Characterization of Laurencia arbuscula spore mucilage and cell walls with stains and FITC-labelled lectins

In most red algae, spores are liberated without a cell wall, within a sheath of mucilage that is responsible for its primary attachment. Utilizing fluorescent-labelled lectins, we identified carbohydrate residues and their location in the mucilage and cell walls of spores of Laurencia arbuscula. Cell wall formation and mucilage composition were studied with Calcofluor, Toluidine Blue (AT-O), Alcian Blue (AB) and periodic acid-Schiff (PAS). In the mucilage, we identified α-d-mannose, α-d-glucose, N-acetyl-glucosamine, N-acetyl-galactosamine and β-d-galactose. All sugar residues were found in the cell wall, in the spore body rather than in the rhizoid, which suggests that the residues may be related to initial substrate adhesion. A cell wall is produced soon after the spore's attachment, beginning with a deposition of cellulose around the spore, as indicated by Calcofluor. A polarization of the cell wall triggers the process of germination. The cell-wall matrix was positive to AB and metachromatic to AT-O, indicating acidic polysaccharides, while neutral polysaccharides were positive to PAS.