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Superoxide dismutase (SOD) in-gel activity assay with selective inhibitors (KCN and H₂O₂) is one of the most commonly used methods for identification of SOD isoform types, i.e., FeSOD, MnSOD or Cu/ZnSOD, and evaluation of oxidative stress response in plants. However, there are potential pitfalls that surround this assay, such as problem to detect isoforms with low activity, comigration of SOD isoforms or application of inappropriate inhibitor concentration. We propose an improved method based on the combination of in-gel analysis of SOD activity and nativePAGE immunoblotting for identification of isoforms and determination of SOD isoenzyme activity pattern in potato. Depending on cultivar and growing conditions, one MnSOD, 3 FeSOD and 5–6 Cu/ZnSOD isoforms were identified in potato leaves. The most important qualitative difference between ex vitro- and in vitro-grown plants was the presence of additional FeSOD and Cu/ZnSOD isoforms in plantlets grown in vitro. Compared with results of in-gel activity assay with selective inhibitors, new method allowed accurate identification of comigrating FeSOD and Cu/ZnSOD isoforms and two protein bands of ambiguous identities. Potato SODs were also characterized by SDS-PAGE immunoblotting and single MnSOD (23.6 kDa), three Cu/ZnSOD polypeptides (17.9, 17 and 16.3 kDa) and single FeSOD (25.1 kDa) polypeptide were detected in leaves of four examined cultivars. The difference in the number of FeSOD and Cu/ZnSOD isoforms/polypeptides between native-PAGE and SDS-PAGE immunoblots suggests that SOD proteins may have undergone post-translational modifications affecting protein mobility or existence of isoforms that differ from each other in total protein charge, but not in molecular weight.
Shoot cultures of rare Balkan hyperaccumulating species Alyssum markgrafii were subjected to high nickel concentrations of 1, 3, 5, and 8 mM. The effects of graded nickel concentrations on toxicity, pigments, and several components of plant antioxidative defense system were characterized. Toxic effects of excess nickel were observed through slower growth and biomass decrease, together with increased reactive oxygen species (ROS) production and lipid peroxidation. Nickel exposure decreased chlorophyll a, b, total chlorophyll as well as carotenoid concentration. Addition of sodium benzoate, potent ROS scavenger, showed concentration-dependent disturbing effect on nickel hyperaccumulation, lowering the content of accumulated nickel in A. markgrafii shoots. General reducing power represented by low molecular weight antioxidants and phenols was inversely correlated with nickel concentration. Among the investigated antioxidative enzymes, POD seems to play important role in ROS level regulation upon excessive nickel in medium.
The aim of the present study was to investigate the effect of sucrose on shoot regeneration potential in Hypericum perforatum L. roots obtained by Agrobacterium rhizogenes transformation. The morphological evaluation of transgenic roots grown on media supplemented with sucrose (0.5, 1, 2, 4, 6 and 8 %) indicated that both genotype and sucrose concentration significantly affected root elongation and branching, as well as shoot regeneration. For two of five analyzed clones, lower sucrose concentrations (up to 2 %) led to intensive shoot regeneration, while the other three clones intensified shoot development only at elevated sucrose concentrations (4 %). For all clones, concentrations above 4 % had a deleterious effect on both root and shoot development. Genetic characterization of regenerated shoots revealed that all tested clones were diploid with an average of 0.670 ± 0.002 pg of DNA per nucleus, with no significant differences between transgenic and non-transformed plants and, according to PCR, with integrated A. rhizogenes rolA, -B, -C and -D genes. Real-time RT-PCR confirmed the expression of rolA, -B and -C, while expression of the rolD gene was not detected. Differences were detected in the absolute amounts of transcripts between analyzed clones, with the highest levels of expression for all three analyzed rol genes in a clone previously defined as having high root differentiation and less effective shoot regeneration potential. The observed variations in morphogenesis potential could be attributed to different levels of expression of integrated rolA, -B and -Cgenes; while sucrose additionally pointed out these trends.
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