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Analyzing the complexity of auxin-related processes and their regulation
Simon, Sibu ; Zažímalová, Eva (advisor) ; Stiborová, Marie (referee) ; Pavlíček, Jiří (referee)
Phytohormone auxin plays an important role in various aspects of plant growth and development. The necessary concentration maxima at the region of its action are achieved by auxin metabolism, passive diffusion of auxin molecules across plasma membrane and by the carrier-mediated auxin transport, as well as by modulation of these processes. In our study we used a group of compounds structurally related to major endogenous auxin indole-3-acetic acid, as well as synthetic auxins 2,4-dichlorophenoxy acetic acid (2,4- D) and naphthalene-1-acetic acid (NAA). We aimed to characterize the auxin specificity of developmentally important processes such as carrier-mediated auxin transport, and 'genomic' (transcriptional) and 'non-genomic' (transcriptional) auxin signaling. In addition to the characterization of these compounds we also hoped to get an insight into the complex regulatory mechanism of auxin-related processes and to possibly find a particular compound with distinct behavior towards particular processes. By making use of such compounds and other molecular tools we aimed to analyze the mechanism of 'non-genomic' auxin signaling, to understand the mode of action of FM (Fei Mao) styryl dyes on the dynamics of membrane- localized auxin transporters, and to study the involvement of other phytohormones...
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Molecular mechanism of transport of plant hormone auxin into cells
Laňková, Martina ; Zažímalová, Eva (advisor) ; Stiborová, Marie (referee) ; Opatrný, Zdeněk (referee)
The non-uniform distribution of the plant growth regulator (phytohormone) auxin is known to mediate many fundamental processes in plant development. Auxin is transported through the plant body either via vascular pathways or from cell to cell by specialized polar auxin transport machinery. This machinery consists of a balanced system of passive diffusion combined with the activities of auxin influx and efflux carriers. This work is focused on the processes that are involved in the uptake of auxin into plant cells. On the basis of molecular-biological and biochemical characterization, the function as an auxin influx carrier was confirmed for PaLAX1 protein from wild cherry (Prunus avium). The sequences of isolated cDNA of the PaLAX1 gene and of its protein product are highly similar to both the cDNAs and the corresponding protein products of the AUX1/LAX-type genes, coding for putative auxin influx carriers in model plant A. thaliana. On the level of organs and single cells, we have shown that the overproduction of PaLAX1 in transgenic lines resulted in an increase of the content of native auxin indole-3-acetic acid as well as of the uptake of synthetic auxin, 2,4-dichlorophenoxyacetic acid. Further, the mechanism of action of putative auxin influx inhibitors 1-naphthoxyacetic acid (1-NOA),...
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Study of cytokinin role in abiotic stress response
Dobrá, Jana ; Vaňková, Radomíra (advisor) ; Ryšlavá, Helena (referee) ; Brzobohatý, Břetislav (referee)
Plants had to evolve, due to their sessile growth habit, a complex system of defence against adverse environmental conditions. Plant abiotic stress responses are regulated by plant hormones, especially by cytokinins (CKs) and abscisic acid (ABA). In order to evaluate the effect of enhanced stress tolerance on the dynamics of hormones (CKs, auxin and ABA) as well as polyamine levels during the drought and/or heat stress (HS) progression, response of tobacco plants with enhanced level of osmolyte proline was compared with the corresponding wild-type. HS (40řC) caused a transient increase in bioactive CK content, accompanied by decrease of ABA, which indicated stimulation of transpiration, important mechanism to cool down the leaf temperature at the early phase of HS. Simultaneously, a transient increase in spermidine and spermine levels was found, more profound in proline-over-producing transformant. The activities of particular polyamine metabolic enzymes correlated well with their content. Drought stress resulted in the establishment of a gradient of bioactive CKs in favour of the upper leaves, crucial for their preferential protection. Application of HS at the end of drought period strongly enhanced the stress severity, mainly due to additional water loss caused by enhanced transpiration....
