Complex cell walls from coenocitic seaweeds Codium fragile and C. vermilara containing sulfated arabinogalactans, hydroxyproline-rich glycoprotein epitopes (AGPs/extensins), and b-mannans

MARINA CIANCIA; LUCIANA KASULIN; AGUSTINA DE DIOS; ALBERTO S. CEREZO; JOSÉ M. ESTEVEZ

Kobe, Japón

Simposio; XIX International Seaweed Symposium; 2007

International Seaweed Association

The distribution of cell wall polymers in the coenocitic green algae Codium fragile and C. vermilara is presented. Major quantities of fibrillar b-(1®4)-mannans, comprising ~ 60 % of the total cell wall, and small amounts of sulfated arabinogalactans, around 10 %, were determined by chemical analysis. Besides, they were localized by general histochemical methods and synchrotron radiation mid-infrared spectroscopy coupled to a microscope. b-(1®4)-mannans were distributed in the middle zone of the cell wall in C. fragile, but in two well-defined layers in C. vermilara, whereas sulfate groups of the arabinogalactans were present in both seaweeds in the boundaries of the cell wall. Interestingly, hydroxyproline-rich glycoproteins with O-glycans of the AGP- and arabinoside-types were detected by immunodot-assays in the water soluble extracts, together with the other soluble cell wall polymers and also immunolocalized with monoclonal antibodies in the boundaries of the cell wall. These HRGPs are minor cell wall components. At least two groups of putative AGPs were detected by gel electrophoresis of the water soluble extracts in C. fragile and three in C. vermilara, two of high molecular weights and another of ~20 kDa. Besides, one extensin epitope of ~12 kDa was detected with two different antibodies in C. vermilara cell walls. These bands do not co-localize with the sulfated arabinogalactans. The finding of AGP- and extensin-epitopes in these green seaweeds has significant implications with regard to the conservation of the whole cellular machinery of HRGPs biosynthesis in the plant kingdom.