Abstract

Plant type II arabinogalactan (AG) polysaccharides are attached to core-proteins of arabinogalactan-proteins (AGPs) usually at hydroxyproline residues. Due to their complex branching structures and tissue-, cell- or perhaps protein-specificities, type II A Gs are overwhelmingly diverse and heterogeneous. To gain insights into the synthesis and function of plant AGPs, it would be useful to have mutants altered in their carbohydrate moieties of cell wall constituents. Here, enzymes able to release oligosaccharides specifically from AGs, high energy Matrix Assisted Laser Desorption Ionisation (MALDI)-Collision Induced Dissociation (CID) mass spectrometry (MS) and Polysaccharide Analysis by Carbohydrate gel Electrophoresis (PACE) were employed to study the carbohydrate component of Arabidopsis leaf AGPs. The structures of AG-specific enzyme digestion products were analysed by PACE and MS. To our knowledge this is the first time a partial structure for the carbohydrate component of Arabidopsis AGPs is proposed. In addition, AG oligosaccharides from leaves of the Fuc-deficient mur1 mutant were identified and their structures were compared with those isolated from wild-type plants. We show that in mur1 mutant, AGPs are lacking Fuc modifications, demonstrating that Arabidopsis mutants in AGP structure can be identified and characterised.