玉米LysM蛋白激酶受体识别丛枝菌根真菌共生信号及转导机制

The arbuscular mycorrhizal (AM) fungi can form a symbiosis with most plants. It not only promotes plant to absorb water and nutrients from the soil, but also improves plant resistance to stress. The interaction response is a key step during the formation of symbiotic relationship. Our previous study found that a LysM protein kinase receptor (ZmLysM1) enables to directly combine Myc factor produced by AM fungi, activating symbiotic gene expressions. However, how the kinase receptor specifically recognizes the ligand and activates the intracellular signal pathway remains not understood. In the present study, the homology or heterology complex formation will be firstly analyzed by protein-protein interaction to clarify the interaction pattern between receptor and ligand. The key LysM unit and the functional sites of amino acids will be also detected by the point mutant and the ligand binding experiment. The phosphorylation sites will be also determined by the functional analysis of kinase domain. The interaction proteins with the intracellular kinase domain of ZmLysM1 will be screened and identified. Finally, the molecular mechanism of symbiotic recognition between ZmLysM1 and AM fungi is revealed. Our results are benefit for broadening the theoretical content of plant-microbial interaction. Moreover, it has an important significance for improving the colonization efficiency of AM fungi, and expanding the scope of the symbiotic host.

丛枝菌根（AM）真菌能与大多数植物形成互惠共生体，不仅能促进根系对土壤中水分和营养元素的吸收，还能提高植株的抗逆性，二者互作应答是共生关系建立的关键。项目组前期发现玉米LysM蛋白激酶受体（ZmLysM1）能够结合AM真菌产生的Myc因子，诱导下游共生基因的表达，但受体如何特异识别Myc信号分子，介导胞内信号转导仍不清楚。本项目通过对LysM激酶受体同源或异源复合物形成的鉴定，确定受体与配体的互作模式。借助定点突变和配体互作实验，明确识别Myc因子的胞外核心LysM结构单元和关键的氨基酸位点。同时对胞内激酶结构域的功能进行验证，探明重要的磷酸化修饰位点。后筛选和鉴定胞内激酶结构域的互作蛋白，最终揭示ZmLysM1识别Myc因子激活下游共生信号的分子机理。研究结果不仅可丰富植物-微生物互作识别机制的理论内容，而且为提高AM真菌的定植效率，扩大宿主共生真菌种群范围具有重要的指导意义。

丛枝菌根（AM）真菌能与大多数植物形成互惠共生体，不仅能促进根系对土壤中水分和磷等营养元素的吸收，还能提高植株的抗逆性，但二者互作应答是共生关系建立的关键。项目组前期发现AM真菌能够促进玉米植株的生长，位于细胞膜表面的LysM蛋白激酶受体ZmLysM1能够识别AM真菌产生的Myc因子，诱导下游共生基因的表达，但受体二者如何识别及介导胞内信号转导途径仍不清楚。本项目发现ZmLysM1可互补结瘤因子受体1（NFR1）的功能，激活下游共生信号通路。对比对LysM激酶受体同源或异源复合物的形成分析，发现ZmLysM1能够与同源蛋白ZmLysM2直接互作，完成对配体Myc因子的识别。借助蛋白表达系统和配体互作实验，明确三个LysM结构蛋白对识别Myc因子均具有重要作用。磷酸化活性分析发现Myc因子能够诱导ZmLysM1胞内结构域的磷酸化活性，而S123和S245是关键的氨基酸磷酸化位点，可激活下游共生信号，调节磷转运蛋白ZmPt9的活性，促进玉米根系对磷的吸收作用。后通过文库筛选和蛋白互作分析，发现ZmLysM1胞内结构域可以直接与E3泛素连接酶蛋白互作，调节下游信号的收敛。研究结果不仅可丰富植物-微生物互作识别机制的理论内容，而且为提高AM真菌的定植效率，扩大宿主共生真菌种群范围具有重要的指导意义。