism and transport tightly. However, lots of studies show the roles and regulation of auxin metabolism and transport separately, providing quite rarely discussion on the cooperation of these two processes. Hence, this thesis aims to sum up and refer to mechanisms and regulation of auxin metabolism and transport as a whole, rather than separately, and underline the importance of the cooperation of both auxin metabolism and transport in the plant development.
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New insights on auxin metabolism
Helusová, Lenka ; Müller, Karel (advisor) ; Ryšlavá, Helena (referee)
Auxin is the longest known phytohormone with many functions. It participates in the development of embryo, in vegetative and generative development, plant stress reaction, and also in their senescence and death. Activity of auxin in plant cells and tissues is quite often compared to the effect of morphogens, i.e. the effect of substances, whose concentrations induce a strictly defined response in tissue and organ formation. Apart from intercellular and intracellular auxin transport, the main determinants of auxin concentration gradients are its biosynthesis and metabolism. Regardless of the long-lasting study of auxin, the complexity of metabolic pathway regulation is still not well known. The aim of this thesis is to summarize current knowledge of the metabolism of auxin in plants, i.e. its biosynthetic pathways, conjugation and oxidation, and put them into a context with older results.
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Plant hormones homeostasis: auxin and cytokinin crosstalk
Doležálková, Lucie ; Zažímalová, Eva (advisor) ; Dračínská, Helena (referee)
5 AbstractAbstractAbstractAbstract It has been since 19th century when the phytohormones and their crosstalk became one of the central themes in plant biology. Due to advances in molecular biology there is number of metabolic pathways linked to certain groups of plant hormones revealed by now, nevertheless much remains to be determined about their cooperation. The aim of this thesis is to evaluate the effect of exogenous cytokinin application on oat leaf segments (Avena sativa) - both specifically towards other phytohormones levels and generally in physiological context (in relation to their senescence). Our results confirmed increased auxin levels due to exogenous application of selected cytokinins and identified biological activity of trans-zeatin-9-glucoside (previously considered as irreversibly deactivated cytokinin type substance) in respective plant model. (In Czech) Key words: phytohormones, auxin, cytokinin, Avena sativa, senescence assay
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Rodina auxinových přenašečů PIN: funkční a evoluční pohled
Skůpa, Petr ; Zažímalová, Eva (advisor) ; Hejátko, Jan (referee) ; Opatrný, Zdeněk (referee)
Growth and development of plant body is dependent on correct and effective integration of information about current deployment of its body parts, as well as on perception and transduction of inputs from environment. Multiple developmental processes within plant body are determined by specific and tightly controlled distribution of molecule with unique signaling mission within plant development - auxin. Spatial distribution of auxin is co-determined by plethora of tightly controlled processes, and the polar auxin transport plays unique role among them. PIN proteins are the plant-specific family of secondary transporters driving movement of auxin across membranes. With their frequent asymmetrical localization within cells, specific expression patterns in developing tissues and their reactiveness to external cues they secure unique, dynamic and asymmetric distribution of auxin within the plant body. This dissertation thesis is focused on characterization of the role different PIN proteins play in determining cellular auxin homeostasis and consequent formation of auxin gradients. Controlled overexpression of PIN proteins in tobacco cells showed, that PIN4 and to some extent also PIN6, function as the direct auxin efflux carriers. In the cellular auxin transport they play the role analogous to other...
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