Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, People's Republic of China.
University of Chinese Academy of Sciences, Beijing, People's Republic of China.
Mol Plant Microbe Interact. 2019 Sep;32(9):1134-1147. doi: 10.1094/MPMI-03-19-0059-R. Epub 2019 Jul 19.
ORS571 can induce nodule formation on the roots and the stems of its host legume, . Plant exudates are essential in the dialogue between microbes and their host plant and, in particular, amino acids can play an important role in the chemotactic response of bacteria. Histidine, arginine, and aspartate, which are the three most abundant amino acids present in seed exudates, behave as chemoattractants toward . A position-specific-iterated BLAST analysis of the methyl-accepting chemotaxis proteins (MCPs) (chemoreceptors) in the genome of was performed. Among the 43 MCP homologs, two MCPs harboring a dCache domain were selected as possible cognate amino acid MCPs. After analysis of relative gene expression levels and construction of a gene-deleted mutant strain, one of them, AZC_0821 designed as TlpH, was confirmed to be responsible for the chemotactic response to the three amino acids. In addition, it was found that these three amino acids can also influence chemotaxis of independently of the chemosensory receptors, by being involved in the increase of the expression level of several and genes involved in the chemotaxis pathway and flagella synthesis. Thus, the contribution of amino acids present in seed exudates is directly related to the role as chemoattractants and indirectly related to the role in the regulation of expression of key genes involved in chemotaxis and motility. This "dual role" is likely to influence the formation of biofilms by and the host root colonization properties of this bacterium.
ORS571 可以在其宿主豆科植物的根和茎上诱导结节形成。植物分泌物对于微生物与其宿主植物之间的对话至关重要，特别是氨基酸可以在细菌的趋化反应中发挥重要作用。组氨酸、精氨酸和天冬氨酸是种子分泌物中含量最丰富的三种氨基酸，它们对 表现出趋化性。对 的甲基接受趋化性蛋白（MCPs）（化学感受器）的基因组进行了位置特异性迭代 BLAST 分析。在 43 个 MCP 同源物中，选择了两个含有 dCache 结构域的 MCP 作为可能的同源氨基酸 MCP。分析相对基因表达水平并构建基因缺失突变菌株后，其中一个命名为 TlpH 的基因被确认为负责对这三种氨基酸的趋化反应。此外，还发现这三种氨基酸可以独立于化学感受受体影响 的趋化作用，通过参与增加参与趋化途径和鞭毛合成的几个 和 基因的表达水平。因此，种子分泌物中氨基酸的贡献直接与其作为趋化剂的作用有关，间接与其在调节参与趋化和运动的关键基因的表达中的作用有关。这种“双重作用”可能会影响 的生物膜形成以及该细菌对宿主根定植的特性。
