Auxin inhibits endocytosis and promotes its own efflux from cells.

For years it has been assumed that auxin, the ubiquitous regulator of plant development, controls plant growth by influencing gene expression. The discovery that auxin inhibits endocytosis, a protein recycling process associated with signalling molecules in other systems, suggests that auxin instead uses an as yet uncharacterized signal transduction pathway. By inhibiting endocytosis, auxin increases the amount of certain proteins, including PIN auxin efflux regulators, at the cell surface. Auxin also promotes its own efflux via a vesicle trafficking-dependent mechanism.