Histochemistry of Spore Mucilage and Inhibition of Spore Adhesion in Champia parvula, A Marine Alga

Abstract

Spores of the marine red alga, Champja parvula, attached initially to plastic or glass cover slips by extracellular mucilage. Adhesive rhizoids emerged from germinating spores, provided a further basis of attachment and rhizoidal division formed the holdfast. Mucilage of holdfasts and attached spores stained for sulfated and carboxylated polysaccharides. Rhizoids and holdfast cells but not mucilage stained for protein. Removal of holdfasts with HCI revealed protein anchors in holdfast cell remnants. Spores detached when incubated in the following enzymes: β-galactosidase, protease, cellulase, α-amylase, hyaluronidase, sulfatase, and mannosidase. The FITC- lectins Con A, LCA, PNA, SBA, and the lectin from Vicia villosa, were used to probe the mucilage of attached spores to detect the sugar haptens α-D-mannose, α-D-glucose, β-D-galactose, and N-acetylgalactosamine, whereas probing with WGA, Phytoloacca americana mitogen (PWM), and UEA did not detect N-acetylglucosamine or α-L-fucose. Adhesion of newly released, floating tetraspores was inhibited by cycloheximide, tunicamycin, sodium molybdate, and Con A. These results indicate that proteins, glycoproteins, sulfated polysaccharides, and α-D- mannose or α-D-glucose, respectively, are all necessary for adhesion. Tetraspores remained attached in the presence of the inhibitors, suggesting that they do not maintain adhesion via synthesis of proteins, glycoproteins, or sulfated polysaccharides. Tetraspores killed with H2SO4 or sodium azide did not attach; therefore tetraspores must be alive to attach. Tetraspores did not detach when killed with sodium azide or DIH2O. Death did not result in detachment unless the mucilage was damaged by H2SO4. Glycoproteins with α-D-mannose and or α-D-glucose sugar moieties may detect the substrate upon contact and convey messages to the cytoplasm which translates spatial information about adhesion into germination and rhizoid production. The sugar moieties may recognize cellular surfaces of hosts on which C. parvula is epiphytic. These glycoproteins are probably embedded in a matrix of adhesive, sulfated polysaccharides which may be cross-linked with proteins, suggesting that several classes of molecules may interact to facilitate adhesion.