Article

Planta

, Volume 209, Issue 4, pp 424-434

Changes in onion root development induced by the inhibition of peptidyl-prolyl hydroxylase and influence of the ascorbate system on cell division and elongation

  • Mario C. De TullioAffiliated withIstituto Botanico, Università di Bari, via E. Orabona 4, I-70125 Bari, Italia
  • , Costantino PaciollaAffiliated withIstituto Botanico, Università di Bari, via E. Orabona 4, I-70125 Bari, Italia
  • , Francesca Dalla VecchiaAffiliated withDipartimento di Biologia, Università di Padova, via G. Colombo 3, I-35121 Padova, Italia
  • , Nicoletta RascioAffiliated withDipartimento di Biologia, Università di Padova, via G. Colombo 3, I-35121 Padova, Italia
  • , Saverio D'EmericoAffiliated withIstituto Botanico, Università di Bari, via E. Orabona 4, I-70125 Bari, Italia
  • , Laura De GaraAffiliated withIstituto Botanico, Università di Bari, via E. Orabona 4, I-70125 Bari, Italia
  • , Rosalia LisoAffiliated withIstituto Botanico, Università di Bari, via E. Orabona 4, I-70125 Bari, Italia
  • , Oreste ArrigoniAffiliated withIstituto Botanico, Università di Bari, via E. Orabona 4, I-70125 Bari, Italia

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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.

Key words:Allium (root development) Ascorbate Cell division Cell expansion Hydroxyproline-containing protein Root development