The Medicago truncatula SUNN gene encodes a CLV1-like leucine-rich repeat receptor kinase that regulates nodule number and root length.
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.
Schnabel
Elise
E
Department of Genetics, Biochemistry and Life Science Studies, Clemson University, 100 Jordan Hall, Clemson, SC, 29634, USA.
Journet
Etienne-Pascal
EP
Laboratoire des Interactions Plantes-Microorganismes, Unité Mixte de Recherche, CNRS-INRA, 31326, Castanet-Tolosan cédex, France.
de Carvalho-Niebel
Fernanda
F
Laboratoire des Interactions Plantes-Microorganismes, Unité Mixte de Recherche, CNRS-INRA, 31326, Castanet-Tolosan cédex, France.
Duc
Gérard
G
lNRA Unité de Recherches en Génétique et Ecophysiologie des légumineuses à graines, BP 86510, F-21065, DIJON cédex, France.
Frugoli
Julia
J
Department of Genetics, Biochemistry and Life Science Studies, Clemson University, 100 Jordan Hall, Clemson, SC, 29634, USA. jfrugol@CLEMSON.EDU.
D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D046913:Medicago truncatula / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D009154:Mutation; D009566:Nitrates / Q000494:pharmacology; D010641:Phenotype; D010802:Phylogeny; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D026801:Synteny
D009566:Nitrates; D020794:Receptor Protein-Tyrosine Kinases