title: Role of vacuolar membrane proton pumps in the acidification of protein storage vacuoles following germination.
abstract: During soybean (Glycine max (L.) Merrill) seed development, protease C1, the proteolytic enzyme that initiates breakdown of the storage globulins β-conglycinin and glycinin at acidic pH, is present in the protein storage vacuoles (PSVs), the same subcellular compartments in seed cotyledons where its protein substrates accumulate. Actual proteolysis begins to be evident 24 h after seed imbibition, when the PSVs become acidic, as indicated by acridine orange accumulation visualized by confocal microscopy. Imidodiphosphate (IDP), a non-hydrolyzable substrate analog of proton-translocating pyrophosphatases, strongly inhibited acidification of the PSVs in the cotyledons. Consistent with this finding, IDP treatment inhibited mobilization of β-conglycinin and glycinin, the inhibition being greater at 3 days compared to 6 days after seed imbibition. The embryonic axis does not appear to play a role in the initial PSV acidification in the cotyledon, as axis detachment did not prevent acridine orange accumulation three days after imbibition. SDS-PAGE and immunoblot analyses of cotyledon protein extracts were consistent with limited digestion of the 7S and 11S globulins by protease C1 starting at the same time and proceeding at the same rate in detached cotyledons compared to cotyledons of intact seedlings. Embryonic axis removal did slow down further breakdown of the storage globulins by reactions known to be catalyzed by protease C2, a cysteine protease that normally appears later in seedling growth to continue the storage protein breakdown initiated by protease C1.
authors.affiliation: Department of Biological Sciences, Binghamton University, Binghamton, NY 13902-6000, USA. Electronic address: kwilson@binghamton.edu.
authors.forename: Karl A
authors.initials: KA
authors.lastname: Wilson
authors.affiliation: Department of Biological Sciences, Binghamton University, Binghamton, NY 13902-6000, USA.
authors.forename: Burzin J
authors.initials: BJ
authors.lastname: Chavda
authors.affiliation: Department of Biological Sciences, Binghamton University, Binghamton, NY 13902-6000, USA.
authors.forename: Gandhy
authors.initials: G
authors.lastname: Pierre-Louis
authors.affiliation: Department of Biological Sciences, Binghamton University, Binghamton, NY 13902-6000, USA.
authors.forename: Adam
authors.initials: A
authors.lastname: Quinn
authors.affiliation: Department of Biological Sciences, Binghamton University, Binghamton, NY 13902-6000, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Tan-Wilson
mesh_terms: D000143:Acids / Q000378:metabolism*; D052179:Antigens, Plant / Q000378:metabolism; D018548:Cotyledon / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018525:Germination / Q000187:drug effects; D005916:Globulins / Q000378:metabolism; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology; D010940:Plant Proteins / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D054328:Proton Pump Inhibitors / Q000494:pharmacology; D017494:Proton Pumps / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism; D055314:Seed Storage Proteins / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D030262:Soybean Proteins / Q000378:metabolism; D013025:Glycine max / Q000187:drug effects / Q000378:metabolism*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000143:Acids; D052179:Antigens, Plant; D004791:Enzyme Inhibitors; D005916:Globulins; D010710:Phosphates; D010940:Plant Proteins; D054328:Proton Pump Inhibitors; D017494:Proton Pumps; D055314:Seed Storage Proteins; D030262:Soybean Proteins; C013894:beta-conglycinin protein, Glycine max; D006180:Proton-Translocating ATPases
keywords: Acidification; Protein storage vacuole; Proteolysis; Seedling growth; Soybean; Storage proteins