Study of receptor-like kinase WAK1 from Arabidopsis thaliana
Highlighting and characterization of the interaction of WAK1 extracellular domain with pectin.
The receptor-like kinase WAK1 (Wall-associated kinase 1), a member of the WAK/WAKL family, is involved in cell elongation and defence responses. WAK1 is a transmembrane protein containing an extracellular domain in contact with the cell wall and a cytoplasmic Ser/Thr kinase domain. The activation of WAK1 could be induced by its interaction with the extracellular matrix. The aim of this work was to highlight and to characterize the interaction of the extracellular domain of WAK1 with pectin. A sub-domain of the extracellular domain of WAK1 from Arabidopsis thaliana was cloned and expressed as a soluble peptide in yeast. By using a modified ELISA, purified pectins and pectins extracted from Arabidopsis thaliana
cell walls, we showed, in vitro, that the extracellular domain of WAK1 recognizes specifically homogalacturonans and oligogalacturonides in an "egg box" conformation. We also highlighted that the extracellular domain of WAK1 probably forms multimers independently of the binding to pectin. In silico analyses (HCA, Hydrophobic Cluster Analysis and RBD, Receptor Binding Domain) of the sequence of the extracellular domain made it possible to identify putative interacting domains. Using site-directed mutagenesis within these domains, we determined that residues R67, R91, R166, K101 and K102 were involved in the binding to pectin.
|Date of Award||2006|
|Supervisor||Johan MESSIAEN (Jury), Pierre Van Cutsem (Jury), Françoise Liners (Jury), J. Dommes (Jury) & B. Watillon (Jury)|