Changes in onion root development induced by the inhibition of peptidyl-prolyl hydroxylase and influence of the ascorbate system on cell division and elongation |
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Authors: | Mario C De Tullio Costantino Paciolla Francesca Dalla Vecchia Nicoletta Rascio Saverio D'Emerico Laura De Gara Rosalia Liso Oreste Arrigoni |
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Institution: | (1) Istituto Botanico, Università di Bari, via E. Orabona 4, I-70125 Bari, Italia, IT;(2) Dipartimento di Biologia, Università di Padova, via G. Colombo 3, I-35121 Padova, Italia, IT;(3) Campus Bio-Medico-Roma, via E. Longoni 83, I-00155 Roma, Italia, IT |
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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 stiffening,
signalling and cell proliferation. Allium cepa L. roots treated with 3,4-DL-dehydroproline (DP), a specific inhibitor of peptidyl-prolyl hydroxylase, showed a 56% decrease in the hydroxyproline content
of HRGP. Administration of DP strongly affected 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 organization 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 ascorbate-specific 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.
Received: 14 October 1998 / Accepted: 31 May 1999 |
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Keywords: | :Allium (root development) Ascorbate Cell division Cell expansion Hydroxyproline-containing protein Root development |
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