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, 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 inArabidopsis 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.

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