Abstract 9316756 We propose to build upon the progress we have made in this system towards understanding how the circadian clock effects changes in the transcription of the Arabidopsis cab2 gene. In particular, we wish to further characterize a 78bp DNA fragment that we have shown to be able to confer circadian regulation upon heterologous promoters. We wish to dissect at the nucleotide level the precise genomic targets for the signal transduction pathways that emanate from the circadian clock and phytochrome. These studies will be greatly enhanced by using a cab2-luciferase gene fusion that provides a bioluminescent marker for monitoring cab2 transcription in living transgenic seedlings. Furthermore, we have identified three specific DNA binding activities that recognize conserved targets within the cab2 5'upstream region. We propose a detailed characterization of these proteins that will define their contribution to regulated transcription and will ultimately result in cloning the genes that encode these factors. This will provide a first step from the genomic targets towards the signal transduction components that regulate cab2 transcription. %%% This proposal describes experiments that address a central question in biology: What is the mechanism of action of the circadian clock? Given the ubiquitous presence of circadian-regulated processes, advances in one particular system should have broad impact. We have chosen higher plants as our model system, and we will focus our studies in Arabidopsis thaliana. ***
