lembryogenèse

Embryogenesis is the developmental process by which an embryo forms and develops from a fertilized egg or other initial cell. It occurs in both animals and plants, though the mechanisms and terminology differ.

In animals, embryogenesis begins with fertilization, followed by cleavage divisions that produce a multicellular blastula. Gastrulation then reorganizes the cells into germ layers, setting up the body plan. In vertebrates, neurulation forms the neural tube, and subsequent organogenesis generates the organs and tissues of the organism. During this period, the zygotic genome becomes transcriptionally active, and interactions among cells and tissues establish the organism’s axes and symmetry. In mammals, additional structures such as the placenta and other extraembryonic membranes support the developing embryo.

In plants, embryogenesis occurs within the ovule as part of seed development and follows zygotic development. The embryo progresses through stages such as globular, heart, and torpedo, ultimately forming the mature embryo that contains the future shoot and root meristems. Patterning is driven largely by plant hormones, especially auxin, and the embryo establishes the basic body axes without forming germ layers. Plants can also undergo somatic embryogenesis in culture, where somatic cells are induced to form embryos using plant growth regulators, a process widely used in cloning and genetic engineering.

Embryogenesis is central to developmental biology and reproductive biology and has practical importance in agriculture, forestry, and biotechnology through seed production, clonal propagation, and the genetic modification of crops.