| Leader of the project: L. Tamás |
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Research team: S. Budíková, J. Huttová, I. Mistrík, P. Paľove-Balang, M. Šimonovičová,
B. Široká
Duration of the project: 2004 - 2006
Grant Agency: VEGA 2/4040/04
In most natural environments the heavy metal content of the soil is low and does not cause significant phytotoxicity. Amongst the heavy metals, cadmium (Cd) is the one with the highest toxicity not only to plants but also to animals and human beings. High toxicity of heavy metals including Cd is caused by their ability to bind to -SH groups of enzymes and proteins leading to their conformation changes, and to produce reactive oxygen species. Both effects inhibit activity of enzymes involved in photosynthetic Calvin cycle, nitrogen and sulphate metabolism and glycolysis, interfere with membrane structure (peroxidation of lipids), and induce DNA injury. Our project is aimed at complex study of the effects of Cd on plants with respect to structural responses and physiological processes. Attention is paid to relationships between localization of uptake and accumulation of Cd in individual root structures, synthesis and accumulation of callose and lignin, and the proteins involved in protection of plants against the harmful effects of Cd. Activity of key enzymes involved in scavenging of reactive oxygen species and expression of polypeptides involved in immobilization of Cd in cells will characterize the possible role of this mechanisms in resistance of plants to heavy metal-induced stress.
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Contribition to the life strategy of species of Colchicum autumnale L. |
| Principal investigator: M. Pšenák, Prof. RNDr., CSc. (Faculty of Pharmacy CU) |
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Research team: O. Gašparíková; L. Franková; V. Banásová (Institute of Botany SAS);
F. Bilka; A. Bilková; V. Blanáriková; M. Obložinský; A. Balážová; L. Bezáková (Faculty of Pharmacy CU),
K. Bóka (ELTE Budapest)
Duration of the project: 2004 - 2006
Grant Agency: VEGA 2/1275/04
C. autumnale belongs to geophytes with hysteranthous leaves and corm (an underground basal stem bulb). The reserves mainly starch have a central importance in a life strategy of hysteranthous geophytes. In addition to starch (50% of dry mass), proteins represent 12% of dry mass. The project is focused on structural, physiological and biochemical aspects of starch and protein metabolism and colchicinoids distribution during the life cycle of the plant growing in natural population. Special attention was paid to: 1- developmental profile of starch and other storage polysaccharides in new corm; 2 - enzymes in storage starch biosynthesis, 3 - enzymes converting sucrose to starch precursors in source and sink organs; 4 - protein content and proteolytic activities in corms; 5 - spectrum and content of free amino acids; and 6 - distribution of β-glucosidase and nitrate reductase activities during the plant life cycle. Within the structural studies the developmental sequence of individual generations were evaluated at the level of meristems, the amyloplast formation and processes of senescence. Altogether the results obtained allowed understanding and explaining the basic life strategy of C. autumnale as a hysteranthous geophyte.
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Metabolic and anatomical responses of the plants to water deficit |
| Leader of the project: M. Luxová |
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Research team: O. Gašparíková, K. Dekánková, J. Huttová, P. Valentovič, L. Kolarovič,
E. Záletová
Duration of the project: 2004 - 2006
Grant Agency: VEGA 2/4036/04
The absence of water is a critical point in the growth and plant productivity. If we want to increase productivity of economically important crops we need to know defense and adaptive mechanisms against the drought, controlling the plant water balance. The aim of this project is to find some changes in anatomical pattern of roots under the long duration of water stress. As we have found some changes in the levels of soluble sugar and starch in the roots and leaves of maize during the drought, we will study the synthesis of osmotically active substances such as a proline and glycine betaine together with the activity of some enzymes of sugar metabolism. This will help us better understand an osmotic adjustment in different tissues and plant organs. Another task will be to determine the induction of alternative oxidase in root mitochondria and, together with the results of the presence or absence of antioxidants (ascorbate, glutathione) and activities of antioxidant enzymes, to find some pattern of defense system in different plant organs (root, mesocotyl, leaves) against the oxidative damages caused by water stress.
