title: Recombination and horizontal transfer of nodulation and ACC deaminase (acdS) genes within Alpha- and Betaproteobacteria nodulating legumes of the Cape Fynbos biome.
abstract: The goal of this work is to study the evolution and the degree of horizontal gene transfer (HGT) within rhizobial genera of both Alphaproteobacteria (Mesorhizobium, Rhizobium) and Betaproteobacteria (Burkholderia), originating from South African Fynbos legumes. By using a phylogenetic approach and comparing multiple chromosomal and symbiosis genes, we revealed conclusive evidence of high degrees of horizontal transfer of nodulation genes among closely related species of both groups of rhizobia, but also among species with distant genetic backgrounds (Rhizobium and Mesorhizobium), underscoring the importance of lateral transfer of symbiosis traits as an important evolutionary force among rhizobia of the Cape Fynbos biome. The extensive exchange of symbiosis genes in the Fynbos is in contrast with a lack of significant events of HGT among Burkholderia symbionts from the South American Cerrado and Caatinga biome. Furthermore, homologous recombination among selected housekeeping genes had a substantial impact on sequence evolution within Burkholderia and Mesorhizobium. Finally, phylogenetic analyses of the non-symbiosis acdS gene in Mesorhizobium, a gene often located on symbiosis islands, revealed distinct relationships compared to the chromosomal and symbiosis genes, suggesting a different evolutionary history and independent events of gene transfer. The observed events of HGT and incongruence between different genes necessitate caution in interpreting topologies from individual data types.
authors.affiliation: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town, South Africa Plant Conservation and Population Biology, KU Leuven, Kasteelpark Arenberg 31, PO Box 02435, 3001 Heverlee, Belgium benny.lemaire@bio.kuleuven.be.
authors.forename: Benny
authors.initials: B
authors.lastname: Lemaire
authors.affiliation: Plant Conservation and Population Biology, KU Leuven, Kasteelpark Arenberg 31, PO Box 02435, 3001 Heverlee, Belgium Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
authors.forename: Jannick
authors.initials: J
authors.lastname: Van Cauwenberghe
authors.affiliation: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town, South Africa.
authors.forename: Samson
authors.initials: S
authors.lastname: Chimphango
authors.affiliation: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town, South Africa.
authors.forename: Charles
authors.initials: C
authors.lastname: Stirton
authors.affiliation: Plant Conservation and Population Biology, KU Leuven, Kasteelpark Arenberg 31, PO Box 02435, 3001 Heverlee, Belgium.
authors.forename: Olivier
authors.initials: O
authors.lastname: Honnay
authors.affiliation: Plant Conservation and Population Biology, KU Leuven, Kasteelpark Arenberg 31, PO Box 02435, 3001 Heverlee, Belgium Naturalis Biodiversity Center, Leiden University, 2300 RA Leiden, the Netherlands.
authors.forename: Erik
authors.initials: E
authors.lastname: Smets
authors.affiliation: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town, South Africa.
authors.forename: A Muthama
authors.initials: AM
authors.lastname: Muasya
mesh_terms: D020561:Alphaproteobacteria / Q000145:classification / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D020562:Betaproteobacteria / Q000145:classification / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D019755:Carbon-Carbon Lyases / Q000235:genetics*; D017753:Ecosystem; D019143:Evolution, Molecular; D007887:Fabaceae / Q000382:microbiology* / Q000502:physiology; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D010802:Phylogeny; D013019:South Africa; D013559:Symbiosis
chemical_list: C033634:1-aminocyclopropane-1-carboxylate deaminase; D019755:Carbon-Carbon Lyases
keywords: Fynbos legumes; Mesorhizobium; acdS, Burkholderia; horizontal gene transfer; nodulation genes