Plant cells show an acquired insensitivity to Brefeldin A

The parameters of Brefeldin A (BFA) action in plant cells have been further investigated in maize root tips. Incubation of maize root tip cells with 1 00 mu g ml(-1) BFA for 2 h induces the vesiculation and aggregation of Golg i membrane to form BFA compartments; an effect that is reversed by incubati on of the cells in BFA-free medium, In this paper, the effects of prolonged incubation with BFA are reported, revealing that Golgi stacks spontaneousl y re-form in the presence of this drug after incubation for 12 h or 24 h. T he observation that the same BFA solution is still able to induce the forma tion of BFA compartments in fresh roots suggests that this recovery is not due to metabolism, detoxification or depletion of the drug. Furthermore, in cubation of maize roots with a fresh 100 mu g ml(-1) BFA solution for 2 h f ollowing 24 h BFA treatment fails to induce the reformation of BFA compartm ents, Thus, an acquired insensitivity to BFA in plant cells, that has not b een observed in mammalian cells to date, is indicated.