ROLE OF A COP1 INTERACTIVE PROTEIN IN MEDIATING LIGHT-REGULATED GENE-EXPRESSION IN ARABIDOPSIS

Arabidopsis seedlings display distinct patterns of gene expression and morphogenesis according to the ambient light condition. An Arabidopsi s nuclear protein, CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1), acts to repr ess photomorphogenesis in the absence of light. The Arabidopsis CIP7 p rotein was identified by its capability to interact with COP1. CIP7 is a novel nuclear protein that contains transcriptional activation acti vity without a recognizable DNA binding motif. CIP7 requires light for its high level of expression, and COP1 seems to play a role in repres sing its expression in darkness. Decreasing CIP7 expression by introdu cing antisense CIP7 RNA resulted in defects in light-dependent anthocy anin and chlorophyll accumulation. Antisense plants also displayed red uced expression of light-inducible genes for anthocyanin biosynthesis and photosynthesis. However, no defect was observed in light-dependent inhibition of hypocotyl elongation. Taken together, our data indicate that CIP7 acts as a positive regulator of light-regulated genes and i s a potential direct downstream target of COP1 for mediating light con trol of gene expression.