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The influence of roots on the chemical properties of the apoplast and the rhizosphere
Puldová, Kristýna ; Fendrych, Matyáš (advisor) ; Šámalová, Markéta (referee)
Chemical properties of the apoplast and rhizosphere are crucial for plant development and its overall well-being. Apoplast includes space outside the plasma membrane and its content, such as gas, water, and solutes. Changes in apoplast properties significantly influence various processes. One of them is cellular growth - the pH-dependent extension of cell walls. The rhizosphere is the soil environment near and under the influence of roots. It is characterised by abiotic factors like the availability of nutrients and toxic compounds. It is also a space with a high representation of microbiome communities. Plants can significantly influence the chemical properties of both apoplast and rhizosphere to improve their growth conditions. This thesis summarises the most important mechanisms of plants' roots that change these chemical properties, focusing on the model plant Arabidopsis thaliana. It shows how and where these mechanisms intersect and in which way they influence each other. Emphasis is placed on the process of growth regulation and mechanisms of increasing nutrient availability. Keywords: apoplast, rhizosphere, H+ ATPase, root growth, rhizodeposition, root exudates, nutrients, microbiome
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Unraveling the Enigmatic World of Auxin Signalling: Subcellular and Tissue- Specific Aspects in the Root of Arabidopsis thaliana
Dubey, Shiv Mani ; Fendrych, Matyáš (advisor) ; Robert Boisivon, Helene (referee) ; Kulich, Ivan (referee)
In this dissertation, my main focus was to advance our understanding of how the plant hormone auxin regulates root growth at the sub-cellular and tissue levels in Arabidopsis thaliana. Auxin controls gene transcription through the SCFTIR1/AFB - Aux/IAA coreceptor complex. Among the TIR1/AFBs auxin receptor family members, TIR1 is strictly localized in the nucleus, while AFB1 is particularly abundant in the cytoplasm but also present in the nucleus. I confirmed the dominant role of AFB1 in controlling rapid auxin responses, such as calcium ion influx, apoplastic alkalinization and rapid root growth inhibition; processes associated with root gravitropism. I discovered a novel AFB1-dependent cytoplasmic auxin perception, and I identified the N-terminal domains of AFB1 and TIR1 crucial in determining their subcellular localization. Furthermore, my research contributed to the discovery that the root surface pH gradient on the root's longitudinal axis is not only regulated by AHA H+ -ATPases, but instead, the rapid auxin response module, comprising the AUX1 auxin influx carrier, AFB1, and the CNCG14 calcium channel, controls the apoplastic pH in the root transition zone. Further, I participated in the discovery of a deeply evolutionarily conserved rapid auxin response pathway that involves the RAF-like kinase,...
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Visualization of root apoplastic pH in plants
Wernerová, Daša ; Fendrych, Matyáš (advisor) ; Paris, Nadine (referee)
Plant oriented movements, or tropisms allow the plant to actively respond to environmental stimuli to get more light, better access to nutrients and to grow roots deeper into the soil. Gravitropism drives the growth of roots along the gravity vector. Perception of gravity is triggered by the sedimentation of statoliths in columella root cap, but the exact signalling pathway behind this process is not known. Perception of gravity results in an unequal redistribution of the phytohormone auxin in the outer cell layers which leads to different rate of growth on the root's upper and lower side and bending of the root. The changes in auxin redistribution are accompanied by changes in apoplastic pH. Knowing an exact pattern of these pH changes could shed light on the mechanisms laying behind the gravitropic response pathway. While microelectrodes can be used to measure pH precisely, they are not suitable for the long-term imaging of growing roots. In the past few years, several pH sensitive dyes and genetically encoded sensors emerged. These can be used for long-term live in vivo imaging of pH changes in growing roots. In this thesis, I analysed the performance of several published pH sensitive genetically encoded sensors and available dyes in the roots of Arabidopsis thaliana. I observed that dyes varied...
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Dynamics and role of the Arabidopsis thaliana IAA17/AXR3 protein in regulation of root growth by auxin
Kubalová, Monika ; Fendrych, Matyáš (advisor) ; Glanc, Matouš (referee)
Auxin is phytohormone that regulates several developmental processes and environmental responses. One of the most well-described outcome of the auxin signalling pathway is regulation of gene transcription. Aux/IAA proteins play an important role in this process, acting as transcriptional repressors. Recent studies revealed that several root growth responses are too rapid to be explained by changes in the level of transcription. The correlation between the amount of Aux/IAAs and the root growth rate suggests that these proteins might be involved in root growth regulation, especially during rapid growth responses that are not associated with transcriptional reprogramming. This work is focused on one of the 29 Arabidopsis Aux/IAA proteins - the IAA17/AXR3 protein. First, we produced stable transgenic lines of Arabidopsis thaliana expressing different combinations of fluorescently labelled AXR3-1 proteins and/or fused to subcellular localization tags under the control of different tissue-specific promoters, in order to characterize the subcellular localization of the studied protein. Subsequent visualization by confocal microscopy methods confirmed information about the role of IAA17/AXR3 protein in root growth responses, its involvement in auxin signalling, and gravitropism. Next, we showed that the...
