The apical-basal axis of the early plant embryo determines the body plan of the adult organism. To establish a polarized embryonic axis, plants evolved a unique mechanism that involves directional, cell-to-cell transport of the growth regulator auxin. Auxin transport relies on PIN auxin transporters, whose polar subcellular localization determines the flow directionality. PIN-mediated auxin transport mediates the spatial and temporal activity of the auxin response machinery that contributes to embryo patterning processes, including establishment of the apical (shoot) and basal (root) embryo poles. However, little is known of upstream mechanisms guiding the (re)polarization of auxin fluxes during embryogenesis. Here, we developed a model of plant embryogenesis that correctly generates emergent cell polarities and auxin-mediated sequential initiation of apical-basal axis of plant embryo. The model relies on two precisely localized auxin sources and a feedback between auxin and the polar, subcellular PIN transporter localization. Simulations reproduced PIN polarity and auxin distribution, as well as previously unknown polarization events during early embryogenesis. The spectrum of validated model predictions suggests that our model corresponds to a minimal mechanistic framework for initiation and orientation of the apical-basal axis to guide both embryonic and postembryonic plant development.

Department of Plant Systems Biology Flanders Institute for Biotechnology and Department of Plant Biotechnology and Genetics Ghent University Technologiepark 927 9052 Gent Belgium

Department of Plant Systems Biology Flanders Institute for Biotechnology Masaryk University 625 00 Brno Czech Republic

Department of Plant Systems Biology Flanders Institute for Biotechnology Masaryk University 625 00 Brno Czech Republic; Institute of Science and Technology Austria 3400 Klosterneuburg Austria

Institute of Plant Sciences University of Bern Altenbergrain 21 3013 Bern Switzerland; Department of Comparative Development and Genetics Max Planck Institute for Plant Breeding Research Carl von Linné Weg 10 50829 Köln Germany

References provided by Crossref.org

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