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Fungi Fusarium spp, their toxicity and relationship to host plant. |
| Leader of the project: A. Šrobárová |
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Research team: Š. Eged, M. Nadubinská, J. Pavlovkin
Duration of the project: 2003 - 2005
Grant Agency: 3051/23
Intraspecific variability among fungi Fusarium spp isolated from ear rot of wheat ( F. culmorum, F. graminearum, F. cerealis, F. sambucinum) were observed in vitro : in growth culture, sporulation, pigmentation, deoxynivalenone production , and in vivo pathogenicity toward wheat seedlings. Interspecific variability was observed only in population of fungus F. graminearum. The role of DON in F. culmorum pathogenesis in wheat and its degradation by some cultivars was recorded. Synergistic effects of fusariotoxins (moniliformin, fumonisin B1, fusaproliferin, zearalenone, zearalenol and deoxynivalenon) on maize plants of resistant (Lucia) and susceptible (Pavla) cultivars were seen as other stress factors. On the membranes of each organelles osmiophilic particles occurred, what suggests us to suppose that fumonisin prevails other toxins, its mechanisms of action may be connected with lipids metabolism. Fusaric acid (FA), at concentration of 1 mM induced at pH 5.5 an early hyperpolarisation followed by a marked depolarization of membrane potential difference (Em) and increased electrolyte leakage from the primary Ricinus roots was determined. Production of FA is inhibited by polysaccharides of cell wall of (glucans) others fungi and by species Trichoderma.
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Involvement of MAP kinases, cytoskeleton proteins and cell wall in root hair development |
| Leader of the project: M. Čiamporová |
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Research team: F. Baluška, K. Dekánková, O. Erdelská, Z. Hanáčková, P. Illéš, M. Ovečka,
H. Vargová
Duration of the project: 2002 - 2004
Grant Agency: 2031/22
In all eukaryotes MAP kinases are universal transducers of extracellular (stress-related) signals. They are an inevitable component of plant developmental processes. Tip-growing root hairs represent unique plant objects for studies on developmental changes in cyto-architecture upon diverse developmental signals and environmental cues. During root hair initiation and subsequent tip growth, local weakness of cell wall imposes local stretch-related stress on the plasma membrane. MAP kinases can be expected to participate also in the signal-mediated tip growth of plant cells. The goals of the project include (1) cytological and ultrastructural study of epidermal cells before and during root hair development, structure of the cell wall and the complex actin filaments - cortical microtubules - plasma membrane - cell wall, and (2) immunolocalisation of MAP kinases in developing root hairs and root cells under control and stress conditions.
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Effect of Al on protein content and composition in Al-tolerant and Al-sensitive barley cultivars |
| Leader of the project: I. Mistrík |
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Research team: S. Budíková, J. Huttová, P. Paľove-Balng, L. Tamás, M. Šimonovičová,
B. Široká, E. Záletová
Duration of the project: 2001 - 2003
Exposure of roots to aluminium induced quantitative changes in protein composition isolated from different parts of barley plants. The number of changes in roots increased with increased distance from the root tip to the above-ground part of barley plants where the changes were most remarkable. Al treatment induced a tremendous enhancement of both hydrogen peroxide production and activity of peroxidase. Increase in the activity of peroxidase correlated with the extent of root growth inhibition. Especially in roots of Al-sensitive barley cultivar the activity of peroxidase was up to 6 times higher than in the control roots, while in the Al-resistant cultivar the increase was only half of that in the sensitive one. Analysis of isoenzyme composition revealed that at least five anionic and four cationic isoperoxidases were stimulated by Al-treatment. Three of anionic isoperoxidases were selectively induced only in the Al-sensitive cultivar.
Concomitantly, considerable increase in the activity of oxalate oxidase (OxO) was observed. The activity of OxO as well as overproduction of hydrogen peroxide started very early after the exposure to Al but only at the concentrations of Al-inhibiting root growth. The time course analysis of OxO gene expression and OxO activity showed that OxO activity increased as soon as after 3 h of exposure of roots to Al, reaching its maximum about 18 h after Al application. Rapid increase in the OxO activity and tremendous increase in hydrogen peroxide content in roots indicate an important role of oxidative stress during Al treatment. Production of reactive oxygen species and subsequent membrane damage during aluminium treatment are the main factors directly involved in the loss of cell viability and death of root epidermal cells.
| Leader of the project: M. Luxová |
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Research team: O. Gašparíková, K. Dekánková, J. Huttová, P. Valentovič, T. Takáč,
L. Franková, T. Ješko
Duration of the project: 2001 - 2003
The effect of drought on growth and morphology of root system in two maize cultivars was investigated. Characteristic parameters affected by water stress were found: the length and branching density of the root system. We have found out that in some metabolic responses to drought the total respiration rate declined in parallel to the accumulation of osmotic solutes (the content of soluble sugars almost doubled). The respiration decrease occurred at the expense of both alternative and cytochrome respiratory pathways.
