Project Number: 5335-21000-027-00
Project Type: Appropriated

Start Date: May 09, 2006
End Date: May 08, 2011

Objective:
The long-term goal of this research is to define the molecular mechanisms by which the phytochrome (phy) family of photoreceptors perceive informational light signals from the environment and transduce them to photoresponsive nuclear genes, thereby controlling plant growth and development. Using genome-scale microarray-based expression profiling, we have begun to define the global transcriptional network regulated by these photoreceptors and have identified a set of rapidly light-induced or -repressed genes (primarily encoding various transcription factors) that are potential direct targets of the phytochrome signaling pathway. The specific objectives of this project plan are: 1. To identify which phy family members are responsible for signaling to each of these genes, by examining light-induced expression profiles in null mutants of each phytochrome. 2. To define the cis elements in the promoters of these genes responsible for coordinate light-regulated expression, using computational analysis coupled with targeted mutagenesis and transgenic expression of promoter::reporter fusion constructs. 3. To identify downstream targets of these genes in the light-regulated transcriptional network, using microarray-based expression profiling in knockout mutants null for each transcription factor, coupled with chromatin immunoprecipitation (ChIP) for target promoter identification and characterization.

Approach:
The specific objectives of this proposal are: (a) to identify which phys are responsible for signaling to these genes; (b) to define the cis elements in the promoters of these genes responsible for coordinate light-regulated expression; (c) to identify downstream targets of these genes in the light-regulated transcriptional network. The experimental approaches will include: (a) microarray-based expression profiling of mutants null for each phy, both to define the phy-regulated transcriptional networks and to identify rapidly light-responsive genes for targeted reverse-genetic mutagenesis; (b) computational analysis of the promoters of these genes, coupled with targeted mutagenesis and transgenic expression of promoter::reporter fusion constructs; (c) expression profiling in knockout mutants null for each transcription factor, coupled with chromatin immunoprecipitation for identification of promoters that are direct targets of these factors. REPLACES 5335-21000-023-00D (4/06). BSL 1; 2/19/08.