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Fig. 5. Diagram summarizing the BFA and latrunculin-B (LAT) effects on AtPIN- and JIM84 labelled compartments in maize root cells. (1) In control cells, PIN- and JIM84-labelled compartments are dispersed throughout the cytoplasm; strong AtPIN polar staining of the basal membrane. G, Golgi stacks labelled with JIM84. E, endosome-like structures labelled with AtPIN. (2) Under latrunculin-B treatment, both populations tend to mix and form small aggregates, suggesting a similar actin dependency for their distribution. However, AtPIN polar staining is still observed, suggesting that actin is not involved in the maintenance of cell polarity. (3) Treatment with brefeldin A results in the formation of typical BFA compartments, trapping both Golgi stacks and endosome-like membranes. These observations are the sum of two distinct dynamic events: first, the gathering of compartments in cytoplasmic subdomains, a phenomenom that is actin dependent and, second, a vesicularisation of compartments that is actin independent - as shown for Golgi membranes (Satiat-Jeunemaitre et al., 1992). (4) In latrunculin pre-treated cells, BFA still targets the BFA-sensitive compartments in an actin-independent process because the polar labelling of the membrane is lost and the small, induced latrunculin aggregates increase significantly in size, probably due to an actin-independent deconstruction process as described in (3).
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