Mechanism of CATA3 induction by cadmium in sunflower leaves

AZPILICUETA CE; BENAVIDES MP; TOMARO ML; GALLEGO SM

PLANT PHYSIOLOGY AND BIOCHEMISTRY

Elsevier

Lugar: Netherlands; Año: 2007 vol. 45 p. 589 - 595

0981-9428

One of the main antioxidant enzymes, catalase (CAT, EC 1.11.1.6), is capable of catalyzing the dismutation of H2O2. This enzyme is involved in signal transduction pathway in plants, controlling the cellular level of this reactive oxygen species. Four different genes, CATA1eCATA4, were identified in Helianthus annuus L. cotyledons. Incubation of sunflower leaf discs with 300 and 500 mM CdCl2 under light conditions increased CATA3 transcript level. However, it was not induced by Cd2þ in etiolated plants. This Cd2þ-induced increase was reverted by adding 10 mM ascorbate. Treatments with 0.4 and 10 mM rose bengal (a generator of 1O2) did not activate CATA3, but 10 mM methyl viologen (an enhancer of O2_ production) and 10 mM H2O2 increased its expression. In isolated chloroplasts, Cd2þ and methyl viologen produced oxidation of the probe 20,70-dichlorofluorescein diacetate indicating ROS formation. Besides, Cd2þ treatment of leaf discs under light decreased CAT activity and increased carbonyl groups content, thus suggesting that enzyme inactivation could be due e in part e to a protein oxidation. These results indicate that light is involved in Cd2þ-induced CATA3 enhancement, which leads to the synthesis of CAT isoforms less sensible to oxidation, and that chloroplast might be the main source of ROS responsible for this process