title: Plant embryogenesis requires AUX/LAX-mediated auxin influx.
abstract: The plant hormone auxin and its directional transport are known to play a crucial role in defining the embryonic axis and subsequent development of the body plan. Although the role of PIN auxin efflux transporters has been clearly assigned during embryonic shoot and root specification, the role of the auxin influx carriers AUX1 and LIKE-AUX1 (LAX) proteins is not well established. Here, we used chemical and genetic tools on Brassica napus microspore-derived embryos and Arabidopsis thaliana zygotic embryos, and demonstrate that AUX1, LAX1 and LAX2 are required for both shoot and root pole formation, in concert with PIN efflux carriers. Furthermore, we uncovered a positive-feedback loop between MONOPTEROS (ARF5)-dependent auxin signalling and auxin transport. This MONOPTEROS-dependent transcriptional regulation of auxin influx (AUX1, LAX1 and LAX2) and auxin efflux (PIN1 and PIN4) carriers by MONOPTEROS helps to maintain proper auxin transport to the root tip. These results indicate that auxin-dependent cell specification during embryo development requires balanced auxin transport involving both influx and efflux mechanisms, and that this transport is maintained by a positive transcriptional feedback on auxin signalling.
authors.affiliation: Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB) and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium Mendel Centre for Genomics and Proteomics of Plants Systems, CEITEC MU - Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic.
authors.forename: Hélène S
authors.initials: HS
authors.lastname: Robert
authors.affiliation: Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB) and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Grunewald
authors.affiliation: University of Potsdam, Institute of Biochemistry and Biology, D-14476 Potsdam, Germany Departamento Molecular de Plantas, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas, 28049 Madrid, Spain.
authors.forename: Michael
authors.initials: M
authors.lastname: Sauer
authors.affiliation: Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB) and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
authors.forename: Bernard
authors.initials: B
authors.lastname: Cannoot
authors.affiliation: Wageningen University and Research Centre, P.O. Box 619, 6700 AP Wageningen, The Netherlands.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Soriano
authors.affiliation: School of Biosciences and Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Swarup
authors.affiliation: Laboratory of Biochemistry, Wageningen University, 6703 HA Wageningen, The Netherlands.
authors.forename: Dolf
authors.initials: D
authors.lastname: Weijers
authors.affiliation: School of Biosciences and Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Bennett
authors.affiliation: Wageningen University and Research Centre, P.O. Box 619, 6700 AP Wageningen, The Netherlands.
authors.forename: Kim
authors.initials: K
authors.lastname: Boutilier
authors.affiliation: Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB) and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium Mendel Centre for Genomics and Proteomics of Plants Systems, CEITEC MU - Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic Institute of Science and Technology Austria (IST Austria), 3400 Klosterneuburg, Austria jiri.friml@ist.ac.at.
authors.forename: Jiří
authors.initials: J
authors.lastname: Friml
mesh_terms: D017360:Arabidopsis / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics / Q000502:physiology; D029688:Brassica napus / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D012639:Seeds / Q000166:cytology* / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
chemical_list: D007210:Indoleacetic Acids; D010940:Plant Proteins
keywords: AUX1; Arabidopsis thaliana embryogenesis; Auxin transport; Brassica napus; LIKE-AUX1 (LAX); MONOPTEROS (ARF5); Microspore; PIN