The protective role of selenium in rape seedlings subjected to cadmium stress.
The effect of selenium (Se) on rape (Brassica napus) seedlings subjected to cadmium (Cd) stress was studied in vitro by investigating plant growth and changes in fatty acid composition, activity of antioxidative enzymes and DNA methylation pattern. Physiological experiments were carried out on seedlings cultured for 2 weeks on Murashige-Scoog (MS) media with Cd concentrations of 0, 400 and 600 microM, and on corresponding media supplied with Se (2 microM). Exposure to increasing Cd concentrations reduced the fresh weight of the upper part (hypocotyls+cotyledons) of the seedlings more strongly than that of the root system, which was accompanied by higher Cd accumulation in these tissues. In the upper part, Cd exposure led to significant changes in the biochemical parameters: fatty acid unsaturation of plasmalemma decreased, the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPOX) diminished and that of ascorbate peroxidase (APX) increased. In contrast, the roots showed an increase in fatty acid unsaturation and in the activity of antioxidative enzymes. In both parts of rape seedlings H(2)O(2) level and lipid peroxidation increased. Se addition to medium considerably reversed the Cd-induced decrease in fresh mass as well as the changes in lipid unsaturation and peroxidation. Se applied separately or in combination with Cd did not significantly affect the activity of antioxidative enzymes in the roots, but diminished it in the upper part. Moreover, the presence of Se in medium prevented changes in the DNA methylation pattern triggered in rape seedlings by high Cd concentrations. Two possible mechanisms for the action of Se were considered: (1) removal of Cd from metabolically active cellular sites, and (2) reduction of oxygen radicals.
Filek
Maria
M
Institute of Plant Physiology, Polish Academy of Sciences, Podłuzna 3, 30-239 Kraków, Poland. mariafilek@excite.com
Keskinen
Rucka
R
Hartikainen
Helina
H
Szarejko
Iwona
I
Janiak
Agnieszka
A
Miszalski
Zbigniew
Z
Golda
Agnieszka
A
D060387:Ascorbate Peroxidases; D029741:Brassica rapa / Q000187:drug effects* / Q000201:enzymology; D002104:Cadmium / Q000633:toxicity*; D002374:Catalase / Q000378:metabolism; D003470:Culture Media; D019175:DNA Methylation / Q000187:drug effects; D005227:Fatty Acids / Q000032:analysis; D005979:Glutathione Peroxidase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008315:Malondialdehyde / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology; D020011:Protective Agents / Q000494:pharmacology*; D036226:Seedlings / Q000187:drug effects* / Q000201:enzymology; D012643:Selenium / Q000494:pharmacology*; D013312:Stress, Physiological / Q000187:drug effects*; D013482:Superoxide Dismutase / Q000378:metabolism
D003470:Culture Media; D005227:Fatty Acids; D020011:Protective Agents; D002104:Cadmium; D008315:Malondialdehyde; D006861:Hydrogen Peroxide; D010544:Peroxidases; D060387:Ascorbate Peroxidases; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D012643:Selenium