Abstract
Superoxide is generated by reduction of molecular oxygen in living cells. Bryophytes are considered as the first land plants and thus adaptive responses to oxidative stress are crucial in their evolution. Superoxide dismutase (SOD) plays an important role to protect cells from toxic effect of superoxide. We found that copper repressed Fe-SOD activity in chloroplasts of a moss, Barbula unguiculata. This regulation was achieved at mRNA level and observed within a few hours. We cloned promoter region of Fe-SOD gene and generated transgenic plants carrying a series of 5' deletions of the Fe-SOD promoter fused to a GUS gene. When the transgenic plant was treated with copper, clear responsiveness to copper as assessed by GUS mRNA level was observed for the -558 construct. This result suggested that the repression of Fe-SOD by copper is regulated at the transcriptional level, at least in part.
