Nitrogen (N) is the most abundant mineral elements in plants, and the application of inorganic N fertilizer makes huge contribution to the crop production and global food security. However, low N use efficiency (NUE) and overapplication of N fertilizers causes ever-growing environmental problems. Understanding the molecular mechanisms of N sensing and signalling in plants will provide molecular basis for NUE improvement of crops. Forward genetics screening and functional analysis have characterized the NRT1.1-NLP centered N signalling pathway at the cellular level. With the incorporation of systems biology approaches, a preliminary N regulatory network has been delineated. Meanwhile, long-distance N signalling has also been unveiled at the whole plant level. This review highlights most recent understanding of the N signalling network in plants, and also discusses how to further integrate hierarchical regulation of N signalling in plants.

中文翻译：

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旨在了解植物中的分层氮信号网络。

氮是植物中最丰富的矿质元素，无机氮肥的应用为作物生产和全球粮食安全做出了巨大贡献。然而，低氮素利用效率（NUE）和氮肥过量使用引起了日益严重的环境问题。了解植物中氮感测和信号传导的分子机制将为改善作物的氮素利用提供分子基础。前向遗传学筛选和功能分析已在细胞水平上表征了以NRT1.1-NLP为中心的N信号通路。随着系统生物学方法的结合，已经划定了初步的N调节网络。同时，长距离N信号也已在整个工厂级别公开。这篇评论重点介绍了植物对N信号网络的最新理解，