title: Identification of Root-Secreted Compounds Involved in the Communication Between Cucumber, the Beneficial Bacillus amyloliquefaciens, and the Soil-Borne Pathogen Fusarium oxysporum.
abstract: 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.
authors.affiliation: 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.
authors.forename: Yunpeng
authors.initials: Y
authors.lastname: Liu
authors.affiliation: 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.
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.affiliation: 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.
authors.forename: Gengwei
authors.initials: G
authors.lastname: Wu
authors.affiliation: 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.
authors.forename: Haichao
authors.initials: H
authors.lastname: Feng
authors.affiliation: 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.
authors.forename: Guishan
authors.initials: G
authors.lastname: Zhang
authors.affiliation: 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.
authors.forename: Qirong
authors.initials: Q
authors.lastname: Shen
authors.affiliation: 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.
authors.forename: Ruifu
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000069977:Bacillus amyloliquefaciens / Q000502:physiology*; D015169:Colony Count, Microbial; D018553:Cucumis sativus / Q000502:physiology*; D060467:Disease Resistance; D005670:Fusarium / Q000502:physiology*; D008401:Gas Chromatography-Mass Spectrometry; D017343:Genes, Plant; D064209:Phytochemicals / Q000378:metabolism*; D053147:Plant Exudates / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism* / Q000382:microbiology; D012988:Soil Microbiology; D014158:Transcription, Genetic
chemical_list: D064209:Phytochemicals; D053147:Plant Exudates