Nitrogen deficiency and senescence in Arabidopsis and oilseed rape: Transcriptome response and the role of nitrate transporters

在主要的大田作物中，油菜具有特别低的氮利用效率（NUE）。提高油菜氮素利用效率的关键在于提高对氮素运转和分配机制的认识，筛选高氮素利用效率的基因型，并对植株氮素状况进行敏感的诊断。我们致力于实现这一目标的两个主题：1）我们的目标是确定基因表达生物标志物，这些生物标志物在表型症状可见之前指示氮缺乏和衰老的早期阶段。通过对缺氮胁迫植物的转录组分析，我们在第一个资助期内确定了数百个生物标志物候选者。目前，缺氮和衰老起始预测候选物的可靠性和稳健性得到了验证，并将在不同条件下生长的各种油菜品种中受到挑战。第一个资助期的结果表明，在拟南芥中，硝酸盐转运蛋白NRT 1.5和NRT 1.7参与了叶片和根之间的N状态信号传递，并参与了植物对N的响应缺乏，包括衰老开始和种子中脂质/蛋白质比例的改变。通过在拟南芥和油菜中过表达这些NRT蛋白，我们想研究NUE是否可以提高。

Among the major field crops oilseed rape has a particularly low nitrogen use efficiency (NUE). For improving the NUE of oilseed rape it is important to advance the understanding of N-remobilization and -allocation mechanisms, to select genotypes with high NUE and to sensitively diagnose the N status of the plants. We work on two topics towards this goal:1) We aim to identify gene expression biomarkers that indicate early stages of N deficiency and senescence before phenotypic symptoms are visible. By transcriptome analysis of N deficiency-stressed plants we have identified hundreds of biomarker candidates in the first funding period. The reliability and robustness of the candidates for N deficiency and senescence initiation prognosis is currently validated and shall be challenged in various oilseed rape cultivars grown under different conditions.2) The results of the first funding period suggest that in Arabidopsis the nitrate transporters NRT1.5 and NRT1.7 are involved in signaling the N status between leaves and roots and in executing the plants' responses to N deficiency, including senescence initiation and an altered lipid/protein ratio in seeds. By overexpressing these NRT proteins in Arabidopsis and oilseed rape we want to investigate whether NUE can be improved.