Rhizobitoxine modulates plant-microbe interactions by ethylene inhibition

Masayuki Sugawara, Shin Okazaki, Noriyuki Nukui, Hiroshi Ezura, Hisayuki Mitsui, Kiwamu Minamisawa

Research output: Contribution to journalReview articlepeer-review

64 Citations (Scopus)


Bradyrhizobium elkanii produces rhizobitoxine, an enol-ether amino acid, which has been regarded as a phytotoxin because it causes chlorosis in soybeans. However, recent studies have revealed that rhizobitoxine plays a positive role in establishing symbiosis between B. elkanii and host legumes: rhizobitoxine enhances the nodulation process by inhibiting ACC (1-aminocyclopropane-1-carboxylate) synthase in the ethylene biosynthesis of host roots. B. elkanii rtxA and rtxC genes are required for rhizobitoxine production. In particular, rtxC gene is involved in the desaturation of dihydrorhizobitoxine into rhizobitoxine. A legume with a mutated ethylene receptor gene produced markedly higher numbers of rhizobial infection threads and nodule primordia. Thus, endogenous ethylene in legume roots negatively regulates the formation of nodule primordia, which is overcome by rhiozbitoxine. Although a plant pathogen Burkholderia andropogonis has been known to produce rhizobitoxine, the genome sequence of Xanthomonas oryzae showed the existence of a putative rhizobitoxine transposon in the genome. The cumulative evidence suggests that rhizobitoxine-producing bacteria modulate plant-microbe interactions via ethylene in the rhizosphere and phyllosphere environments. In addition, rhizobitoxine-producing capability might be utilized as tools in agriculture and biotechnology.

Original languageEnglish
Pages (from-to)382-388
Number of pages7
JournalBiotechnology Advances
Issue number4
Publication statusPublished - 2006 Jul


  • Bradyrhizobium elkanii
  • Ethylene
  • Legume
  • Rhizobia
  • Rhizobitoxine

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology


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