title: Cell wall O-glycoproteins and N-glycoproteins: aspects of biosynthesis and function.
abstract: Cell wall O-glycoproteins and N-glycoproteins are two types of glycomolecules whose glycans are structurally complex. They are both assembled and modified within the endomembrane system, i.e., the endoplasmic reticulum (ER) and the Golgi apparatus, before their transport to their final locations within or outside the cell. In contrast to extensins (EXTs), the O-glycan chains of arabinogalactan proteins (AGPs) are highly heterogeneous consisting mostly of (i) a short oligo-arabinoside chain of three to four residues, and (ii) a larger β-1,3-linked galactan backbone with β-1,6-linked side chains containing galactose, arabinose and, often, fucose, rhamnose, or glucuronic acid. The fine structure of arabinogalactan chains varies between, and within plant species, and is important for the functional activities of the glycoproteins. With regards to N-glycans, ER-synthesizing events are highly conserved in all eukaryotes studied so far since they are essential for efficient protein folding. In contrast, evolutionary adaptation of N-glycan processing in the Golgi apparatus has given rise to a variety of organism-specific complex structures. Therefore, plant complex-type N-glycans contain specific glyco-epitopes such as core β,2-xylose, core α1,3-fucose residues, and Lewis(a) substitutions on the terminal position of the antenna. Like O-glycans, N-glycans of proteins are essential for their stability and function. Mutants affected in the glycan metabolic pathways have provided valuable information on the role of N-/O-glycoproteins in the control of growth, morphogenesis and adaptation to biotic and abiotic stresses. With regards to O-glycoproteins, only EXTs and AGPs are considered herein. The biosynthesis of these glycoproteins and functional aspects are presented and discussed in this review.
authors.affiliation: Laboratoire de Glycobiologie et Matrice Extracellulaire Végétale, UPRES EA 4358, Institut de Recherche et d'Innovation Biomédicale, Grand Réseau de Recherche-Végétal, Agronomie, Sol, Innovation, UFR des Sciences et Techniques, Normandie Université - Université de Rouen Mont-Saint-Aignan, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Nguema-Ona
authors.affiliation: Laboratoire de Glycobiologie et Matrice Extracellulaire Végétale, UPRES EA 4358, Institut de Recherche et d'Innovation Biomédicale, Grand Réseau de Recherche-Végétal, Agronomie, Sol, Innovation, UFR des Sciences et Techniques, Normandie Université - Université de Rouen Mont-Saint-Aignan, France.
authors.forename: Maïté
authors.initials: M
authors.lastname: Vicré-Gibouin
authors.affiliation: Laboratoire de Glycobiologie et Matrice Extracellulaire Végétale, UPRES EA 4358, Institut de Recherche et d'Innovation Biomédicale, Grand Réseau de Recherche-Végétal, Agronomie, Sol, Innovation, UFR des Sciences et Techniques, Normandie Université - Université de Rouen Mont-Saint-Aignan, France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Gotté
authors.affiliation: Laboratoire de Glycobiologie et Matrice Extracellulaire Végétale, UPRES EA 4358, Institut de Recherche et d'Innovation Biomédicale, Grand Réseau de Recherche-Végétal, Agronomie, Sol, Innovation, UFR des Sciences et Techniques, Normandie Université - Université de Rouen Mont-Saint-Aignan, France.
authors.forename: Barbara
authors.initials: B
authors.lastname: Plancot
authors.affiliation: Laboratoire de Glycobiologie et Matrice Extracellulaire Végétale, UPRES EA 4358, Institut de Recherche et d'Innovation Biomédicale, Grand Réseau de Recherche-Végétal, Agronomie, Sol, Innovation, UFR des Sciences et Techniques, Normandie Université - Université de Rouen Mont-Saint-Aignan, France.
authors.forename: Patrice
authors.initials: P
authors.lastname: Lerouge
authors.affiliation: Laboratoire de Glycobiologie et Matrice Extracellulaire Végétale, UPRES EA 4358, Institut de Recherche et d'Innovation Biomédicale, Grand Réseau de Recherche-Végétal, Agronomie, Sol, Innovation, UFR des Sciences et Techniques, Normandie Université - Université de Rouen Mont-Saint-Aignan, France ; Institut Universitaire de France Paris, France.
authors.forename: Muriel
authors.initials: M
authors.lastname: Bardor
authors.affiliation: Laboratoire de Glycobiologie et Matrice Extracellulaire Végétale, UPRES EA 4358, Institut de Recherche et d'Innovation Biomédicale, Grand Réseau de Recherche-Végétal, Agronomie, Sol, Innovation, UFR des Sciences et Techniques, Normandie Université - Université de Rouen Mont-Saint-Aignan, France ; Plate-Forme de Recherche en Imagerie Cellulaire de Haute-Normandie, Institut de Recherche et d'Innovation Biomédicale, Faculté des Sciences et Techniques, Normandie Université Mont-Saint-Aignan, France.
authors.forename: Azeddine
authors.initials: A
authors.lastname: Driouich
keywords: Golgi apparatus; arabinogalactan protein; cell wall; endoplasmic reticulum; extensin; glycan; glycosyltransferase; plants