Disruption of the Golgi apparatus and secretory mechanism in the desmid, Closterium acerosum, by brefeldin A

The mucilage-secreting desmid, Closterium acerosum, is sensitive to the sec retory inhibiting drug, brefeldin A (BFA). After 5 min of treatment with 5 pg ml(-1) of BFA, the Golgi body displays the following alterations: the nu mber of cisternae decreases from 12-15 to 6-7; peripheries of cisternae fro m the same Golgi body often fuse to yield unique profiles; secretory vesicl es still emerge from the Golgi body; the cisternal stack dissociates to for m irregular masses in the valleys of cytoplasm created by the lobes of the chloroplast. Fluoresbrite bead labelling shows that muciliage production ce ases in cells treated with BFA even after only 5 min of treatment. Immunogo ld labelling using anti-mucilage antibody reveals that mucilage production still occurs in the Golgi body and associated vesicles. Helix pomatia lecti n-gold labelling shows that wall synthesis still occurs in BFA-treated Golg i bodies and wall precursors accumulate in the perforate cis-ternal/vesicul ar masses seen in the TGN region of the Golgi stack.