title: cPrG-HCl a potential H+/Cl- symporter prevents acidification of storage vacuoles in aleurone cells and inhibits GA-dependent hydrolysis of storage protein and phytate.
abstract: The putative H+/Cl- symporter cycloprodigiosin-HCl (cPrG-HCl) was used to investigate the role of vacuole acidification in cereal aleurone cell function. The protein storage vacuole (PSV) becomes acidified rapidly when aleurone cells are treated with gibberellic acid (GA) but not abscisic acid (ABA). We show that cPrG prevents PSV acidification in aleurone layers and prevents synthesis of secretory proteins such as alpha-amylase. Our data support the hypothesis that decreased hydrolase synthesis is a consequence of decreased hydrolysis of storage proteins in PSV. Support for this hypothesis comes from experiments showing that breakdown of barley 7S globulins and phytate is inhibited by cPrG in GA-treated aleurone layers. Decreased mobilization of PSV reserves is accompanied by reductions in the free amino acid pool size and in the amount of ions released from the aleurone layer. Vacuolation of the aleurone cell is a diagnostic feature of the response to GA, and vacuolation is also inhibited by cPrG. Evidence that cPrG acts as a potential H+/Cl- symporter in aleurone is presented. We show that cPrG does not inhibit the synthesis and secretion of alpha-amylase when Cl- ions are omitted from the incubation medium. Although cPrG blocks many GA-induced responses of aleurone layers, it does not affect early steps in GA signaling. The SLN1 protein, a negative regulator of GA signaling, is turned over in GA-treated cells in the presence and absence of cPrG. Similarly, synthesis of the transcriptional activator GAMYB is unaffected by the presence of cPrG in GA-treated cells.
authors.affiliation: Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102, USA.
authors.forename: Yong-sic
authors.initials: YS
authors.lastname: Hwang
authors.forename: Paul C
authors.initials: PC
authors.lastname: Bethke
authors.forename: Frank
authors.initials: F
authors.lastname: Gubler
authors.forename: Russell L
authors.initials: RL
authors.lastname: Jones
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D017920:Antiporters / Q000494:pharmacology*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D005875:Gibberellins / Q000494:pharmacology*; D001467:Hordeum / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007211:Indoles / Q000494:pharmacology*; D008856:Microscopy, Fluorescence; D008903:Minerals / Q000378:metabolism; D010833:Phytic Acid / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011758:Pyrroles / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017527:Receptor, IGF Type 2; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects; D014617:Vacuoles / Q000187:drug effects* / Q000502:physiology; D000516:alpha-Amylases / Q000235:genetics / Q000378:metabolism
chemical_list: D017920:Antiporters; D005875:Gibberellins; D007211:Indoles; D008903:Minerals; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011758:Pyrroles; D012333:RNA, Messenger; D017527:Receptor, IGF Type 2; D018160:Receptors, Cytoplasmic and Nuclear; C034304:cation-dependent mannose-6-phosphate receptor; C114260:hydrogen-chloride symporter; D000040:Abscisic Acid; D010833:Phytic Acid; C108328:cycloprodigiosin; C007842:gibberellic acid; D000516:alpha-Amylases; D003546:Cysteine Endopeptidases; C100994:EPB1 protein, Hordeum vulgare