Forms of retranslocated nitrogen during leaf senescence and nitrogen deficiency

氮素(N)从衰老的叶片向籽粒的再转运是肥料N有效利用的限制因素之一。我们以前的研究表明，尿素-N可以占重新转运的氨基酸N的13%，尿素转运蛋白DUR3可以通过回收韧皮部负载上游的质外体尿素来增加N的再转运。本项目旨在进一步研究不同氮素形态及其感官调控转运体在衰老叶片氮素回收和氮素再转运中的作用。在大麦中，15N标记的尿素和其他N形式的再转移效率将在野生型和膜转运体或转录因子表达发生变化的转基因植物中进行评估。这些N转运体与上游转录因子和水杨酸作为假定的叶片固有信号的调节联系将在模式物种拟南芥中进行研究。为了确定叶片固有信号与油菜氮素再运输的相关性，将在水培和田间进行生理和分子分析。重点介绍在田间条件下氮素效率突出的油菜杂交种。关键词：韧皮部负荷、氮素再运转、AMT、DUR3、氮素饥饿、氮素效率。

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.