title: Biological nitrogen fixation in non-legume plants.
abstract: BACKGROUND
  Nitrogen is an essential nutrient in plant growth. The ability of a plant to supply all or part of its requirements from biological nitrogen fixation (BNF) thanks to interactions with endosymbiotic, associative and endophytic symbionts, confers a great competitive advantage over non-nitrogen-fixing plants.
  
  
  METHODS
  Because BNF in legumes is well documented, this review focuses on BNF in non-legume plants. Despite the phylogenic and ecological diversity among diazotrophic bacteria and their hosts, tightly regulated communication is always necessary between the microorganisms and the host plant to achieve a successful interaction. Ongoing research efforts to improve knowledge of the molecular mechanisms underlying these original relationships and some common strategies leading to a successful relationship between the nitrogen-fixing microorganisms and their hosts are presented.
  
  
  CONCLUSIONS
  Understanding the molecular mechanism of BNF outside the legume-rhizobium symbiosis could have important agronomic implications and enable the use of N-fertilizers to be reduced or even avoided. Indeed, in the short term, improved understanding could lead to more sustainable exploitation of the biodiversity of nitrogen-fixing organisms and, in the longer term, to the transfer of endosymbiotic nitrogen-fixation capacities to major non-legume crops.
authors.affiliation: Université de Perpignan, Via Domitia, Avenue Paul Alduy, 66100 Perpignan, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Santi
authors.forename: Didier
authors.initials: D
authors.lastname: Bogusz
authors.forename: Claudine
authors.initials: C
authors.lastname: Franche
mesh_terms: D018556:Crops, Agricultural / Q000382:microbiology / Q000502:physiology*; D000458:Cyanobacteria / Q000378:metabolism; D060026:Endophytes / Q000502:physiology; D009586:Nitrogen Fixation; D018517:Plant Roots / Q000382:microbiology / Q000502:physiology; D013559:Symbiosis / Q000502:physiology