Modulator role of ascorbic acid on coniferyl alcohol oxidation by a basic peroxidase from tomato hairy roots

MELINA A. TALANO*, ELIZABETH AGOSTINI, ANA L. WEVAR OLLER, MARÍA I. MEDINA, SILVIA R. MILRAD DE FORCHETTI

PLANT SCIENCE

Elsevier

Año: 2008 p. 724 - 730

0168-9452

We demonstrated the involvement of a highly basic peroxidase (HBPx) isoenzyme from tomato hairy roots (HR) in the lignosuberization process. In the present study we analysed if it was also involved in the detoxification of H2O2 through an ascorbate peroxidase activity (APx) or if AA could affect the coniferyl alcohol peroxidase (CAPx) activity of HBPx, since salt-treated HR grew without browning by oxidation and they were less lignosuberized. The peroxidase isoenzymes from culture medium (CMPx) showed APx activity, however we could not detect oxidation of ascorbic acid (AA) by the purified HBPx. Nevertheless, CAPx activity of the HBPx was inhibited by AA when it was added 1 min after the beginning of the reaction. The addition of AA, 1-10 mM, produced 20% reduction in CA oxidation while higher concentrations (20-40 mM) generated 70-90% CAPx activity inhibition and induced a lag phase. Although, apoplastic AA contents were not significantly different between salt-treated and control HR, the AA concentration found in treated tissues (around 17 mM) suggests that the participation in the lignosuberization of HBPx would be, at least partially inhibited, under this condition. The effect of AA on HBPx and other peroxidases in relationship with salt-treated HR phenotype is discussed.