The pattern of organ-specific expression of Arabidopsis thaliana peroxidase was similar to that in horseradish. Tobacco plants transformed with the gus gene fused to the -580 bp deletion (Ea-580) of A. thaliana exhibited high GUS expression in roots. Gel retardation and footprinting analyses showed that at least three domains of fragment between -172 and -1 bp have cis-acting element activities. Several physiological functions for plant peroxidases have been suggested; for example, a metabolic adaptation to salinity in the environment can be induced by certain specific elements of the peroxidase gene. The prxEa promoter fragments (Ea-580 and Ea-390) show multiple cis-acting elements in the control of expression in high-salt stress. These data suggest that the DNA-binding factor may be involved in the regulation of gene expression in specific organ and salt stress.