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The physiological basis of abiotic stress tolerance in Fragaria genus plants.
Hamet, Jaromír ; Lipavská, Helena (advisor) ; Tylová, Edita (referee)
Abiotic stresses - drought, salinity or extreme temperatures - cause morphological and physiological changes, affect growth, development and plant productivity. In crops, these limitations often reduce yields up to 50%. Plants have developed various mechanisms ensuring some degree of abiotic stress tolerance, which undoubtedly include changes in carbohydrate metabolism. The nature of many defense mechanisms is not yet fully understood, moreover, most findings were obtained by studying model plants and little is known about their validity in crops. This work was therefore focused on woodland strawberry (Fragaria vesca L.) from economically important family Rosaceae. Controlled conditions and targeted exposure to stress factors was obtained through the cultivation in vitro. Strawberry plants and callus cultures were exposed to various stresses and their combinations, better reflecting the natural conditions. At various stages of stress reaction, growth characteristics, changes in the content and the spectrum of soluble carbohydrates and oxidative stress levels were monitored and compared with plants growing under optimal conditions. Abiotic stress responses of strawberry plants were very inhomogeneous, which complicated the obtaining of statistically significant results. The only significant response...
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Root apoplastic barriers in adverse environmental conditions.
Blascheová, Zuzana ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
Differentiation of apoplastic barriers in roots is affected by adverse environmental conditions (e.g. heavy metal toxicity, salinity or flooding). The apoplastic barriers, exodermis and endodermis, differ from each other in response to environmental conditions. The exodermis is more affected by these conditions and its occurence is more variable. The presence of differentiated barriers affects root transport features like uptake, accumulation and entrance of polutants or nutrients. Key words: apoplastic barriers, heavy metals, differentiation, root, Casparian strips, suberin lamellae
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Cellular mechanisms of differentiation of root apoplastic barriers
Namyslov, Jiří ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
Apoplastic barriers (exodermis and endodermis) are primarily used to regulate the free movement of substances within apoplast due to modifications of cell walls. While at the anatomical level, the barriers are studied for a long time, only recently the molecular mechanisms that are behind the emergence of these modifications are gradually identified. The most important modifications are Casparian strips that fill the space between the adjacent cells in exodermis and endodermis. Casparian strips are lignin-based structures formed with the help of CASP proteins located in equatorial region of plasmalema (called CSD membrane domain). In addition to CASP proteins, the formation of Casparian strip involves activity of site-specific enzymes of lignin synthesis (PER64 peroxidase, NADPH oxidase RBOHF). In these cell layers shortly after differentiation of Casparian strips, the deposition of suberin occurs between plazmalema and primary cell wall leading to formation of suberin lamellae also serving to block the apoplast. Next step of differentiation is the formation of U-shaped tertiary thickenings that are formed by deposition of secondary cell wall, whose formation mechanism in the root endodermis is not yet well-known. Processes responsible for formation of apoplastic barriers are thus related to the...
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Glutamine synthetases and their role in nitrogen metabolism in plant shoot
Kobercová, Eliška ; Fischer, Lukáš (advisor) ; Tylová, Edita (referee)
Glutamine synthetase is a key enzyme for ammonium assimilation and glutamine biosynthesis in plants. Ammonium ions are important intermediates in nitrogen metabolism, but their elevated concentration is toxic to plants. Correct function of glutamine synthetase is essential to plant life - glufosinate, a specific inhibitor of glutamine synthetase acts as a total herbicide. Glutamine synthetase is involved in a number of important metabolic processes: primary assimilation of nitrogen nutrients, in reassimilation of ammonium ions released during photorespiration or metabolism of phenylpropanoids and in nitrogen remobilization in developing seeds, during germination or senescence. According to localization in the cell glutamine synthetases in angiosperms are divided into the plastid form (GS2), which is typically encoded by a single gene, and the cytosolic form (GS1), which is encoded by a small multigene family. The various isoforms of glutamine synthetases have different location within plant organs and tissues, ways of regulation and role in nitrogen metabolism. Keywords: plastid and cytosolic glutamine synthetase, ammonium assimilation, nitrogen metabolism, photorespiration
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Regulation of phosphate uptake by strigolactones
Balín, Michal ; Vaňková, Radomíra (advisor) ; Tylová, Edita (referee)
This Bachelor thesis is focused on the reactions of plants to low levels of available phosphorus, which is essential element for plant nutrition. In the context of plant stress, plant hormones strigolactones play very important role. Strigolactones influence growth and development of the whole plant. Biosynthesis of strigolactones increases under phosphate deficiency. This thesis consists of three parts. The first part is concentrated on phosphorus, its compounds and its availability in the environment. The second part is mainly dedicated to phosphate stress - its sensing by plants, their adaptations to stress and local as well as long distance signalling. Attention is also paid to phytohormones, namely auxins, cytokinins, gibberellins, ethylene, abscisic acid and other signal molecules, like sucrose, the phosphate molecule itself and microRNAs. The third part is focused mainly on the structure, biosynthesis, signal transduction and the mode of action of strigolactones during phosphate stress. Keywords: phosphate, deficiency, strigolactone, phytohormones, stress
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Uptake and metabolism of 137Cs in plants
Šustr, Marek ; Tylová, Edita (advisor) ; Maršík, Petr (referee)
Plants are able to uptake radiocesium from soil, which is the potential route to enter the food chain. Cesium mobility in soil is determined by clay particles. Cesium can be reversibly ad- sorbed on their surface or can be fixed between layers. Mineral illit has the highest selectivity for cesium due to its frayed edges. Organic matter determines cesium mobility only in soil with organic matter content above 90 %. Cesium is more available for plants in this soil. Cesium uptake varies among species. Many plant species accumulating big amounts of cesium belong to family Chenopodiaceae. Cesium uptake is affected by other cations in soil solution. Potassium is the most effective one. Increasing of external potassium concentration from 50 μM to 250 μM decreased cesium uptake thirty-fold. Potassium affects cesium mobili- ty in soil and plant uptake. Due to chemical similarities of cesium and potassium some potassium transporters efficiently transport both cations. Potassium transporters are therefore considered the main entrance site in plant roots. Great contribution to cesium uptake is dedi- cated to high-affinity potassium transporter HAK5. Another great part of cesium uptake is mediated by non-selective cation channels. Plants can uptake up to 80 % of cesium applied on shoot surface. Cesium is highly...
