Failure to fix nitrogen by non-reproductive symbiotic rhizobia triggers host sanctions that reduce fitness of their reproductive clonemates

Ryoko Oono, Carolyn G. Anderson, R. Ford Denison

Research output: Contribution to journalArticlepeer-review

75 Scopus citations

Abstract

The legume-rhizobia symbiosis is a classical mutualism where fixed carbon and nitrogen are exchanged between the species. Nonetheless, the plant carbon that fuels nitrogen (N2) fixation could be diverted to rhizobial reproduction by 'cheaters'-rhizobial strains that fix less N2 but potentially gain the benefit of fixation by other rhizobia. Host sanctions can decrease the relative fitness of less-beneficial reproductive bacteroids and prevent cheaters from breaking down the mutualism. However, in certain legume species, only undifferentiated rhizobia reproduce, while only terminally differentiated rhizobial bacteroids fix nitrogen. Sanctions were, therefore, tested in two legume species that host non-reproductive bacteroids. We demonstrate that even legume species that host non-reproductive bacteroids, specifically pea and alfalfa, can severely sanction undifferentiated rhizobia when bacteroids within the same nodule fail to fix N2. Hence, host sanctions by a diverse set of legumes play a role in maintaining N2 fixation.

Original languageEnglish (US)
Pages (from-to)2698-2703
Number of pages6
JournalProceedings of the Royal Society B: Biological Sciences
Volume278
Issue number1718
DOIs
StatePublished - Sep 7 2011

Keywords

  • Alfalfa
  • Bacteroid differentiation
  • Mutualism
  • Pea
  • Rhizobia
  • Sanction

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