本项目以模式豆科植物百脉根为材料，在发现有丝分裂原蛋白激酶MAPK级联反应参与根瘤菌共生信号转导的基础上，开展豆科植物根瘤形成中共生信号与细胞分裂素信号对话的分子机制研究。利用蛋白相互作用技术和磷酸化作用机制及活性检测，分离和鉴定出MAPK激酶级联反应下游靶蛋白；在明确LjMPK6与组氨酸蛋白激酶LHK1相互作用的基础上，通过酵母双杂交和蛋白激酶磷酸化技术，分离和鉴定出由LHK1导致的细胞分裂素信号转导中下游磷酸转移蛋白（HPT）及靶蛋白应答调节子（RR）。探讨豆科植物受到根瘤菌感染、接受根瘤菌结瘤因子信号后，如何启动侵入线的形成和内皮层细胞分裂。其目的旨在阐明豆科植物共生信号与细胞分裂素信号转导转导途径相互协调、共同调控根瘤器官产生的作用机制。为揭示根瘤菌与豆科植物早期共生关系的形成和建立提供分子生物学证据。

Mitogen-activated protein kinases (MAPKs) play a pivotal role in controlling numerous cellular processes, including differentiation, mitogenesis, oncogenesis, and apoptosis. Base on the MAP kinase cascade involved in the rhizobial symbiotic signal transduction in a model legume Lotus japonicus in our previous works, the project will be focused on the molecular determinants of symbiotic signaling talking with cytokinin signaling during nodule formation in legumes. Using protein-protein interaction and measuring phosphorylation activity, the target proteins of LjMPK6 will be isolated and characterized for confirming the active mechanism of MAP kinase cascade in symbiosis signaling. Using yeast two-hybrid and phosphorylation approach, histidine phosphotransfer proteins (HPT) and response regulators (RR) will be isolated and characterized for investigating the relationship between Nod factor signaling and cytokinin signal transduction because LjMPK6 is specifically interacted with cytokinin receptor LHK1 in our previous works. The aim of the proposed project is to elucidate the roles and activation mechanism of MAPK cascade in Nod factor signal transduction and the obtained results will help to understand the processes of symbiosis formation between rhizobia and legume plants.