MUCILAGE PROCESSING AND SECRETION IN THE GREEN-ALGA CLOSTERIUM .1. CYTOLOGY AND BIOCHEMISTRY

Placoderm desmids (Conjugales, Chlorophyta) such as Closterium exhibit a gliding locomotory behavior. This results from the forceful extrusi on of an acidic polysaccharide from one pole of the cell causing the c ell to glide in the opposite direction. A biochemical and cytological analysis of gliding behavior was performed. The mucilage is a high mol ecular weight polysaccharide rich in glucuronic acid and fucose. Under normal growth conditions, 3 mu g of mucilage is produced per cell in 30 days. Mucilage production increased 3-4 fold in cells challenged wi th low phosphate or nitrate conditions. A polyclonal antibody was rais ed against the mucilage and used in immunofluorescence studies. These results show that upon contact with another object Closterium aligns i tself parallel to that object by a ''jack-knife'' motion. Subsequently , large amounts of mucilage are released to form elongate tubes enmesh ing the cell with that object. In post-cytokinetic phases of the cell cycle, mucilage is extruded only through the pole of the developing se mi-cell. Chlorotetracyclene-labeling of mucilage-secreting cells shows a correlation between calcium-rich loci on the cell surface and sites of mucilage release.