Interaction of osmotic stress, temperature, and abscisic acid in the regulation of gene expression in arabidopsis

The impact of simultaneous environmental stresses on plants and how they re spond to combined stresses compared with single stresses is largely unclear . By using a transgene (RD29A-LUC) consisting of the firefly luciferase cod ing sequence (LUC) driven by the stress-responsive RD29A promoter, we inves tigated the interactive effects of temperature, osmotic stress, and the phy tohormone abscisic acid (ABA) in the regulation of gene expression in Arabi dopsis seedlings. Results indicated that both positive and negative interac tions exist among the studied stress factors in regulating gene expression. At a normal growth temperature (22 degrees C), osmotic stress and ABA act synergistically to induce the transgene expression. Low temperature inhibit s the response to osmotic stress or to combined treatment of osmotic stress and ABA, whereas low temperature and ABA treatments are additive in induci ng transgene expression. Although high temperature alone does not activate the transgene, it significantly amplifies the effects of ABA and osmotic st ress. The effect of multiple stresses in the regulation of RD29A-LUC expres sion in signal transduction mutants was also studied. The results are discu ssed in the context of cold and osmotic stress signal transduction pathways .