Nicotianamine synthase specifically expressed in root nodules of Lotus japonicus

T. Hakoyama, H. Watanabe, J. Tomita, A. Yamamoto, S. Sato, Y. Mori, H. Kouchi, N. Suganuma

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

In dicotyledonous plants, nicotianamine synthase (NAS) is thought to play a role in the intercellular transport of iron (Fe). Fe is an essential metal for nitrogen-fixing root nodules of legumes, prompting us to characterize the role of the NAS gene in detail. We previously compared gene-expression profiles in ineffective nodules formed on a Lotus japonicus Fix- mutant, sen1, with those in wild-type-effective nodules, and showed that expression of an expressed sequence tag (EST) clone encoding an NAS (EC 2.5.1.43) homologue was repressed in the ineffective nodules. In the present study, two EST clones encoding NAS homologues were found in the EST database. We named them LjNAS1 and LjNAS2. Both were detected as single-copy genes in the L. japonicus genome, and conferred NAS activities in transformed Saccharomyces cerevisiae. LjNAS2 was expressed only in nodules, but LjNAS1 was expressed mainly in leaves, stems, and cotyledons. The level of LjNAS2 transcripts was highest in the nodules 24 days after inoculation with Mesorhizobium loti, and was localized in vascular bundles within the nodules. Expression of LjNAS2 was suppressed in ineffective nodules formed on Fix- mutants other than sen1. By contrast, nitrogenase activities of nodules were not influenced in LjNAS2-suppressed plants. We discuss the role of LjNAS2 from the aspect of Fe translocation in nodules.

Original languageEnglish
Pages (from-to)309-317
Number of pages9
JournalPlanta
Volume230
Issue number2
DOIs
Publication statusPublished - 2009 Jul
Externally publishedYes

Keywords

  • Fix mutant
  • Iron
  • Lotus
  • Nicotianamine synthase
  • Nitrogen fixation

ASJC Scopus subject areas

  • Genetics
  • Plant Science

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