title: Restricted access of proteins to mannan polysaccharides in intact plant cell walls.
abstract: How the diverse polysaccharides present in plant cell walls are assembled and interlinked into functional composites is not known in detail. Here, using two novel monoclonal antibodies and a carbohydrate-binding module directed against the mannan group of hemicellulose cell wall polysaccharides, we show that molecular recognition of mannan polysaccharides present in intact cell walls is severely restricted. In secondary cell walls, mannan esterification can prevent probe recognition of epitopes/ligands, and detection of mannans in primary cell walls can be effectively blocked by the presence of pectic homogalacturonan. Masking by pectic homogalacturonan is shown to be a widespread phenomenon in parenchyma systems, and masked mannan was found to be a feature of cell wall regions at pit fields. Direct fluorescence imaging using a mannan-specific carbohydrate-binding module and sequential enzyme treatments with an endo-β-mannanase confirmed the presence of cryptic epitopes and that the masking of primary cell wall mannan by pectin is a potential mechanism for controlling cell wall micro-environments.
authors.affiliation: Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Marcus
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Blake
authors.forename: Thomas A S
authors.initials: TA
authors.lastname: Benians
authors.forename: Kieran J D
authors.initials: KJ
authors.lastname: Lee
authors.forename: Callum
authors.initials: C
authors.lastname: Poyser
authors.forename: Lloyd
authors.initials: L
authors.lastname: Donaldson
authors.forename: Olivier
authors.initials: O
authors.lastname: Leroux
authors.forename: Artur
authors.initials: A
authors.lastname: Rogowski
authors.forename: Henriette L
authors.initials: HL
authors.lastname: Petersen
authors.forename: Alisdair
authors.initials: A
authors.lastname: Boraston
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Gilbert
authors.forename: William G T
authors.initials: WG
authors.lastname: Willats
authors.forename: J Paul
authors.initials: JP
authors.lastname: Knox
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism*; D004951:Esterification; D019085:Fluorescent Antibody Technique, Direct; D019684:Magnoliopsida; D008297:Male; D008351:Mannans / Q000378:metabolism*; D010368:Pectins / Q000378:metabolism; D028223:Pinus; D051381:Rats; D017208:Rats, Wistar; D044902:beta-Mannosidase / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D008351:Mannans; D010368:Pectins; D044902:beta-Mannosidase; C003181:polygalacturonic acid