The role of auxin signaling in early embryo pattern formation

•Auxin activity in the embryo is dynamic and tightly regulated.•Oriented cell divisions and identity specification together pattern the embryo.•Diverse target genes mediate specific auxin functions.•Auxin signaling controls many aspects of early pattern formation.•Vascular development is closely linked to and follows high auxin signaling. Pattern formation of the early Arabidopsis embryo generates precursors to all major cell types, and is profoundly controlled by the signaling molecule auxin. Here we discuss recent milestones in our understanding of auxin-dependent embryo patterning. Auxin biosynthesis, transport and response mechanisms interact to generate local auxin accumulation in the early embryo. New auxin-dependent reporters help identifying these sites, while atomic structures of transcriptional response mediators help explain the diverse outputs of auxin signaling. Key auxin outputs are control of cell identity and cell division orientation, and progress has been made towards understanding the cellular basis of each. Importantly, a number of studies have combined computational modeling and experiments to analyze the developmental role, genetic circuitry and molecular mechanisms of auxin-dependent cell division control.