Abstract: The present invention involves the isolation and characterization of the first discovered phytochrome-regulated transcriptional factor, a protein designated CCA1 which binds to the promoter region of the chlorophyll binding protein gene (Lhcb1*3) of Arabidopsis. The Lhcb1*3 gene of Arabidopsis is known to be regulated by phytochrome in etiolated seedlings where a brief illumination by red light results in a large increase in the level of mRNA from this gene. A DNA binding activity, designated CA-1, that interacts with the promoter region of Lhcb1*3 was previously discovered in cellular extracts. This binding activity was used to obtain a cDNA clone for a transcription factor that binds specifically to the Lhcb1*3 promoter. Modification of the expression of CCA1 using techniques of genetic engineering results in unexpected changes in the timing of plant flowering. When CCA1 is overexpressed, it appears that the normal circadian rhythms of the plant are disrupted.

Abstract: The present invention involves the isolation and characterization of the first discovered phytochrome-regulated transcriptional factor, a protein designated CCA1 which binds to the promoter region of the chlorophyll binding protein gene (Lhcb1*3) of Arabidopsis. The Lhcb1*3 gene of Arabidopsis is known to be regulated by phytochrome in etiolated seedlings where a brief illumination by red light results in a large increase in the level of mRNA from this gene. A DNA binding activity, designated CA-1, that interacts with the promoter region of Lhcb1*3 was previously discovered in cellular extracts. This binding activity was used to obtain a cDNA clone for a transcription factor that binds specifically to the Lhcb1*3 promoter. Modification of the expression of CCA1 using techniques of genetic engineering results in unexpected changes in the timing of plant flowering. When CCA1 is overexpressed, it appears that the normal circadian rhythms of the plant are disrupted.