DMI3/IPD3-DELLA-NSP1/NSP2蛋白复合体调控根瘤共生分子机制的研究

根瘤共生中，DMI3磷酸化IPD3，解码钙震荡，从而起始植物与根瘤菌的共生。最新的研究发现DELLA蛋白可以连接DMI3/IPD3和NSP1/NSP2转录因子复合体激活下游根瘤响应基因的表达，并且DELLA蛋白可以增强DMI3对IPD3的磷酸化，但是这种磷酸化水平的提高在根瘤共生中的作用以及DELLA调节DMI3/IPD3和NSP1/NSP2转录活性的分子机理都不清楚。本项目拟通过ChIP-seq技术分析在IPD3, NSP1和/或DELLA存在与否的条件下，IPD3和NSP1调节的基因及其差异；通过瞬时转录激活和毛根转化等手段研究DELLA协调DMI3/IPD3和NSP1/NSP2蛋白复合体转录活性的分子机制；通过质谱技术鉴定IPD3的磷酸化位点，运用点突变、酵母三杂等实验手段分析受DELLA调控的磷酸化位点在根瘤共生中的功能与作用机理。为豆科植物根瘤共生固氮的分子改良提供科学依据。

In Legume-Rhizobium symbiosis, DMI3 phosphorylates IPD3 and initiates rhizobial symbiosis. Our latest results showed that DELLA proteins can bridge the DMI3/IPD3 and NSP1/NSP2 complexes to activate the expression of nodulation specific genes, and enhance the phosphorylation of IPD3 by DMI3. However, the role of the increased phosphorylation of IPD3 by DELLA, and the mechanism by which DELLAs coordinate DMI3/IPD3 and NSP1/NSP2 to regulate the expression of downstream genes are still unknown. In this project, ChIP-seq technique will be employed to identify the differential genes expressed in the absence or presence of DELLAs, IPD3 and NSP1, and to explore molecular mechanisms how DELLAs coordinate DMI3/IPD3 and NSP1/NSP2 complexes to promote the genes expression; We will use mass spectrometry to identify the phosphorylation sites of IPD3 by DMI3, Y3H and CoIP to examine the effect of these phosphorylation sites to the complex stability. The aim of this research is to elucidate the molecular mechanism underlying the DMI3/IPD3-DELLA-NSP1/NSP2 complex-regulated gene expression, and to provide theoretical support for improving symbiotic nitrogen fixation of legume root nodules.