A novel ankyrin-repeat membrane protein, IGN1, is required for persistence of nitrogen-fixing symbiosis in root nodules of Lotus japonicus

Hirotaka Kumagai, Tsuneo Hakoyama, Yosuke Umehara, Shusei Sato, Takakazu Kaneko, Satoshi Tabata, Hiroshi Kouchi

研究成果: Article査読

68 被引用数 (Scopus)

抄録

Nitrogen-fixing symbiosis of legume plants with Rhizobium bacteria is established through complex interactions between two symbiotic partners. Similar to the mutual recognition and interactions at the initial stages of symbiosis, nitrogen fixation activity of rhizobia inside root nodules of the host legume is also controlled by specific interactions during later stages of nodule development. We isolated a novel Fix- mutant, ineffective greenish nodules 1 (ign1), of Lotus japonicus, which forms apparently normal nodules containing endosymbiotic bacteria, but does not develop nitrogen fixation activity. Map-based cloning of the mutated gene allowed us to identify the IGN1 gene, which encodes a novel ankyrin-repeat protein with transmembrane regions. IGN1 expression was detected in all organs of L. japonicus and not enhanced in the nodulation process. Immunoanalysis, together with expression analysis of a green fluorescent protein-IGN1 fusion construct, demonstrated localization of the IGN1 protein in the plasma membrane. The ign1 nodules showed extremely rapid premature senescence. Irregularly enlarged symbiosomes with multiple bacteroids were observed at early stages (8-9 d post inoculation) of nodule formation, followed by disruption of the symbiosomes and disintegration of nodule infected cell cytoplasm with aggregation of the bacteroids. Although the exact biochemical functions of the IGN1 gene are still to be elucidated, these results indicate that IGN1 is required for differentiation and/or persistence of bacteroids and symbiosomes, thus being essential for functional symbiosis.

本文言語English
ページ(範囲)1293-1305
ページ数13
ジャーナルPlant physiology
143
3
DOI
出版ステータスPublished - 2007 3月
外部発表はい

ASJC Scopus subject areas

  • 生理学
  • 遺伝学
  • 植物科学

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