Journal Article

Wall-associated Kinase WAK1 Interacts with Cell Wall Pectins in a Calcium-induced Conformation

Annabelle Decreux and Johan Messiaen

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 2, pages 268-278
Published in print February 2005 | ISSN: 0032-0781
Published online February 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci026
Wall-associated Kinase WAK1 Interacts with Cell Wall Pectins in a Calcium-induced Conformation

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Wall-associated kinase 1 (WAK1) is a transmembrane protein containing a cytoplasmic Ser/Thr kinase domain and an extracellular domain in contact with the pectin fraction of the plant cell walls. In order to characterize further the interaction of WAK1 with pectin, a 564 bp DNA sequence corresponding to amino acids 67–254 of the extracellular domain of WAK1 from Arabidopsis thaliana was cloned and expressed as a soluble recombinant peptide in yeast. Using enzyme-linked immunosorbent assays (ELISA), we show that peptide WAK67–254 binds to polygalacturonic acid (PGA), oligogalacturonides, pectins extracted from A. thaliana cell walls and to structurally related alginates. Our results suggest that both ionic and steric interactions are required to match the relatively linear pectin backbone. Binding of WAK67–254 to PGA, oligogalacturonides and alginates occurred only in the presence of calcium and in ionic conditions promoting the formation of calcium bridges between oligo-and polymers (also known as ‘egg-boxes’). The conditions inhibiting the formation of calcium bridges (EDTA treatment, calcium substitution, high NaCl concentrations, depolymerization and methylesterification of pectins) also inhibited the binding of WAK67–254 to calcium-induced egg-boxes. The relevance of this non-covalent link between WAK67–254 and cell wall pectins is discussed in terms of cell elongation, cell differentiation and host–pathogen interactions.

Keywords: Arabidopsis thaliana; Cell wall; Egg-box; Pectin; Receptor kinase; Wall-associated kinase; DM, degree of methylesterification; DP, degree of polymerization; ELISA, enzyme-linked immunosorbent assay; GRP, glycine-rich protein; GulA, guluronic acid; HRGP, hydroxyproline-rich glycoprotein; INA, 2,6-dichloroisonicotinic acid; ManA, mannuronic acid; PGA, polygalacturonic acid; PMSF, phenylmethylsulfonyl fluoride; TMB, 3,3′,5,5′-tetramethylbenzidine; WAK, wall-associated kinase; WAKL, WAK-like.

Journal Article.  8915 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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