Post-translational hydroxylation of peptide- bound proline residues, catalyzed by peptidyl-prolyl-4 hydroxylase (EC 1.14.11.2) using ascorbate as co- substrate, is a key event in the maturation of a number of cell wall-associated hydroxyproline-rich glycoproteins (HRGPs), including extensins and arabinogalactan- proteins, which are involved in the processes of wall stiening, signalling and cell proliferation. Allium cepa L. roots treated with 3,4-DL-dehydroproline (DP), a speci®c inhibitor of peptidyl-prolyl hydroxylase, showed a 56% decrease in the hydroxyproline content of HRGP. Administration of DP strongly aected the organization of specialized zones of root development, with a marked reduction of the post-mitotic isodiametric growth zone, early extension of cells leaving the meristematic zone and a huge increase in cell size. Electron-microscopy analysis showed dramatic alterations both to the orga- nization of newly formed cell walls and to the adhesion of the plasma membranes to the cell walls. Moreover, DP administration inhibited cell cycle progression. Root tips grown in the presence of DP also showed an increase both in ascorbate content (+53%) and ascor- bate-speci®c peroxidase activity in the cytosol (+72%), and a decrease in extracellular ``secretory'' peroxidase activity ()73%). The possible interaction between HRGPs and the ascorbate system in the regulation of both cell division and extension is discussed.
Changes in onion root development induced by the inhibition of peptydil-prolyl-hydroxylase and influence of the ascorbate system on cell division and elongation
DALLA VECCHIA, FRANCESCA;RASCIO, NICOLETTA;
1999
Abstract
Post-translational hydroxylation of peptide- bound proline residues, catalyzed by peptidyl-prolyl-4 hydroxylase (EC 1.14.11.2) using ascorbate as co- substrate, is a key event in the maturation of a number of cell wall-associated hydroxyproline-rich glycoproteins (HRGPs), including extensins and arabinogalactan- proteins, which are involved in the processes of wall stiening, signalling and cell proliferation. Allium cepa L. roots treated with 3,4-DL-dehydroproline (DP), a speci®c inhibitor of peptidyl-prolyl hydroxylase, showed a 56% decrease in the hydroxyproline content of HRGP. Administration of DP strongly aected the organization of specialized zones of root development, with a marked reduction of the post-mitotic isodiametric growth zone, early extension of cells leaving the meristematic zone and a huge increase in cell size. Electron-microscopy analysis showed dramatic alterations both to the orga- nization of newly formed cell walls and to the adhesion of the plasma membranes to the cell walls. Moreover, DP administration inhibited cell cycle progression. Root tips grown in the presence of DP also showed an increase both in ascorbate content (+53%) and ascor- bate-speci®c peroxidase activity in the cytosol (+72%), and a decrease in extracellular ``secretory'' peroxidase activity ()73%). The possible interaction between HRGPs and the ascorbate system in the regulation of both cell division and extension is discussed.
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