Genetic control of identity and growth in the early Arabidopsis embryo

Plants can grow complex and elaborate structures, in some species for thousands of years. Despite the diversity in form and shape, plants are built from a limited number of fundamental tissue types, and their arrangement is deeply conserved in the plant kingdom. A key question in biology is how these fundamental tissues, i.e. epidermal, ground and vascular tissue, are specified and organized in time and space. In the present paper, I discuss the use of the early Arabidopsis embryo as a model system to dissect the control of tissue formation and patterning, as well as the specification of the stem cells that sustain post-embryonic growth. I present recent insights into the molecules and mechanisms that control both the specification and the subsequent growth of the different cell types within the embryonic root. Finally, I discuss major unanswered questions and future challenges in using the embryo as a model to decipher the regulatory logic of plant development.