Tracking the genome-wide occupancy of Arabidopsis LEAFY COTYLEDON1 in endosperm development.

Endosperm development is crucial for embryo growth and seed maturation. LEAFY COTYLEDON1 (LEC1), expressed in both endosperm and embryo, serves as a key regulator of seed development, orchestrating processes such as embryogenesis and seed maturation. LEC1 expression in the endosperm is detectable within a day after fertilization, yet its specific regulatory networks and developmental functions in this tissue remain unclear. To address this, we employed a modified INTACT system to isolate endosperm nuclei and performed ChIP-seq to map the genome-wide binding profile of LEC1 in developing endosperm. Integrating ChIP-seq with transcriptomic analyses, we uncover a critical role for LEC1 in regulating diverse biological pathways. Differential gene expression analysis in the endosperms of lec1 mutant and wild type shows substantial changes, particularly in genes involved in secondary cell wall biogenesis, photosynthesis, and lipid metabolism. Notably, LEC1's regulatory networks in the endosperm shift significantly after cellularization, with distinct genes being activated in the cellular and degeneration stages. The absence of LEC1 causes significant alterations in endosperm metabolism, particularly affecting storage lipid fatty acid composition. These findings provide insights into the essential role of LEC1 in endosperm development and its broader impact on seed formation.