title: Heterogeneity of silica and glycan-epitope distribution in epidermal idioblast cell walls in Adiantum raddianum laminae.
abstract: Laminae of Adiantum raddianum Presl., a fern belonging to the family Pteridaceae, are characterised by the presence of epidermal fibre-like cells under the vascular bundles. These cells were thought to contain silica bodies, but their thickened walls leave no space for intracellular silica suggesting it may actually be deposited within their walls. Using advanced electron microscopy in conjunction with energy dispersive X-ray microanalysis we showed the presence of silica in the cell walls of the fibre-like idioblasts. However, it was specifically localised to the outer layers of the periclinal wall facing the leaf surface, with the thick secondary wall being devoid of silica. Immunocytochemical experiments were performed to ascertain the respective localisation of silica deposition and glycan polymers. Epitopes characteristic for pectic homogalacturonan and the hemicelluloses xyloglucan and mannan were detected in most epidermal walls, including the silica-rich cell wall layers. The monoclonal antibody, LM6, raised against pectic arabinan, labelled the silica-rich primary wall of the epidermal fibre-like cells and the guard cell walls, which were also shown to contain silica. We hypothesise that the silicified outer wall layers of the epidermal fibre-like cells support the lamina during cell expansion prior to secondary wall formation. This implies that silicification does not impede cell elongation. Although our results suggest that pectic arabinan may be implicated in silica deposition, further detailed analyses are needed to confirm this. The combinatorial approach presented here, which allows correlative screening and in situ localisation of silicon and cell wall polysaccharide distribution, shows great potential for future studies.
authors: Botany and Plant Science and Ryan Institute for Environmental, Marine and Energy Research, School of Natural Sciences, National University of Ireland, Galway, University Road, Galway, Ireland.
authors: Olivier
authors: O
authors: Leroux
authors: Frederic
authors: F
authors: Leroux
authors: Alexandra Antunes
authors: AA
authors: Mastroberti
authors: Fernanda
authors: F
authors: Santos-Silva
authors: Denis
authors: D
authors: Van Loo
authors: Agnieszka
authors: A
authors: Bagniewska-Zadworna
authors: Luc
authors: L
authors: Van Hoorebeke
authors: Sara
authors: S
authors: Bals
authors: Zoë A
authors: ZA
authors: Popper
authors: Jorge Ernesto
authors: JE
authors: de Araujo Mariath
mesh_terms: D035681:Adiantum / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D000911:Antibodies, Monoclonal / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism* / Q000648:ultrastructure; D000939:Epitopes / Q000276:immunology*; D019441:Plant Epidermis / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D018515:Plant Leaves / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D011134:Polysaccharides / Q000276:immunology*; D012825:Silicon / Q000378:metabolism; D012822:Silicon Dioxide / Q000276:immunology*; D014057:Tomography, X-Ray Computed
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D011134:Polysaccharides; D012822:Silicon Dioxide; D012825:Silicon