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Function of the Tetratrico-peptide Thioredoxin-Like (TTL) gene family in root system development
Xin, Pengfei ; Soukup, Aleš (advisor) ; Vaňková, Radomíra (referee) ; Ovečka, Miroslav (referee)
The root system performs fundamental plant functions such as uptake of nutrients and water, anchoring in the substrate, and interacting with the rhizosphere abiotic and biotic interactions, playing an important role in meeting the food security needs of today's world. Lateral roots (LR) are essential components of the plant root system. We have identified the TETRATRICOPEPTIDE-REPEAT THIOREDOXIN- LIKE 3 (TTL3) gene as being related to LR emergence and later development. Loss-of-function of TTL3 results in a reduced number of emerging LRs due to delayed development of lateral root primordia (LRP). In the Arabidopsis TTL gene family, except for TTL2 which was specifically involved in male gametophyte development, the expressions of the other three TTLs (TTL1, TTL3 and TTL4) were all related to root growth and development. The temporal and spatial distribution of TTL3 expression was consistent with its role in LR growth preceding and following LRP emergence. In the subcellular localization of TTL1, TTL2 and TTL3, all were shown to be associated with microtubules during the transient transformation of tobacco leaves, and TTL3 was confirmed to interact with microtubules. TTL3 was also associated with the endomembrane system and was known to be interacting with the brassinosteroid (BR) signaling pathway....
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Hormonal responses to cold stress
Šturma, Vít ; Vaňková, Radomíra (advisor) ; Tylová, Edita (referee)
Low temperatures are an increasingly common stress factor for plants. Sudden and intense temperature fluctuations are thus a serious cause for lower crop yields. For this reason, it is important to understand what mechanisms are used by plants to defend themselves against damage caused by cold and freezing. An important component of this defence is represented by plant hormones, phytohormones, which create a complex network of signalling pathways. Phytohormones then control via their signalling pathways plant responses to cold stress. A few phytohormones affect the plant ability to cope with the cold stress, and the interactions among all these phytohormones are important for an efficient response to cold and freezing. Recently, research has revealed that the complex signalling network has a greater impact than previously thought. The phytohormone research in relation to cold stress responses is attracting more and more attention. The main aim of this thesis is to summarize the current knowledge on the role of phytohormones in the responses to cold stress. The thesis describes the signalling pathways of individual phytohormones and clarifies how the components of these pathways are involved in the response to cold stress. Also, the dynamics of phytohormone levels and signalling components in...
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It takes two to tango; signal perception during male-female interaction in flowering plants
Vlasák, Jonáš ; Honys, David (advisor) ; Vaňková, Radomíra (referee)
This thesis summarizes the current understanding of the communication between partners during the progamic phase of pollen with focus on the cruciferous family After attachment of conspecific pollen to stigma, pollen coat peptides (PCP) competitively inhibit the signaling perceived by the FERONIA receptor in the papillary cell and thus allow pollen acceptance. Contrary, the interaction of pollen protein SCR (S-LOCUS CYSTEIN RICH PROTEIN) with SRK receptor (S-LOCUS RECEPTOR KINASE) determines pollen incompatibility. The regulation of oriented secretion is essential for pollen tube (PT) growth. During the growth of the PT, the components of the extracellular matrix as well as stiffness and preassure are perceived. On its way to the egg, the PT matures and acquires the competence to perceive signals. The PT exits the transmitting tract thanks to the ovular signalisation. The PT is accepted by synergids, communication takes place involving RALF peptides (RAPID ALKALIZATION FACTOR) and the FERONIA receptor. The signaling results in the rupture of the PT and the transport of sperm cells to the female gametes. Sperm cells bind to the egg cell and the central cell and after confirmation, fuse with the female gametes. After fertilization, the egg cell degrades signaling molecules and the persistent synergid also...
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The characterisation of organ-specific phytohormone responses to nutrient deficiency and biotic stress
Kramná, Barbara ; Vaňková, Radomíra (advisor) ; Hronková, Marie (referee) ; Plíhalová, Lucie (referee)
Abiotic and biotic stresses lead to crop yield losses and ultimately negatively affect agriculture production. Elucidation of the mechanisms of plant stress responses and their regulation could help to understand plant defence and improve stress tolerance. Phytohormones stand behind both plant growth and developmental changes as well as stress signalling. This thesis summarises the results published in two articles focused on phytohormone dynamics in response to abiotic and biotic stresses, namely phosphate shortage and Plasmodiophora brassicae infection. A review article focuses in depth on strigolactones as master regulators of phosphate deficiency responses. The main emphasis is put on organ-specific reactions and exogenous phytohormone treatment with the potential to convey stress tolerance. In the case of phosphate shortage, the universal reaction in all organs was a decrease in active cytokinin trans-zeatin and gibberellin GA4 with a concurrent elevation of abscisic acid. Also, the high- affinity phosphate transporters (PHT1;4 and PHT1;7) exhibited increased gene expression within the whole plant. Shoot apical meristems showed numerous changes in gene expression and were the most affected organ during the lack of phosphate. Only in roots, we observed a substantial elevation of low active...
