Effects of brefeldin A on the structure and function of the Golgi apparatus in the marine red alga Erythrocladia subintegra Rosenvinge IOANNES TSEKOS, NICOLAS OROLOGAS and ARETI DIMOPOULOU Department of Botany, School of Biology, Aristotle University of Thessaloniki, 54124, Thessaloniki, Macedonia, Greece Abstract The fungal macrocyclic lactone brefeldin A (BFA) was used to investigate the functional organization and trafficking through the Golgi apparatus of the Erythrocladia subintegra thallus cells. Treatment with increasing concentration and incubation time leads in a distortion of Golgi cisternae which gradually curve until they become round and the Trans-Golgi-Net (TGN) became replaced by the BFA compartment. Examination of the plasma membrane of BFA-treated cells after freeze-fracture revealed a decreased number of linear terminal complexes (TCs). After a 24-hour-incubation in BFA, significant structural and functional changes in the Golgi apparatus are evident. Dictyosomes are no longer visible in their typical form and having almost entirely been replaced by vesicles encountered in the BFA area. TCs and "tetrads" appeared in the plasma membrane. Thus, it is obvious that on the one hand no zymogenic particles (globules) responsible for cellulose synthesis (zymogen precursor of the TC) exist, and on the other hand no synthesis of amorphous polysaccharidic matrix takes place due to the absence of "tetrads". Both the zymogenic particles and the tetrads, which initially were formed in the Golgi complex, are transported to the plasma membrane via Golgi vesicles.   < back .