Abstract
In Cyanobacteria, the amount of photosystem (PS) I complex decreases under high-light conditions. Although the decrease of PSI content is mainly achieved by the coordinate down-regulation of promoter activities of PSI genes, the mechanism by which PSI promoter activities are modulated is totally unknown. In this study, we investigated promoter architecture of psaAB encoding reaction center subunits of PSI. To identify cis-regulatory elements, various fragments of psaAB upstream region were fused to luxAB reporter gene, and luminescence levels from each construct were compared. It was found that psaAB has two light-responsive promoters (P1, P2), and each promoter possesses positive and negative cis-elements that do not confer the light-response. DNA mobility shift assay showed that each promoter binds different proteins. Now we are trying to identify light-responsive elements by introducing base substitutions to both promoter regions.
