Plant embryogenesis

The subject of this review is the development of the plant embryo. Plant embryogenesis is a unique process in the sense that it can be started not only from the fertilized egg but can also be initiated from other cells of the reproductive apparatus and even from somatic cells. One of the challenges of this field is therefore to unravel the molecular mechanisms that lead to the formation of a cell destined to form an embryo. A second important area of research is to determine the molecular basis of pattern formation in the embryo, a process that results in a stereotyped organization of a seedling. On the one hand, the pattern formation process has to establish precisely arranged tissue organization, but on the other hand sufficient flexibility during plant development has to be maintained to allow continuous formation of new organs from meristems. In this review we summarize recent work that employs a variety of experimental systems that range from genetic dissection of pattern formation in the zygotic embryo, androgenesis and in vitro fertilization to somatic embryogenesis. While each of these systems highlights a different aspect of embryogenesis, they can be mutually beneficial in helping to understand the making of the plant embryo.