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Gravitropism mechanisms in single-celled organs and multicellular organs of plants
Nehasilová, Martina ; Fendrych, Matyáš (advisor) ; Kurtović, Katarina (referee)
Plants react to various environmental stimuli by oriented growth. The growth responses are called tropisms. Gravitropism is a directed growth concerning the gravity vector. Plant shoots grow up, negatively gravitropically, to catch the light. Roots are positively gravitropic; they grow down to anchor the plant in the substrate and seek water and minerals. The process of gravitropism consists of three stages: signal perception, signal transmission, and growth response. These stages can all occur in a single cell or separately in different parts of a multicellular organ. Single-cell gravitropic systems are represented by algal rhizoids or moss protonemata. They need minimal signal transmission because gravity vector perception and growth response happen in the same cell. The multicellular systems, represented here by angiosperm roots, have a more robust signal transmission phase. This thesis compares mechanisms of plant gravitropism based on the two categories - single-cell vs. multicellular. Despite their different cellular arrangements, single-cell and multicellular gravitropism share several characteristics, such as statolith sedimentation, Ca2+ fluxes, pH changes, and altered vesicular trafficking. Still, the lack of knowledge about the single-cell systems and high inner variability within the...
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Perception of the Cell wall integrity system signals in plant cells
Hercíková, Anna ; Fendrych, Matyáš (advisor) ; Cifrová, Petra (referee)
The cell wall is a key compartment of the plant cell for elementary physiological processes such as cell growth, division, or differentiation, simultaneously protecting the cell from influences of the external environment. The mechanical support of the cell wall maintains the shape of the cell, and at the same time allows it to grow. Thus, the cell wall must not be limiting to cell expansion, but if it becomes too loose, the cell may rupture. Supervised adaptive reorganisation of the cell wall based on external and internal conditions is therefore essential for plant cell, as indicated by the presence of a complex signalling system. The Cell wall integrity (CWI) system represents the set of all mechanisms that together ensure the continuous compactness of the cell wall. My bachelor thesis will discuss the individual components of the CWI system, focusing on the CrRLK1Ls, receptors from the broader Receptor-like kinase (RLK) family.
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Molecular mechanism of mechanoreception in plants
Jelínková, Barbora ; Martinek, Jan (advisor) ; Fendrych, Matyáš (referee)
Plant, as sedentary organism, does not have many possibilities to physically escape it's unpleasant surroundings, instead it adapts oneself. One of many plant senses that are crucial for tracking environment changes is mechanoreception. Plant senses and differentiates between many mechanical cues, some of them affecting plant immunity and morphogenesis. The whole plant cell reacts to mechanical cues and many cellular structures are involved in mechanoreception. Any change in cell wall - a borderline between the cell and it's surroundings - is transduced to plasma membrane, then to the cytoskeleton and potentially to other structures. Concept of this cell wall-plasma membrane-cytoskeleton continuum and it's use as an instrument to illuminate molecular mechanisms of mechanoreception in plants are the key topics of my thesis.
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Interaction of ectomycorrhizal and ericoid mycorrhizal host plants via ectomycorrhizal, ericoid mycorrhizal and pseudomycorrhizal fungi
Fendrych, Matyáš ; Albrechtová, Jana (advisor) ; Gryndler, Milan (referee)
Abstract 9. Abstract Roots of ectomycorrhizal and ericoid mycorrhizal plants are believed to be colonized by fungi belonging to different taxonomic groups. However, both frequent isolations of ericoid mycorrhizal fungi from ectomycorrhizal root tips and a few recent studies (Vrålstad et al. 2000, 2002b, Piercey et al. 2002, Hambleton & Sigler 2005) indicate that there is a group of mycobionts colonizing both types of roots. Ectomycorrhizal morphotype Piceirhiza bicolorata was shown to be induced by Meliniomyces sp. belonging to the Rhizoscyphus ericae aggregate (Vrålstad et al. 2000). The ability to colonize roots of potentially ectomycorrhizal and ericoid plants simultaneously was proven in in vitro experiments in the case of Rhizoscyphus ericae (Pirecey et al. 2002) and Cadophora finlandica (VillarrealRuiz et al. 2004). DSE fungi ("dark septate endophytes", formerly termed pseudomycorrhizal) represent another group of mycobionts colonizing both ericoid and potentially ectomycorrhizal plant roots. In the present work, we inoculated roots of ericoid (Vaccinium myrtillus) and potentially ectomycorrhizal plants (Picea abies, Pinus sylvestris and Betula nana) with typically ectomycorrhizal and ericoid mycorrhizal fungi and...
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Tissue-specific knockout of starch synthesis in columella cells of Arabidopsis thaliana and gravitropic response
Bogdan, Michal ; Fendrych, Matyáš (advisor) ; Retzer, Katarzyna (referee)
Since the studies of plant gravitropism by Charles Darwin, the identity of specific sensors of gravity in plants has been uncertain. To this date, statoliths - starch granules in the root tips - are considered to play a key role in gravity sensing. The role of statoliths as organelles that mediate the gravity sensing ability of plant roots is based on research that uses plants which have severely impaired ability to synthesize starch in general or have their cells that contain statoliths removed or damaged. This represents methodical imperfections that give rise to alternative explanations, like disturbed auxin flow due to heavy damage to the root tip or unknown involvement of starch from other parts of the plant in gravity perception. Thanks to advances in the field of CRISPR/Cas9 technology, we are now able to produce tissue-specific mutants that might help with clarification of whether starch granules in the root tip are involved in sensing gravity and if so, how significant is this involvement. This diploma thesis aimed to answer these questions by adapting the tissue-specific CRISPR/Cas9 system and using it for the creation of mutants that are starchless specifically in the columella cells. Using this approach, we generated one tissue non-specific mutant line and three tissue-specific mutant...
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