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The Role of selected exocyst subunits in response of plants to pathogen
Sabol, Peter ; Kulich, Ivan (advisor) ; Burketová, Lenka (referee) ; Dagdas, Yasin (referee)
In the recent years, there has been a growing number of publications indicating at the involvement of plant secretory pathway in defense against phytopathogens. Specifically, roles of plant exocyst complex have been explored in deeper detail in current research. Yet, exactly how exocyst- mediated exocytosis contributes to secretion of antimicrobials and cell wall-based defense remains unclear. In the presented Dissertation, I provide both experimental evidence and devise further hypotheses on selected exocyst's subunits in plant immune reactions. Particularly, I show that EXO70B1 exocyst subunit interacts with immunity-related RIN4 protein. Cleavage of RIN4 by AvrRpt2 Pseudomonas syringae effector protease releases both RIN4 fragments and EXO70B1 from the plasma membrane when transiently expressed in Nicotiana benthamiana leaves. I speculate on how this might have an implication in regulation of polarized callose deposition. In a co-authored opinion paper, we also hypothesize that EXO70B1-mediated autophagic degradation of TN2 resistance protein prevents its hyperactivation and lesion mimic phenotype development. In addition, in collaboration with my colleagues, I present data on EXO70H4's engagement in PMR4 callose synthase secretion, required for silica deposition. Representing a possible...
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Plant meteoreception
Kampová, Anna ; Vosolsobě, Stanislav (advisor) ; Kulich, Ivan (referee)
Flowering is a crucial event in a life cycle of every single plant. Various plant species are differently affected by weather in this time of their life cycle. Weather may have an impact on flower opening speed and timing and also on flower longevity. Timing of flower opening is very important. If flower opening takes place when weather conditions are unsuited, it can be for such plant terminal, or more precisely terminal for its ability to reproduce. Flower can be very important for male fitness protection. Flower opening is regulated by phytohormones and some other signal pathways - pathways of vernalization, gibberellins, photoperiod and an autonomous one which is independent from photoperiod. Phytohormones and regulation pathways mentioned above may respond to exogenous factors, namely temperature, light, air humidity and rain. Furthermore, an anther dehiscence is the key stage of flowering. Its timing and process have a huge effect on success of plant reproduction. It is also controlled by changing of weather conditions and by phytohormones, jasmonic acid is the main trigger of this process. Environmental factors influence on anther dehiscence was not examined in detail. Key words: flower opening, anther dehiscence, environmental factors
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Mechanisms and regulation of callose deposition to the cell wall of Arabidopsis thaliana
Modráčková, Jana ; Kulich, Ivan (advisor) ; Šustr, Marek (referee)
Callose (β-1,3-glucan) is a significant plant cell wall polysaccharide, which participates in many developmental and stress responses. Despite the importance of this polymer, the knowledge on the causes of callose synthesis, its regulation and the meaning of callose deposition are still limited. The family of callose synthases was revealed thanks to molecular and genetic methods. They are responsible for callose deposition in diferent reactions and the diferent spaces of the plant body. This thesis summarizes the knowleadge about the processes, in which callose is involved, and it presents an overview of the individual proteins from callose synthase family including their phylogenetic analysis and the comparison with the cellulose synthase focusing on the model plant Arabidopsis thaliana. Key words: Arabidopsis thaliana, β-1,3-glucan, callose, callose synthase, plant cell wall polymer
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Vazba paralogů EXO70 na ATG8 a funkční rozdělení rodiny EXO70 dle účasti v autofagii (Arabidopsis thaliana).
Semerádová, Hana ; Kulich, Ivan (advisor) ; Motyka, Václav (referee)
The exocyst, an octameric protein complex conserved among all eukaryotes, mediates tethering of the vesicle prior to its fusion with the target membrane. Apart from the function of exocyst in exocytosis, new studies from both mammalian and plant fields report its involvement in the cellular self-eating process called autophagy. In land plants the number of paralogs of some exocyst subunits is extraordinarily large. There are 23 paralogs of Exo70 subunit in Arabidopsis thaliana. It is supposed that these paralogs have acquired functional specialization during the evolution - including involvement in autophagy. Using yeast two- hybrid assay it is shown here that Exo70B1 and Exo70B2, but not other Arabidopsis Exo70 paralogs interact with Atg8, an autophagosomal marker. The proximity of these two paralogs and Atg8 in vivo was confirmed by independent Förster resonance energy transfer (FRET) method. Interestingly, interaction of Atg8f with Exo70B2 paralog appears to be stronger than with Exo70B1. Exo70B1-mRUBY expressed under the natural promoter shows punctate membrane structures that are mostly static. That changes after the tunicamycin treatment - movement of some of these dots was induced. Homology modeling of Exo70B1 and Exo70B2 proteins tertiary structure in combination with bioinformatic prediction based...
