Brefeldin A affects synthesis and integrity of a eukaryotic flagellum.

Eukaryotic flagella and cilia are highly dynamic organelles. In green algae like Chlamydomonas reinhardtii, flagella absorption and resynthesis is a normal process during the vegetative cell cycle. Rapid regeneration also occurs after stress-induced shedding of flagella. Ca2+ ions, protein synthesis, and a kinase activity are the main factors known to affect resynthesis. Recently, we have detected that certain small G proteins (Ypt/Rab) and a GTPase regulator (GDP dissociation inhibitor), known as regulatory elements of intracellular vesicle transport, are present in flagellar membranes of green algae, raising the possibility that the organelle's synthesis and/or integrity depends on functional membrane traffic. In this study, we examined the effect of brefeldin A (BFA), an inhibitor of intracellular membrane flow and Golgi function in animal and plant cells, on flagella regeneration in the colonial green alga Gonium pectorale. We show that low BFA concentrations (< 1 microgram/ml) inhibit flagella out-growth, while higher amounts cause dose-dependent deflagellation and cell death. Our findings provide experimental evidence for a direct connection between intracellular transport and eukaryotic flagella synthesis.