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The evolution of auxin metabolism, signalling and transport in the green lineage (Viridiplantae)
Schmidt, Vojtěch ; Petrášek, Jan (advisor) ; Fendrych, Matyáš (referee)
Phytohormone auxin is an essential coordinator of growth and development within land- plants. Mechanisms of auxin action in algae is still poorly understood, given that related research has begun recently. Current progress is derived mainly from available sequence data, which are necessary for analysis of gene homology with higher plants. In this case with the genes related to auxin action mechanisms, e.g. metabolism, signaling and transport. Auxin biosynthesis predated the split of Chlorophyta and Streptophyta, but tighter regulation of auxin levels is the matter of land-plants. First auxin responses were probably non-transcriptional. Transcription-regulating nuclear signaling pathway assembled from more ancient domains, some of them were identified in Charophyta, but whole pathway was complete after colonization of land. Auxin transport out of the cell was one of the original mechanisms of regulating its levels. More sophisticated auxin carrier system was proposed to evolve in Charophyta, where polar auxin transport was identified. Auxin as a signaling molecule was present in primitive algae groups, but its response spectrum dramatically increased after colonization of land. Future research of auxin action evolution needs more model organisms to be established, especially from Charophyta....
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Molecular basis for regulation of cell wall pH in Arabidopsis thaliana
Bogdan, Michal ; Fendrych, Matyáš (advisor) ; Retzer, Katarzyna (referee)
The cell wall is one of the defining parts of the plant cell. Cell walls resist turgor pressure, give plants their rigidity and still allow the cell to grow despite their stiffness. The plant cell wall is a composite material that consists of different elements; thus, the knowledge of the plant cell wall composition helps us understand the impact of the mentioned pH changes. Alterations of plant cell wall properties result in a change of plant cell growth rate. A prime example of this is the modification of wall properties by pH change, termed the acid growth. Although acid growth has been studied for a long time, we still do not fully understand the underlying mechanisms, as we have not yet identified all the agents involved in acid growth and our ability to determine apoplastic pH is limited. Local cell wall pH fluctuations arise also due to plant organs having different roles and being affected by a diverse range of stimuli. Despite the fact that new pH measurement techniques, such as genetically encoded fluorescent probes, were developed in the last two decades, there is still a need to provide a higher spatiotemporal resolution of pH analysis. Key words: Arabidopsis, apoplastic pH, cell growth, acid growth theory, cell wall, auxin, apoplastic pH measurement
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Plant tomosyns and their role in secretion
Dejová, Lilly ; Hála, Michal (advisor) ; Fendrych, Matyáš (referee)
Tomosyn is a protein belonging to the Lgl family and conserved across the animal and plant kingdom. Tomosyn is composed of N-terminal domain containing WD40 motif and Cterminal domain, where the R-SNARE motif is located at the end of the C-terminal domain. This motif is classified as homologous to R-SNARE motif of synaptobrevine, which is a protein located on the surface of the vesicles and participating in the formation of SNARE complex and subsequent fusion of the vesicles with the plasma membrane. Thus the role of this tomosyn is mainly the regulation of exocytosis. Apart from the animal tomosyn, its yeast homolog Sro7/Sro77 is also examined, however during the evolution it has lost its R-SNARE motif and therefore the plant tomosyns remain unexplored. The aim of this diploma thesis was to characterize both of the plant tomosyns: AtTYN1 and AtTYN2 in Arabidopsis thaliana plant. The experimental thesis included the bioinformatic analysis, the DNA construct creation, a search for interactors by yeast two-hybrid system and monitoring the localization using the confocal microscope. The bioinformatic analysis results, including the creation of phylogenetic tree, not only revealed the conservation of tomosyns across the different classes, but also the division of both tomosyns into different clusters. There was...
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Role of the exocyst complex in stomata dynamics
Drs, Matěj ; Pečenková, Tamara (advisor) ; Fendrych, Matyáš (referee)
The exchange of gases between the plant and the environment is mediated by guard cells, which, by changing their volume, regulate the size of the stomatal pore where the exchange takes place. Unique properties of stomata are given by a specifically designed cell wall, allowing asymmetric cell expansion. During the opening of stomata, there is a large increase in turgor pressure, accompanied by the uptake of considerable amount of water. For this reason, it is necessary to quickly change the inner surface of the guard cell. This process is ensured by the dynamic movement of the membranes inside the cell. During these processes, the vesicles are removed from the plasma membrane and reintegrated back during stomatal closure. One of the important regulators of the polarized transport of vesicles within the cell is a multiprotein complex exocyst. Due to the multiplication of exocyst subunits, the exocyst complex functions in plants are extensively diversified and involved in many cellular processes. In this thesis the effect of mutation in subunits exo70B1, exo70B2 and its combination exo70B1/exo70B2, on stomatal dynamics is studied. Both of these mutations affect the opening of the stomata during increased light intensity. The mutation of exo70B1 is in this case affected in greater manner. These...
