EXPRESSION OF ANTIOXIDANT ENZYMES IN RESPONSE TO ABSCISIC-ACID AND HIGH OSMOTICUM IN TOBACCO BY-2 CELL-CULTURES

We have monitored the changes in antioxidative enzyme activities and t heir mRNA levels in tobacco (Nicotiana tabacum L. cv.) Bright Yellow 2 (BY-2) cell cultures subjected to salt stress, polyethylene glycol (P EG)-induced drought stress, and exogenous abscisic acid (ABA). Both Na Cl and PEG treatments led to an increase in the total superoxide dismu tase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities, whereas glutathione reductase (GR) activity remained unchanged. Increa se in total SOD and APX activities was observed in cells grown in the presence of ABA. CAT activity remained constant whereas GR activity wa s reduced after the ABA treatment. All osmotic stress and ABA treatmen ts had a differential effect on the accumulation of transcripts of the tested antioxidant genes. Our results show that osmotic stress alters the enzymatic defense reactions in tobacco BY-2 cell suspensions and suggest that ABA is not a secondary messenger in the induction of all antioxidant genes upon osmotic stress. (C) 1998 Elsevier Science Irela nd Ltd. All rights reserved.