Clathrin-mediated endocytosis-independent function of VAN3 ARF GTPase Activating Protein at the plasma membrane

ARF small GTPases in plants serve important cellular functions in subcellular trafficking and developmental functions in auxin-mediated patterning of the plant body. The Arabidopsis thaliana ARF regulator ARF-GAP VAN3 has been implicated to act at the plasma membrane (PM) and linked functionally to the clathrin- and dynamin-mediated endocytosis. Here we re-evaluated the localization of VAN3 at the PM and its function in endocytosis. Using Total Internal Reflection Fluorescence microscopy we observed remarkably transient associations of VAN3 to the PM at discrete foci, however, devoid of clathrin, the dynamin isoform DRP1A, or the ARF regulator GNOM, which is also involved in a developmental patterning function mediated from the PM. Clathrin-coated pits are abundant and endocytosis appears to proceed normally in van3-1 knockout mutant. In turn, post-translational silencing of clathrin expression indicates that the localization of VAN3 at the PM depends on clathrin function, presumably on clathrin-mediated endocytosis.