H3K27me3 epigenetic mark crucial for callus cell identity and regeneration capacity [ChIP-seq]

Plant callus cells possess a remarkable ability to regenerate organs that often differ from their respective origins or even entire new individuals. Yet, the mechanisms underlying their pluripotent state remain elusive. We propose a strategy that involves two independent mechanisms to endow callus cells with pluripotency: (1) maintaining a unique transcriptional profile, characterised by the expression of genes from diverse developmental pathways that allows rapid response to developmental cues; (2) preventing premature differentiation through H3K27 methylation-mediated silencing of key transcription factors such as WUCHEL and SPEECHLESS. This strategy relies on a mechanism to silence the pluripotency network upon regenerative stimuli, enabling a single developmental pathway to dominate. Our study reveals that the EMF2 complex, a key regulator of H3K27 tri-methylation, plays a crucial role in this process. Callus derived from the emf2 mutant, deficient in H3K27me3, exhibits severely impaired regeneration. Comparative analyses of chromatin states and transcription profiles between wild-type and emf2 calli revealed that the loss of EMF2 leads to upregulation of key transcription factors in callus, and identified the genes regulated solely by EMF2. Our findings suggest that suppressing pluripotency networks through H3K27me3 is essential for executing specific developmental programs to ensure effective regeneration. Overall design: ChIP-seq profiling of wild-type Arabidopsis callus, and emf2 mutant-derived callus