PRC2 and TrxG interactions required for the acquisition of new cell identity during regeneration in Arabidopsis

Certain somatic plant cells retain plasticity and are capable under appropriate stimuli, in vivo after wounding, or in vitro stimulated by plant hormones, to switch their developmental program, re-enter the cell cycle and form a mass of less - differentiated totipotent cells, termed callus. Those cells acquire competence to respond rapidly to diverse stimuli taking on new fate accordingly, which often includes direct embryogenesis.

To study the molecular mechanism underlying the competency to differentiate into all cell types, we combined ChIP-Seq and genetic approaches and analyzed genome wide the chromatin features of wild-type callus as well as calli derived from Polycomb Repressive Complex 2 (PRC2) and Trithorax group (TrxG).

We also generated a set of mutants with gradual reduction in the H3K4me3 and H3K27me3 marks, expressing a mutated form of the histone H3, and further tested the regenerative capacity.

We show that maintaining callus cell identity with the capacity to regenerate requires a mechanism to silence a set of dominant genes, mainly transcription factors, while simultaneously keeping active numerous genes from diverse developmental programs.

We reveal that reduction in H3K4me3 accelerate the entry into a proliferate stage and callus formation, whereas reduction in H3K27me3 leads to impaired capacity to regenerate.