H3K27me3 epigenetic mark crucial for Arabidopsis callus cellular identity and regeneration capacity

Plant callus cells possess a great capacity to regenerate organs or even whole plants. The mechanisms by which these cells maintain a proliferative state while retaining their pluripotent identity are poorly understood. By taking a multi-omics approach integrating epigenetic regulation (via chromatin immunoprecipitation and sequencing) with transcriptional output, we identify two complementary strategies that support callus cell pluripotency. First, callus cells prevent differentiation by promoting proliferation through activating cell cycle genes, and concurrently repress differentiation-promoting factors via H3K27me3. Second, callus cells exhibit a unique transcriptional profile enriched in diverse developmental regulators, thereby maintaining a primed pluripotent state that enables a rapid regenerative response. This strategy relies on a mechanism to silence the pluripotency network in response to regenerative stimuli, allowing a single developmental pathway to predominate. To test whether the Polycomb Repressive Complex 2 (PRC2), which mediates H3K27me3 silencing, is essential for maintaining callus identity and regenerative capacity, we analyzed the transcriptional state of Arabidopsis thaliana wild-type and PRC2 mutant emf2 calli. In emf2 mutants, many differentiation-associated transcription factors were up-regulated, and regenerative capacity was severely impaired. Our findings provide new insight into how pluripotency is regulated. We propose a novel model in which PRC2 governs callus identity and regenerative potential.