Effect of glutamine on the induction of nitrate reductase

作者：Xiuzhen Li, Dawn E. Larson, Marija Glibetić, Ann Oaks · 发表于：Physiologia Plantarum · 年份：1995 · DOI：10.1111/j.1399-3054.1995.tb05125.x · 被引用次数：41 · 研究领域：Plant nutrient uptake and metabolism、Polyamine Metabolism and Applications、Plant Stress Responses and Tolerance

Nitrate reductase (NR. EC 1.6.6.1/2) is a substrate inducible enzyme that could be repressed by its end product glutamine or amino acids. To test this hypothesis, 6‐day‐old maize seedlings (Zea mayscv. W64A × W182E) were grown hydroponically in a 1/10 strength Hougland's salt solution modified to contain no nitrogen. Previous experiments had established that after a 24‐h induction with NO3−(5 mM KNO3−) the level of NR activity and protein had reached a constant level. In the present experiments when glutamine (5 mM) was included together with NO3−, there was a significant reduction in NR activity (34% of the control values). NR protein and NR mRNA accumulation in the root. In the shoot, on the other hand, glutamine additions had little or no effect on the levels of either NR activity (81% of control) or NR protein. Inhibition of glutamine synthetase by methionine sulfoximine (MSX) resulted in reduced levels of glutamine in both root and shoot tissues. Contrary in our prediction, however, it had no effect on NR activity and mRNA content in roots. In the shoot, on the other hand, there was a marked reduction of NR activity (34% of the control value) and NR protein, but no apparent effect on NR mRNA. When detached shoots were treated with MSX and other inhibitors of glutamine synthetase (tabtoxinine‐β‐lactam or phosphinothricin) the induction of NR activity by NO3−was also inhibited. Glutamine additions 15 or 50 mM to detached shoots had essentially no effect on the induction of...