1 Key Laboratory of Microbial Resources Collection and Preservation, Ministry of Agriculture, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, P.R. China; and.
2 Jiangsu Key Lab and Engineering Center for Solid Organic Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing, 210095, P.R. China.
Mol Plant Microbe Interact. 2017 Jan;30(1):53-62. doi: 10.1094/MPMI-07-16-0131-R. Epub 2017 Jan 27.
Colonization of plant growth-promoting rhizobacteria (PGPR) is critical for exerting their beneficial effects on the plant. Root exudation is a major factor influencing the colonization of both PGPR and soil-borne pathogens within the root system. However, the tripartite interaction of PGPR, plant roots, and soil-borne pathogens is poorly understood. We screened root exudates for signals that mediate tripartite interactions in the rhizosphere. In a split-root system, we found that root colonization of PGPR strain Bacillus amyloliquefaciens SQR9 on cucumber root was significantly enhanced by preinoculation with SQR9 or the soil-borne pathogen Fusarium oxysporum f. sp. cucumerinum, whereas root colonization of F. oxysporum f. sp. cucumerinum was reduced upon preinoculation with SQR9 or F. oxysporum f. sp. cucumerinum. Root exudates from cucumbers preinoculated with SQR9 or F. oxysporum f. sp. cucumerinum were analyzed and 109 compounds were identified. Correlation analysis highlighted eight compounds that significantly correlated with root colonization of SQR9 or F. oxysporum f. sp. cucumerinum. After performing colonization experiments with these chemicals, raffinose and tryptophan were shown to positively affect the root colonization of F. oxysporum f. sp. cucumerinum and SQR9, respectively. These results indicate that cucumber roots colonized by F. oxysporum f. sp. cucumerinum or SQR9 increase root secretion of tryptophan to strengthen further colonization of SQR9. In contrast, these colonized cucumber roots reduce raffinose secretion to inhibit root colonization of F. oxysporum f. sp. cucumerinum.
植物促生根际细菌（PGPR）的定殖对于发挥其对植物的有益作用至关重要。根分泌是影响 PGPR 和土壤病原菌在根系内定殖的主要因素。然而，PGPR、植物根系和土壤病原菌的三方相互作用知之甚少。我们筛选了根分泌物中的信号，以介导根际中的三方相互作用。在分根系统中，我们发现 PGPR 菌株解淀粉芽孢杆菌 SQR9 在黄瓜根上的定殖明显增强了预先接种 SQR9 或土壤病原菌尖孢镰刀菌黄瓜专化型，而预先接种 SQR9 或尖孢镰刀菌黄瓜专化型则减少了尖孢镰刀菌黄瓜专化型的定殖。分析预先接种 SQR9 或尖孢镰刀菌黄瓜专化型的黄瓜根分泌物，鉴定出 109 种化合物。相关分析突出了与 SQR9 或尖孢镰刀菌黄瓜专化型根定殖显著相关的 8 种化合物。用这些化学物质进行定殖实验后，发现棉子糖和色氨酸分别显著促进尖孢镰刀菌黄瓜专化型和 SQR9 的根定殖。这些结果表明，被尖孢镰刀菌黄瓜专化型或 SQR9 定殖的黄瓜根增加了色氨酸的根分泌，以加强 SQR9 的进一步定殖。相比之下，这些定殖的黄瓜根减少棉子糖的分泌，从而抑制尖孢镰刀菌黄瓜专化型的根定殖。
