title: Rhizobial Diversity and Nodulation Characteristics of the Extremely Promiscuous Legume Sophora flavescens.
abstract: In present study, we report our extensive survey on the diversity and biogeography of rhizobia associated with Sophora flavescens, a sophocarpidine (matrine)-containing medicinal legume. We additionally investigated the cross nodulation, infection pattern, light and electron microscopies of root nodule sections of S. flavescens infected by various rhizobia. Seventeen genospecies of rhizobia belonging to five genera with seven types of symbiotic nodC genes were found to nodulate S. flavescens in natural soils. In the cross-nodulation tests, most representative rhizobia in class α-Proteobacteria, whose host plants belong to different cross-nodulation groups, form effective indeterminate nodules, while representative rhizobia in class β-Proteobacteria form ineffective nodules on S. flavescens. Highly host-specific biovars of Rhizobium leguminosarum (bv. trifolii and bv. viciae) and Rhizobium etli bv. phaseoli could establish symbioses with S. flavescens, providing further evidence that S. flavescens is an extremely promiscuous legume and it does not have strict selectivity on either the symbiotic genes or the species-determining housekeeping genes of rhizobia. Root-hair infection is found as the pattern that rhizobia have gained entry into the curled root hairs. Electron microscopies of ultra-thin sections of S. flavescens root nodules formed by different rhizobia show that the bacteroids are regular or irregular rod shape and nonswollen types. Some bacteroids contain poly-β-hydroxybutyrate (PHB), while others do not, indicating the synthesis of PHB in bacteroids is rhizobia-dependent. The extremely promiscuous symbiosis between S. flavescens and different rhizobia provide us a basis for future studies aimed at understanding the molecular interactions of rhizobia and legumes.
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, Beijing 100193, China; College of Biological Sciences and Rhizobia Research Center, China Agricultural University, Beijing 100193, China;
authors.forename: Yin Shan
authors.initials: YS
authors.lastname: Jiao
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, Beijing 100193, China; College of Biological Sciences and Rhizobia Research Center, China Agricultural University, Beijing 100193, China;
authors.forename: Yuan Hui
authors.initials: YH
authors.lastname: Liu
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, Beijing 100193, China; College of Biological Sciences and Rhizobia Research Center, China Agricultural University, Beijing 100193, China;
authors.forename: Hui
authors.initials: H
authors.lastname: Yan
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, Beijing 100193, China; College of Biological Sciences and Rhizobia Research Center, China Agricultural University, Beijing 100193, China;|2 Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México D. F. 11340, México;
authors.forename: En Tao
authors.initials: ET
authors.lastname: Wang
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, Beijing 100193, China; College of Biological Sciences and Rhizobia Research Center, China Agricultural University, Beijing 100193, China;
authors.forename: Chang Fu
authors.initials: CF
authors.lastname: Tian
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, Beijing 100193, China; College of Biological Sciences and Rhizobia Research Center, China Agricultural University, Beijing 100193, China;
authors.forename: Wen Xin
authors.initials: WX
authors.lastname: Chen
authors.affiliation: 3 Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100193, China.
authors.forename: Bao Lin
authors.initials: BL
authors.lastname: Guo
authors.affiliation: 1 State Key Laboratory of Agrobiotechnology, Beijing 100193, China; College of Biological Sciences and Rhizobia Research Center, China Agricultural University, Beijing 100193, China;
authors.forename: Wen Feng
authors.initials: WF
authors.lastname: Chen
mesh_terms: D017343:Genes, Plant; D009586:Nitrogen Fixation; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology; D012231:Rhizobium / Q000145:classification / Q000235:genetics / Q000502:physiology*; D012988:Soil Microbiology; D029909:Sophora / Q000382:microbiology*; D013559:Symbiosis