title: Egg box conformation of oligogalacturonides: the time-dependent stabilization of the elicitor-active conformation increases its biological activity.
abstract: Circular dichroism spectrometry was used on oligogalacturonides (OGAs) and showed the existence of a calcium/sodium-induced conformational state that is intermediate between single-isolated chains and calcium-associated multimer chains. This conformation is interpreted as being egg box dimers. Using the 2F4 monoclonal antibody that specifically binds such an egg box dimer conformation of pectin, the stability of OGA dimers was investigated over a period of 24 hours. The extent to which egg box dimers were recognized by the antibody was dependent on the temperature and duration of preincubation of the OGA. This suggests a "maturation" process of the egg-box structure that consists in a progressive increase in the length of the junction sequences between two chains that slide along each other in order to form a maximum number of calcium bridges and dimer ends. The maturation of egg boxes induced both a significant increase in their binding to wall-associated kinase 1 (WAK1) and an increased extracellular alkalinization when applied to Arabidopsis thaliana cell suspensions. The chemical modification of the reducing end of the OGAs largely diminished their elicitating activity but did not hinder either dimerization or binding of these end-reduced egg boxes to WAK1. We conclude that there are at least two different perception systems for egg box dimers. One binds egg box junctions and the other binds egg box ends. The relevance of these results is discussed in terms of pectic signal perception and plant-pathogen interaction.
authors.affiliation: Unité de Recherche en Biologie Cellulaire Végétale, Facultés Universitaires Notre-Dame de Paix, Namur B-5000, Belgium.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Cabrera
authors.forename: Aurelien
authors.initials: A
authors.lastname: Boland
authors.forename: Johan
authors.initials: J
authors.lastname: Messiaen
authors.forename: Pierre
authors.initials: P
authors.lastname: Cambier
authors.forename: Pierre
authors.initials: P
authors.lastname: Van Cutsem
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002236:Carbohydrate Conformation; D019281:Dimerization; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism; D010368:Pectins / Q000737:chemistry* / Q000378:metabolism; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D009844:Oligosaccharides; C412763:oligogalacturonic acid; D010368:Pectins; D011494:Protein Kinases; C101093:WAK1 protein, Arabidopsis; D002118:Calcium