Nitrate-independent expression of plant nitrate reductase in Lotus japonicus root nodules

Kazuhisa Kato, Yoshimichi Okamura, Koki Kanahama, Yoshinori Kanayama

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24 Citations (Scopus)


Nitrate-independent nitrate reductase (NR) activity is generally found in legume root nodules. Therefore, the effects of nitrate on plant NR activity and mRNA were investigated in the root nodules of Lotus japonicus (L. japonicus). Both NR activity and mRNA levels in roots and root nodules were up-regulated by the addition of nitrate. In the absence of nitrate, NR activity and mRNA were detected in root nodules but not in roots. Southern blotting analysis indicates that NR is encoded by a single gene in L. japonicus. No nitrate was detected in the root nodules or roots of plants grown in the absence of nitrate, while its accumulation was observed in plants supplied with exogenous nitrate. These results indicate that inducible-type NR can be expressed in root nodules in the absence of nitrate. The activation state of the nitrate-independent activity of NR was as high as that of NR activity induced by nitrate. NR mRNA expressed independently of nitrate in root nodules without nitrate was localized in the infected regions of the root nodules. Thus, the expression could be related to the specific structure and environment of root nodules.

Original languageEnglish
Pages (from-to)1685-1690
Number of pages6
JournalJournal of experimental botany
Issue number388
Publication statusPublished - 2003 Jul 1


  • Lotus japonicus
  • Nitrate
  • Nitrate reductase
  • Nitrogen fixation
  • Root nodule

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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