title: Bioinformatic analysis of the CLE signaling peptide family.
abstract: BACKGROUND
  Plants encode a large number of leucine-rich repeat receptor-like kinases. Legumes encode several LRR-RLK linked to the process of root nodule formation, the ligands of which are unknown. To identify ligands for these receptors, we used a combination of profile hidden Markov models and position-specific iterative BLAST, allowing us to detect new members of the CLV3/ESR (CLE) protein family from publicly available sequence databases.
  
  
  RESULTS
  We identified 114 new members of the CLE protein family from various plant species, as well as five protein sequences containing multiple CLE domains. We were able to cluster the CLE domain proteins into 13 distinct groups based on their pairwise similarities in the primary CLE motif. In addition, we identified secondary motifs that coincide with our sequence clusters. The groupings based on the CLE motifs correlate with known biological functions of CLE signaling peptides and are analogous to groupings based on phylogenetic analysis and ectopic overexpression studies. We tested the biological function of two of the predicted CLE signaling peptides in the legume Medicago truncatula. These peptides inhibit the activity of the root apical and lateral root meristems in a manner consistent with our functional predictions based on other CLE signaling peptides clustering in the same groups.
  
  
  CONCLUSIONS
  Our analysis provides an identification and classification of a large number of novel potential CLE signaling peptides. The additional motifs we found could lead to future discovery of recognition sites for processing peptidases as well as predictions for receptor binding specificity.
authors.affiliation: School of Biochemistry and Molecular Biology, The Australian National University, Canberra, ACT, Australia. karsten.oelkers@anu.edu.au
authors.forename: Karsten
authors.initials: K
authors.lastname: Oelkers
authors.forename: Nicolas
authors.initials: N
authors.lastname: Goffard
authors.forename: Georg F
authors.initials: GF
authors.lastname: Weiller
authors.forename: Peter M
authors.initials: PM
authors.lastname: Gresshoff
authors.forename: Ulrike
authors.initials: U
authors.lastname: Mathesius
authors.forename: Tancred
authors.initials: T
authors.lastname: Frickey
mesh_terms: D000595:Amino Acid Sequence; D019295:Computational Biology / Q000379:methods*; D017124:Conserved Sequence; D046913:Medicago truncatula / Q000737:chemistry; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D010455:Peptides; D010940:Plant Proteins