PLoS ONE (Jan 2013)

Burkholderia species are the most common and preferred nodulating symbionts of the Piptadenia group (tribe Mimoseae).

  • Caroline Bournaud,
  • Sergio Miana de Faria,
  • José Miguel Ferreira dos Santos,
  • Pierre Tisseyre,
  • Michele Silva,
  • Clémence Chaintreuil,
  • Eduardo Gross,
  • Euan K James,
  • Yves Prin,
  • Lionel Moulin

DOI
https://doi.org/10.1371/journal.pone.0063478
Journal volume & issue
Vol. 8, no. 5
p. e63478

Abstract

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Burkholderia legume symbionts (also called α-rhizobia) are ancient in origin and are the main nitrogen-fixing symbionts of species belonging to the large genus Mimosa in Brazil. We investigated the extent of the affinity between Burkholderia and species in the tribe Mimoseae by studying symbionts of the genera Piptadenia (P.), Parapiptadenia (Pp.), Pseudopiptadenia (Ps.), Pityrocarpa (Py.), Anadenanthera (A.) and Microlobius (Mi.), all of which are native to Brazil and are phylogenetically close to Mimosa, and which together with Mimosa comprise the "Piptadenia group". We characterized 196 strains sampled from 18 species from 17 locations in Brazil using two neutral markers and two symbiotic genes in order to assess their species affiliations and the evolution of their symbiosis genes. We found that Burkholderia are common and highly diversified symbionts of species in the Piptadenia group, comprising nine Burkholderia species, of which three are new ones and one was never reported as symbiotic (B. phenoliruptrix). However, α-rhizobia were also detected and were occasionally dominant on a few species. A strong sampling site effect on the rhizobial nature of symbionts was detected, with the symbiont pattern of the same legume species changing drastically from location to location, even switching from β to α-rhizobia. Coinoculation assays showed a strong affinity of all the Piptadenia group species towards Burkholderia genotypes, with the exception of Mi. foetidus. Phylogenetic analyses of neutral and symbiotic markers showed that symbiosis genes in Burkholderia from the Piptadenia group have evolved mainly through vertical transfer, but also by horizontal transfer in two species.