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

在主要大田作物中，油菜氮素利用效率（NUE）特别低。提高油菜氮素再调动和分配机制，选择高氮素利用效率基因型，对油菜氮素状况进行灵敏诊断，是提高油菜氮素利用效率的重要途径。为了实现这一目标，我们研究了两个主题：1)我们的目标是识别基因表达生物标志物，这些生物标志物可以在表型症状出现之前表明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已经确定了数百个候选生物标志物。目前，候选品种对缺氮和衰老启动预测的可靠性和稳健性已经得到验证，并将在不同条件下生长的各种油菜品种中受到挑战。2)第一个资助期的结果表明，拟南芥中硝酸盐转运体NRT1.5和NRT1.7参与叶片和根间氮状态的信号传递，并执行植物对氮缺乏的响应，包括衰老启动和种子脂蛋白比的改变。通过在拟南芥和油菜中过表达这些NRT蛋白，我们想研究是否可以改善NUE。

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.