Origins of cheating and loss of symbiosis in wild Bradyrhizobium.
J Evol Biol
; 23(5): 1075-89, 2010 May.
Article
em En
| MEDLINE
| ID: mdl-20345811
ABSTRACT
Rhizobial bacteria nodulate legume roots and fix nitrogen in exchange for photosynthates. These symbionts are infectiously acquired from the environment and in such cases selection models predict evolutionary spread of uncooperative mutants. Uncooperative rhizobia - including nonfixing and non-nodulating strains - appear common in agriculture, yet their population biology and origins remain unknown in natural soils. Here, a phylogenetically broad sample of 62 wild-collected rhizobial isolates was experimentally inoculated onto Lotus strigosus to assess their nodulation ability and effects on host growth. A cheater strain was discovered that proliferated in host tissue while offering no benefit; its fitness was superior to that of beneficial strains. Phylogenetic reconstruction of Bradyrhizobium rDNA and transmissible symbiosis-island loci suggest that the cheater evolved via symbiotic gene transfer. Many strains were also identified that failed to nodulate L. strigosus, and it appears that nodulation ability on this host has been recurrently lost in the symbiont population. This is the first study to reveal the adaptive nature of rhizobial cheating and to trace the evolutionary origins of uncooperative rhizobial mutants.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Filogenia
/
Simbiose
/
Adaptação Biológica
/
Bradyrhizobium
/
Transferência Genética Horizontal
/
Nódulos Radiculares de Plantas
/
Lotus
Tipo de estudo:
Prognostic_studies
País/Região como assunto:
America do norte
Idioma:
En
Revista:
J Evol Biol
Assunto da revista:
BIOLOGIA
Ano de publicação:
2010
Tipo de documento:
Article
País de afiliação:
Estados Unidos