Forms of retranslocated nitrogen during leaf senescence and nitrogen deficiency

氮素从衰老叶片向籽粒的再转运是氮肥有效利用的限制因素之一。我们以前的研究表明，尿素-N可以占再转运的氨基酸-N的>13%，并且尿素转运蛋白DUR 3可以通过在韧皮部装载上游回收质外体尿素来增加N再转运。本项目5再转运氮的形式3项目旨在进一步调查不同的N形式和它们的感生调节转运蛋白对衰老叶片中的N回收和N再转运的贡献。在大麦中，15 N标记的尿素和其他N形式的再转运效率将在野生型和转基因植物中进行评估，膜转运蛋白或转录因子的表达发生改变。这些N转运蛋白的上游转录因子和水杨酸作为一个假定的叶固有的信号的监管环节将在模式物种拟南芥进行调查。为了确定油菜叶片固有信号与氮素再转运的相关性，将在水培和田间进行生理和分子分析。重点将放在油菜杂交品系，在田间条件下具有突出的N效率。关键词：韧皮部负荷，氮再转运，AMT，DUR 3，氮饥饿，氮效率。

Nitrogen (N) retranslocation from senescing leaves to the grains is one of the limiting factors for an efficient utilization of fertilizer N. Our previous studies showed that urea-N can account for >13% of retranslocated amino acid-N and that the urea transporter DUR3 can increase N retranslocation by retrieval of apoplastic urea upstream of phloem loading. The present Project 5 Forms of retranslocated nitrogen 3 project aims at investigating further the contribution of different N forms and their sense-cence-regulated transporters to N retrieval in senescing leaves and to N retranslocation. In barley, the retranslocation efficiency of 15N-labeled urea and other N forms will be assessed in wild-type and transgenic plants with altered expression of membrane transporters or transcription factors. A regulatory link of these N transporters to upstream transcription factors and to salicylic acid as a putative leaf-inherent signal will be investigated in the model species Arabidopsis. To determine the relevance of leaf-inherent signals for N retranslocation in rapeseed, physiological and molecular analyses will be performed in hydroponics and in the field. Emphasis will be placed on rapeseed hybrid lines that have an outstanding N efficiency under field conditions.Keywords: phloem loading, nitrogen retranslocation, AMT, DUR3, nitrogen starvation, nitrogen efficiency.