Polycomb Response Elements (PREs) and Polycomb Recruitment in Plants

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Intellectual Merit: In eukaryotes, genomic DNA is highly compacted in the nucleus. This compaction renders portions of the genomic DNA inaccessible to transcription factors or the general transcriptional machinery. A large fraction of the inaccessible DNA consists of gene-poor heterochromatin. Portions of the gene-rich euchromatin are also inaccessible or silenced. A hallmark of this silencing is that it occurs only in certain conditions, for example in some cell types or in the absence of an environmental cue. In multicellular eukaryotes, euchromatic silencing is largely mediated by Polycomb repression. Polycomb repressors do not have inherent sequence specificity; instead, they need to be targeted to the correct genomic loci. This project will identify DNA sequence motifs that direct Polycomb repressors to euchromatic genomic regions in Arabidopsis thaliana for proper plant development and proper plant stress responses. The ultimate goal of the project is to be able to predict--based on the presence of the DNA sequence motifs--which genomic regions Polycomb repressors can be recruited to in this, and in other, plant species and to identify the sequence-specific binding factors involved in the recruitment. Broader Impacts: The project will train the next generation of scientists in state-of the art research. Undergraduate researchers, including underrepresented minorities, will conduct individual independent laboratory research and conduct research in new one-semester-long lab modules. The research will be related to the main objectives of the project. In the past, the undergraduate contributions have been excellent and have warranted authorships on scientific publications. The project will teach topics related to chromatin-mediated regulation of genome accessibility to high-school students in a summer course and to Biology teachers of inner city high schools during professional development sessions. Finally, the project will train researchers from other labs and institutions in critical techniques used in this field. In plants, Polycomb repression regulates the transition to reproductive development, flower formation and seed development as well as response to abiotic stress. Understanding and consequently being able to manipulate the recruitment of these activities to certain regions in the plant DNA should thus allow improvement of agricultural traits such as biomass and seed production as well as water stress tolerance.