From storage compartment to lytic organelle: The metamorphosis of the aleurone protein storage vacuole

Protein storage vacuoles are found in a variety of tissues but are especially abundant in the storage organs of fruits and seeds. In this review, we focus on the protein storage vacuoles of cereal aleurone. In the mature grain, these organelles are repositories for reserve nitrogen, carbon and minerals. Following imbibition, protein storage vacuoles of cereal aleurone change from storage compartments to lytic organelles. Changes in protein storage vacuole structure and enzymatic activity during this transition are discussed. It is emphasized that protein storage vacuoles are poised for reserve mobilization, and that gibberellin perception by the aleurone cell initiates a signalling cascade that promotes acidification of the vacuole lumen and activation of enzymes and transporters. (C) 1998 Annals of Botany Company