GOLGI-MEMBRANE DYNAMICS ARE CYTOSKELETON DEPENDENT - A STUDY ON GOLGISTACK MOVEMENT INDUCED BY BREFELDIN-A

Brefeldin A (BFA) induces a major aggregation of the Golgi apparatus ( GA) in root cells followed by a complete, but reversible, vesiculation of the Golgi stacks which form two or more BFA compartments in the cy tosol. This effect is monitored by the immunofluorescence of a Golgi a ntigen stained with a monoclonal antibody JIM 84, and by transmission electron microscopy. Depolymerisation of the microtubule cytoskeleton after oryzalin or colchicine treatment does not disturb the three dime nsional organisation of the GA in control cells and does not affect an y BFA induced Golgi stack movements. After disruption of the actin cyt oskeleton with cytochalasin D many aggregates of Golgi stacks can be o bserved in root cells and these are sensitive to BFA treatment, formin g multiple BFA compartments. N-ethyl-maleimide has no effect on the or ganisation of the GA in control roots but totally inhibits the action of BFA. Thus, it appears that spatial organisation of the GA and the B FA induced Golgi stack movements are actin dependent whilst BFA induce d vesiculation of the GA is a structurally separate event.