Regulation of the Early Phase of Seed Development: An Illustrative Review

Seeds are the central innovation of angiosperms, earliest developmental steps of which hinge on tightly coordinated fate decisions across sporophytic and gametophytic tissues. This review synthesizes recent advances in the regulation of the early phase of seed devel-opment, beginning with ovule primordium growth and the specification of a single mega-spore mother cell (MMC), through female gametophyte maturation, double fertilization, and the onset of embryo–endosperm–seed coat programs. Canonical regulators (e.g., SPL/NZZ-centered networks and auxin transport/threshold control) operate alongside re-pressive safeguards mediated by small-RNA pathways, transposon silencing, and Poly-comb/RBR1-linked cell-cycle gates that prevent premature proliferation and autonomous seed formation. After fertilization, parent-of-origin epigenetic asymmetries and dynamic chromatin states reshape transcriptional competence in endosperm and embryo, with auxin emerging as a key mobile coordinator of endosperm growth, integument differentia-tion, and seed coat initiation. Mechanical inputs, including endosperm turgor and mech-anosensitive responses in maternal tissues, are integrated with hormone signaling to tune seed growth and the timing of endosperm cellularization. Together with the accompany-ing figures, the review provides an illustrative depiction of the earliest regulatory logic underlying successful seed formation.