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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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Role of exocyst complex in growth and development of moss Physcomitrella patens
Rawat, Anamika Ashok ; Žárský, Viktor (advisor) ; Binarová, Pavla (referee) ; Fendrych, Matyáš (referee)
During the course of evolution the early land plants gained extensive innovations that can be seen in modern day plants. The polar growth is an ancient feature of eukaryotic cells and is one of preadaptations that helped plants in successful colonization of land. The polar growth in plants regulates not only the direction of cell expansion and structural properties of cell wall but especially also the orientation of cell division, and is governed by various factors, including the exocyst complex. The exocyst is a well conserved vesicle tethering multi-subunit complex involved in tethering of secretory vesicles to the target membrane. The essential role of the exocyst complex in regulation of various cellular processes in Angiosperms is now well documented. Here I present results of a doctoral project that contributed to phylogenetic analyses of the land plant exocyst complex and especially to uncovering functions of three moss exocyst subunits, namely EXO70 (isoform PpEXO70.3d), SEC6 and SEC3 (isoforms PpSEC3A and PpSEC3B) in the model organism Physcomitrella patens. Various knock-out (KO) mutants in several moss exocyst subunits (Ppexo70.3d, Ppsec6, Ppsec3a and Ppsec3b) show pleiotropic defects directly or indirectly linked to the cell polarity regulation. Cell elongation and differentiation,...
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Kortikální cytoskelet, exocytický komplex exocyst a jejich role v morfogenzi rostlinných buněk
Fendrych, Matyáš ; Žárský, Viktor (advisor) ; Baluška, František (referee) ; Hašek, Jiří (referee)
Plant cell morphogenesis is largely dependent on the coordination of cytoskeletal elements, plasma membrane, and vesicle trafficking. Formin proteins are nucleators of the actin cytoskeleton. Plant Class I family formins are integral membrane proteins and thus have the ability to coordinate cytoskeletal dynamics with the plasma membrane localization. We identified Arabidopsis thaliana formin AtFH4 as a microtubule associated protein. The binding is conferred by a novel domain located between the transmembrane domain and the formin homology 1 domain. The protein associated with actin in in vitro conditions. Overexpressed AtFH4 accumulated in the endoplasmic reticulum, and induced coalignment of endoplasmic reticulum membranes with microtubules. Together, these data suggest that the combination of plant-specific and conserved domains enables AtFH4 to function as an interface between membranes and both major cytoskeletal networks . Secretory pathways supported by the activity of the Golgi apparatus play a crucial role in cytokinesis in plant cells. Prior to their fusion with the plasma membrane, secretory vesicles are tethered at exocytic sites by the exocyst, an octameric protein complex. We analysed the mutant in the EXO84b exocyst subunit, and discovered that the mutant plants were dwarfed and exhibited...
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Plant competition in the early ontogeny
Čiháková, Klára ; Weiser, Martin (advisor) ; Fendrych, Matyáš (referee)
Competitive impacts on early stages of plant ontogeny are being reviewed in this thesis. Those processes select for evolutionary or phenotypically plastic responses in timing of emergence, seed morphological properties, maternal effects and reaction on environmental cues. However, pattern of the strong selective pressure is sometimes not apparent, due to the lack of data and knowledge on the influence of the other factors in plant's life.
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Advanced methods of endocytosis and exocytosis visualisation on plant cell membrane
Ortmannová, Jitka ; Fendrych, Matyáš (advisor) ; Krtková, Jana (referee)
Endocytosis and exocytosis participate in developmental program of plants.The ability to target exocytic vesicles to particular domains of plasma membrane is crucial for polarization, growth and development. Plasma membrane are recycled via various mechanisms of endocytosis which participates also in establishing plant cell polarity. To extend our knowledge of membrane transport it is essential to observe the activity of its components with high resolution in living cells of intact organisms in real time. Such methods belong mainly into the field of light microscopy and nanoscopy exceeding often diffraction limit (200 nm). Nanoscopic techniques like PALM, STORM, SIM, STED, offer multicoloured visualization of fluorophores and high resolution 3D reconstruction of cellular component. These methods have been used only sporadically in the field of plant biology but there should be no serious obstacles for they employment. The key words: clathrin, difraction limit, endocytosis, exocytosis, exocyst, fluorophore, plant cell, microscopy, resolution
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