Recently we reported the identification of a novel B-box transcription factor SALT TOLERANCE HOMOLOG 2 (STH2) that interacts genetically with two key regulators of the light-signaling pathway, HY5 and COP1.1 We also provided phenotypic and genetic characterization of the sth2 mutant suggesting that STH2 plays a positive role in regulating photomorphogenesis both independently or together with HY5. Functional assays in protoplasts revealed that STH2 could act as a transcriptional activator. To our knowledge this is the first report of a B-box domain containing protein playing a direct role in activating transcription in plants. Here we discuss the possible position of STH2 in the transcriptional network and comment on the role of the B-box domain in plants.
Keywords: B-box; COP1; HY5; arabidopsis; photomorphogenesis; transcription.