Overexpression of nitrate reductase in tobacco delays drought-induced decreases in nitrate reductase activity and mRNA
Overexpression of nitrate reductase in tobacco delays drought-induced decreases in nitrate reductase activity and mRNA
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DOI：
10.1104/pp.117.1.293
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发表时间：
1998-05-01
期刊：
影响因子：
7.4
通讯作者：
Foyer, CH
中科院分区：
文献类型：
--
作者：
Ferrario-Méry, S;Valadier, MH;Foyer, CH
转化的（花椰菜花叶病毒35 S启动子[S-35]）烟草（Nicotiana plumbaginifolia L.）组成型表达硝酸还原酶（NR）的植物和未转化的对照经受干旱5天。干旱引起的生物量积累和光合作用的变化在两个线的植物。经过4 d的水分剥夺，一个大的增加，地上部干重与鲜重的比例进行了观察，随着光合CO2同化率的下降。在水分胁迫过程中，两条线的叶片蔗糖增加，但己糖增加，只有在未转化的控制叶片。叶片NO3-迅速下降，在两个线，并在2天内的水分剥夺发病减半。总叶片氨基酸减少水分剥夺后，两个线的叶片。失水4d后，未转化植株的叶片中没有检测到NR活性，而35 S-NR转化体的叶片中仍有约50%的NR活性。NR mRNA比NR活性稳定得多。NR mRNA丰度增加的35 S-NR植物的叶片中，并保持恒定的控制，为第一个3天的干旱。但在第4天，两个品系的NR mRNA突然下降。再水化在第3天造成快速恢复（24小时内）的35 S-NR转录，但没有恢复观察到的控制。蛋白质的磷酸化状态是不变的长期干旱。两个品系的最大可提取NR活性与环境光合作用之间存在很强的相关性。我们的结论是，干旱首先导致NR蛋白周转增加，然后加速NR mRNA周转。组成型NR表达暂时延迟干旱引起的NR活性损失。因此，35 S-NR的表达可能允许更快地恢复短期水分亏缺后的N同化。
Transformed (cauliflower mosaic virus 35S promoter [S-35]) tobacco (Nicotiana plumbaginifolia L.) plants constitutively expressing nitrate reductase (NR) and untransformed controls were subjected to drought for 5 d. Drought-induced changes in biomass accumulation and photosynthesis were comparable in both lines of plants. After 4 d of water deprivation, a large increase in the ratio of shoot dry weight to fresh weight was observed, together with a decrease in the rate of photosynthetic CO2 assimilation. Foliar sucrose increased in both lines during water stress, but hexoses increased only in leaves from untransformed controls. Foliar NO3- decreased rapidly in both lines and was halved within 2 d of the onset of water deprivation. Total foliar amino acids decreased in leaves of both lines following water deprivation. After 4 d of water deprivation no NR activity could be detected in leaves of untransformed plants, whereas about 50% of the original activity remained in the leaves of the 35S-NR transformants. NR mRNA was much more stable than NR activity. NR mRNA abundance increased in the leaves of the 35S-NR plants and remained constant in controls for the first 3 d of drought. On the 4th d, however, NR mRNA suddenly decreased in both lines. Rehydration at d 3 caused rapid recovery (within 24 h) of 35S-NR transcripts, but no recovery was observed in the controls. The phosphorylation state of the protein was unchanged by long-term drought. There was a strong correlation between maximal extractable NR activity and ambient photosynthesis in both lines. We conclude that drought first causes increased NR protein turnover and then accelerates NR mRNA turnover. Constitutive NR expression temporarily delayed drought-induced losses in NR activity. 35S-NR expression may therefore allow more rapid recovery of N assimilation following short-term water deficit.