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Keywords:

  • AM symbiosis;
  • GRAS transcription factor;
  • Medicago truncatula ;
  • NSP1;
  • SYM pathway

Summary

  • Nodulation and arbuscular mycorrhization require the activation of plant host symbiotic programs by Nod factors, and Myc-LCOs and COs, respectively. The pathways involved in the perception and downstream signaling of these signals include common and distinct components. Among the distinct components, NSP1, a GRAS transcription factor, has been considered for years to be specifically involved in nodulation.
  • Here, we analyzed the degree of conservation of the NSP1 sequence in arbuscular mycorrhizal (AM) host and non-AM host plants and carefully examined the ability of Medicago truncatula nsp1 mutants to respond to Myc-LCOs and to be colonized by an arbuscular mycorrhizal fungus.
  • In AM-host plants, the selection pressure on NSP1 is stronger than in non-AM host ones. The response to Myc-LCOs and the frequency of mycorrhizal colonization are significantly reduced in the nsp1 mutants.
  • Our results reveal that NSP1, previously described for its involvement in the Nod factor signaling pathway, is also involved in the Myc-LCO signaling pathway. They bring additional evidence on the evolutionary relatedness between nodulation and mycorrhization.