Wound-regulation and tissue specificity of the tomato prosystemin promoter in transgenic tobacco plants

Abstract

To investigate whether the systemic defense signaling pathway in tobacco ( Nicotiana tabacum) plants may be regulated by a polypeptide signal related to tomato prosystemin, tobacco plants were transformed with a chimeric gene consisting of a 2200 bp fragment containing the promoter region of the tomato prosystemin gene fused to the β-glucuronidase coding region. Histochemical and enzymatic assays demonstrated a low constitutive expression of the reporter gene and a wound- and methyl jasmonate induction of the gene specifically in the vascular bundles of leaves and petioles. Synthesis of the prosystemin-GUS fusion protein in the vascular bundle, regulated by wounding and methyl jasmonate, is similar to the synthesis of prosystemin in tomato plants, from which the promoter was obtained. Although a prosystemin protein or mRNA has not been identified in tobacco using Northern and Western blotting with tomato prosystemin cDNA or antibodies, the transcriptional elements necessary to recognize the tomato prosystemin promoter to express methyl jasmonate-inducibility and tissue specificity are present in tobacco vascular bundle cells. This suggests that an analog related to tomato prosystemin gene may be present in tobacco leaves that is regulated in the same manner as the tomato prosystemin gene.