miR172c/NNC1模块调控大豆共生固氮和生长发育分子机理研究

大豆共生固氮的遗传机理不仅是最基本的生物学问题, 也是关乎其产量和品质重要问题。在氮匮缺时，植物诱导根瘤菌产生结瘤因子（NF），在其被植物结瘤因子受体识别后激发信号级联完成根瘤菌侵染、结瘤、固氮和调控植物发育过程。前期我们发现miR172c/NNC1分子模块在大豆结瘤和根瘤数量调控中发挥核心作用，还发现它们参与植物对低氮响应、根瘤菌侵染、根瘤固氮和植物发育, 但miR172c/NNC1模块调控这些生物过程的分子机制还不清楚。在本研究中，我们将：1）利用ChIP-seq和转录组分析鉴定NNC1的靶基因；2）用酵母双杂和免疫共沉淀-质谱法筛选NNC1的互作蛋白；3）挖掘miR172c/NNC1优异等位变异；4）选择代表性NNC1靶基因和互作蛋白，研究其功能及作用机制。研究结果将解析miR172c/NNC1调控大豆共生固氮及植物发育的分子网路，为培育高固氮效率大豆提供科学依据。

Symbiotic nitrogen fixation (SNF) is a fundamental scientific question in biology. The SNF efficiency is critical for plant growth, yield and seed quality in legumes. Under low nitrogen, plants release flavonoids to induce production of Nod factors in rhizobia, which in turn activate nodulation signaling cascades through recognition by Nod factor receptors (NFRs). As a result, root nodules form to fix N2 to NH4+, which can promote plant growth and development. Previously, we identified a key molecular module miR172c/NNC1 that regulates rhizobia infection, nodule formation and nitrogen fixation of mature nodules; recently we found that the module also mediates nitrogen sensing, nitrogen assimilation, and plant growth and flowering. We hypothized that miR172c/NNC1 may act as nod to integrate various signaling pathways through NNC1 target genes. However, the molecular mechanism underlying miR172c/NNC1-mediated regulatory network that control a variety of biological processes during nodulation remain is unclear. In this study, we will 1) adopt the combinatorial approach including ChIP-seq and RNA-seq to identify the target genes of NNC1 during nodulation; 2) use yeast two hybrid assay to find the NNC1-interacting proteins; 3) search the natural variations of miR172c/NNC1 that confer enhanced SNF efficiency; 4) functionally investigate the selected key genes or proteins. The goal is to elucidate the molecular regulatory network that precisely modulates nitrogen sensing, rhizobia infection, nodule organogenesis, nitrogen fixation, nitrogen assimilation and plant growth & development in soybean. The findings will facilitate further understanding of SNF and the link between SNF and plant development in legumes.