title: South african papilionoid legumes are nodulated by diverse burkholderia with unique nodulation and nitrogen-fixation Loci.
abstract: The root-nodule bacteria of legumes endemic to the Cape Floristic Region are largely understudied, even though recent reports suggest the occurrence of nodulating Burkholderia species unique to the region. In this study, we considered the diversity and evolution of nodulating Burkholderia associated with the endemic papilionoid tribes Hypocalypteae and Podalyrieae. We identified distinct groups from verified rhizobial isolates by phylogenetic analyses of the 16S rRNA and recA housekeeping gene regions. In order to gain insight into the evolution of the nodulation and diazotrophy of these rhizobia we analysed the genes encoding NifH and NodA. The majority of these 69 isolates appeared to be unique, potentially representing novel species. Evidence of horizontal gene transfer determining the symbiotic ability of these Cape Floristic Region isolates indicate evolutionary origins distinct from those of nodulating Burkholderia from elsewhere in the world. Overall, our findings suggest that Burkholderia species associated with fynbos legumes are highly diverse and their symbiotic abilities have unique ancestries. It is therefore possible that the evolution of these bacteria is closely linked to the diversification and establishment of legumes characteristic of the Cape Floristic Region.
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, Gauteng, South Africa. chrizelle.beukes@fabi.up.ac.za
authors.forename: Chrizelle W
authors.initials: CW
authors.lastname: Beukes
authors.forename: Stephanus N
authors.initials: SN
authors.lastname: Venter
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Law
authors.forename: Francina L
authors.initials: FL
authors.lastname: Phalane
authors.forename: Emma T
authors.initials: ET
authors.lastname: Steenkamp
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005075:Biological Evolution; D019117:Burkholderia / Q000235:genetics* / Q000378:metabolism; D007887:Fabaceae / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology*; D022761:Gene Transfer, Horizontal; D056426:Genetic Loci; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation / Q000235:genetics*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012231:Rhizobium / Q000235:genetics / Q000378:metabolism; D013019:South Africa; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D010088:Oxidoreductases; C029130:nitrogenase reductase; D000217:Acyltransferases; C060770:NodA protein, Rhizobiales; D009584:Nitrogen