Identification of Chemotaxis Compounds in Root Exudates and Their Sensing Chemoreceptors in Plant-Growth-Promoting Rhizobacteria Bacillus amyloliquefaciens SQR9
Identification of Chemotaxis Compounds in Root Exudates and Their Sensing Chemoreceptors in Plant-Growth-Promoting Rhizobacteria Bacillus amyloliquefaciens SQR9
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根系分泌物中趋化化合物的鉴定及其在植物促进根际细菌解淀粉芽孢杆菌 SQR9 中的传感化学感受器
DOI：
10.1094/mpmi-01-18-0003-r
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发表时间：
2018-10-01
影响因子：
3.5
通讯作者：
Zhang, Ruifu
中科院分区：
文献类型：
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作者：
Feng, Haichao;Zhang, Nan;Zhang, Ruifu
趋化作用是植物根际促生细菌（PGPR）通过甲基化趋化蛋白（MCP）介导的对根系分泌物的反应，对植物根际定殖和发挥有益功能具有重要意义。系统地鉴定复杂根系分泌物中的化学引诱物及其感受化学受体有助于促进植物根际促生菌的招募和定殖。在这项研究中，39个化学引诱剂和5个化学排斥剂，包括氨基酸，有机酸和糖，确定了从98个测试组分的根分泌物的充分研究的PGPR菌株解淀粉芽孢杆菌SQR 9。有趣的是，突变菌株SQR 9 Δ 8 mcp，所有8种推定的化学感受器完全缺失，失去了对这44种化合物的趋化反应。基因互补、趋化性测定和等温滴定量热分析表明，McpA主要负责有机酸和氨基酸的传感，而McpC主要负责氨基酸的传感。这两种化学感受器可能在SQR 9的根际趋化过程中发挥重要作用。相反，B.解淀粉酶独特的化学受体McpR特异性负责精氨酸，残基Tyr-78、Thr-131和Asp-162对精氨酸结合至关重要。本研究不仅加深了对PGPR-根系相互作用的认识，而且为提高PGPR的根际趋化性和定殖能力提供了有益的信息，将促进PGPR在农业生产中的应用。
Chemotaxis-mediated response to root exudates, initiated by sensing-specific ligands through methyl-accepting chemotaxis proteins (MCP), is very important for root colonization and beneficial functions of plant-growth-promoting rhizobacteria (PGPR). Systematic identification of chemoattractants in complex root exudates and their sensing chemoreceptors in PGPR is helpful for enhancing their recruitment and colonization. In this study, 39 chemoattractants and 5 chemorepellents, including amino acids, organic acids, and sugars, were identified from 98 tested components of root exudates for the well-studied PGPR strain Bacillus amyloliquefaciens SQR9. Interestingly, mutant stain SQR9Δ8mcp, with all eight putative chemoreceptors completely deleted, lost the chemotactic responses to those 44 compounds. Gene complementation, chemotaxis assay, and isothermal titration calorimetry analysis revealed that McpA was mainly responsible for sensing organic acids and amino acids, while McpC was mostly for amino acids. These two chemoreceptors may play important roles in the rhizosphere chemotaxis of SQR9. In contrast, the B. amyloliquefaciens-unique chemoreceptor McpR was specifically responsible for arginine, and residues Tyr-78, Thr-131, and Asp-162 were critical for arginine binding. This study not only deepened our insights into PGPR-root interaction but also provided useful information to enhance the rhizosphere chemotaxis mobility and colonization of PGPR, which will promote their application in agricultural production.