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Lateral roots and root nodules - similarities and differences
Šnajdrová, Tereza ; Soukup, Aleš (advisor) ; Kulich, Ivan (referee)
Postranní orgány kořene, kořenové hlízky a postranní kořeny, se zakládají endogenně, a až na výjimky mimo apikální meristém. Tyto orgány mohou být různě modifikovány. Některé rostliny mají, právě díky těmto postranním orgánům, schopnost vstupovat do symbiotických interakcí s jinými organismy. Při vzniku symbiotické, dusík-fixující hlízky se uplatňuje signalizace obou budoucích partnerů, aby byl zajištěn vstup do kořene pouze organismu hostitelsky specifickému k rostlině. Pronikání bakterie Rhizobium či Frankia do kořene se standardně děje přes kořenový vlásek pokožkové buňky, ale není to jediný možný mechanismus vstupu. Zároveň s tímto vstupem se začne vytvářet hlízkové primordium. Pletivo, z něhož se hlízka vytváří, i výsledná podoba hlízky, se liší u různých rostlin. V centrální zóně dospělé hlízky dochází, díky nitrát reduktáze, k fixaci vzdušného dusíku. Tato vlastnost zvýhodňuje rostliny, schopné této hlízkové symbiózy, při kolonizaci půdy, chudé na dusík. Postranní kořeny se zakládají v pericyklu, aktivací malého počtu jeho buněk. Po výstupu z pletiv mateřského kořene dochází k aktivaci meristému bočního kořene. Oba tyto postranní orgány spolu s primárním kořenem tvoří dynamický kořenový systém, regulovaný vnitřními i vnějšími faktory.
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Role of exocyst at plant pathogen defense
Sabol, Peter ; Kulich, Ivan (advisor) ; Šašek, Vladimír Matěj (referee)
Exocyst is a protein complex conserved in yeast, animals and plants. It mediates tethering of a secretory vesicle to the plasma membrane in the semifinal step of exocytosis. Several roles of exocyst in the processes of cell polarization in plant cells have been implied, including polarized growth of polen tubes and root hairs, cytokinesis, deposition of seed coat pectin and possibly autophagy. One of the most recent roles of exocyst includes also a response to bacterial and fungal pathogens. Exo70B2 and Exo70H1 subunits were shown to play prominent roles in this respect, with Exo70H1 being responsible for mediating defense against bacterial (Pseudomonas syringae) and Exo70B2 defense against both bacterial and fungal (Blumeria graminis) pathogens. Recently, new data appeared indicating the interaction between Exo70B1 and RIN4 and Exo70A1 and NOI6, respectively. RPM-1 interacting protein 4 (RIN4) is a well known negative regulator of both basal and effector-triggered resistance. This thesis shows interaction between NOI6 and several exocyst subunits, confirming previous data. I show here that exocyst subunints interact specifically with N terminus of NOI6 protein and that this interaction is lost in the shorter version of NOI6 mimicking AvrRpt2 cleavage. Since AvrRpt2 is an effector protein from...
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Auxin Transport in Arabidopsis thaliana: From the whole plant to suspension cultured cells
Seifertová, Daniela ; Zažímalová, Eva (advisor) ; Opatrný, Zdeněk (referee) ; Hejátko, Jan (referee)
in English Plants with their sessile life-style are exposed to many stimuli from environment. They have developed mechanisms how to coordinate their growth and development, which allows them to survive sometimes in very difficult conditions. Plant hormones are one of the most important regulators of this signal transduction. Auxins, as the oldest known group of plant hormones, play important role in many physiological processes in plants. To allow perceiving the information in every single cell, auxin molecule is transported by cell-to-cell manner. Auxin molecules enter the cell by passive diffusion or by active uptake by auxin influx carriers. To reach the next cell, they are transported actively out of the cell by auxin efflux carriers. Athough active auxin transport has been studied for almost four decades, past two decades contributed to the identification and characterization of particular auxin carriers remarkably. This thesis contributes to the knowledge on the auxin efflux and influx carriers and their involvement in the processes occurring from a single cell level to the level of a whole plant. Firstly, it brings detailed description of auxin transport characteristics in Arabidopsis thaliana cell suspension cells (Ath cells). Secondly, it shows that the overproduction of PIN1 auxin efflux...
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Effect of nutrients deficiencies on root architecture and growth of winter wheat
Rattanapichai, W. ; Klem, Karel
The study of the effects of N, P, K deficiencies on root architecture and growth was tested in phenotyping platform with winter wheat (Bohemia variety). The experiment was arranged with 4 treatments: Complete nutrient, Without N, Without P and Without K. The root were grown on the surface of vertically fixed black filter paper sheets (30x60cm), covered from both sides by black plastic sheets (PVC-P). The system was setup with a micro-irrigation channel in the top of sheets to ensure circulation of hydroponic medium as hydroponic system. Eighteen days after transplanting, we took the root images by the standard RGB digital camera. To evaluate the root architecture parameters the "SmartRoot" software was used. The results showed that nutrient deficiency had effect on root architecture of winter wheat. N deficiency increase in total seminal root and lateral root length and root/shoot ratio, while P deficiency resulted in increase of mean root diameter, total root area when compared to the control. N deficiency also decreased root and shoot dry weight and total leaf area. However, nutrient deficiency slightly decreased lateral density. There was a slight effect of K deficiency on root architecture when compared to the complete nutrient application. The increasing of leaf dry weight was related with the increased of root dry weight.
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