Nitrate reductase in Zea mays L. under salinity
Nitrate reductase in Zea mays L. under salinity
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DOI：
10.1046/j.1365-3040.2000.00568.x
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发表时间：
2000-05-01
影响因子：
7.3
通讯作者：
Kaiser, WM
中科院分区：
文献类型：
--
作者：
Abd-El Baki, GK;Siefritz, F;Kaiser, WM
在水培条件下，将玉米幼苗(Zea Mays L.cv.Giza 2)暴露在中等盐度下。测定了叶片和根的NADH-硝酸还原酶(NR)活性(E.C.1.6.6.1)、NR的活化态、NR-mRNA的稳态水平和主要溶质含量。随着外盐浓度的增加，Na+、Cl-、糖、氨基酸和季铵化合物在叶片和根中积累，且叶中的含量大于根中的含量。叶片硝酸盐含量降低，而根中硝酸盐含量增加。盐胁迫也改变了硝酸还原酶活性和硝酸还原酶基因表达的日变化规律，但并未影响硝酸还原酶的活性状态。在第一个光照阶段，对照植物叶片中的最大硝酸还原酶活性迅速增加，而盐化植株叶片中的最大硝酸还原酶活性上升较慢。因此，从全天来看，盐胁迫植株的硝酸还原酶活性低于对照植株。对照植株的NR转录水平在夜间较低，在第二个夜间阶段开始增加，然后在光照后2 h出现一个明显的峰值，这一较大的‘清晨高峰’几乎不受盐度的影响，而盐化植株在夜间初期m-RNA水平的缓慢上升几乎不存在。这被认为是盐渍植物前半天硝酸还原酶活性低的原因之一。这也表明，硝酸盐是影响盐胁迫下硝酸还原酶表达和活性的主要信号。糖和氨基酸似乎不那么重要。
Young maize seedlings (Zea mays L. cv.Giza 2) were exposed to moderate salinity in hydroponic culture. NADH-nitrate reductase (NR) activity (E.C. 1.6.6.1), NR activation state, NR-mRNA-steady state levels and major solute contents in leaves and roots were investigated. With increasing external salt concentration, Na+, Cl-, sugars, amino acids and quarternary ammonium compounds accumulated in leaves and roots, with concentrations in leaves exceeding those in roots. The nitrate content of leaves decreased, but increased in roots. The diurnal pattern of NR activity and of NR-mRNA was also changed under salinity, but the NR activation state was not affected, In the first light phase, maximum NR activity increased rapidly in leaves of control plants, but was much slower in leaves from salinized plants. Thus, integrated over the whole day, the NR activity of salt-stressed plants was lower than in control plants. NR transcript levels of control plants were low in the early night phase, started to increase in the second night phase, followed by a distinct peak at 2 h into the light period, This large 'early morning peak' of NR-mRNA was hardly affected by salinity, whereas the initial slow increase of m-RNA levels in the early night phase was almost absent in salinized plants. This is considered as one reason for the low NR activity of salinized plants in the first half of the day. It is also suggested that nitrate is a major signal affecting NR expression and activity under salinity. Sugars and amino acids appeared less important.