Plant Molecular Biology

, Volume 58, Issue 6, pp 809–822 | Cite as

The Medicago truncatula SUNN Gene Encodes a CLV1-like Leucine-rich Repeat Receptor Kinase that Regulates Nodule Number and Root Length

  • Elise Schnabel
  • Etienne-Pascal Journet
  • Fernanda de Carvalho-Niebel
  • Gérard Duc
  • Julia Frugoli


Four Medicago truncatula sunn mutants displayed shortened roots and hypernodulation under all conditions examined. The mutants, recovered in three independent genetic screens, all contained lesions in a leucine-rich repeat (LRR) receptor kinase. Although the molecular defects among alleles varied, root length and the extent of nodulation were not significantly different between the mutants. SUNN is expressed in shoots, flowers and roots. Although previously reported grafting experiments showed that the presence of the mutated SUNN gene in roots does not confer an obvious phenotype, expression levels of SUNN mRNA were reduced in sunn-1 roots. SUNN and the previously identified genes HAR1 (Lotus japonicus) and NARK (Glycine max) are orthologs based on gene sequence and synteny between flanking sequences. Comparison of related LRR receptor kinases determined that all nodulation autoregulation genes identified to date are the closest legume relatives of AtCLV1 by sequence, yet sunn, har and nark mutants do not display the fasciated clv phenotype. The M. truncatula region is syntenic with duplicated regions of Arabidopsis chromosomes 2 and 4, none of which harbor CLV1 or any other LRR receptor kinase genes. A novel truncated copy of the SUNN gene lacking a kinase domain, RLP1, is found immediately upstream of SUNN and like SUNN is expressed at a reduced level in sunn-1 roots.


Medicago truncatula nodule regulation RLP1 SUNN supernodulation 


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Copyright information

© Springer 2005

Authors and Affiliations

  • Elise Schnabel
    • 1
  • Etienne-Pascal Journet
    • 2
  • Fernanda de Carvalho-Niebel
    • 2
  • Gérard Duc
    • 3
  • Julia Frugoli
    • 1
  1. 1.Department of Genetics, Biochemistry and Life Science StudiesClemson UniversityClemsonUSA
  2. 2.Laboratoire des Interactions Plantes-MicroorganismesUnité Mixte de Recherche, CNRS-INRACastanet-Tolosan cédexFrance
  3. 3.lNRA Unité de Recherches en Génétique et Ecophysiologie des légumineuses à grainesDIJON cédexFrance

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