CRISPR/dCas9-targeted H3K27me3 demethylation at the CUC3 boundary gene triggers ectopic transcription and impacts plant development.

Chromatin modifications are deemed to correlate with gene expression patterns, yet their direct causal effect on transcription and cell fate remains unestablished. The H3K27me3 modification, highly conserved in eukaryotes, is strongly associated with the repression of developmental genes. Here, we establish the genuine function of H3K27me3 in planta by leveraging a CRISPR-dCas9-based epigenetic editing tool to specifically remove this methylation mark at the Arabidopsis CUP SHAPED COTYLEDON 3 (CUC3) boundary gene. Targeted recruitment of the JMJ13 H3K27me3 demethylase to the CUC3 locus induces ectopic transcription and gene expression patterns, leading to altered leaf morphology and meristem integrity. Combining molecular and phenotypic analyses, we thus establish evidence directly linking H3K27me3-mediated repression to developmental outcomes. Our study highlights locus-specific epigenetic editing as a powerful approach to dissect the functional impacts of histone modifications on transcription and morphogenesis, and provides a framework for unveiling the causal role of chromatin dynamics in plant developmental plasticity.