Effect of short-term salinity on the nitrate reductase activity in cucumber roots

• Published in: Plant science (Limerick) 2011-06, Vol.180 (6), p.783-788
• Main Authors: Reda, Małgorzata, Migocka, Magdalena, Kłobus, Grażyna
• Format: Article
• Language: English
• Subjects: adenosine triphosphate; Adenosine Triphosphate - analysis; Biological and medical sciences; Cantharidin - pharmacology; Cucumber; cucumbers; Cucumis sativus; Cucumis sativus - drug effects; Cucumis sativus - enzymology; EDTA (chelating agent); enzyme activity; Enzyme Inhibitors; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic; genes; Hydroponics; magnesium; microcystin-LR; Microcystins - pharmacology; Nitrate reductase; Nitrate Reductases - drug effects; Nitrate Reductases - genetics; Nitrate Reductases - metabolism; nutrient solutions; phosphoprotein phosphatase; Phosphorylation; Plant Roots - drug effects; Plant Roots - enzymology; Posttranslational regulation; protein phosphorylation; Protein Processing, Post-Translational; roots; salinity; Salt stress; sodium chloride; Sodium Chloride - pharmacology; Stress, Physiological; Time Factors
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2011.02.006

In short-term experiments, the effect of high salinity on cucumber (Cucumis sativus) nitrate reductase activity was studied. The 60-min exposure of cucumber roots to 200mM NaCl resulted in significant increase of the actual NR activity (measured in the presence of Mg²⁺), whereas the total enzyme activity (measured with EDTA) was not affected. NaCl-induced stimulation of the actual NR activity was rapidly reversed upon transfer of roots to salt-free solution. The increase in actual activity was completely prevented by microcystin-LR and cantharidin, protein phosphatases inhibitors. In addition, a significant decrease in ATP level was also observed in roots incubated with NaCl. These data suggest that the reversible protein phosphorylation is involved in the induction of NR activity during the first hour of salt stress. The effect of short-term salinity on the expression of genes encoding for nitrate reductase in cucumber roots was also studied. 200mM NaCl diminished the increase in CsNR1 expression observed in control roots. During the same time period, the expression of CsNR2 was not affected, whereas the expression of CsNR3 decreased significantly after 1h incubation of the excised roots in both, control and salt-containing nutrient solutions. Incubation of roots in the presence of iso-osmotic concentration of PEG had no effect on both, NR activity and expression. This indicates that only the ionic component of salt stress was involved in the salt-induced modifications of nitrate reductase activity.