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，油菜的氮素利用率(NUE)特别低。为了提高油菜的氮素利用效率，提高对氮素再动员和分配机制的认识，选择氮素利用效率高的品种，并对植株的氮素状况进行灵敏的诊断具有重要意义。我们朝着这个目标做了两个方面的工作：1)我们的目标是识别基因表达生物标记物，这些标记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确定了数百个候选生物标记物。缺氮和衰老启动预测候选基因的可靠性和稳健性目前已得到验证，并将在不同条件下生长的不同油菜品种中受到挑战。2)第一个资助期的结果表明，在拟南芥中，硝酸盐转运体NRT1.5和NRT1.7参与传递叶片和根之间的氮状态，并执行植物对缺氮的反应，包括衰老启动和种子中脂肪/蛋白质比的改变。通过在拟南芥和油菜中过表达这些NRT蛋白，我们想要研究是否可以改善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.