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Mechanisms of transmembrane auxin transport in a broader evolutionary context.
Rubešová, Magdaléna ; Petrášek, Jan (advisor) ; Tylová, Edita (referee)
Auxin, represented by the molecule indole-3-acetic acid (IAA), is one of the main phytohormones involved in the regulation of plant development. Its intercellular transport establishes concentration gradients in individual cells that control gene expression and a number of downstream processes. In plants, a complex mechanism for efficient IAA transport has evolved, involving both long-distance transport and intercellular transport within individual tissues. Because our understanding of the auxin transport mechanisms is still incomplete, this thesis attempts to summarize the literature data on all modes of auxin transport across cell membranes that have been recognized to date and places them in a broader evolutionary context. The presence of IAA in many prokaryotic and eukaryotic organisms, together with the similarly wide occurrence of carriers from "auxin efflux carrier" transporter family, evolutionarily related PIN-FORMED-like carriers, points to the possibility that IAA transport may also be evolutionarily very ancient and may functionally derive from more general mechanisms of ions or amino acids.
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Creating and testing bioluminescence sensors for cytokinins in Arabidopsis thaliana
Novotná, Lenka ; Petrášek, Jan (advisor) ; Vosolsobě, Stanislav (referee)
Advances in microscopy and the sensitivity of novel biosensors have enabled the development of new methods for monitoring phytohormones with low invasiveness and relatively high resolution, providing greater insight into phytohormone function in plants. Genetically encoded indirect biosensors for cytokinins, one of the main plant hormones, are widely used for the tracking of dynamic changes in their levels during plant development and growth. The cytokinin-sensitive synthetic promoters used as cytokinin biosensors are being continuously improved, providing better insight into cytokinin function. However, the reporter systems used for the visualizations are either based on the enzymatic reaction producing colour or on the usage of fluorescence proteins. Luminescence-based biosensors are often used to visualize signaling outputs of plant hormones, but they are based on exogenous addition of luciferin substrate. Therefore, in this thesis, I have introduced a new technique for the generation of cytokinin signaling output sensors based on autonomous bioluminescence. This autonomous bioluminescence represents a non-invasive technique that depends on the expression of the whole autonomous bioluminescence system from fungi Neonothopanus nambi, in particular, the caffeic acid cycle with the fungal...
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Physiological basis of the tradeoff between growth and defense against abiotic stress: the role of carbon balance
Doložílek, Jakub ; Konrádová, Hana (advisor) ; Petrášek, Jan (referee)
Similarly to other organisms, plants must coordinate growth and development with their energetic status. Besides that, considering their sessile way of life, they need to adapt very precisely to the environmental conditions of their habitats. However, from the point of view of invested resources, the defence mechanisms may be very expensive, and so, their activation is usually accompanied by a restriction of growth. Hence, establishing functional dynamic balance between investment to growth and defensive reactions ("G-D tradeoff") is essential for the plants fitness, competitiveness and reproduction success. The thesis examines the mechanisms that are fundamentally contributing to this balancing. In this work, evolutionarily conserved axis coordinating growth and development with energetic status consisting of TOR kinase, positive growth regulator during favourable conditions, and her antagonist, the SnRK kinase, inducer of resources mobilization in purpose of realizing defensive measures securing energetic homeostasis, is discussed. Further, this thesis focuses on plant-specific pathway which links the TOR-SnRK1 axis with perception of environmental conditions. The main components of this pathway are the SnRK2 kinases, coordinators of specific defensive reactions, PP2C phosphatases and...
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Cellular determinants of the distribution of PIN auxin transporters in the plasma membrane
Stelate, Ayoub ; Petrášek, Jan (advisor) ; Mravec, Jozef (referee) ; Nodzynski, Tomasz (referee)
Asymmetric localization of auxin carriers has always attracted the attention of many scientists around the world. However, to address this topic while focusing on the plasma membrane (PM), requires advanced microscopy techniques and knowledge of biophysics and biology. This doctoral work bridges the two disciplines to contribute to our understanding of the dynamics and distribution of PIN-FORMED auxin carriers from tobacco (NtPINs) within the PM. I have developed a novel correlative light electron microscopy (CLEM) method using total internal reflection fluorescence microscopy (TIRFM) and advanced environmental scanning electron microscopy (A-ESEM). To my knowledge, this is the first effort to achieve a correlation between immunofluorescence and electron microscopy imaging of plant integral PM proteins. As I have shown, individual NtPINs are organized differently within the PM. Dynamic analyses that quantify individual nanodomains' diffusion rates allowed me to show that NtPINs have constraints behavior with different diffusion rates. I have investigated the role of the cell wall and cytoskeleton in the organization and dynamics of NtPINs. Using pharmacological treatments, I have shown that they differentially affect the mobility and organization of NtPINs within the PM. Complete removal of the...
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The role of actin cytoskeleton in the targeting of auxin carriers to the plasma membrane.
