title: The protein storage vacuole: a unique compound organelle.
abstract: Storage proteins are deposited into protein storage vacuoles (PSVs) during plant seed development and maturation and stably accumulate to high levels; subsequently, during germination the storage proteins are rapidly degraded to provide nutrients for use by the embryo. Here, we show that a PSV has within it a membrane-bound compartment containing crystals of phytic acid and proteins that are characteristic of a lytic vacuole. This compound organization, a vacuole within a vacuole whereby storage functions are separated from lytic functions, has not been described previously for organelles within the secretory pathway of eukaryotic cells. The partitioning of storage and lytic functions within the same vacuole may reflect the need to keep the functions separate during seed development and maturation and yet provide a ready source of digestive enzymes to initiate degradative processes early in germination.
authors.affiliation: Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: L
authors.initials: L
authors.lastname: Jiang
authors.forename: T E
authors.initials: TE
authors.lastname: Phillips
authors.forename: C A
authors.initials: CA
authors.lastname: Hamm
authors.forename: Y M
authors.initials: YM
authors.lastname: Drozdowicz
authors.forename: P A
authors.initials: PA
authors.lastname: Rea
authors.forename: M
authors.initials: M
authors.lastname: Maeshima
authors.forename: S W
authors.initials: SW
authors.lastname: Rogers
authors.forename: J C
authors.initials: JC
authors.lastname: Rogers
mesh_terms: D020346:Aquaporins; D015415:Biomarkers; D002451:Cell Compartmentation / Q000502:physiology; D003546:Cysteine Endopeptidases / Q000032:analysis; D043564:Inorganic Pyrophosphatase; D007425:Intracellular Membranes / Q000378:metabolism; D018551:Solanum lycopersicum; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism; D008854:Microscopy, Electron; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011755:Pyrophosphatases / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure*; D014617:Vacuoles / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D020346:Aquaporins; D015415:Biomarkers; D008565:Membrane Proteins; D010940:Plant Proteins; C091845:gamma-TIP protein, plant; D003546:Cysteine Endopeptidases; C046726:aleurain; D011755:Pyrophosphatases; D043564:Inorganic Pyrophosphatase