Patterns of auxin transport and gene expression during primordium development revealed by live imaging of the Arabidopsis inflorescence meristem. Local, efflux-dependent auxin gradients as a common module for plant organ formation. Reporters for sensitive and quantitative measurement of auxin response. Roles of the middle domain-specific WUSCHEL-RELATED HOMEOBOX genes in early development of leaves in Arabidopsis. Temporal integration of auxin information for the regulation of patterning. Patterns of stem cell divisions contribute to plant longevity. Quantitative analysis of auxin sensing in leaf primordia argues against proposed role in regulating leaf dorsoventrality. Cell type boundaries organize plant development. Microsurgical and laser ablation analysis of leaf positioning and dorsoventral patterning in tomato. Experiments on the cause of dorsiventrality in leaves. Auxin depletion from leaf primordia contributes to organ patterning. Boundary formation through a direct threshold-based readout of mobile small RNA gradients. Pattern formation via small RNA mobility. The Sussex signal: insights into leaf dorsiventrality. Evolution of carnivorous traps from planar leaves through simple shifts in gene expression. phantastica: a gene required for dorsoventrality of leaves in Antirrhinum majus. Auxin thus serves as a single morphogenic signal that orchestrates distinct, spatially separated responses to coordinate the positioning and emergence of a new organ with its patterning. Our data show that spatial information from an AS2–KAN1 meristem prepattern governs the conversion of a uniform auxin input into an ARF-dependent binary auxin response output to specify adaxial–abaxial polarity. As the primordium emerges, dynamic shifts in auxin distribution and auxin-related gene expression gradually resolve this initial polarity into the stable regulatory network known to maintain adaxial–abaxial polarity within the developing organ. This occurrence triggers a transient induction of ARF3 and an auxin transcriptional response in AS2-marked progenitors that distinguishes adaxial from abaxial identity. Here, by combining time-lapse confocal imaging, cell lineage tracing and molecular genetic analyses, we demonstrate that a stable boundary between adaxial and abaxial cell fates is specified several plastochrons before primordium emergence when high auxin levels accumulate on a meristem prepattern formed by the AS2 and KAN1 transcription factors. Despite its central importance, the mechanism by which leaf primordia acquire adaxial versus abaxial cell fates to establish dorsiventrality remains a topic of much debate. In plants, specification of dorsiventrality is critical to leaf morphogenesis. Developmental boundaries play an important role in coordinating the growth and patterning of lateral organs.

Define leaf primordia