Increase in apoplastic peroxidases activities during the development of sunflower leaves

LECHNER, L.; PINEDO, M.; DOSIO, G.A.A.; AGUIRREZABAL, L.

Rosario, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Peroxidases are enzymes associated to a wide variety of physiological processes including defense responses and auxin catabolism. They are involved in H2O2 reduction by using auxins, lignin precursors and other biomolecules as substrates. Paradoxically, the extracellular isoforms grouped in the class III subfamily, have been associated to both, the inhibition as well as the promotion of cell growth. In this work we examined apoplastic activities during the development of leaves inserted in even shoot positions of sunflower plants. Seeds of Helianthus annuus Ha 89 variety were grown in greenhouse under no limiting conditions. At different times from sowing intercellular washing fluids were obtained by infiltration and centrifugation of the leaves. The peroxidase activity was spectrophotometrically recorded every 10 seconds using tetramethylbenzidine as substrate (3 mg/ml). Results showed that, independently of the position in the shoot, the apoplastic peroxidase activity increased continuously with development of the leaves, reaching its maximun value when they became fully expanded. The contribution of this phenomenon to the regulation of cell development will be discussed.