CONICET | Buscador de Institutos y Recursos Humanos

Cell walls in the coencocytic green seaweed Codium vermilara (Olivi) Delle Chiaje (Bryopsidales, Chlorophyta) are composed by ~32 % w/w of b-(1®4)-D-mannans, ~12 % of sulfated polysaccharides (SP), and small amounts of hydroxyproline-rich glycoproteins-like (HRGPs-L) compounds of the arabinogalactan-proteins (AGPs)- and arabinosides-type (extensins). Similar quantities of mannans and SP were found previously in the related seaweed C. fragile (Suringar) Hariot. Overall both seaweed cell walls comprise ~40-44 % of their dry weights. Within SP group, a variety of polysaccharide structures from pyruvylated arabinogalactan sulfate, pyruvylated galactan sulfate, to pyranosic arabinan sulfate are present in Codium cell walls. In this article, the in situ distribution of the main cell wall polymers in the green seaweed C. vermilara was studied comparing their arrangements with those observed in cell walls from C. fragile. The utricle cell wall in C. vermilara showed by transmission electron microscopy (TEM) a sandwich structure of two fibrillar-like layers of similar width delimiting a middle amorphous-like zone. By immuno- and chemical-imaging, the in situ distribution of b-(1®4)-D-mannans and HRGP-like epitopes was shown to consist in two distinct cell wall layers whereas SP are distributed in the middle area of the wall. The overall cell wall polymer arrangement of the SP, HRGPs-like, and mannans in the utricles of C. vermilara is different from the ubiquitous green algae C. fragile, in spite of both being phylogenetically very close. In addition, a preliminary cell wall model of the utricle moiety is proposed for both seaweeds C. fragile and C. vermilara.