embryogenese

Embryogenesis, also referred to as embryogenese, is the process by which a fertilized egg develops into a multicellular embryo. It includes early cell divisions, the establishment of the body plan, and the differentiation of tissues and organs. While the general idea is common across living kingdoms, the specifics differ between animals and plants.

In animals, embryogenesis begins with fertilization followed by cleavage divisions that produce a multicellular blastula. Gastrulation then forms the germ layers—ectoderm, mesoderm, and endoderm—and establishes the primary body axes. Subsequent organogenesis and, in many vertebrates, neurulation build organs and the nervous system. The timing of genome activation and the pace of development vary by species. Patterning is directed by signaling molecules and gene regulatory networks, including morphogens and transcription factors that govern body plan development.

In plants, embryogenesis occurs inside the seed. The zygote divides asymmetrically to form a proembryo with established apical-basal polarity. The shoot and root meristems are set up, and the embryo differentiates tissues such as cotyledons. Plant hormones, particularly auxin, coordinate patterning and organ formation. Embryogenesis in plants is closely linked to seed maturation, dormancy, and resource allocation within the seed.

Regulation of embryogenesis involves genetic, epigenetic, and hormonal controls, with contributions from maternal factors in some species. Disruptions can lead to developmental defects. The study of embryogenesis uses model organisms to illuminate fundamental processes in development, with applications in medicine, agriculture, and breeding.