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Cell cycle regulation in plants: the role of CDK activatory dephosphorylation at entry into mitosis
Mašková, Petra ; Macháčková, Ivana (advisor) ; Havel, Ladislav (referee) ; Vaňková, Radomíra (referee)
t I I I I I I I I I I I I I I Summary of PhD. thesis Cel1 division representsone of fundamentalattributesof all living creatuÍes.Basic molecular mechanisms operating during cell proliferation seem to be evolutionary conservedamongeukaryotes.The cell cycle is dividedin four subsequentphases;themost regulatoryeventsareconcentratedin Gr/S andGzlM checkpoints. The key regulatory proteins, cyclin-dependentkinases (CDKs), govern the progress throughthe whole cell cycle. Their function is strictly dependenton catalytic cyclin subunits.The correspondingcyclin partnerbinding CDK determinesthe time window of the specific CDlVcyclin complex actionin individual cell cycle phase.To becomefully active, the complex requiresfurtherposttranslationalmodificationincluding activatory phosphorylationanddephosphorylationof theCDK on specificaminoacidresidues. Plant cell cycle, besideswell-conservedmechanismscoÍlmonto all eukaryotes,exhibits other specific mechanismsresultingfrom plant survival strategy.The Gr/S transitionis stronglyaffectedby extemalandinternalsignals,mainlyphytohormonesandmetabolites, reflectingthe elementaryconditionssuitablefor accomplishmentof the whole cell cycle. The centralmoleculerespondingto thesesignalsat Gr/S is D cyclin, whoseexpressionis regulatedby cýokinin and sucrose(Riou-Khamlichi et aI.,...
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Characterization of the role of cytokinins and abscisic acid during abiotic stress response
Přerostová, Sylva ; Vaňková, Radomíra (advisor) ; Havel, Ladislav (referee) ; Doležal, Karel (referee)
Abiotic stresses significantly reduce crop yield, causing serious problems in agriculture. Understanding the mechanisms of plant stress responses could contribute to the improvement of their stress tolerance. Phytohormones play an important role in plant stress defence as well as in regulation of growth and development. This thesis summarizes the results published in four articles focused on the evaluation of the effects of phytohormones during abiotic stresses, namely salinity, drought, ZnO nanoparticle treatment and cold stress. The main emphasis is put on abscisic acid as the key regulator of water status and stress defence, and on cytokinins, which regulate plant growth and stabilize photosynthetic machinery. Cytokinins act antagonistically to abscisic acid. Our results showed that abscisic acid is a general abiotic stress response regulator. Stress- tolerant plants (halophyte Thellungiella salsuginea or winter line of einkorn wheat Triticum monococcum) had a higher basal level of this hormone, especially in shoot meristematic tissues (apices, crowns), than stress-sensitive plants. Stress-tolerant plants reacted faster and in a more flexible way to stress. Active cytokinins were negatively affected by stress, which was associated with growth suppression. The drought stress study showed that...
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Transport and Metabolism of Radio-Labelled Cytokinins in Plant Cells and Tissues
Nedvěd, Daniel ; Ryšlavá, Helena (advisor) ; Vaňková, Radomíra (referee)
Cytokinins are a large group of phytohormones. Since their discovery in the 1950s, they have shown to play a pivotal role in plant physiology. Most studies so far focused on cytokinin action mechanisms and their metabolic regulation. Identification of AtABCG14 and AtPUP14 as cytokinin-specific membrane carriers brought researchers' attention to cytokinin membrane transport, too. In this thesis, we performed experiments with radio-labelled cytokinin tracers. We show that trans-zeatin and isopentenyladenine, two major biologically active cytokinins, are readily transported across the plasma membrane in tobacco BY-2 cell suspension. Making use of mathematical modelling, we show that BY-2 cells possess a membrane transport system with an affinity toward cytokinins. Next, we show that atabcg14 and atpup14 mutations affect cytokinin metabolism in Arabidopsis thaliana plants. Keywords: cytokinin, Arabidopsis thaliana, tobacco BY-2 cell lines, membrane transport, purine permease, ATP-binding cassette, radio-labelling
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Regulation of phosphoenolpyruvate carboxylase in tobacco plants during potyviral infection
Müller, Karel ; Ryšlavá, Helena (advisor) ; Vaňková, Radomíra (referee) ; Luhová, Lenka (referee)
Charles University in Prague Faculty of Science, Department of Biochemistry Regulation of phosphoenolpyruvate carboxylase in tobacco plants during potyviral infection Regulace fosfoenolpyruvátkarboxylasy v rostlinách tabáku během virové infekce Karel Müller Supervisor: RNDr. Helena Ryšlavá CSc. Prague, 2008 2 Table of contents / Obsah Introduction........................................................................................................................................ 3 Aim of the work................................................................................................................................. 4 Results and discussion ....................................................................................................................... 5 Isolation of PEPC from tobacco leaves ......................................................................................... 5 Characterization of tobacco PEPC................................................................................................. 5 Regulation of tobacco PEPC during viral infection....................................................................... 7 Effect of cytokinins in tobacco leaves during stress.................................................................... 10...
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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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Function of phospholipases D and lipid phosphate phosphatases in the regulation of plant cell morphogenesis
Bezvoda, Radek ; Žárský, Viktor (advisor) ; Hašek, Jiří (referee) ; Vaňková, Radomíra (referee)
of the thesis The presented work explores the function and regulation of intracellular signaling that utilizes phospholipase D (PLD) and phosphatidic acid (PA), especially in the context of cellular morphogenesis of plants. PLDs cleave membrane phospholipids to phosphatidic acid, which has important biophysical and signaling role in many contexts, such as stress response, regulation of cytoskeletal dynamics and vesicular transport. Vesicular transport is essential in focused tip growth of plant pollen tubes and root hairs. Part of the work deals with NADPH oxidases, that are an emerging counterpart of PLD/PA signaling. Tobacco pollen tubes served as the main experimental model, as it enables assessing of changes in secretory pathway after pharmacological or genetic treatments. A technique utilizing antisense oligonucleotides was used for selective knock-down of PLD isoforms, NADPH oxidase and newly studied family of lipid phosphate phosphatases (LPPs) in pollen tubes. This enabled to assess functions of individual isoforms. For studying of selected gene families, various bioinformatic tool were utilized, such as dendrogram construction, analysis of available expression data and creating of virtual proteome. These tools together enabled to select potentially important genes for further experimental...
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