A NEGATIVELY LIGHT-REGULATED GENE FROM ARABIDOPSIS-THALIANA ENCODES A PROTEIN SHOWING HIGH SIMILARITY TO BLUE COPPER-BINDING PROTEINS

A negatively photo-regulated gene (bcb) has been isolated by means of differential hybridization of a genomic library of Arbidopsis thaliana. In mature plants, a 20-fold increase in the amount of steady-state bcb mRNA can be detected upon 48 h of dark adaption. The expression level of the gene is also dependent upon the developmental stage of the plant. The 21.5-kDa gene product (BCB) shows extensive similarity with blue Cu2+-binding proteins such as plastocyanin and stellacyanin. The protein abundance increases only twofold upon dark adaption, which implies the presence of post-transcriptional control. The isolation of a novel negatively photoregulated gene allows us to investigate the complex expression profile of genes responding to the absence of light.