title: Directional auxin transport mechanisms in early diverging land plants.
abstract: The emergence and radiation of multicellular land plants was driven by crucial innovations to their body plans. The directional transport of the phytohormone auxin represents a key, plant-specific mechanism for polarization and patterning in complex seed plants. Here, we show that already in the early diverging land plant lineage, as exemplified by the moss Physcomitrella patens, auxin transport by PIN transporters is operational and diversified into ER-localized and plasma membrane-localized PIN proteins. Gain-of-function and loss-of-function analyses revealed that PIN-dependent intercellular auxin transport in Physcomitrella mediates crucial developmental transitions in tip-growing filaments and waves of polarization and differentiation in leaf-like structures. Plasma membrane PIN proteins localize in a polar manner to the tips of moss filaments, revealing an unexpected relation between polarization mechanisms in moss tip-growing cells and multicellular tissues of seed plants. Our results trace the origins of polarization and auxin-mediated patterning mechanisms and highlight the crucial role of polarized auxin transport during the evolution of multicellular land plants.
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Viaene
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Linnean Centre of Plant Biology in Uppsala, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden.
authors.forename: Katarina
authors.initials: K
authors.lastname: Landberg
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Linnean Centre of Plant Biology in Uppsala, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden.
authors.forename: Mattias
authors.initials: M
authors.lastname: Thelander
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium; Mendel Centre for Genomics and Proteomics of Plants Systems, Central European Institute of Technology (CEITEC MU), Masaryk University, 625 00 Brno, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Medvecka
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Linnean Centre of Plant Biology in Uppsala, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden.
authors.forename: Eric
authors.initials: E
authors.lastname: Pederson
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium.
authors.forename: Elena
authors.initials: E
authors.lastname: Feraru
authors.affiliation: Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, MD 20742, USA.
authors.forename: Endymion D
authors.initials: ED
authors.lastname: Cooper
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium.
authors.forename: Mansour
authors.initials: M
authors.lastname: Karimi
authors.affiliation: Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, MD 20742, USA.
authors.forename: Charles F
authors.initials: CF
authors.lastname: Delwiche
authors.affiliation: Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Ljung
authors.affiliation: Plant Biology, Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Geisler
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Linnean Centre of Plant Biology in Uppsala, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Sundberg
authors.affiliation: Department of Plant Systems Biology, VIB, and Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium; Institute of Science and Technology Austria (IST Austria), 3400 Klosterneuburg, Austria; Mendel Centre for Genomics and Proteomics of Plants Systems, Central European Institute of Technology (CEITEC MU), Masaryk University, 625 00 Brno, Czech Republic. Electronic address: jiri.friml@ist.ac.at.
authors.forename: Jiří
authors.initials: J
authors.lastname: Friml