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Lateral root development in response to mineral nutrients; signal mechanisms and pathways.
Halamková, Daniela ; Tylová, Edita (advisor) ; Lhotáková, Zuzana (referee)
TTL3 gene was identified by forward screening of genes involved in lateral root development in Arabidopsis thaliana based on its expression pattern. TTL3 belongs to the TTL (TETRATRICOPEPTIDE-REPEAT THIOREDOXIN-LIKE) gene family. The diploma thesis is aimed on characterisation of changes in TTL1, TTL3 a TTL4 promotor activities in response to external conditions (availability of nitrogen or phosphorus) that affect root growth. Obtained data should elucidate possible relation among TTL gene expression activities, root growth rate, and apical meristem activity. Nitrogen or phosphorus deficiency triggered changes in root growth and root system morphology of experimental plants. Short-term nitrogen deficiency stimulated root growth. Short-term phosphorus deficiency induced gradual growth cessation in main root and long laterals. Long-term deficiency reduced root growth of both N-deficient and P-deficient plants compared to control. The root system size of N-deficient and P-deficient plant was almost similar. Determination of promotor activity using β-glucuronidase reporter gene showed changes in expression activity and its localization in response to root growth intensity. TTL4 gene promotor activity was the most responsive. Its activity was generally higher in slowly growing roots, particularly under...
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Characterization of changes induced by Schizosaccharomyces pombe cdc25 gene related to earlier flowering onset
Čiháková, Klára ; Lipavská, Helena (advisor) ; Tylová, Edita (referee)
The study is focused mainly on mechanisms related to flowering acceleration in plants expressing cdc25 from Schizosaccharomyces pombe (Spcdc25 plants). In yeast, the gene in question codes a phosphatase responsible for activatory dephosphorylation at mitosis entry. In higher plants, however, the ortholog has not been identified yet. Some doubts even exist on the importance of this activatory dephosphorylation, though dephosphorylation itself has been documented in plants. Previous studies of our team revealed many differences in Spcdc25 tobacco plants; majority of them can be induced in WT by cytokinin application and thus, the hypothesis of cytokinin-like effect of Spcdc25 expression have been proposed. As the earlier flowering was one of the most pronounced effects, the aim of this study has been to characterize mechanisms, responsible for this phenomenon. The analyses of phloem exudates revealed weak tendency to lower saccharide transport to the apex in transformants. The sacharide content in the apex, however, was similar or slightly higher with significantly higher glucose proportion in transformants. Thus, a role of saccharides in flowering regulation should not be excluded. The analysis of the flowering-inducing genes expression has shown the only change: the expression of the tobacco homologue of...
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Aluminum toxicity in plant cell
Schiebertová, Lucie ; Schwarzerová, Kateřina (advisor) ; Tylová, Edita (referee)
Aluminium being the third most abundant metal in the earth's crust is in its toxic form a serious threat for crop productivity in acid soils, which comprise almost half of the arable land. As the most phytotoxic form is considered free ion Al3+ , which affects root growth by acting in the root apical zone, resulting in growth inhibition in a very short time at micromolar concentrations. At cellular and molecular level, many cell components are affected by aluminium toxicity including cell wall, plasma membrane, signal transduction pathways, calcium homeostasis, DNA and numerous cytoplasmic enzymes. Although it is difficult to distinguish the primary targets from the secondary effects so far, understanding of the target sites of aluminium toxicity is helpful to elucidate the mechanisms by which aluminium exerts its deleterious effects in root growth. On the other hand, some plant species have evolved mechanisms to cope with aluminium toxicity. In the future, the attention should be paid to basic mechanisms of aluminium toxicity and our understanding of the current problem should be unified. Key words: Al toxicity, Al resistance/tolerance, phytotoxicity, Al stress, acid soils, root elongation
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Control of lateral root development in response to availability of principal mineral nutrients.
Halamková, Daniela ; Tylová, Edita (advisor) ; Smetana, Ondřej (referee)
Lateral roots are, due to their large absorption surface, a part of the root system with significant importance for the plant's ingestion of water and nutrients. Their development depends on heterogeneity of soil environment, which enables the plant to optimize the acquisition of resources under current conditions. The availability of mineral nutrients (type of nutrient, form, distribution in soil and mobility) is one of key factors that determine root system morphogenesis. Another important aspect is the amount of nutrient in the plant; in other words, the plant's current demand for the element. The most important nutrients that influence the architecture of the root system are two macroelements - nitrogen and phosphorus. Both of these elements trigger positive and negative effects on the development of lateral roots. Nitrate, important source of nitrogen, induces two entirely different regulatory mechanisms of lateral root development. Under nitrogen limiting condition, a local stimulation of lateral root elongation is triggered in nitrate-rich patches. This response integrates the signalling pathways of auxin and nitrate. In contrast, high and homogenous availability of nitrate in rhizosphere (≥ 10 mM) causes inhibition of lateral root growth. This systemic inhibitory effect was similarly...
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