High nitrogen (N) fertilization for maximizing crop yield commonly leads to postponed flowering time (heading date in rice) and ripening, thus affecting resources use efficiency and followed planting time. We found that N-mediated heading date-1 (Nhd1) can directly activate florigen gene OsHd3a in rice. Inactivation of either Nhd1 or OsHd3a results in delay and insensitivity to N supply of flowering time. Knockout of Nhd1 increases N uptake and utilization efficiency at low-to-moderate N level under both short- and long-day field conditions. Increasing glutamine, the product of N assimilation, can upregulate expression of Nhd1, which in turn downregulates OsFd-GOGAT expression and OsFd-GOGAT activity, displaying a Nhd1-controlled negative feedback regulatory pathway of N assimilation. Moreover, N fertilization effect on rice flowering time shows genetically controlled diversity, and single-nucleotide polymorphism in Nhd1 promoter may relate to different responses of flowering time to N application. Nhd1 thus balances flowering time and N use efficiency in addition to photoperiod in rice.

为最大限度地提高作物产量而进行的高氮 (N) 施肥通常会导致开花时间（水稻的抽穗期）和成熟期推迟，从而影响资源利用效率和种植时间。我们发现 N 介导的抽穗 date-1 (Nhd1) 可以直接激活水稻中的成花基因OsHd3a。Nhd1或OsHd3a 的失活导致开花时间延迟和对 N 供应不敏感。在短日照和长日照田间条件下，敲除Nhd1 可提高中低氮水平下的氮吸收和利用效率。增加谷氨酰胺（氮同化的产物）可以上调 Nhd1 的表达，进而下调OsFd-GOGAT表达和 OsFd-GOGAT 活性，显示 Nhd1 控制的 N 同化负反馈调节途径。此外，施氮对水稻开花时间的影响表现出遗传控制的多样性，Nhd1启动子的单核苷酸多态性可能与开花时间对施氮的不同反应有关。因此，除了光周期外，Nhd1 还平衡了开花时间和氮利用效率。