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Phenotypic analysis of epidermal cells in Arabidopsis thaliana plants with impaired actin cytoskeleton
Miklánková, Pavlína ; Schwarzerová, Kateřina (advisor) ; Kulich, Ivan (referee)
Actin cytoskeleton is involved in regulation of many processes in plants, for instance proper morphogenesis of the cells and of the whole organisms, organelle movement, regulation of cell division. Its dynamics and polymerization is regulated by various complexes and associated proteins which include ARP2/3 complex. This complex nucleates new actin filaments de novo and helps their branching. This diploma thesis deals with the role of actin and ARP2/3 complex in diverse processes in plant cells. The first part of the thesis concentrates on the role of actin in morphogenesis; the second section is focused on the endocytosis in epidermal cells. The investigation of the importance of individual plant cytoskeletal components suggests that microtubules are of key importance for plant growth. Impairing of actin cytoskeleton by latrunculin B caused inhomogeneous reaction of the plants. It is known that loss of ARP2/3 complex in A. thaliana plants results in the specific malformation of trichomes which are known as distorted trichomes. It was found that the loss of actin isoforms is not associated with severe malformation of trichomes. The most pronounced phenotype was observable in case of ACT7 protein loss. It was further found that the distorted phenotype was not induced by application of latrunculin B...
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Conventional and Novel Functions of the Exocyst Complex in Plants
Kulich, Ivan ; Žárský, Viktor (advisor) ; Baluška, František (referee) ; Hašek, Jiří (referee)
Exocyst is an octameric protein complex, conserved across all Eukaryotes. Its role, originally described in yeast, resides in a tethering of the secretory vesicles to the plasma membrane prior to the membrane fusion of the two membranes. Subunits SEC3 and EXO70 are believed to be spatial landmarks for the vesicles delivery. While yeast genome encodes single EXO70, we find dozens of them in land plants (23 in Arabidopsis). This work is focused at a role of the exocyst complex in plant cells. Its first part documents, that exocyst is essential for delivery of the cell wall components, namely pectins, but also for pathogen induced secondary cell wall thickening. Second part reveals an unconventional role of EXO70B1 subunit harboring exocyst subcomplex at an autophagic pathway to the vacuole and raises many questions about plant secretory pathway.
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Vesicular trafficking into the plant vacuole
Semerádová, Hana ; Kulich, Ivan (advisor) ; Vosolsobě, Stanislav (referee)
Vacuole is very important plant cell organelle which can occupy 90% of cell volume. It provides wide range of functions. Considering enormous size of the vacuole, vesicle trafficking into the plant vacuole is major vesicle movement inside the cell. Transport pathway into the vacuole is very dynamic field of plant cell biology. This sorting machinery shares similarities within all eukaryotes, but plants also have their own specificities. Soluble cargo is targeted through secretory pathways by vacuolar sorting receptors (VSRs). These proteins due to its transmembrane localization can interact with sorted cargo and take it to the right organelle within the cell. Membrane fusion is facilitated with Rab-GTPase and SNARE protein complexes. A special kind of vesicle traffic is autophagy, the self consuming process that protects the cell from various type of stress or enables apoptosis.
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Function of root apical meristem
Benešová, Šárka ; Soukup, Aleš (advisor) ; Kulich, Ivan (referee)
A root apical meristem is the only source of cells for all tissues in the root. The root growth relies on its function. Regulation of a cell division frequency and cell differentiation affects organization and function of the differentiated tissues and the proper meristem function. If the cell differentiation overbalances the cell proliferation, the meristem exhaustion occurs and the root growth irreversibly terminates. This thesis describes existing knowledge about regulation of the primary root apical meristem of model plants Arabidopsis thaliana and Zea mays, explains these findings in the context of plant postembryonal development and provides informations about how and under what conditions the primary root growth might be terminated.
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Mechanoreception in plants
Martinek, Jan ; Vosolsobě, Stanislav (advisor) ; Kulich, Ivan (referee)
Because of their sessile nature, plants are unable to change their location and thus they are forced to adapt as much as possible to the environment they grow in. Plants evolved the ability to sense many environmental cues, which enables them to perceive the conditions in their surroundings. One class of these stimuli are mechanical forces - from wind sways to contact with obstacles, herbivores or other plants - other mechanical stimuli are e.g. gravity or sound waves. Carnivorous or climbing plants have structures specialised for perception and rapid response to mechanical stimuli. Intriguingly, there is a less spectacular but maybe even more interesting and important response to mechanical perturbation in non-specialized plants. This thesis tries to summarize ubiquity of mechanoperception in plant kingdom and its adaptive importance for the plant life - from activation of traps, to morphological adaptation for growth at windy sites, tendril coiling in climbing plants and root navigation through obstacles in soil. In the following part, the thesis summarizes the recent knowledge of molecular processes accompanied with mechanoreception, signal transduction and integration, and response to mechanostimulation. In the last part I proppose a scheme of mechanosensing workflow from initial mechanical...
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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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