Transient assay system for the analysis of PR-1a gene promoter in tobacco BY-2 cells

In order to develop a rapid and versatile assay system suitable for the analysis of regulated expression of tobacco pathogenesis-related protein 1a (PR-1a) gene, we investigated the use of the transient gene expression system in tobacco BY-2 cells by microprojectile bombardment. Using dual luciferase assay as a reporter gene expression detection system, we observed significant induction of PR-1a promoter activity by salicylic acid (SA) treatment. On the other hand, treatment with 4-hydroxybenzoic acid (4-HBA) resulted in no detectable increase in luciferase activity. Co-expression of a trans-acting factor, the NPR1/NIM1 protein of Arabidopsis, resulted in the induction of higher expression levels of the PR-1a promoter. These results suggest that the assay system is applicable for the analysis of factors involved in the regulated expression of SA-inducible defense-related genes.