Auxin regulation of embryo development

Important steps in plant development are made shortly after fertilization. In a brief succession of cell divisions, the zygote is transformed into an embryo, a multicellular structure carrying all fundamental tissue types and the meristems. Hence, embryogenesis offers excellent opportunities to dissect the molecular control and cellular mechanisms underlying plant development. In the past decades, forward and reverse genetics studies have revealed that the plant hormone auxin plays a central role in the establishment of pattern and polarity in the Arabidopsis embryo. Here, we review the roles that localized auxin biosynthesis, directional transport and cell type-specific response play in embryo development. We focus on the molecular mechanisms, as well as the feedbacks that connect these disparate levels of regulation. Finally, we discuss the potential for hormonal cross-talk in auxin-dependent control of the key events during the earliest, formative phase of plant life.