苎麻水氮胁迫响应基因表达规律与调控机制

Ramie is one of the most important industrial crop in China. Excessively applied nitrogen has impacted sustainable development of ramie production seriously. Combined water and nitrogen stress, caused by frequently sudden turn from drought to flood, leads to a very low nitrogen utilization efficiency (NUE) of ramie, especially in Changjiang River Basin. Fundamental empirical modes were used for discussing effects of individual stress on ramie to enhancing the NUE of the crop but studies had revealed neither effects of combined water and nitrogen stress on ramie nor molecular response and regulation mechanism of them. We had discussed differential gene expression of ramie under individual nitrogen stress and obtained transcriptome information in previous studies. Based on this, we will explore the expression pattern and regulation mechanism of ramie genes response to combined water and nitrogen stress. 2 ramie varieties, which show remarkable difference in NUE, will be used in the study. Individual and combined water and nitrogen stress treatments will be conducted in potted experiments and analyzed by morphological, physiological, molecular-biological methods. This word is unique in exploring the genotypical difference in NUE and molecular regulation mechanism of ramie under combined water and nitrogen stress, including: effects of water-nitrogen interactions on morphology, physiology and nutrient distribution characteristics of ramie; identification, expression and regulation mechanism of sensitive target genes of different parts of ramie; genotypical differences of gene expression of ramie response to water-nitrogen interactions. The results will benefit for breeding of high nitrogen efficiency varieties and resource-conserving cropping system of ramie.

苎麻是我国重要的特色经济作物，过量施氮是限制苎麻可持续发展的重要因素。以长江流域为主的苎麻产区，旱涝急转频发、水氮互作关系复杂，导致苎麻氮素利用效率低下。为加强苎麻氮素利用，前人基于经验模式研究了苎麻响应水、氮单因素胁迫的特征，但缺乏对水氮互作条件的分析，更没有涉及分子应答与调控机制的探讨。申请人前期对单因素氮胁迫下苎麻差异基因表达特征进行了研究，获得了转录组信息。在此基础上，本项目拟以氮效率存在显著差异的2个苎麻基因型为材料，采取形态、生理和分子生物学技术相结合的方法，研究苎麻响应水氮复合胁迫的相关基因表达规律与调控机制。主要包括：水氮互作下苎麻形态、生理响应特征及水氮分配规律；苎麻响应水氮复合胁迫敏感目标基因筛选与表达调控机制；水氮调控苎麻基因表达的基因型差异。该研究将为氮高效苎麻分子育种及苎麻控水减氮生产模式和理论的建立提供依据。

苎麻是我国重要的特色经济作物，水氮运筹不合理是限制苎麻水肥效率提升的重要因素。针对单因素胁迫研究无法说明水氮互作关系，且缺少分子机制研究的问题，本研究：（1）以氮效率存在显著差异的2个苎麻基因型为材料，探讨了苎麻响应氮素胁迫的基因型差异，发现了苎麻通过酶系统、渗透调节适应低氮胁迫的特征，并筛选出3类关键基因，其中前期加载基因94个、压力耐受基因8个和胁迫极化基因170个；（2）利用转录组和蛋白组相结合的方法，研究了淹水条件下苎麻响应低氧胁迫的分子调控机制，发现24个乙醛脱氢酶（ALDH）家族基因对低氧胁迫具有重要调控作用，并通过酵母过表达试验鉴定出关键基因BnALDH18；（3）通过水氮复合胁迫试验，构建了苎麻抗旱耐贫瘠组学数据库，发现了糖酵解、光合作用、乙烯调控等4个与苎麻适应干旱低氮环境关联的代谢通路，筛选出UGT、ATP合酶、碳酸盐脱水酶等关键基因；（4）通过复水复氮试验，发现了前期胁迫对补偿性生长机制的影响特征，分析了水氮互作对作物表型多重影响的复杂性机制，表现为复水后叶片补偿性生长加速而复氮后株高补偿性生长加速，获得了与作物补偿性生长紧密关联的基因，为下一步关键基因的精细定位、克隆及分子育种打下了基础。