ISOLATION AND REGENERATION OF PROTOPLASTS FROM HEALTHY AND VIRUS-INFECTED GAMETOPHYTES OF ECTOCARPUS-SILICULOSUS (PHAEOPHYCEAE)

Up to 1.3 X 10(8) protoplasts per g fresh weight were obtained from healthy gametophytes of Ectocarpus with an enzyme solution containing cellulase and a crude extract of abalone acetone powder. Virus-infected gametophytes gave lower yields of protoplasts than the healthy material. Culture conditions and algal growth influenced protoplast yields: old cultures and slowly growing parts, such as cells of the main axis, produced few protoplasts. In contrast, cell walls of meristematic regions were easily digested. Protoplasts regenerated cell walls within a few days, and after 6-7 weeks the resulting mature plants were identical with their donor specimens. Regenerates from the normal gametophytes developed mature gametangia, whereas those from the virus-infected gametophytes produced pathological symptoms upon maturity. Gametangia or infection symptoms frequently occurred very early and before the regenerates established new filaments (neoteny). In contrast to zoids, protoplasts were not infected by freshly released virus particles. The results show that the viral genome is latently present in somatic cells of infected gametophytes, where it is duplicated during mitosis and eventually expressed upon maturity of the host.