ALTERATIONS OF BRASSINOSTEROID HOMEOSTASIS IMPAIR ASCORBATE-GLUTATHIONE CYCLE IN TOMATO

MAZORRA, LUIS M.; GERGOFF, GUSTAVO; FANELLO, DIEGO D.; TAMBUSSI, EDUARDO; CARRIÓN, CRISTIAN A.; NUÑEZ, M.; BISHOP, G.; BARTOLI, CARLOS G.

San Miguel de Tucumán

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Ascorbate-glutathione (AA-GSH) system is a major antioxidant mechanism involved in plant adaptation to a changing environment, and brassinosteroids (BR), are plant steroidal hormones implicated in plant growth and development. The aim of this work is to study the AA-GSH system in tomato dwarf and over-growing plants resulting from deficiency (dx) or excess (35SD) of endogenous BR, respectively. Under moderate irradiance, leaves of BR-deficient plants and BRaccumulating plants (35SD) displayed low AA accumulation with a more oxidised state than wt. However, GSH content remained unchanged. Plants with altered BR levels showed the activities of stromal ascorbate peroxidase and glutathione reductase (GR) lower than those observed in wt, while cytosolic ascorbate peroxidase (cAPX) and dehydroascorbate reductase activities were similar to those in wt. In addition, these plants showed decreased stomata conductance but only dx plants present an inhibition of photosynthesis. A sudden exposure of plants to a combined heat and high irradiance stress, did not affect AA levels but increased leaf GSH content and GR activity, and kept low activity of cAPX in both groups of plants with altered BR levels. Taken together, these results suggest that an altered BR homeostasis through either defect or excess of BR lead to similar disruptions of AA-GSH cycle.