Structural features of the cell wall components from Codium fragile and C. vermilara (Bryopsidales, Chlorophyta)

. CIANCIA, ESTEVEZ J.M., AND A. S. CEREZO

Kobe, Japón

Simposio; XIX International Seaweed Symposium; 2007

Internation Seaweed Asociation

Cell walls in the green seaweeds Codium fragile (Suringar) Hariot and Codium vermilara (Olivi) Delle Chiaje are composed by ~60 % of b-(1®4)-mannans and ~10 % of sulfated arabinogalactans (SAGs). b-(1®4)-mannans that comprise highly regular and non-substituted polysaccharide backbones could be involve in the structural support of the cell walls, and functionally replaces cellulose as the main plant cell wall structural polymer. Chemical imaging by synchrotron radiation Fourier transform infrared micro-spectroscopy and by immunolocalization revealed large differences in the distribution of b-(1®4)-mannans and in the sulfate groups of the arabinogalactans between the utricules cell walls from C. fragile compared with those in C. vermilara. Surprisingly, hydroxyproline-rich glycoproteins (HRGPs) with O-glycans of the arabinogalactan-proteins (AGPs)- and arabinosides-types (extensins) were also detected and immunolocalized in the boundaries of the cell wall, especially in the utricule apical zone. Accordingly, 20-40 % of Pro units were hydroxylated as 4-hydroxyproline. Based on the SDS-PAGE immunoblots few groups of AGPs and extensins-epitopes with different Mrs were detected both in C. fragile and C. vermilara cell wall-derived fractions. Although these HRGPs seem to partially co-localize with the SAGs in the cell walls, they do not co-migrate in the SDS-PAGE profiles, indicating that they are different cell wall macromolecules. The global cell wall polymer arrangement and extractability of the SAGs, HRGPs, and b-mannans is quite different in both species, in spite of being phylogenetically very close. This work is the first direct evidence that shows HRGPs of AGP- and extensin-type can be present in a seaweed cell wall and it has significant implications with regard to the conservation of the whole cellular machinery of HRGPs biosynthesis in the plant kingdom.