title: Xylans Provide the Structural Driving Force for Mucilage Adhesion to the Arabidopsis Seed Coat.
abstract: Arabidopsis (Arabidopsis thaliana) seed coat epidermal cells produce large amounts of mucilage that is released upon imbibition. This mucilage is structured into two domains: an outer diffuse layer that can be easily removed by agitation and an inner layer that remains attached to the outer seed coat. Both layers are composed primarily of pectic rhamnogalacturonan I (RG-I), the inner layer also containing rays of cellulose that extend from the top of each columella. Perturbation in cellulosic ray formation has systematically been associated with a redistribution of pectic mucilage from the inner to the outer layer, in agreement with cellulose-pectin interactions, the nature of which remained unknown. Here, by analyzing the outer layer composition of a series of mutant alleles, a tight proportionality of xylose, galacturonic acid, and rhamnose was evidenced, except for mucilage modified5-1 (mum5-1; a mutant showing a redistribution of mucilage pectin from the inner adherent layer to the outer soluble one), for which the rhamnose-xylose ratio was increased drastically. Biochemical and in vitro binding assay data demonstrated that xylan chains are attached to RG-I chains and mediate the adsorption of mucilage to cellulose microfibrils. mum5-1 mucilage exhibited very weak adsorption to cellulose. MUM5 was identified as a putative xylosyl transferase recently characterized as MUCI21. Together, these findings suggest that the binding affinity of xylose ramifications on RG-I to a cellulose scaffold is one of the factors involved in the formation of the adherent mucilage layer.
authors.affiliation: INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.) marie-christine.ralet@nantes.inra.fr helen.north@versailles.inra.fr.
authors.forename: Marie-Christine
authors.identifier: 0000-0002-0292-5272
authors.initials: MC
authors.lastname: Ralet
authors.affiliation: INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.).
authors.forename: Marie-Jeanne
authors.initials: MJ
authors.lastname: Crépeau
authors.affiliation: INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.).
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Vigouroux
authors.affiliation: INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.).
authors.forename: Joseph
authors.identifier: 0000-0002-4624-0363
authors.initials: J
authors.lastname: Tran
authors.affiliation: INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.).
authors.forename: Adeline
authors.initials: A
authors.lastname: Berger
authors.affiliation: INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.).
authors.forename: Christine
authors.initials: C
authors.lastname: Sallé
authors.affiliation: INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.).
authors.forename: Fabienne
authors.identifier: 0000-0001-6810-2853
authors.initials: F
authors.lastname: Granier
authors.affiliation: INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.).
authors.forename: Lucy
authors.initials: L
authors.lastname: Botran
authors.affiliation: INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.) marie-christine.ralet@nantes.inra.fr helen.north@versailles.inra.fr.
authors.forename: Helen M
authors.identifier: 0000-0002-5749-2603
authors.initials: HM
authors.lastname: North
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D016000:Cluster Analysis; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008040:Genetic Linkage; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D006603:Hexuronic Acids / Q000378:metabolism; D009154:Mutation; D010368:Pectins / Q000737:chemistry / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry; D062087:Plant Mucilage / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D012210:Rhamnose / Q000378:metabolism; D012639:Seeds / Q000201:enzymology / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013194:Staining and Labeling; D014990:Xylans / Q000737:chemistry / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D006603:Hexuronic Acids; D010936:Plant Extracts; D062087:Plant Mucilage; D014990:Xylans; C042491:rhamnogalacturonan I; C007819:galacturonic acid; D010368:Pectins; D002482:Cellulose; D014994:Xylose; C568259:CESA5 protein, Arabidopsis; D005964:Glucosyltransferases; D012210:Rhamnose