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Analysis of the relationship between the function of the ARP2/3 protein complex and exocytosis in plant cells
Ničová, Klára ; Schwarzerová, Kateřina (advisor) ; Synek, Lukáš (referee)
Plant cells exhibit two types of growth: diffuse and apical. Mutation of the ARP2/3 complex, which is an actin nucleator, leads to phenotypic expression in both diffusely and apically growing cells. Many of these changes, such as impaired epidermal cell adhesion of hypocotyl cells or slower growth of pollen tubes, suggest that the observed phenotypes are cell wall related. Cell wall components are transported into the apoplastic space by exocytosis. Many factors are involved in controlled exocytosis, one of the most studied being the exocyst tethering complex. Mutants of the exocyst complex show phenotypes in both diffusely and apically growing cells, indicating that this complex is important for both types of growth. In addition, subunit EXO84b of the exocyst complex interacts with subunits of the ARP2/3 complex. In this thesis, I investigated the effect of mutation of ARP2/3 complex subunits on exocytosis of diffusely and apically growing cells by observing the localization and dynamics of the fluorescently labeled marker EXO84b-GFP. In epidermal hypocotyl cells (a model of diffuse growth), EXO84b-GFP had a shorter lifetime at the plasma membrane in ARP2/3 mutants compared to wild type. The pattern of its localization to the plasma membrane was also slightly different. It was not possible to...
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Plant cuticle
Voloshina, Mariia ; Schwarzerová, Kateřina (advisor) ; Synek, Lukáš (referee)
The cuticle is a lipidic structure covering plant aerial organs, providing mechanical rigidity and acting as a protective barrier. It contains the cutin polyester and waxes, which are derived from very-long-chain fatty acids. These compounds are synthesised in two separate pathways. The cuticular biosynthetic machinery is incredibly complex and employs a multitude of enzymes, some of which are functionally redundant, are present in different tissues or catalyse reactions with substrates of various chain lengths. The mechanisms of how these compounds are transported and how the cuticle is assembled rely on ABC transporters, LTP lipid carrier proteins, cutin synthases, and cutinsomes. Knowledge of these highly dynamic processes is very fragmented and the integrated model of cutin synthesis is yet to be elucidated. A tight connection between the cuticle and the cell wall, conventionally seen as two separate entities, has also been implied. The complexity of these mechanisms is also reflected in their transcriptional and post-transcriptional regulation. While SHINE and MIXTA-like transcriptional factors and the WW-domain protein CFL1 regulate the cuticle's synthesis throughout a plant's development, ABA-dependent MYB transcriptional factors are important during abiotic stress. Recent research also...
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Functions of the exocyst complex in secretion and cell wall biogenesis
Vukašinović, Nemanja ; Synek, Lukáš (advisor) ; Růžička, Kamil (referee) ; Kost, Benedikt (referee)
The mechanical strength of plant tissues and organs can be attributed to specific properties of the cell wall. In many cases, in order to establish their final shape, cells deposit various cell wall materials in a localized manner. This is achieved by highly organized action of the endomembrane system which is essential for biosynthesis and secretion of cell wall proteins and polysaccharides. The exocyst complex is a conserved tethering complex in eukaryotes and it is involved in tethering of secretory vesicles to the sites of secretion at the plasma membrane. In this study, we address several aspects of the plant exocyst complex architecture and cell wall development using molecular biology techniques and advanced confocal microscopy. We demonstrated that two SEC10 exocyst subunits are present in Arabidopsis thaliana and share redundant functions. We also showed that the architecture of the plant exocyst complex shares several structural features with the yeast one. We demonstrated the importance of the functional EXO84b exocyst subunit for normal tracheary element development and showed that the main constituents of the secondary cell walls are deposited normally in exocyst mutants. We described a clear difference in the exocyst microtubule-independent dynamics in epidermal cells vs. cell type...
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