ALFIN-LIKE H3K4me3 reader proteins regulate embryogenesis in Arabidopsis

Development of multicellular organisms requires the precise coordination of gene expression programs. Whereas histone modifications are key regulators of transcriptional states, how these modifications are interpreted during early development remains poorly understood. Here, we investigate the role of H3K4me3 recognition during embryogenesis in Arabidopsis thaliana We identify ALFIN-LIKE (AL) proteins as essential H3K4me3 readers required for early seed development. Loss of AL function leads to severe defects in embryogenesis, including impaired asymmetric zygotic division, disrupted patterning, and loss of lineage restriction. At the molecular level, AL deficiency results in widespread transcriptional misregulation and is associated with local changes in chromatin state, including reduced H3K4me3 and a concomitant increase in H3K27me3 at a subset of loci, including key developmental and flowering-time regulators. Together, our results show that interpretation of H3K4me3 by AL proteins is required for proper gene expression during early development and reveal a context-dependent relationship between activating and repressive chromatin states, highlighting a role for H3K4me3 in shaping gene expression during plant embryogenesis.