National Repository of Grey Literature 20 records found  1 - 10next  jump to record: Search took 0.01 seconds. 
The role of NO in plant senescence
Kramná, Barbara ; Wilhelmová, Naďa (advisor) ; Lhotáková, Zuzana (referee)
1 Abstract Nitric oxide (NO) is a lipophilic free radical gaseous molecule able to readily diffuse through membranes and thus influence the adjacent cells from its source. It belongs among important physiological modulators of a plant life despite of its short life span, which is in most cases, only a few seconds. NO influences plants during their whole life cycle and predominantly acts via a modulation of gene expression or post-translation modifications. An enzymatic production of NO has been documented in apoplast, cytosol and organels such as mitochondria, chloroplasts and peroxisomes, apart from its spontaneous production in reducting conditions. The possible cytoprotective or cytotoxic effects of NO in plant cells depends on its concentration. High concentrations have been proved to be rather cytotoxic. Plant senescence is often accompanied by a vast oxidative damage, which results in high concentrations of ROS, such as O2∙- and H2O2, lipid peroxidation and a decrease of antioxidant enzymes activities. NO has been proved to retard or entirely prevent a senescent phenotype of stress-treated plants. Thus a role as a negative regulator of plant senescence has been proposed for it. The most often method used for NO level modulation in plant tissues is an exogenous aplication of various NO donors. Other...
Oxidative damage to cellular components after oxidative stress induction by specific herbicides
Kramná, Barbara ; Wilhelmová, Naďa (advisor) ; Ryšlavá, Helena (referee)
Oxidative stress is caused by overproduction and overaccumulation of ROS (reactive oxygen species). This state is responsible for cellular damage during unfavorable environmental conditions such as drought, low temperatures, salinity. In order to directly study oxidative stress at tobacco plants (Nicotiana tabacum cv. Xanthi) I used specific herbicides, MV (methyl viologen) and 3-AT (3- aminotriazole). There were several markers used for monitoring oxidative damage to cellular components: DNA damage detected by a comet assay, lipid peroxidation, carbonylated proteins and modification of activities of antioxidant enzymes CAT (catalase) and APX (ascorbate peroxidase). Fluorescent microscopy documented changes in a redox state of tobacco cells and a specific signal for peroxisomes was observed after treatment with higher concentrations of MV and 3-AT. Application of both herbicides caused significant DNA damage, while they worked in a different concentrations, MV in µM and 3-AT in mM. Another convincing oxidative stress marker for MV was protein carbonylation. The inhibition of antioxidant enzymes CAT and APX was less significant when compared to the effects of 3-AT. Decreasing membrane stability proved to be an universal oxidative stress marker for both herbicides. On the other hand, lipid...
Study of selected plant exocyst subunits and its interactors in autophagy pathway.
Rácová, Denisa ; Žárský, Viktor (advisor) ; Wilhelmová, Naďa (referee)
Exocyst is a binding protein complex, which is evolutionary conserved in yeast, animal and in plant cells. It has crucial role in regulation of cell morfogenesis and cell polarity. The function of the exocyst complex is binding of secretoric vesicle to the proper side on plasma membrane in penultimate step of exocytosis. This process is essecial for function and survival of cell. Another process crucial for the cell is autophagy. In plants autophagy plays important role in the responses to nutrient starvation, senescence, abiotic and biotic stress. RabG3b are small GTPases, which have positive role in autophagy. In this work I described the interaction between RabG3b and some of subunits of exocyst complex: Exo70B1, Exo70B2 and Exo84b. I also studied changes in morfogenesis of tonoplast by induction and inhibition of authophagy and induction of anthocyans synthesis in Arabidopsis thaliana.
Antioxidant enzymes response to abiotic stress. Impact of decreased cytokinin level.
Lubovská, Zuzana ; Wilhelmová, Naďa (advisor) ; Prášil, Ilja (referee) ; Kočová, Marie (referee)
Charles University in Prague, Faculty of Science Department of Experimetnal Plant Biology Ph.D. study program: Plant physiology and anatomy Abstract Antioxidant enzymes response to abiotic stress. Impact of decreased cytokinin level. Zuzana Lubovská Supervisor: RNDr. Naďa Wilhelmová, CSc. Supervisor-consultant: RNDr. Helena Štorchová, CSc. Praha, 2015 The response of the antioxidant enzyme system to drought, heat and a combination of these stresses was followed in tobacco plants overexpressing cytokinin oxidase/dehydrogenase1 (CKX1) under the root-specific WRKY6 promoter (W6:CKX1 plants) and under the constitutive 35S promoter (35S:CKX1 plants) and in the corresponding wild type (WT). CKX1 over-producing lines developed a bigger root system, which contributed to their stress tolerance. The high stress tolerance of 35S:CKX1 plants was also associated with a dwarf shoot phenotype and changed leaf morphology. The genes for chloroplastic antioxidant enzymes, stroma ascorbate peroxidase (sAPX), thylakoid ascorbate peroxidase (tAPX) and chloroplastic superoxide dismutase (FeSOD), which are responsible for scavenging of reactive oxygen species produced via electron transfer during photosynthesis, were all strongly transcribed in control conditions. All the tested stresses down-regulated expression of these genes...
Effect of cytokinin deficiency on oxidative damage and antioxidant defence during ageing and abiotic stress
Mýtinová, Zuzana ; Wilhelmová, Naďa (advisor) ; Ryšlavá, Helena (referee) ; Prášil, Ilja (referee)
Conchsiom l) Leaves of Úmsgenie tobmo with refuced lwd of CK agedmme sbwly, cmtrary to the contol leaves' AtcKx2 planÉsmaintainedhigher Chl cont€nt ed protein cmtd' md alsohigherphotosyntfuticperformmoein theoldestleaves. 2) We observed elevated mtioxidmt (bott enrynalc md low-moleculr) ftnctional alreadyin theyoungestleavesof AICI(X2. 3) Enhmoementof oertaindioxidmt defencecould be cased oryenscory eff€ct of tb€ decÍeas€ in the level of Úotd CKq assumedas potedial m-ea4nnďic mtioxidmts or as a resultof oxidative súessin&rcedby thelack ďCKs in yorog deve|opingleaves. 4) It is plarrsible thaÍthe higba mtioxidant defeirce migbt comĚute to retÚdation of ageingwitt a consequ€Írc€ of postponedonsetof serrescencein lwes with a defioienoy ofCKs. 5) Tbe responsesof AoE a.tiúties to individual sresses ditreredbetweenleavesmd roots ofboth WT mdAtCKX2 torbacoofuts. ó) The higho toleranceof AICKX2 plms cotúdbe affiib}t€d to noticeably higber activity of GR in leaves md APX SOD md CAT in roots displayed aheady mder cmnol conditions. Althougb rrmsgenic tobacco plmts possess, ď l€ast prtiďy' berer ffiioxidd protection in non-stressedoonditions,they were not oonfirmed to be more tolermt to abiotic sb€ss€s. 7) The ďfference between md WT plants in theř stess Í€spons€s could be associďed with ďvergent seosfiúý to imposed...

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