Abstract
Transgenic Arabidopsis overexpressing spermidine synthase (SPDS) genes under the control of 35S CaMV promoter exhibits increased tolerance to environmental stress over the wild-type plants. Since stress injury of plants often correlates with excess generation of reactive oxygen species, the antioxidant enzyme activities in chilled leaves were compared between the transgenic and wild-type plants. Chilling the plants at 5C in a moderate light caused a reduction in Fv/Fm and an increase in H2O2 in leaves, both of which were less pronounced in the transgenic plants. During chilling, SOD and APX activities increased over time particularly in the transgenic plants. An SPDS inhibitor applied to the transgenic plants suppressed the chill-induced increase of SOD activity while spermidine application to the wild-type plants enhanced it. The results suggest that high cellular levels of spermidine may promote the induction of antioxidant enzyme activities in chill-stressed leaves.
