Finding balance: the dynamic interplay between H3K27me3 writers and erasers in regulating environmental plasticity and memory.

Subject to an ever-changing world, plants must respond to harmful conditions and environmental fluctuations. Their evolutionary success can be attributed to their plasticity in both perceiving and integrating these variations to facilitate adaptation. The epigenetic control of gene expression through histone modification affords plants this flexibility by fine-tuning gene expression and imprinting a transcriptional memory of specific conditions. Histone H3 lysine 27 trimethylation (H3K27me3) is a repressive modification held in balance across the genome by its writer, the Polycomb Repressive Complex 2, and its erasers, Jumonji-class histone lysine demethylases. While extensively studied as a mark controlling cell-fate identity and developmental transitions, recent efforts have shown that stress-responsive loci are also regulated by H3K27me3. In this review, I explore the emerging roles of these H3K27me3 writers and erasers as central hubs in stress adaptation, highlighting their context-dependent regulation and interplay with other chromatin marks. By examining H3K27me3 dynamics, I provide an updated perspective on its versatile functions beyond development, emphasising its relevance in enhancing plant adaptation and resilience to changing environments.