Establishment and maintenance of repressive chromatin during development in plants

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This project will study how plants control expression of specific genes during development by changing how the genes are packaged in the nucleus. In plants, like in other eukaryotic organisms, the very large genome is packaged into the small space of the cell's nucleus by winding the genomic DNA around proteins to form a compacted DNA-protein complex called chromatin. Very tightly compacted chromatin can prevent gene expression by mechanisms that are not fully understood. Exploring these mechanisms is the focus of this proposal. A long-term goal will be to use the research outcomes to manipulate development in plants to increase their agricultural potential. The research will be carried out by undergraduate and graduate students working together, providing an authentic research experience for undergraduate students and mentoring opportunities for the graduate students. In addition, analysis of the genomic data generated in the project will be incorporated into a new computational genomics course to teach students how to analyze large datasets using computational approaches. All of the data generated by the project will be deposited in public databases.In eukaryotes, including the model plant Arabidopsis thaliana, trimethylation of lysine 27 on histone H3 (H3K27me3) in nucleosomal chromatin is associated with transcriptional repression, but how this histone modification is imposed, maintained, and read is poorly understood. The chromatin remodeler named PICKLE (PKL) has been shown previously to promote tissue- and developmental-specific repressive chromatin, defined by the presence of H3K27me3. Recent evidence suggests that PKL may function as a pre-nucleosome maturation factor that acts with a histone methyltransferase, a second remodeler, and a histone H2A variant to control conditional expression from H3K27me3-enriched loci. This relationship will be tested by combining genetic, genomic, and biochemical approaches to relate chromatin-mediated changes in gene expression to whole-plant developmental phenotypes. The results are expected to reveal the role of H3K27me3 homeostasis in formation and maintenance of repressive chromatin states.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.