Alginates along the filament of the brown alga Ectocarpus help cells cope with stress

• Published in: Scientific reports Vol. 9; no. 1; pp. 12956 - 17
• Main Authors: Rabillé, Hervé, Torode, Thomas A., Tesson, Benoit, Le Bail, Aude, Billoud, Bernard, Rolland, Elodie, Le Panse, Sophie, Jam, Murielle, Charrier, Bénédicte
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10-09-2019; Nature Publishing Group
• Subjects: 13; 14/1; 14/19; 14/3; 631/80; 704/829; Algae; Alginates - metabolism; Alginic acid; Atomic force microscopy; Calcium; Cell differentiation; Cell Wall - chemistry; Cell Wall - metabolism; Cell walls; Cellular Biology; Cellulose; Cytoskeleton - physiology; Development Biology; Ectocarpus; Gels; Hexuronic Acids - metabolism; Humanities and Social Sciences; Hydrogels; Laboratories; Life Sciences; Mannuronic acid; Mechanical properties; Microscopy; Monoclonal antibodies; Morphogenesis; multidisciplinary; Phaeophyceae - physiology; Polysaccharides; Roles; Science; Science (multidisciplinary); Stress, Mechanical; Subcellular Processes; Surface Properties; Tensile Strength; Tensile stress; alginate; stress; immunolocalization; Ectocarpus; brown alga; cell wall; biophysics
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-49427-z

Ectocarpus
is a filamentous brown alga, which cell wall is composed mainly of alginates and fucans (80%), two non-crystalline polysaccharide classes. Alginates are linear chains of epimers of 1,4-linked uronic acids, β-D-mannuronic acid (M) and α-L-guluronic acid (G). Previous physico-chemical studies showed that G-rich alginate gels are stiffer than M-rich alginate gels when prepared
in vitro
with calcium. In order to assess the possible role of alginates in
Ectocarpus
, we first immunolocalised M-rich or G-rich alginates using specific monoclonal antibodies along the filament. As a second step, we calculated the tensile stress experienced by the cell wall along the filament, and varied it with hypertonic or hypotonic solutions. As a third step, we measured the stiffness of the cell along the filament, using cell deformation measurements and atomic force microscopy. Overlapping of the three sets of data allowed to show that alginates co-localise with the stiffest and most stressed areas of the filament, namely the dome of the apical cell and the shanks of the central round cells. In addition, no major distinction between M-rich and G-rich alginate spatial patterns could be observed. Altogether, these results support that both M-rich and G-rich alginates play similar roles in stiffening the cell wall where the tensile stress is high and exposes cells to bursting, and that these roles are independent from cell growth and differentiation.