Competitive activity as a constitutive promoter in the 5′-proximal regulatory region of the Capsicum capsanthin–capsorubin synthase gene

Depending on the nature of the Capsicum capsanthin–capsorubin synthase gene (CaCcs) showing a chromoplast specificity, the 5′-upstream region of CaCcs from −2279 to +30 was isolated from the Korean red pepper genomic library for promoter analysis. The full-length 2.3-kb promoter and its deletion mutants similarly drove GUS expression in chromoplastic tissues such as anthers and styles in transgenic Arabidopsis flowers. However, the shortest 397-bp promoter (CaCcs-P1) containing the −367 to +30 region displayed histochemically high GUS expression in non-chromoplastic tissues such as sepals and leaves, as well as in chromoplastic tissues. The efficient constitutive expression of CaCcs-P1 was higher than that of the dual 35S promoter (d35S-P) with respect to mRNA expression (at least threefold) and enzyme activity (fourfold) and was maintained in the whole body of plants during all developmental stages. Ubiquitous GUS expression by CaCcs-P1 was elicited at the highest level in stems, followed by leaves, flowers, roots, young siliques, and mature seeds, with respect to both transcript levels and enzyme activity. More effective activity of CaCcs-P1 compared to d35S-P (1.4-fold higher) was also confirmed in transgenic tobacco plants. Together with the prediction of cis-acting motifs that allow diverse spatial specificity, we report a promoter displaying efficient constitutive characteristics with the advantages of a plant origin and size competitiveness compared with the 35S promoter.