Involvement of active oxygen species in the regulation of a tobacco defence gene by phorbol ester

Abstract

Tobacco cell suspension cultures respond to treatment with phorbol 12-myristate 13-acetate (PMA), by the accumulation of transcripts for hsr203J, a plant defence gene. We provide evidence that the effect of PMA on hsr203J gene expression depends upon a transient production of active oxygen species (AOS), an early response of the cell suspensions to PMA. Pre-treatment with diethyldithiocarbamate (DDC), an inhibitor of superoxide dismutase (SOD), abolishes the PMA-induced generation of AOS and the subsequent expression of the hsr203J gene. Conversely, a direct application of hydrogen peroxide to the cell suspensions causes an increase in hsr203J transcripts level, indicating that AOS such as hydrogen peroxide act as signalling molecules to induce the expression of the hsr203J gene. Collectively, these data establish that AOS are critical intermediates mediating PMA action on hsr203J gene expression.