根瘤菌侵染IRLC类豆科植物后，将在根瘤中分化为具有固氮能力的终极形式类菌体。类菌体分化受根瘤菌bacA基因和宿主植物的根瘤特异富含半胱氨酸（NCR）多肽调控，但类菌体分化中的信号响应和分子互作机制仍需进一步揭示和阐明。本项目的前期工作中，从华癸中慢生根瘤菌中筛选得到与BacA相互作用的TypA蛋白，它编码一种核糖体结合型GTPase酶，并发现typA突变体在类菌体分化中的表型与bacA高度相似。本申请拟开展研究，旨在获得直接证据，一方面阐明TypA是否以及如何与BacA相互作用，从而调控根瘤菌类菌体分化发育；同时，基于对TypA突变体根瘤的全局蛋白组测定，结合转录组数据，分析以typA介导的类菌体分化信号途径，查明其中潜在的关键功能蛋白。从而揭示typA在介导华癸根瘤菌类菌体分化中的作用机制，为不定型根瘤类菌体分化的分子机理提供创新的研究进展。

After invading the IRLC legumes, rhizobia will differentiate into bacteroid in nodule with nitrogen fixing activity. It was reported that bacteroid terminal differentiation was controlled by bacA from rhizobia and nodule-specific cysteine-rich peptides (NCRs) from host plant. However, the signal responsing and molecular interactive mechanism during bacteroid differentiation have not yet been expounded, more research and experiment evidences are needed. Recently, our laboratory has identified a TypA protein from Mesorhizobium huakuii which can interact with the BacA protein by bacterial two hybrid. The phenotypes of the typA mutant during bacteroid differentiation was highly similar to those in bacA mutant. TypA protein belongs to a type of ribosome-binding GTPase. It was hypothesized that TypA plays an essential role in bacteroid differentiation by interacting with BacA. The aims of this proposal is to answer following questions. 1) Does and how TypA interacts with BacA under symbiotic conditions and determines the bacteroids differentiation? Meanwhile, 2) By analyzing the global proteome of typA mutant, the responding signalling pathway for the bacteroid differentiation mediated by the typA will be discovered, and a few key functional peoteins will also be identified. By this project, the anticipated results will expound the functional mechanism of the typA gene to mediate bacteroid differentiation in M. huakuii, and as well as , it will provide advanced research progresses and novel insights into the molecular mechanism to control bacteroid differentiation in indeterminate-type nodules.