Abstract:

Nitrate is the major forms of nitrogen that plants absorb from the soil, and its uptake and utilization is a highly coordinated and complex process. For the sake of survive in various environmental conditions, plants have evolved suitable nitrate uptake and utilization mechanisms to adapt to a wide range of environmental conditions. There are various types of nitrate receptors in plant roots, which can sense different concentrations of external nitrate. The low- or high-affinity nitrate uptake system was activated to absorb nitrate from the environment according to the levels of external nitrate. Once nitrate is taken up into root cells, most of it is transported to shoots for assimilation, and synthesizes macromolecular substances to optimize plant growth. When the nitrate supply is too much for use immediately, the plant can store the excess nitrate into vacuoles and mediate it efflux from vacuoles to the cytosol for assimilation when needed. During plant growth and development, nitrate in the old and mature leaves can be redistributed into developing tissues to promote their growth. Many genes related to nitrate absorption, transportation, storage, assimilation and signaling regulation are activated orderly and work coordinately to absorb and utilize nitrate efficiently. This review summarizes the NRT1 and NRT2 nitrate uptake-related genes and their functions, as well as related transcription factors involved in primary nitrate response and small signal peptides in nitrate signaling transduction and exchange among different tissues. In order to further understand the mechanisms of plant uptake and utilize nitrate, and therefore provides new ideas in increasing nitrogen-use efficiency of crop by breeding and cultivation techniques.

Key words: nitrate, transporter, signaling, nitrogen-use efficiency

摘要：

硝态氮是植物吸收利用的主要氮源,其吸收利用是一个高度协调复杂的调控过程。植物为了在各种变化的环境中生存,进化出了适宜不同环境的硝态氮吸收利用机制。植物根系中存在不同类型的硝态氮受体,可以感受外界硝态氮浓度变化,并启用高亲和力或低亲和力硝态氮吸收系统,从而吸收硝态氮;硝态氮进入根系后,大部分被运输到地上部进行同化作用,合成大分子物质,以促进植物生长;如果地上部硝态氮含量过多,植物可把多余的硝态氮运送到液泡内储存,待需要时再从液泡转运至细胞质中利用。植物生长发育过程中,老叶和成熟叶片中的硝态氮可被转运到新生组织中,促进新生组织生长。硝态氮吸收利用过程中大量硝态氮吸收、转运、储存、同化和信号调控基因被有序激活并协调工作,促进植物高效吸收利用硝态氮。本文主要针对NRT1和NRT2硝态氮吸收转运相关基因及其功能,以及参与初级硝态氮反应的相关转录因子和小信号多肽在硝态氮信号传导和组织间的信号交流进行综述,以便深入理解植物吸收利用硝态氮的机理,为高效利用氮素的作物育种和栽培技术的创建提供新的思路。

关键词: 硝态氮, 转运体, 信号, 氮素利用率