Department of Plant Physiology, Institute of Plant Biology, University of Wrocław, Kanonia 6/8, 50-328 Wrocław, Poland.
Plant Sci. 2011 Jun;180(6):783-8. doi: 10.1016/j.plantsci.2011.02.006. Epub 2011 Feb 21.
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 200 mM 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. 200 mM 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.
在短期实验中，研究了高盐度对黄瓜（Cucumis sativus）硝酸还原酶活性的影响。黄瓜根在 200mM NaCl 中暴露 60 分钟导致实际 NR 活性（在存在 Mg²+的情况下测量）显著增加，而总酶活性（用 EDTA 测量）不受影响。将根转移到无盐溶液中后，NaCl 诱导的实际 NR 活性的增加迅速逆转。微囊藻毒素-LR 和斑蝥素，蛋白磷酸酶抑制剂完全阻止了实际活性的增加。此外，还观察到在含 NaCl 的根中 ATP 水平显著降低。这些数据表明，可逆的蛋白质磷酸化参与了盐胁迫最初 1 小时内 NR 活性的诱导。还研究了短期盐度对黄瓜根中硝酸盐还原酶编码基因表达的影响。200mM NaCl 减弱了对照根中观察到的 CsNR1 表达增加。在同一时间段内，CsNR2 的表达不受影响，而在对照和含盐营养液中培养的离体根中，CsNR3 的表达在 1 小时后显著降低。在存在等渗浓度 PEG 的情况下孵育根对 NR 活性和表达均没有影响。这表明只有盐胁迫的离子成分参与了盐诱导的硝酸盐还原酶活性的改变。