The increase of activities of antioxidative enzymes superoxid dismutase, catalase and ascorbate peroxidase was determined during the drought in roots, mesocotyl and leaves. No changes in isozymes pattern of ascorbate peroxidase were found between the cultivars but some differences appeared among the studied organs. Lipid peroxidation in the roots and leaves under dry conditions was higher whereas in mesocotyl no significant differences were detected.
The determination of Si content in two different cultivars of sorghum resulted in about 50% higher content of Si in the drought tolerant cultivar than in the sensitive one. It means that silica plays a very important role in adaptation of plants to dry conditions.
| Leader of the project: A. Šrobárová |
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Research team: Š. Eged, M. Nadubinská, A. Pavlová
Duration of the project: 2000 - 2002
The occurrence of potentially toxigenic Fusarium species involved in head and ear blight of wheat and maize had been monitored in Slovakia during three years. The fungi were localised in endosperm of caryopses of either symptomatic and asymptomatic spikes or ears. Beside the most frequent F. culmorum, the species F. graminearum, F. sambucinum and rarely also F. pseudocerealis were involved. Each of these species is a potential producer of the mycotoxins trichothecenes and zearalenone. The most frequent species isolated from maize kernels were anamorphs of the section Liseola, besides the species F. graminearum. Using the method of "mating population" and based on the toxins profile, three (A, D, and E) of the seven Fusarium spp. populations known in the world were identified in addition to the sterile ones. The most frequent was the population A, the strains of which produce all the characteristic mycotoxins (fumonisin, fusaproliferin, and beuvericin) in amounts below the provisional limit of (0.5 mg / kg-1). Under in vitro conditions their concentration was higher hundredfold, revealing the potential capacity of the populations in Slovakia. A production in vivo higher than the limit considered as risk concentration was recorded with the toxins of the species F. graminearum: deoxynivalenol (DON) and zearalenone (ZON). The role of the mycotoxin DON in pathogenesis of the species F. culmorum in wheat and resistance to its accumulation in some cultivars during spike ripening was proved. We evaluated dynamics in fusaric acid productivity during ontogenesis of the fungi Fusarium oxysporum f. sp. lycopersici of different provenience in relation to its role in pathogenesis on tomato plants (Lycopersicon esculenta L.).
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Cytoskeleton and cellular membranous structures in the process of morphogenesis |
| Leader of the project: M. Čiamporová |
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Research team: F. Baluška, M. Čiamporová K. Dekánková, Z. Hanáčková, M. Hauskrecht,
O. Erdelská, M. Ovečka
Duration of the project: 1999 - 2001
Cellsof the root apex and particularly root-hair forming epidermal cells are suitable model systems to study morphogenetic processes like cell proliferation and growth patterns, and cell differentiation, in plants. Microscopy with immunofluorescence and morphometric techniques provided a suitable approach to characterise the behaviour and a role of structural components and associated protein molecules during these processes. A new semiquantitative fluorescence evaluation technique has been developed to determine the cell cycle phases. This in combination with immunofluorescence enables to reveal relationships between the morphogenetic processes, the cell type, age, and cell cycle phase. The results showed that dynamic actin-based cytoskeleton is inevitable for rapid elongation of root cells as well as for initiation and tip growth of root hairs. In contrast, mitotic divisions occur also in F-actin devoid plants however, with aberrant division planes. Cellular endomembranes are important for root hair initiation. Proteins associated with actin cytoskeleton (myosins, profilins, actin-depolymerising factors) are co-distributed with the dynamic F-actin, in relation to the stage of cell differentiation. Profilins and some MAP kinases seem to participate in signal-transducing pathways between plasma membrane, cytoskeleton, and cytoplasmic components including the nucleus, ultimately leading to developmental patterns adjusted to environmental conditions.
