Sortin1 was found to redirect the vacuolar destination of plant carboxypeptidase Y and other proteins in Arabidopsis suspension cells and cause these proteins to be secreted. In Arabidopsis seedlings, the application of Sortin1 and -2 led to reversible defects in vacuole biogenesis and root development. Sortin1 treatment of whole Arabidopsis seedlings also resulted in carboxypeptidase Y secretion, indicating that the drug has a similar mode of action in cells and intact plants. Structure-activity relationship studies conducted in Arabidopsis revealed the structural requirements for Sortin1 bioactivity and demonstrated that overlapping Sortin1 substructures can be used to discriminate between vacuolar-flavonoid accumulations and vacuolar-biogenesis defects [1][2].