Glycobiology Advance Access originally published online on October 2, 2008
Glycobiology 2009 19(3):212-228; doi:10.1093/glycob/cwn101
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Chemical and in situ characterization of macromolecular components of the cell walls from the green seaweed Codium fragile
4 Carnegie Institution of Washington, Plant Biology, Stanford University, Stanford, CA 94305, USA
5 Cátedra de Química de Biomoléculas, Departamento de Biología Aplicada y Alimentos (CIHIDECAR-CONICET), Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina
6 Department of Biochemistry, University of Cambridge, Building O, Downing site, Cambridge, CB2 1QW, UK
1 To whom correspondence should be addressed: Tel/Fax: +54-11-4524-8088; e-mail: ciancia{at}agro.uba.ar
Received on June 11, 2008; revised on September 15, 2008; accepted on September 29, 2008
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 of 31% (w/w) of linear (1
4)-β-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 β-D-mannans and pAGS are placed in the middle part of the cell wall, whereas HRGP epitopes (arabinogalactan proteins (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 β-L-arabinopyranose units and at C-4 and/or C-6 of the 3-linked β-D-galactopyranose residues. In addition, high levels of ketals of pyruvic acid were found mainly at 3,4- of some terminal β-D-Galp units forming a five-membered ring. Ramification was found at some C-6 of the 3-linked β-D-Galp units. In agreement with the immunolabeled AGP epitopes, a nonsulfated branched furanosidic arabinan with 5-linked 
-L-Araf, 3,5-linked -L-Araf, and terminal -L-Araf units and a nonsulfated galactan structure composed of 3-(3,6)-linked β-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.
Key words: β-mannan / Codium cell wall / green seaweed / HRGP epitope / pyruvylated arabinogalactan sulfate
2 Present address: Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria – Pabellón 2, 1428 Buenos Aires, Argentina.
3 Research member of the National Research Council of Argentina (CONICET).