Chemical and in situ characterization of macromolecular components of the complex cell walls from the coenocitic green alga Codium fragile

JOSÉ M. ESTEVEZ, LUCIANA KASULIN, PAULA V. FERNÁNDEZ, PAUL DUPREE, MARINA CIANCIA

GLYCOBIOLOGY

OXFORD UNIV PRESS INC

Año: 2009 vol. 19 p. 212 - 228

0959-6658

A comprehensive analysis of the carbohydrate-containing macromolecules from the coencocytic green seaweed Codium fragile and their arrangement in the cell wall was carried out. Cell walls in this seaweed are highly complex structures composed by 31 % (w/w) of linear (1®4)-b-d-mannans, 9 % (w/w) of pyruvylated arabinogalactan sulfates (pAGS), and low amounts of hydroxyproline rich-glycoprotein epitopes (HRGP). In situ chemical imaging by synchrotron radiation Fourier transform infrared (SR-FTIR) microspectroscopy and by immunolabeling using antibodies against specific cell wall carbohydrate-epitopes revealed that b-d-mannans and pAGS are placed in the middle part of the cell wall, whereas HRGP-epitopes (AGPs and extensins) are located on the wall boundaries, especially in the utricle apical zone. pAGS are sulfated at C-2 and/or C-4 of the 3-linked b-l-arabinopyranose units and at C-4 and/or C-6 of the 3-linked b-d-galactopyranose residues. In addition, high levels of ketals of pyruvic acid were found mainly at 3,4- of some terminal b-d-Galp units forming a five-membered ring. Ramification was found at some C-6 of the 3-linked b-d-Galp units. In agreement with the immunolabeled AGP-epitopes, a non-sulfated branched furanosidic arabinan with 5-linked a-l-Araf, 3,5-linked a-l-Araf, and terminal a-l-Araf units and a non-sulfated galactan structure composed by 3-(3,6)-linked b-d-Galp residues, both typical of type-II AG glycans were found, suggesting that AGP structures are present at low levels in the cell walls of this seaweed. Based on this study, it is starting to emerge that Codium has developed unique cell wall architecture, when compared, not only with that of vascular plants, but also with other related green seaweeds and algae.