Epigenetic modifications are dynamically deposited and removed from genes to control gene expression and drive developmental processes in plants. The trimethylation
of the K27 residue of histone 3 (H3K27me3) is a silencing epigenetic mark especially
pertinent to plant development. Though the placement of H3K27me3 across the
genome is well studied, its removal to allow reactivation of gene expression is less
well understood. Three H3K27me3 demethylases, ELF6, REF6, and JMJ13, have
been previously identified, and in this study we aim to understand the role of these
H3K27me3 demethylases in regulating developmental processes in Arabidopsis.
We firstly undertake a unique chromatin state analysis to understand the broader
context of H3K27me3 within the genome and demonstrate the importance of this
mark in epigenetic regulation. We then aim to understand the functions of ELF6,
REF6, and JMJ13 in two distinct developmental process; floral development, and
regeneration. First, we reveal that ELF6 and JMJ13 play antagonistic roles in floral development. We find that ELF6 promotes out-crossing by regulating gynoecia
growth through the epigenetic reactivation of expansin genes. Conversely, we show
that JMJ13 promotes self-fertility by regulation of carpel and stamen growth via
epigenetic regulation of hormone response transcription factors. Next, we study
the role of H3K27me3 demethylases in plant regeneration using novel single cell
RNA sequencing techniques. Using this technology, we conceive a new framework
to understand leaf cell dedifferentiation, and find that REF6 promotes the dedifferentiation of leave cells into pluripotent callus stem cells. The final chapter aims to
study the mechanisms by which ELF6 is recruited to target genes in a dynamic and
precise fashion, but is yet to yield novel results.
Overall this study demonstrates that the H3K27me3 demethylases each play
distinct roles in epigenetic reactivation to regulate Arabidopsis development.