Submitted to: Science Magazine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2000
Publication Date: 5/5/2000
Citation: Martinez-Garcia, J.F., Huq, E., Quail, P.H. 2000. Direct targeting of light signals to a promoter element-bound transcription factor. Science Magazine 288(5467):859-863. Interpretive Summary: Our goal was to define the mechanism by which phytochrome photoreceptors of plants turn genes on or off in response to light signals from the environment. The light-activated phytochrome molecule was shown to bind directly to another protein, PIF3, which is in turn bound to the regulatory DNA region of light-induced genes. These data are the first report of a direct signaling pathway from the photoreceptor to target gene switches. Discovery of this mechanism provides targets for future intervention in production of agronomically superior crop plants.
Technical Abstract: Light signals perceived by the phytochrome family of sensory photoreceptors are transduced to photoresponsive genes by an unknown mechanism. Here, we show that the basic helix-loop-helix transcription factor PIF3 binds specifically to a G-box DNA-sequence motif present in various light-regulated gene promoters, and that phytochrome B binds reversibly to G-box-bound PIF3 specifically upon light-triggered conversion of the photoreceptor to its biologically active conformer. We suggest that the phytochromes may function as integral light-switchable components of transcriptional regulator complexes, permitting continuous and immediate sensing of changes in this environmental signal directly at target gene promoters.