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Amino-acid cycling drives nitrogen fixation in the legume-Rhizobium symbiosis

  • Arthur Hosie
Research Output: Contribution to journal Article Peer-review

Abstract

The biological reduction of atmospheric N2 to ammonium (nitrogen fixation) provides about 65% of the biosphere's available nitrogen. Most of this ammonium is contributed by legume–rhizobia symbioses1, which are initiated by the infection of legume hosts by bacteria (rhizobia), resulting in formation of root nodules. Within the nodules, rhizobia are found as bacteroids, which perform the nitrogen fixation: to do this, they obtain sources of carbon and energy from the plant, in the form of dicarboxylic acids2, 3. It has been thought that, in return, bacteroids simply provide the plant with ammonium. But here the authors show that a more complex amino-acid cycle is essential for symbiotic nitrogen fixation by Rhizobium in pea nodules. The plant provides amino acids to the bacteroids, enabling them to shut down their ammonium assimilation. In return, bacteroids act like plant organelles to cycle amino acids back to the plant for asparagine synthesis. The mutual dependence of this exchange prevents the symbiosis being dominated by the plant, and provides a selective pressure for the evolution of mutualism.

Publication Information

Output type

Research Output: Contribution to journal Article Peer-review

Original language

English

Pages from-to (Number of pages)

Pages 722-726

Journal (Volume, Issue Number)

Nature (Volume 422)

Publication milestones

  • Published - 01/01/2003

Publication status

Published - 01/01/2003

ISSN

0028-0836

External Publication IDs

  • handle.net: 10547/293977
  • Scopus: 0037452053

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