title: Nodulation in Dimorphandra wilsonii Rizz. (Caesalpinioideae), a threatened species native to the Brazilian Cerrado.
abstract: The threatened caesalpinioid legume Dimorphandra wilsonii, which is native to the Cerrado biome in Brazil, was examined for its nodulation and N(2)-fixing ability, and was compared with another, less-threatened species, D. jorgei. Nodulation and potential N(2) fixation was shown on seedlings that had been inoculated singly with five bradyrhizobial isolates from mature D. wilsonii nodules. The infection of D. wilsonii by two of these strains (Dw10.1, Dw12.5) was followed in detail using light and transmission electron microscopy, and was compared with that of D. jorgei by Bradyrhizobium strain SEMIA6099. The roots of D. wilsonii were infected via small transient root hairs at 42 d after inoculation (dai), and nodules were sufficiently mature at 63 dai to express nitrogenase protein. Similar infection and nodule developmental processes were observed in D. jorgei. The bacteroids in mature Dimorphandra nodules were enclosed in plant cell wall material containing a homogalacturonan (pectic) epitope that was recognized by the monoclonal antibody JIM5. Analysis of sequences of their rrs (16S rRNA) genes and their ITS regions showed that the five D. wilsonii strains, although related to SEMIA6099, may constitute five undescribed species of genus Bradyrhizobium, whilst their nodD and nifH gene sequences showed that they formed clearly separated branches from other rhizobial strains. This is the first study to describe in full the N(2)-fixing symbiotic interaction between defined rhizobial strains and legumes in the sub-family Caesalpinioideae. This information will hopefully assist in the conservation of the threatened species D. wilsonii.
authors.affiliation: Departamento de Botânica, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Márcia Bacelar
authors.initials: MB
authors.lastname: Fonseca
authors.forename: Alvaro
authors.initials: A
authors.lastname: Peix
authors.forename: Sergio Miana
authors.initials: SM
authors.lastname: de Faria
authors.forename: Pedro F
authors.initials: PF
authors.lastname: Mateos
authors.forename: Lina P
authors.initials: LP
authors.lastname: Rivera
authors.forename: Jean L
authors.initials: JL
authors.lastname: Simões-Araujo
authors.forename: Marcel Giovanni Costa
authors.initials: MG
authors.lastname: França
authors.forename: Rosy Mary dos Santos
authors.initials: RM
authors.lastname: Isaias
authors.forename: Cristina
authors.initials: C
authors.lastname: Cruz
authors.forename: Encarna
authors.initials: E
authors.lastname: Velázquez
authors.forename: Maria Rita
authors.initials: MR
authors.lastname: Scotti
authors.forename: Janet I
authors.initials: JI
authors.lastname: Sprent
authors.forename: Euan K
authors.initials: EK
authors.lastname: James
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D018533:Biomass; D020369:Bradyrhizobium / Q000378:metabolism; D001938:Brazil; D021901:DNA, Intergenic; D000939:Epitopes / Q000737:chemistry; D007887:Fabaceae / Q000378:metabolism*; D016013:Likelihood Functions; D046529:Microscopy, Electron, Transmission / Q000379:methods; D009584:Nitrogen / Q000737:chemistry; D010088:Oxidoreductases / Q000378:metabolism; D010368:Pectins / Q000737:chemistry; D010802:Phylogeny; D018517:Plant Roots / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000378:metabolism*; D012987:Soil; D012988:Soil Microbiology; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D021901:DNA, Intergenic; D000939:Epitopes; C060773:NodD protein, Bacteria; D012336:RNA, Ribosomal, 16S; D012987:Soil; D010368:Pectins; D010088:Oxidoreductases; C029130:nitrogenase reductase; D009584:Nitrogen; C003181:polygalacturonic acid