Brefeldin A inhibits clathrin-dependent endocytosis and ion transport in Chara internodal cells.

BACKGROUND: The Characeae are multicellular green algae, which are closely related to higher plants. Their internodal cells are a convenient model to study membrane transport and organelle interactions.

RESULTS: In this study we report on the effect of brefeldin A, an inhibitor of vesicle trafficking, on internodal cells of Chara australis. Brefeldin A induced the commonly observed agglomeration of Golgi bodies and trans Golgi network into "brefeldin compartments" at concentrations between 6 and 500 μM and within 30-120 min treatment. In contrast to most other cells, however, brefeldin A inhibited endocytosis and significantly decreased the number of clathrincoated pits and clathrincoated vesicles at the plasma membrane. Brefeldin A did not inhibit secretion of organelles at wounds induced by puncturing or local light damage but prevented the formation of cellulosic wound walls probably because of insufficient membrane recycling. We also found that brefeldin A inhibited the formation of alkaline and acid regions along the cell surface ("pH banding pattern") which facilitates carbon uptake required for photosynthesis; we hypothesize that this is due to insufficient recycling of ion transporters. During long-term treatments over several days, brefeldin A delayed the formation of complex 3D plasma membranes (charasomes). Interestingly, brefeldin A had no detectable effect on clathrin-dependent charasome degradation. Protein sequence analysis suggests that the peculiar effects of brefeldin A in Chara internodal cells are due to a mutation in the guanine nucleotide exchange factor GNOM required for recruitment of membrane coats via activation of ADP-ribosylation factor proteins.

CONCLUSIONS AND SIGNIFICANCE: This work provides an overview on the effects of brefeldin A on different processes in Chara australis. It revealed similarities but also distinct differences in vesicle trafficking between higher plant and algal cells. It shows that characean internodal cells are a promising model to study interactions between seemingly distant metabolic pathways. This article is protected by copyright. All rights reserved.