Regulatory sequences involved in the peroxidase gene expression in Arabidopsis thaliana.

Organ-specific expression of two peroxidase genes (prxCa and prxEa) from Arabidopsis thaliana was studied. The prxCa gene showed non-specific expression with relatively high levels of mRNA accumulation in the roots, stems and leaves of A. thaliana. The prxEa gene, on the other hand, accumulated high levels of mRNA only in roots. Promoter fragments from each gene were fused to the coding region of β-glucuronidase (gusA) reporter gene introduced into tobacco. Promoter/gusA contructs were transferred to tobacco (Nicotiana tabacum BY-2) protoplasts by electroporation or to N. tabacum SR-1 by Agrobacterium tumefaciens-mediated leaf disk transformation. Transient expression in tobacco protoplasts showed that the 580 fragment from prxEa (Ea-580) expressed thirteen-fold and eight-fold higher GUS activity than prxCa (Ca-622) fragment and CaMV35S promoter, respectively. Tobacco plants transformed with the gusA gene, fused to the -580 deletion (Ea-580), exhibited high GUS expression in roots. The root-specific expression of GUS gene was also observed when the -281 bp deletion end point was used. Although the GUS activity in transgenic tobacco under the control of Ca-622 was low, the activity was found in all organs examined. Histochemical analyses of stem and root tissues of Ea-580 showed that the GUS gene was expressed specifically in phloem and pith parenchyma cells. For Ca-622, high level, specific expression of the gusA gene was observed in the xylem of roots. The results of this study implicate multiple cis-elements in the control of transcription from the prxEa promoter.