Brefeldin A affects the system of contractile vacuoles in Mesostigma viride (Streptophyta)

Brefeldin A was used to disrupt the contractile vacuoles (CVs) of the streptophyte green flagellate Mesostigma viride. Treatment of M. viride with BFA caused enlarged CVs, as well as a decrease in the number of CVs, and finally the cells burst. In addition, BFA treated cells revealed the typical changes in Golgi structure (decrease in number of cisternae and Golgiassociated COP1 vesicles) observed in other systems. It is well known that treatment with BFA inhibits the formation of COP1-coated vesicles and some types of clathrin-coated vesicles (CCV). Clathrin coated pits (CCPs) and clathrin coated vesicles are associated with the CVs in Mesostigma viride. However, electron microscopically analysis revealed that the number of CCVs did not decrease upon treatment with BFA. We conclude that the molecular cause for BFA effect on the CV must be localized at the Golgi, probably due to the inhibition of transport of proteins from the Golgi to the CV.