The mechanism of a shoot-induced regulation of N2-fixation in soybean

该提案的一个主要目标是将在模式豆科植物蒺藜苜蓿上获得的结果转移到重要的经济作物大豆上。蒺藜苜蓿固氮的调节明显是芽诱导的，并依赖于芽的N-状态。几个环境和营养因素诱导一个一致的，有节奏的时间过程的N2固定，减少每天固定氮的量。在这些不同的因素是铵的应用，以根或形成大量的根瘤的超根瘤突变体。在项目开始时，将确定施铵或大豆芽变暗后固氮的精确时间进程。基于芽诱导对结节的作用与miRNA相关的假设，随后将在结节的节律性N2固定期间的精确定义的时间点进行全面的比较mRNA和miRNA转录组谱分析（RNAseq）。作为下一步，在诱导观察到的节律性N2固定超过24小时的各种因素的影响下，通过qPCR跟踪鉴定的候选物的表达。在这些因素中，豆荚形成的影响或突变体中不寻常的大量结节的影响是在自动调节功能的缺陷。这些结果将是一个先决条件，可能的努力，以生产大豆是独立的，在其N2固定的铵浓度在土壤中，并可能固定氮更有效地在一个状态下的supercriteration。这两个因素对大豆的生产力都很重要。

A main objective of the proposal is to transfer results obtained on the model legume Medicago truncatula to the economically important crop soybean. The regulation of N2 fixation in Medicago truncatula is clearly shoot-induced and dependent on the N-status of the shoot. Several environmental and nutritional factors induce a consistent, rhythmic time-course of N2 fixation, that decreases the per day amount of fixed nitrogen. Among these diverse factors is the application of ammonium to the roots or the formation of a high number of nodules in supernodulating mutants. The precise time-course of N2-fixation after ammonium application or darkening of the shoots of soybean will be ascertained in the beginning of the project. Based on the hypotheses that the shoot induced effect on nodules is related to miRNA, a comprehensive comparative mRNA and miRNA transcriptome profiling (RNAseq) will subsequently be performed at precisely defined point in time during the rhythmic N2-fixation of the nodules. As a next step, identified candidates will be followed in their expression by qPCR under the influence of various factors that induce the observed rhythmic N2 fixation over a 24 h period. Among these factors is the influence of pod-formation or that of an unusual large number of nodules in a mutant that is defect in the autoregulation of nodulation. The results will be a prerequisite for a possible effort to produce soybean that is independent in its N2 fixation of the ammonium concentration in the soil and might fix nitrogen more efficiently in a state of supernodulation. Both factors could be of significant importance for the productivity of soybean.