EXTRACELLULAR-MATRIX ASSEMBLY IN DIATOMS - (BACILLARIOPHYCEAE) - III - ORGANIZATION OF FUCOGLUCURONOGALACTANS WITHIN THE ADHESIVE STALKS OFACHNANTHES-LONGIPES

Achnanthes longipes is a marine, biofouling diatom that adheres to sur faces via adhesive polymers extruded during motility or organized into structures called stalks that contain three distinct regions: the pad , shaft, and collar. Four monoclonal antibodies (AL.C1-AL.C4) and anti bodies from two uncloned hybridomas (AL.E1 and AL.E2) were raised agai nst the extracellular adhesives of A. longipes. Antibodies were screen ed against a hot-water-insoluble/ hot-bicarbonate-soluble-fraction. Th e hot-water-insoluble/hot-bicarbonate-soluble fraction was fractionate d to yield polymers in three size ranges: F-1, greater than or equal t o 20,000,000 M-r; F-2, congruent to 100,000 M-r; and F-3, <10,000 M-r relative to dextran standards. The congruent to 100,000-M-r fraction c onsisted of highly sulfated (approximately 11%) fucoglucuronogalactans (FGGs) and low-sulfate (approximately 2%) FGGs, whereas F-1 was compo sed of O-linked FGG (F-2)-polypeptide (F-3) complexes. AL.C1, AL.C2, A L.C4, AL.E1, and AL.E2 recognized carbohydrate complementary regions o n FGGs, with antigenicity dependent on fucosyl-containing side chains. AL.C3 was unique in that it had a lower affinity for FGGs and did not label any portion of the shaft. Enzyme-linked immunosorbent assay and immunocytochemistry indicated that low-sulfate FGGs are expelled from pores surrounding the raphe terminus, creating the cylindrical outer layers of the shaft, and that highly sulfated FGGs are extruded from t he raphe, forming the central core. Antibody-labeling patterns and oth er evidence indicated that the shaft central-core region is related to material exuded from the raphe during cell motility.