Kebrlová, Štěpánka ; Petrášek, Jan (advisor) ; Pernisová, Markéta (referee)
Auxin plays an important morphogenic role in plant development, mainly through its effect on gene expression, but also through a number of faster processes that are directly dependent on its concentration. Therefore, in many plant tissues, directional auxin transport using specific transporters in the plasma membrane, is important for the coordination of morphogenic stimuli. The amount of auxin carriers in the plasma membrane directly affects the resulting auxin concentration inside the cell. Although the localization of auxin transporters and their abundance in the plasma membrane could be determined primarily by the actin cytoskeleton and its involvement in vesicle transport processes, this relationship is currently still unclear. Therefore, in this study, we were interested in how the localization and function of auxin transporters is affected when the function of the actin cytoskeleton is affected in a given cell type. To this end, the localization of the auxin transporters PIN3, PIN4, PIN7, and AUX1 was studied in epidermal cells of cotyledons in young seedlings of Arabidopsis thaliana whose morphogenesis was affected by mutations in subunits of the actin nucleation complex ARP2/3. Crosses of mutants in the ARP2/3 complex subunits with marker lines carrying fluorescently labeled auxin carriers...
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Hormonal regulation of plant cell division and elongation
Petrášek, Jan ; Zažímalová, Eva (advisor) ; Griga, Miroslav (referee) ; Procházka, Stanislav (referee)
a I I T T T I I a I I a T I T I t r T T I Jml PnrnÁŠnx Suvnalnv SuuuuARyoF DtssERTATtoNTHEsts This thesisis focusedon thehormonalregulationof plantcelldivisionand growth.Both these processes are crucial in shaping sessile plant body. The manifestationof directionalityin ce||p|ateformationduringcýokinesisas we||as in celle|ongationcou|d be found in a form of various shapes of cells, organs and whole plants.Equal and inequal cell division,cell elongationand isodiametriccell growth- they all allow establishing,formingand maintainingcharacterof tissues,organsand whole bodies duringplantdevelopment. Scientificresearchhas alwaysbeenfocusedon regulatorycompounds,the actionof which induces detectable and observable responses. By uncovering the exact mechanisms of their mode of action, many intermediatemessengers were found. However,classicalconceptof "majorregulators'surviveduntilthesedays.lndeed,plant hormones, small organic molecules with wide range of effects, are typical representativesof such compounds,which are studiedalready around one hundred years.They are synthesisedand utilisedin varioustissuesthroughoutthe wholeplant and theycouldbe transportedin vasculatureto longdistances. Auxins and cýokinins - regu|atorsof plant development The researchof recentyears contributedremarkablyto the understandingof...
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Auxin transport in algae
Skokan, Roman ; Petrášek, Jan (advisor) ; Bíšová, Kateřina (referee)
Phytohormone auxin plays an important role in regulating plant development. Directional (polar) cell-to-cell auxin transport creates auxin gradients within plant tissues, which trigger a specific developmental response. The vast majority of available data concerns angiosperms. Lower land plants have been much less explored in this regard, but the important auxin-related mechanisms (including polar auxin transport) are already present in mosses. To uncover the origins of auxin action, one must focus on green algae, especially of clade Streptophyta, which are the direct ancestors of all land plants. In this study, the possible effects of auxins, both native and synthetic, were investigated on two algae: basal, unicellular Chlorella lobophora and advanced, filamentous Spirogyra sp. The latter received comparably more attention, since it belongs to a clade now acknowledged as a sister group to land plants. Chlorella lobophora culture growth was irresponsive to synthetic auxin NAA. The average Spirogyra sp. cell length was, however, changed by auxins at high concentrations. By conducting accumulation assays of radioactively labelled auxins and HPLC analysis, auxin metabolism and transport was investigated in Spirogyra sp. This alga was able to metabolize the plant-native IAA, but not synthetic auxins...
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The role of toll-like receptors in the pathogenesis of liver diseases
Petrášek, Jan ; Jirsa, Milan (advisor) ; Tlaskalová - Hogenová, Helena (referee) ; Červinková, Zuzana (referee)
Identifikační záznam: PETRÁŠEK, Jan. ÚLOHA TOLL-LIKE RECEPTORŮ V PATOGENEZI JATERNÍCH ONEMOCNĚNÍ. [The role of toll-like receptors in the pathogenesis of liver diseases]. Praha, 2010. 198s., Disertační práce. Univerzita Karlova v Praze, 1. lékařská fakulta, Laboratoř Experimentální Hepatologie IKEM. Vedoucí práce: Milan Jirsa. Abstrakt Společným jmenovatelem nejčastějších onemocnění jater je aktivace mechanismů vrozené imunity, které přispívají k rozvoji zánětu a poškození jaterního parenchymu. Klíčovou úlohu v rozvoji jaterního poškození hrají Toll-like receptory, jejichž charakterizace v posledním desetiletí vedla přehodnocení patofyziologie některých jaterních onemocnění. Předkládaná práce studuje význam alelických variant v genech kódujících proteiny Toll-like receptorové signální kaskády a mezibuněčné signalizace v patogenezi alkoholické nemoci jater, přináší nový pohled na probiotika v léčbě nealkoholické steatohepatitidy a nové poznatky o protizánětlivém působení interferonů I. typu u některých jaterních chorob. Abstract Recent reports suggest that majority of chronic and acute liver diseases share a significant degree of liver inflammation and injury attributable to innate immunity, activated through Toll-like receptors. Detailed characterization of Toll-like receptor sigaling cascades in the last...
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