FOR 948: Nitrogen Uptake, Metabolism and Remobilisation in Leaves during Plant Senescence

建立无害环境的农业要求通过更有效地利用土壤和肥料氮来减少作物生产中的氮预算盈余。这就需要培育和栽培更有效利用氮的基因型，允许减少氮供应而不影响产量。作物的氮效率主要取决于（1）生殖生长期间根系对氮的吸收能力的维持和（2）鼓粒期氮素从营养器官向生殖器官的有效再转运，导致叶片衰老。由于叶片衰老导致减少分配的光合产物的根（减少氮的吸收）和种子（减少粮食产量）的微调叶片衰老的动员N生殖生长和维持光合能力是必要的。研究单位的总体假设是，深入了解控制叶片衰老的生理和分子过程，与N动员和分配到生殖生长将允许开发用于培育N高效作物基因型的性状。为了迎接这一挑战，研究股由具有农业和/或分子生物学背景的植物科学家和一家种子育种公司组成，该公司综合了分子、生物化学、生理学、细胞学和整株植物水平的研究。作为作物，油菜和大麦已被选定。此外，拟南芥将被用于识别调控衰老的关键基因，并通过反向遗传学对其功能进行表征。参与研究小组的实验补充方法的主要目标是：（1）确定和比较发育调控衰老与缺氮诱导衰老的生理过程和分子信号：（2）确定衰老相关参数随时间的变化，解释氮吸收和再转运效率的潜在瓶颈;（3）研究衰老过程中的氮素再动员是否以及在何种条件下与衰老过程中根系的氮素吸收能力有关，是受库限制还是受源限制：（4）通过调控转录因子、信号传导元件、酶和转运蛋白基因的表达，确定提高作物氮素效率的潜力。

Establishment of environmentally sound agriculture raises demands for a reduction of nitrogen (N) budget surpluses in crop production through a more efficient use of soil and fertilizer nitrogen. This requires the breeding and cultivation of genotypes with more efficient use of N, allowing a reduction in N supply without yield penalty. N efficiency of crops mainly depends on (1) maintenance of the N uptake capacity in the roots during reproductive growth and (2) efficient retranslocation of N from vegetative to reproductive plants organs during the seed-filling period resulting in leaf senescence. Since leaf senescence leads to decreased allocation of photosynthates to roots (reducing N uptake) and seeds (reducing grain yields) a fine-tuning of leaf senescence regarding the mobilisation of N for reproductive growth and the maintenance of photosynthetic capacity is necessary. The overall hypothesis of the Research Unit is that an in-depth understanding of the physiological and molecular processes controlling leaf senescence in relation to N mobilisation and allocation to reproductive growth will allow developing traits for the breeding of N-efficient crop genotypes. In order to meet this challenge, the Research Unit is composed of plant scientists with agricultural and/or molecular biological background and a seed breeding company integrating studies at the molecular, biochemical, physiological, cytological and whole-plant level. As crops, oilseed rape and barley have been selected. In addition, Arabidopsis will be used for the identification of key genes regulating senescence and for their functional characterisation by reverse genetics. The main objectives of the experimental complementary approaches of the participating research groups are: (1) to characterise and compare the physiological processes and molecular signals governing developmentally regulated senescence versus N deficiency-induced senescence; (2) to determine time-dependent changes of senescence-associated parameters deciphering the potential bottlenecks in N uptake and retranslocation efficiencies; (3) to investigate whether and under which conditions N remobilisation during senescence is sink- or source-limited in relation to N uptake capacities of roots under progressing senescence; (4) to determine the potential for increasing N efficiency in crops by manipulating the expression of genes encoding transcription factors, signalling components, enzymes and transporters.