Cell Type-Specific Gene Regulatory Network of the Polycomb Repressive Complex 2 in Arabidopsis

Chromatin is a dynamic structure that responds to innumerable stimuli to regulate accessibility of DNA. The covalent modification of histones is the principal process used by the cell to modulate nucleosome mobility and turnover. The Polycomb Repressive Complex 2 (PRC2) catalyzes the trimethylation of Histone 3 at lysine 27 (H3K27me3), which acts as a repressive chromatin mark.

 PRC2 composition is conserved from humans to plants, but key questions remain unclear concerning their spatiotemporal regulation and function. The model plant Arabidopsis thalianahas 12 homologs of Drosophila PRC2 subunits. The three PRC2 complexes described in Arabidopsis control the expression of genes involved in the regulation of developmental transitions. It is also also known that the PRC2 is required to maintain organ identity and to keep cells appropriately differentiated, however their role in cell type identity and patterning remains unknown.

Our work describes the role of the PRC2 in controlling cell proliferation and differentiation in the Arabidopsis root.  PRC2 subunits are differentially expressed in root cell types, being highly present in the dividing/pluripotent cells of the meristem. To better understand this spatiotemporal regulation and function, we have resolved the transcriptional regulatory network that controls PRC2 expression in different root cell types. We have also generated vascular specific profiling of the H3K27me3 and H3K4me3 marks and correlated these with vascular specific gene expression. This multi-layered transcriptional regulatory network will allow us to understand how epigenetic modifications are dynamically regulated in space and time to control cell type and tissue specification, differentiation and function.