Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan.
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
Nat Plants. 2020 Sep;6(9):1126-1135. doi: 10.1038/s41477-020-00758-0. Epub 2020 Aug 31.
Increasing nitrogen use efficiency (NUE) is critical to improve crop yield, reduce N fertilizer demand and alleviate environmental pollution. N remobilization is a key component of NUE. The nitrate transporter NRT1.7 is responsible for loading excess nitrate stored in source leaves into phloem and facilitates nitrate allocation to sink leaves. Under N starvation, the nrt1.7 mutant exhibits growth retardation, indicating that NRT1.7-mediated source-to-sink remobilization of stored nitrate is important for sustaining growth in plants. To energize NRT1.7-mediated nitrate recycling, we introduced a hyperactive chimeric nitrate transporter NC4N driven by the NRT1.7 promoter into the nrt1.7 mutant. NRT1.7p::NC4N::3' transgenic plants accumulated more nitrate in younger leaves, and NO tracing analysis revealed that more N was remobilized into sink tissues. Consistently, transgenic Arabidopsis, tobacco and rice plants showed improved growth or yield. Our study suggests that enhancing source-to-sink nitrate remobilization represents a new strategy for enhancing NUE and crop production.
提高氮利用效率（NUE）对于提高作物产量、减少氮肥需求和减轻环境污染至关重要。氮再利用是 NUE 的一个关键组成部分。硝酸盐转运蛋白 NRT1.7 负责将储存在源叶中的多余硝酸盐装载到韧皮部，并促进硝酸盐分配到汇叶。在氮饥饿下，nrt1.7 突变体表现出生长迟缓，表明 NRT1.7 介导的储存硝酸盐的源到汇再利用对于维持植物生长很重要。为了为 NRT1.7 介导的硝酸盐再循环提供能量，我们引入了一种由 NRT1.7 启动子驱动的超活嵌合硝酸盐转运蛋白 NC4N 到 nrt1.7 突变体中。NRT1.7p::NC4N::3' 转基因植物在较年轻的叶片中积累了更多的硝酸盐，而 NO 示踪分析显示更多的 N 被再利用到汇组织中。一致地，转基因拟南芥、烟草和水稻植物表现出更好的生长或产量。我们的研究表明，增强源到汇硝酸盐再利用是提高 NUE 和作物产量的一种新策略。
