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Mechanisms that control physiological seed dormancy
Řezková, Natálie ; Ponert, Jan (advisor) ; Vosolsobě, Stanislav (referee)
Physiological dormancy is an important developmental trait ensuring that seed does not germinate when the environmental factors are appropriate only temporary. The transition from seed dormancy to germination is regulated by a large number of factors and the phytohormone abscisic acid (ABA) plays a crucial role. Enhanced response to ABA and its biosynthesis is a key mechanism in dormancy induction and maintenance. ABA interacts antagonistically with gibberellins (GAs). Therefore GA biosynthesis and ABA catabolism are positive germination regulators. However, other phytohormones are also involved in the regulation of dormancy and germination. The most studied is ethylene which supports germination similarly to GA. Numerous factors affect dormancy at molecular level, namely chromatin remodeling, gene products that function only in dormancy regulation [e.g. DELAY OF GERMINATION 1 (DOG1)] or gene products that mediate seed response to environmental factors. The dormancy, its induction, depth and release, is driven not only by environmental conditions affecting mature seeds, but also by conditions acting during seed maturation in a maternal plant when the primary dormancy is induced. Requirements for dormancy release and germination induction may vary considerably between species. The physiological...
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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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Endocytic transport in cytokinesis
Koudelová, Kristina ; Libusová, Lenka (advisor) ; Vosolsobě, Stanislav (referee)
Cytokinesis represents a very complex and highly orchestrated process. For many years, the mechanism of animal cell cytokinesis was described as a result of actomyosin ring constriction. By contrast, in plant cells the division was seen as an outcome of vesicle fusion at the cell plate region between two daughter cells. Recent studies, however, uncover the involvement of vesicular trafficking in animal cell cytokinesis. This thesis aims to highlight the importance of endocytic transport and the necessity of its proper regulation. At first, the origin of vesicles is debated. Afterwards, three main types of endocytic vesicles are examined - Rab11/FIP3 endosomes, Rab35-endosomes and PI(3)P-enriched endosomes, along with their function and interacting partners. Finally, the attention is given to the mechanism of abscission and midbody inheritance. Ongoing processes are accompanied by changes in membrane composition, cytoskeleton reorganization and targeted delivery of distinct cargo molecules. Failure in cytokinesis has been implicated in the etiology of many diseases, such as cancer. Therefore, better understanding of associated endocytic trafficking may provide us with new therapeutic strategies.
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The effect of desiccation on streptophyte algae - mechanisms of stress resistance
Pošmourný, Martin ; Pichrtová, Martina (advisor) ; Vosolsobě, Stanislav (referee)
In this thesis I dealt streptophyta algae resistance against desiccation. Even though the area previously devoted only a few people. Considerable amount of work in recent years has been published on the subject. They were found interesting information and discovered new facts. Research continues on and on, and it would be useful to look at what was observed. I believe that understanding this phenomenon is the key to understanding some of the events in the evolution of nature and realizing how tough life can be on the very border of its possible occurrence. I tried to sort out the current knowledge about the mechanisms of stress resistance streptophyta algae and hope that I obtained an overview will help me understand better this issues. So far, it has been observed several approaches to defend against drying. Preventing drying, adaptation to water shortage and tolerance to desiccation. Among the preventive methods of defense include creating clusters of cells, multi-layered mats or secretion mucilage. As an adaptation to the lack of water algae evolved more complex answers in the form of changes in ultrastructure, or regulation of physiological processes. Klebsormidium is capable of half an hour to start the production of significant quantities callose and incorporate it into the cell wall. This...
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Interplay of cytoskeleton and secretory pathway during exocytosis in plant cells
Aldorfová, Klára ; Sekereš, Juraj (advisor) ; Vosolsobě, Stanislav (referee)
Cytoskeleton is known to participate in exocytosis of yeast and animal cells. The role of plant cytoskeleton during exocytosis has not been fully understood yet. However, both actin and microtubules evidently contributes to the secretion of specific cargo proteins or cell wall components. Plant cytoskeleton influences the dynamics of exocytosis through various functions. First, secretory vesicles are delivered near the plasma membrane. Second, microtubules were shown to mark the place of exocytosis. Third, cytoskeleton is able to prevent membrane fusion by simple separation of compartments. Fourth, cytoskeleton potentially mediates the interaction between molecules of secretory apparatus. Secretion of certain cargo molecules appears to be dependent on different cytoskeleton types and the exocytosis seems to be specifically regulated in each tissue. This thesis aims to describe interplay of cytoskeleton and secretory pathway on the example of tip growth and to predict future direction of research on secretory pathway based on cellulose synthase secretory data.
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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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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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Characterization of membrane protein DREPP
Vosolsobě, Stanislav ; Schwarzerová, Kateřina (advisor) ; Cvrčková, Fatima (referee)
Proteins of DREPP family (20-25 kDa, syn. PCaP1 in Arabidopsis thaliana) first appeared in ferns and we have shown that several independent duplications of DREPP protein occurred during evolution of large families (Poaceae, Brassicaceae, Solanaceae and Asteraceae) and in group Coniferophyta. Secondary losses of one paralogue occurred in subfamilies Pooideae and Solanoideae.We have also detected two large-scale modification of DREEP protein in Asparagales and Brassicaceae (this divergent paralogue was previously described as MAP18 protein). We have examined colinearity of chromosome fragments in vicinity both PCaP1 and MAP18 paralogues in Arabidopsis thaliana and we hypothesize that MAP18 gene arose during genome duplication on the origin of Brassicaceae family. DREPP protein was previously identified in detergent-resistant membrane microdomain fraction and a myristyl anchor was shown to be necessary for their membrane localization. Membrane association was shown to be modified by the interaction of unique N-terminal domain with PtdInsPs, which was inhibited by binding of Ca-calmodulin (Nagasaki et al., 2008). The mutation of Gly2 by Ala in the myristilation site, or C-terminal GFP-fusion (GFP-DREPP), affect membrane association in Arabidopsis thaliana (Nagasaki et al., 2008). Several DREPP paralogues in...
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