Regulation of chloroplastic FeSOD gene by copper via GTACT motif in the moss Barbula unguiculata

Abstract

Superoxide dismutase (SOD) catalyzes the disproportionation of superoxide radicals. Plants possess three types of SODs, (i.e., FeSOD, MnSOD and Cu/ZnSOD). We found that copper repressed FeSOD activity in chloroplasts of a moss Barbula unguiculata. This copper-mediated repression involves regulation at the level of transcription.
We showed that multiple GTACT motifs are negative cis-elements of FeSOD gene in response to copper by analysis of FeSOD promoter using transgenic moss plants. SBP (SQUAMOSA promoter binding protein)-domains bind to GTAC core sequence, and then we indicated that PpSBPs bind specifically to GTACT sequences of FeSOD promoter in vitro. The Moss FeSOD gene was negatively regulated by copper in transgenic tobacco plants. Arabidopsis FeSOD (FSD1) gene promoter also contains multiple GTACT motifs, and analysis using transgenic Arabidopsis plants revealed the copper responsiveness of the Arabidopsis FSD1 promoter. These results suggested that the copper-dependent repression via GTACT motif is conserved from moss to land plants.