85 Regeneration of protoplasts from disintegrated cells of the multi‐cellular marine green alga microdictyon umbilicatum

Abstract

Protoplast regeneration from extruded cytoplasm of the multi‐cellular marine green alga Microdictyon umbilicatum (Velley) Zanardini (Cladophorales, Anadyomenaceae) was investigated. The early process of protoplast formation is comprised of two steps: agglutination of cell organelles into protoplasmic masses followed by generation of a temporary enclosing envelope around them. Agglutination of cell organelles was mediated by a lectin‐carbohydrate complementary system. Three sugars, D‐galactosamine, D‐glucosamine, and a‐D‐mannose, inhibited the agglutination process, and three complementary lectins for the above sugars, peanut agglutinin, Ricinus communis agglutinin and concanavalin A, bound to the surfaces of chloroplasts. Agglutination assay using human erythrocytes showed the presence of lectins specific for the above sugars in the algal vacuolar sap. The lectin has been purified by the use of D‐mannose agarose affinity column. Its Molecular weight was shown to be 36,000 dalton by SDS‐PAGE gel electrophoresis. When the basic regeneration process was accomplished, the cells chose one of two developmental strategies; about 70% of one‐celled protoplasts transformed into reproductive cells within two weeks after wounding, while others began cell division and grew into typical Microdictyon plants. Quadriflagellate swarmers were liberated from the reproductive cells, and they germinated into mature plants