EMF genes encode chromatin proteins that are master regulators of Arabidopsis development, including the regulation of flowering time. This project studies how the two EMF genes keep plants from flowering. Maintaining floral repression is critical for vegetable crops such as cabbage. A genome-wide approach employing ChIP-chip technology will enable comprehensive identification of EMF/PcG target genes and characterization of the roles of EMF1 and EMF2 in establishing histone methylation (H3K27me3) and transcriptional regulation. A molecular genetic approach will be employed to investigate the function of EMF1-target gene interaction. This project will uncover the EMF-regulated genetic network that controls vegetative development, and the role EMF1 plays in epigenetic regulation of gene expression. Data will be made available to the public via Gene Expression Omnibus (www.ncbi.nlm.nih.gov/geo/), a curated online resource maintained by NCBI. The proposed research will provide training opportunities in developmental genetics, chromatin biology and genomics for a postdoctoral fellow and student researchers, including students from underrepresented and disadvantaged backgrounds.
Plants develop in phases – embryonic, vegetative, reproductive and flowering – each specified through activation and inactivation of specific sets of genes. How the transcriptional program for each phase is established and maintained is of central interest to developmental biology. In particular, because plants grow continuously while undergoing developmental transitions, they require special mechanisms to reprogram cell fates and memory during phase changes. Nonetheless, plants and animals share many regulatory mechanism, and knowledge about plant development also contributes to our understanding of human biology. Polycomb group (PcG) proteins regulate development in plants, humans and many other species by maintaining repression of specific genes. Trithorax group (TrG) proteins also contribute to development, but by promoting gene activity. We investigated EMBRYONIC FLOWER 1 (EMF1), an unconventional PcG protein in the model plant Arabidopsis thaliana. We discovered that the EMF1 protein is crucial for PcG function. EMF1 binds to and regulates the expression of thousands of genes, among them many key regulators of plant development. Our findings explain the drastic developmental phenotypes of plants with reduced EMF1 activity. We also found that the ULTRAPETALA1 gene is an antirepressor with a TrG function that counteracts EMF1 action on target genes. Our results have important implications for our understanding of the regulation of plant development and the evolution of PcG regulatory mechanisms.
