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Plant recognition of symbiotic bacteria requires two LysM receptor-like kinases


Although most higher plants establish a symbiosis with arbuscular mycorrhizal fungi, symbiotic nitrogen fixation with rhizobia is a salient feature of legumes. Despite this host range difference, mycorrhizal and rhizobial invasion shares a common plant-specified genetic programme controlling the early host interaction. One feature distinguishing legumes is their ability to perceive rhizobial-specific signal molecules. We describe here two LysM-type serine/threonine receptor kinase genes, NFR1 and NFR5, enabling the model legume Lotus japonicus to recognize its bacterial microsymbiont Mesorhizobium loti. The extracellular domains of the two transmembrane kinases resemble LysM domains of peptidoglycan- and chitin-binding proteins, suggesting that they may be involved directly in perception of the rhizobial lipochitin-oligosaccharide signal. We show that NFR1 and NFR5 are required for the earliest physiological and cellular responses to this lipochitin-oligosaccharide signal, and demonstrate their role in the mechanism establishing susceptibility of the legume root for bacterial infection.

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Figure 1: Root hair response after M. loti inoculation or Nod-factor application.
Figure 2: Membrane depolarization and pH changes in the extracellular root hair space after application of Nod-factor purified from M. loti.
Figure 3: Expression of the NIN and ENOD2 genes in wild type, nfr1-1, nfr5-1 and symRK-1 mutants.
Figure 4: Positional cloning of the NFR1 gene and domain structure of the NFR1 protein.
Figure 5: NFR1, NFR5 and SYMRK gene expression.
Figure 6: Induction of NIN gene and LjCBP1 gene-promoter activity.
Figure 7: Working model for the functional role of NFR1 and NFR5 in plant perception of rhizobial and mycorrhizal signals.


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We thank J. Webb for making the LjCBP1–GUS line available. S.R. was supported by an EU Marie Curie Fellowship.

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Correspondence to Jens Stougaard.

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Radutoiu, S., Madsen, L., Madsen, E. et al. Plant recognition of symbiotic bacteria requires two LysM receptor-like kinases. Nature 425, 585–592 (2003).

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