Uptake of Lucifer Yellow by plant cells in the presence of endocytotic inhibitors

Lucifer Yellow (LY), a membrane-impermeant anion, was able to enter Arabidopsis thaliana cells. LY was taken up by fluid-phase endocytosis and a plasmalemmal anionic carrier mechanism. Both mechanisms were shown to be concentration-dependent. At 0.1 mg/ml, LY was mainly taken up via fluid-phase endocytosis and concentrated in vesicular-like structures. At a ten-fold higher concentration (1 mg/ml), a plasmalemmal anionic carrier system allowed LY uptake and its accumulation in the central vacuole by a vacuolar anionic transporter. Chloroquine, cytochalasin B, monensin, and phorbol-12-myrisrate-13-acetate (PMA) hindered LY endocytosis. Brefeldin A did not modify LY uptake. The probenecid sensitive carrier uptake machinery showed sensitivity to chloroquine and PMA. Therefore the probenecid-sensitive transport mechanism seems to be complex and involve both acidification of a compartment and protein kinase C activity.