LIKE HETEROCHROMATIN PROTEIN 1: a Polycomb-beyond Composite Regulator of Chromatin in Development, Stress, and Defense

Abstract Amidst its dynamic roles within Polycomb group (PcG) complexes, a growing body of work shows that LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) interacts with diverse protein and long non-coding RNA (lncRNA) partners and integrates multiple epigenetic pathways to sculpt chromatin states and modulate gene activity. We survey expanding, integrative networks that position LHP1 as a regulatory hub in Arabidopsis thaliana and crops, ensuring developmental timing and fidelity, establishing bivalent chromatin domains and growth–stress/defense tradeoffs, and contributing to lineage-specific functional innovation. These multifaceted attributes qualify LHP1 as a Polycomb-beyond Composite Regulator 1 (PCR1), a designation that honors its PcG heritage while accommodating broader and evolving roles in gene regulation. This synthesis delineates conceptual and translational frontiers in chromatin biology, informing strategies to engineer resilient, high-performing crops.