提高氮肥利用效率是提高作物产量、减少氮肥需求、减轻环境污染的关键。氮素再活化是氮素利用效率的重要组成部分。硝酸盐转运蛋白 NRT1.7负责将贮存在源叶中的多余硝酸盐运输到韧皮部，促进硝酸盐分配到库叶中。在 氮 饥饿条件下，nrt1.7突变体表现出生长迟缓，说明 nrt1.7介导的硝酸盐库源再调动对植物的生长具有重要作用。
为了激活 NRT1.7介导的硝酸盐循环，我们在 NRT1.7突变体中引入了由 NRT1.7启动子驱动的高活性嵌合硝酸盐转运体 NC4N。NRT1.7 p: : NC4N: : 3′转基因植株在幼叶中积累了较多的硝酸盐，15NO3示踪分析表明15N 向库组织中转运较多。同样，在转基因拟南芥、烟草和水稻植株表现出生长或产量的改善。
研究表明，提高硝酸盐的源库再转化是提高作物氮素利用率和产量的新策略。
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 15NO3− tracing analysis revealed that more 15N 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.
农业氮肥的过量施用和作物对氮素吸收的限制，提出了培育高氮效率作物的紧迫性。近年来，通过控制硝酸盐的再转移来提高作物的氮素利用率和产量已经成为一种新的策略。林鸿宣院士团队点评了该项工作，认为“用较少的氮肥也可实现作物更高的产量”。
相关链接：
https://www./articles/s41477-020-00758-0
https://www./articles/s41477-020-00763-3
