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Plant peroxisomes: structure, localization, function.
Pivoňka, Jaroslav ; Schwarzerová, Kateřina (advisor) ; Kutík, Jaromír (referee)
Plant cell is a complex and complicated environment where countless biochemical processes and metabolic pathways take place independently of each other. Some of them could pose a threat to a plant cell or be a cause of organism lethality altogether, mainly because of their antagonistic character or by their toxicity. To eliminate this danger and ensure the most effective course of these reactions, a separation into properly separated and safe compartments is being applied. This phenomenon is called cellular compartmentalization and these sections are called organelles. Peroxisomes are one of them. They are highly dynamic and metabolically diverse vesicles of spherical nature, formed by a single-layered membrane. They contain crucial enzymes that operate in processes such as reactive oxygen species (ROS) metabolism, photorespiration, storage oils breakdown followed by β-oxidation of fatty acids, glyoxylate cycle, phytohormones biosynthesis, and more and more of other metabolic pathways. By that, they stand as an essential imaginary crossroad connecting these critical processes in plant development and physiological responses to abiotic and biotic stresses. This work is focused on reviewing these peroxisomal functions in plant cells, as well as the peroxisomal structure, its proteome and biogenesis....
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Inducible RNAi against essential genes of nitrogen metabolism as a tool for control of GM plants
Kobercová, Eliška ; Fischer, Lukáš (advisor) ; Tylová, Edita (referee)
Uncontrolled spreading of genetically modified (GM) plants is one of the main concerns about their cultivation. Inducible RNA interference against an essential gene could be a tool for control of GM plants. After spraying with a chemical inducer, the essential gene will be silenced so the treated GM plant will die. For testing this strategy we chose two key enzymes of nitrogen metabolism, glutamate synthase (GOGAT) and glutamine synthetase (GS). GS processes ammonium ions into glutamine, then GOGAT transfers the amide group from glutamine to 2-oxoglutarate to form two glutamates. GS/GOGAT cycle is the main pathway for assimilation of ammonium ions, which could be toxic to plants in a higher concentration. Disruption of ammonium assimilation during photorespiration causes a strong inhibition of photosynthesis. The aim of this work was to describe the effects of silencing GOGAT and GS genes in Arabidopsis thaliana. To induce silencing, RNAi hairpin constructs under a control of constitutive or estradiol-inducible promoter were prepared. In selected independent transformants with the inducible hairpin against GOGAT, chlorosis and reduced growth were observed after the estradiol treatment in in vitro conditions. However, the spraying with estradiol was tricky, at the whole plant level, the induction of...
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Glutamine synthetases and their role in nitrogen metabolism in plant shoot
Kobercová, Eliška ; Fischer, Lukáš (advisor) ; Tylová, Edita (referee)
Glutamine synthetase is a key enzyme for ammonium assimilation and glutamine biosynthesis in plants. Ammonium ions are important intermediates in nitrogen metabolism, but their elevated concentration is toxic to plants. Correct function of glutamine synthetase is essential to plant life - glufosinate, a specific inhibitor of glutamine synthetase acts as a total herbicide. Glutamine synthetase is involved in a number of important metabolic processes: primary assimilation of nitrogen nutrients, in reassimilation of ammonium ions released during photorespiration or metabolism of phenylpropanoids and in nitrogen remobilization in developing seeds, during germination or senescence. According to localization in the cell glutamine synthetases in angiosperms are divided into the plastid form (GS2), which is typically encoded by a single gene, and the cytosolic form (GS1), which is encoded by a small multigene family. The various isoforms of glutamine synthetases have different location within plant organs and tissues, ways of regulation and role in nitrogen metabolism. Keywords: plastid and cytosolic glutamine synthetase, ammonium assimilation, nitrogen metabolism, photorespiration
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