低氮能诱导小麦根系伸长以增加其利用深层土壤中氮素的能力，挖掘相关调控基因对提高小麦氮素利用效率，选育氮高效新品种具有重要意义。申请人在青年基金资助下，发现一个受低氮诱导上调表达的未知功能基因，编码产物为包含65个氨基酸残基的分泌型小肽。在拟南芥中超表达后能显著增加侧根长，将其命名为TaLNR1。本项目拟在前期工作基础上，对其功能和作用机理开展进一步研究。拟首先克隆该基因对应于小麦A、B和D基因组的成员并进行遗传定位，明确其表达的主要成员和组织部位；进而通过在小麦中超量表达和RNAi减量表达该基因以及通过人工合成小肽进行根系饲喂试验深入研究TaLNR1基因的功能；最后，在野生型、超表达系和减量表达系以及根系饲喂试验处理前后的植株中，检测调控根系发育和氮素吸收利用相关基因的表达变化情况，对该基因的作用机理进行分析。以期通过上述研究解析TaLNR1基因的功能及其作用的分子机理。

Low nitrogen stress can induce wheat root elongation for acquiring nitrogen in deep soil. However, we know very little about the molecular mechanism of it. Identification and functional analysis of regulatory genes of wheat root elongation induced by low nitrogen stress would be very meaningful for genetic improvement of wheat nitrogen use efficiency. In the former project supported by NSFC, we isolated a low nitrogen responsive gene and named it as TaLNR1, which encoding a small secreted peptide consists of 65 amino acid residues. Overexpression of this gene lead to a longer lateral root system compared to wild type in both normal and low nitrogen conditions. We proposed this project here to further investigate the function of TaLNR1 gene. The content of this project includes the following components: (1) To clone and perform expression analysis of different members of TaLNR1 gene corresponding to A, B and D genome in wheat. (2) To analysis the function of TaLNR1 gene by overexpressing and underexpressing it in wheat; (3) To investgate the phenotype of root trait of wheat plants after fed with synthetic small peptides in both modified or non-modified forms. (4) To measure the expression level of genes in regulatory pathways of root development and nitrogen use efficiency in wild type, overexpressing and underexpressing transgenic lines, and plants fed with synthetic peptides. This research will improve the understanding of the biological function and molecular mechanism of TaLNR1 gene.