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 resynthe sis is a normal process during the vegetative cell cycle. Rapid regene ration also occurs after stress-induced shedding of flagella. Ca2+ ion s, 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 inhibito r), known as regulatory elements of intracellular vesicle transport, a re present in flagellar membranes of green algae, raising the possibil ity that the organelle's synthesis and/or integrity depends on functio nal membrane traffic. In this study, we examined the effect of brefeld in A (BFA), an inhibitor of intracellular membrane flow and Golgi func tion in animal and plant cells, on flagella regeneration in the coloni al green alga Gonium pectorale. We show that low BFA concentrations (< 1 mu g/ml) inhibit flagella outgrowth, while higher amounts cause dose -dependent deflagellation and cell death. Our findings provide experim ental evidence for a direct connection between intracellular transport and eukaryotic flagella synthesis. (C) 1998 Academic Press.