Normal development relies on regulated gene expression, which in many organisms is achieved by balanced activity of protein complexes that turn genes on or off at the right time and in the right place. A major unsolved question is how silencing proteins locate and turn off their target genes. The focus of this research is to discover how genes are targeted and inactivated by the silencing protein complex known as the "polycomb group" (PcG) complex. As a study system, the project will use the fungus, Fusarium graminearum, which has economic importance as a source of beneficial natural products and biofuels and agronomic importance as a plant pathogen. Thus, the results of the research could translate into better methods for manipulating the beneficial traits of the fungus, while minimizing its negative impact on crop plants. The project will have educational impacts by providing research training opportunities for underserved students, laboratory and professional development workshops for high school science teachers, and science presentations to the general public.
This project addresses chromatin-based gene silencing by PcG proteins in a novel model organism, the filamentous fungus Fusarium graminearum. The work will take advantage of the fact that Fusarium uses one Polycomb Repressive Complex2 (PRC2) to deliver histone H3 lysine 27 trimethylation (H3K27me3) to specific genes. Preliminary data suggest that the gene recognition is mediated by PRC2 subunits or by interacting proteins and that the subsequently modified genes are sequestered as transcriptionally silent "PRC2 bodies" with clear boundaries to euchromatin. The main objectives of this project are to uncover the mechanism for PRC2 targeting and to define the composition of PRC2 complexes. The aims will be achieved by multi-faceted approaches, including: forward and reverse genetics by undirected selections and screens, gene deletions, and site-directed mutagenesis; biochemistry by chromatin immunoprecipitation, genome-wide expression analyses and mass spectrometry; and cytology by examination of PRC2 bodies in association with DNA. In combination, these techniques will allow identification and characterization of PRC2 signals and proteins involved in gene silencing. Novel components of PRC2-mediated gene silencing in Fusarium will be characterized, and distribution of H3K27me3 and PRC2 in normal and mutant strains will be mapped. The research will provide key knowledge on PRC2-mediated silencing in eukaryotes.